Computer Physics Communications 28 (1982)109—151 North-Holland Publishing Company
109
LPOTF PION AND KAON ELASTIC SCATFERING FROM SPIN MOMENTUM SPACE -
4
NUCLEI IN
Rubin H. LANDAU Department of Physics, Oregon State University, Corvallis, OR 97331, USA and Department of Physics, University of Surrey, Guildford, Surrey GU2 5XH, England * Received 1 December 1981; in revised form 9 June 1982
PROGRAM SUMMARY Title: LPOTT Computer: CDC Cyber 170/72. Present version also runs on CDC 7600; Installation: Computer Center, Oregon State University, Corvallis, OR 97331, USA Operating system: NOS 1.4 Program language: FORTRAN 77 Memory required: 132.7 K
8 (46.5 K10) words to load (102 K8 — LPOTT, 11 K — FORTRAN libe, rest-system), 121.7 ~ (41.9 ~ words to run
No. of bits per word: 60 (14—15 decimal place accuracy, 1—4 instructions/word) Peripherals used: disk files (8 files on “program” card, 4 supplied with program, I scratch, 2 output, I computed and stored) Number of cards: 5037 FORTRAN, 1127 input data Card punching code: BCD (026 punch) Keywords: optical potential, pion, kaon, elastic scattering, charge exchange scattering, momentum space, spin ~ nuclei, multiple scattering theory, o(9), ~
panded in Legendre series and the resulting one-dimensional, coupled Lippmann—Schwinger integral equations are reduced to linear equations and solved by matrix inversion. Differential and total scattering cross sections, polarizations and coordinate space wave functions are calculated for both the elastic and single charge exchange scattering of ~ ii~ ~O K~ or K°. The theory includes nuclear spin ~ with realistic form factors, nucleon recoil and binding (2- or 3-body subenergies), Lorentz invariant relations between amplitudes and kinematic variables in different reference frames (angle and momentum transformations), the most recent elementary phase shifts, theoretical off-energy-shell behavior generated from separable potential models, Pauli effects, an “exact” inclusion of the Coulomb force, and a second-order potential to represent the effects of true absorption. Typical running time Most of the running 2C timescattering is used toatset50upMeV the potential with 10 matrix. partial The waves, testtakes case, ~20 s‘ without Pauli modifications and 28 s with Pauli modifications. These times are nearly doubled for a spin ~ nucleus, and doubled again for charge exchange since LPOYF does 71~(K~)and then ir°(K°).As the nucleus gets larger and/or the energy increases, an increase in running time approximately proportional to the increased number of partial waves will occur. However, the program saves some time by use of the Born approximation for higher partial waves. Restrictions
Method of solution A theoretical momentum-space optical potential is generated from elementary meson—nucleon amplitudes * * and realistic nuclear matter and spin form factors. The potential is cx*
**
Spin 0 ® spin 0, spin 0 0 spin
~,
0 ~ 71,, ~ 1.5 GeV, 0 ~ TK ~ I GeV.
Some subroutines written by S.C. Phatak, A.W. Thomas and M.J. Paez. Supported in part by the National Science Foundation (USA) and the Science Research Council (UK). Future versions of LPOTF will be published for nucleon—nucleus scattering (spin ~ 0
OO1O-4655/82/0000—0000/$02.75 © 1982 North-Holland
110
R.H. Landau
/
Pion and kaon elastic scattering
No. of meson—nucleus (nucleon) partial waves 30 (8) in corn, Number of grid points for numerical integration of wave equation 32 (must modify one DIMENSION statement to
increase). Exact Coulomb only for elastic scattering (not charge exchange). Variety of nuclear densities possible, but not at all energies. Variety of kinematic prescriptions possible.
LONG WRITE-UP
Contents
3.1. Solution of the Lippmann—Schwinger equation by matrix inversion
I. Introduction 2. Equations computed by LPOTT 2.1. Equations computed 2.2. Cross sections 2.3. Inclusion of the Coulumb force 2.4. Form of the first-order potential 2,5. Nuclear form factors 2.5.1. Harmonic oscillator density 2.5.2. Modified Wood—Saxon density 4He 2.5.3. 2.5.4. 3He (3H) 2.5.5. 2H 2.6. Two body Tmatrices 2.6.1. Kinematic transformation 2.6.2. Partial wave expansion and phase shifts 2.6.3. Relation of off-to on-shell Tmatrices . 2.6.4. Inclusion of the Pauli exclusion 2.6.5. Fermi averaging — “folding” 2.7. Annihilation potential 3. Numerical techniques
110 112 112 114 115 117 118 118 119 119 120 120 121 121 122 124 125 126 127 127
127
3.2. Coordinate space wavefunction 4. Description of subroutines 4.1. Subroutine tabulation 4.2. Storage 4.2.1. Common blocks 4.2.2. EQUIVALENCE in MAIN 4.2.3. TAPE 7 4.3. Running on IBM 5. Running LPOTT 5.1. Files 5.2. Run parameters 5.2.1. FORMATS 5.2.2. Definitions 5.3. Coordinate space wavefunctions 5.4. Output of off-shell and 2 body Tmatrices . . 6. Test case and set up 6.1. Description of output 6.2. Output for spin~ nucleus and charge exchange 6.3. Set up
129 129 129 135 135 136 138 138 138 138 139 139 140 143 144 144 144 145 145
1. Introduction For better or for worse, the basic working tool of meson—nucleus theories is still some form of multiple scattering theory in which the meson—nucleus (‘irA) t matrix, T, is expressed as a series of multiple scatterings involving some form of the meson—nucleon (~N)I matrix t, T=~t,+~t 1Gt~+ ~ I
t.Gt1Gt~+....
(I)
i~j~k
Since this series may converge slowly, and the higher order terms are increasingly difficult to calculate, (1) is often separated into a wave equation for the nucleus remaining in its ground state (the operator P0) T’=U+UGP0T’
(2a)
U + UGP0U + UGP0UGPØU +
...,
(2b)
and an optical potential operator: 1~QGU,UW= (A l)T. (3) U= UW+ U~ The solution of the wave equation (2a) then sums implicitly the infinite Born series (2b) for any U. In —
R.H. Landau
/
Pion and kaon elastic scattering
Ill
principle this procedure is a complete, consistent and microscopic solution of the A + 1 body problem with its major shortcomings being the assumption of a two body (irN) potential and the neglect of relativistic dynamic and field theoretic effects (there is theoretical difficulty in including meson creation and annihilation). During the past ten years we developed an approach to projectile—nucleus reactions which uses Watson’s [1]multiple scattering theory to calculate the momentum space optical potential. Landau, Phatak and Tabakin [2] did the original (and still fundamental) pion—nucleus work; Landau [3—5]followed with a number of extensions (e.g. to spin 0 ® ~) and improvements introduced during research on the pion—three nucleon interaction; Landau and Thomas [6—8]applied to the optical potential calculation some of the sophisticated techniques used in three-body (ITNN) studies, and extended the calculations to very low (T ~ 30 MeV) energies; Alexander and Landau [9] successfully applied this same formulation to proton— 4He scattering; Paez and Landau [10, 111 recently examined K + elastic and charge exchange scattering from the light nuclei and especially 3He and 3H; finally, Paez is presently extending the formulation to p—3He scattering (~® ~) as part of his thesis work. The momentum space program LPOTT is the computer code developed in the above and other applications. It is a powerful, general and useful tool for theoretical and computational physics research and for this reason we wish to make it available. Clearly, it is impossible and inappropriate to describe herein all the physics and techniques it contains and we refer the interested reader to the above references for deeper understanding. Although a practical calculation must ignore some higher order terms, the theoretical formulation in LPO’IT is both microscopic (if the 2-body potential is considered elementary) and consistent (the 2- and many-body problems use the same wave equation). In addition, the user has the option of varying or including a large number of important physical ingredients: 1) 2) 3) 4) 5) 6)
Pion, kaon or nucleon* projectile, elastic or charge exchange scattering, no “small angle” approximations, 2 ~ A ~ 208, 0 ~ T ~ I GeV, realistic nuclear form factors for both matter and spin [3,4], 7) finite-ranged, 2-body forces [12—14], 8) covariant, relativistic kinematics and ampli-
tude transformations for all angles [6,8], 9) all needed, elementary, partial waves, 10) various prescriptions for binding and recoil effects, 11) several types of nonlocalities for the 2-body and many body potentials, 12) “exact” inclusion of the Coulomb force [15], 13) elastic unitarity via the 3-body energy [6,8], 14) all orders of multiple scattering (of course).
The power of the momentum space approach is the relatively small number of approximations needed to make a direct application of multiple scattering theory. For example, Lee [16] has shown how to extend this formulation to inelastic scattering. The code “PIPIT” [17] by Eisenstein and Tabakin also calculates the LPT optical potential with the theory of Ref. [2] and consequently is similar to LPOTT. The reader may benefit from studying the descriptions of that computer program as background for LPOTT. Whereas PIPIT is a rewritten version of Phatak and Landau’s [2] program PINUC, LPOTT has evolved gradually with use from PINUC and contains some features not present in PIPIT, e.g. 1) scattering of spin 0 ® 2) spin and matter form factors for 3He, 3H, 4He, ~,
*
13C,
3) the three body formulation of the optical potential, 4) K4’ scattering,
The full nucleon version for spin ~ 0 ~ scattering will be presented separately.
112
R. H. Landau
/
Pion and kaon elastic scattering
5) charge exchange scattering to analog states, 6) various “angle transformations”, 7) modern 7rN and 4’ N phase shifts valid at low and intermediate energies,
8) Modern ~rN potentials valid at low and intermediate energies, 9) Pauli modification of the TTN t matrix, 10) annihilation potential terms for pions.
In all cases, LPOTT, PIPIT, PINUC, etc. denote names of computer programs and not theories or optical potentials. In our view, when referring to a theory, credit should be given to the original developers. We prefer LPOTT be referenced as a tool not a theory. In section 2 we indicate the equations computed by LPOTT and some of the options available. In section 3 we discuss the key numerical techniques. In section 4 we provide some flow charts for the subroutines in LPOYT. Finally, in section 5 we provide instructions for actually running LPOTT.
2. Equations computed by LPOTT 2.1. Equations computed We solve the momentum space representation of the Lippmann—Schwinger equation (2a) in the meson—nucleus (irA) center-of-momentum reference frame (pion momentum k —s k’). Here the general form for the outgoing scattered wave Green’s function is
(k’IGEIk)
8(k’
=
—
k)/[ E
—
E,,(k)
—
EA(k) +
i],
(4)
where E, the energy in the com*, is E
=
E(k0)
=
E,,(k0) + E4(k0),
(5)
and the on-energy-shell com momentum is k0. This solution is equivalent to a solution of the usual nonrelativistic Schrodinger equation at the same energy E, if we use: 2/2m,,, EA(k) mA + k2/2m E,,(k) m,, + k 4. (6) =
=
The “Schrodinger equation with relativistic kinematics” is produced by using a relativistic definition of energy E,,(k)=~+k2,
EA(k)=~+k2.
(7)
Although this is our standard choice it has no familiar coordinate space transform. The user can also choose to solve eq. (2) with the choice: 2/2ji E=k~/2p.0, E,,(k)+E~(k)=k 0, (8a) (8b) which is equivalent [2] to an approximate form of the Klein—Gordon equation, 2~ (E2-2EU)~. (9) (_ ~2+~2)~ (E- U) Although this is often used in coordinate space calculations, we do not recommend its use due to the approximations in (9) and the inconsistency with the two-body dynamics. Goldberger and Watson [18] indicate in some detail that for spin 0 ® ~ scattering the potential and *
NB. use MeV units.
R. H.
Landau / Pion and kaon elastic scattering
113
matrix to be used in eq. (2) must have a central and a spin-dependent (spin—orbit) term: Kk’IT’Ik~ (k’ITNFIk) n=kXk’,
ian(k’ITFIk),
(10) (11)
(k~IUdIk)+ iu.nKkFIUsIk~,
(12)
=
(k’IUIk).
=
+
(n
where i~ ~‘nd 12’ are unit vectors is not). Mathematically, it is convenient to expand the central and spin-dependent parts of the potential in a series of Legendre polynomials (“partial wave” series): (13)
Kk~IUdIk)=~U~(k~Ik)PL(cosO), L
Kk!IUsIk)=~U~(k~Ik)PL(cosO), cosO=1212’.
(14)
L
However, orbital angular momentum L is not conserved by the potential (10), and consequently the dynamics are simpler to describe in terms of eigenstates of the total angular momentum J L ±~ (~L ±): =
(k’~ )~k\=~~ {(L+I)(~)(k’Ik)+L(~)(k’Ik)1PL(cos9), NF 2ir L=O TL+ TL_
\
/
PL=dPL(x)/dx.
(l5a,b)
(16a,b)
We can solve for:
(~):UL±(klk)2L+l{UL(klk)+((L+l))UL(klk)I.
(l7a,b)
The Lippmann—Schwinger equation now has a diagonal representation, T’L±( k’ik )-—U L±(k’ik ~ ~
~o
18
E(ko)-E~(p)-EA(p)+ii
The prime indicates that the KMT [11] convention (see section 2.2), we must rescale to obtain the actual matrix: TL±=[A/(A
—
1)}T~÷(KMT).
t
(19)
Since the principal value treatment of the singularly in the Green’s function is easier to compute than the i~ procedure, in place of (18) we actually solve for the reaction matrix R: RL±(k’Ik)= ~ where with our conventions —
TL±—
*
(20) *
RL±(koIko) [ A I +1PERL±(koIko)\A —1, .
N.B. RL±= ~iTRL± (Goldberger—Watson).
~,
(
a)
114
RH. Landau
/
Pion and kaon elastic scattering
E~(ko)EA(kQ) PE2kol~t~~A2ko[E(k)+E(k)]
(21b)
.
2.2. Cross sections
The t matrix elements obtained by solving eqs. (19)—(2l) are related to the complex irA phase shifts S, 4 via ~
(22a) ~~±(ko1ko)/(—pE),
(22b)
with the tL ± normalized to modulus 1. The real phase shift ~R and absorption parameter i~ are related via 2a 71e28k (23) e The conventional spin nonflip and spin-flip scattering amplitudes are proportional to the central and spin dependent parts of Kk’ITIk)~after resolving (17) these are:
f(O)
[(L + i)~÷(k
~
=
01k0)
+
Lt~(k01k0)] P1(cos 9).
(24)
o L=O
g(9)=~ ~ [~i.+(kotko)—~~(koIko)JPL(cos9). o L=l
(25)
The differential cross section for an unpolarized target contains a nonflip and a spin-flip term [18]: 2+ sin29~g(9)~2,
d~2
unpol
=
f(9)~
(26)
with the polarization after scattering now given by p(O) =ii2Im(g~Kf)sin O/(If~2+
1g12
sin29).
(27)
LPO1T also calculates the total elastic, total reaction (called inelastic) and total cross sections via the formulae: aiot4ilmf(0O)4ir
~ [(L+ 1)Im ~ k 0
~
~ 1
~ineI
—
=
+
L Im
p,],
(28)
L=O
{(L+l)ti~L+I2+LIi~Ll2],
L=O
(29) (30)
0e
These total cross section formulae are meaningful only if the Coulomb force is not included. For spin 0 0 0 scattering the formulae given so far reduce to the familiar ones when the spin-dependent potential is set equal to zero. In this case Kk’IT~’Ik~ (k’IU”~k) g(9) =
UL+
=
=
=
0,
(31)
U 1_
=
2L±~
(32)
R. H. Landau
(k’~(~ ~ NF
\
/
/ Pion and kaon elastic scattering
115
(33)
2ir
L
TL+
(34)
~
To better understand a calculation, LPOYT also computes cross sections with just the first term in eq. (20). This is the “Born approximation” to eq. (18) or (20), =
PEUL±(kO
ic0),
(35)
~B _1 ~ ii A — ~ ~B L±L /~ JJ L±~
For a first-order potential this will also be the single scattering term of the full multiple scattering series (1). As a further indication of the convergence of the Born series (2b), LPOTT has the option of calculating the sum of just single plus double scattering, Rn,: ~
(37)
Single charge exchange scattering to anand isospin state computed by first calculating the pure 4’ (K4’) ir ~oranalogue ir° (K°), andis then invoking isospin symmetry * to hadronic elastic scattering of ir determine the hadronic CEX amplitudes [4,5,11]: T(ir4’,ir°)=[T(ir4’,ir~’)—T(ir,ir’)]/V’~
(38a)
=Q~[u~’ ~
(38b)
—
~r°) %/5..I[T(ir4’ =
,
(39)
ir~’)— T(ir°,~r0)]
(40)
~
2.3. Inclusion of the Coulomb force
LPOTT has the option of including the effect of the Coulomb force in several ways. The “exact” procedures are based on observations by Vincent and Phatak [15], the first being that since the Coulomb potential cut off at a very large radius (R~~ 1) has no singularity in momentum space at q 1k’ — kI 0, it can be included in our integral equation. We thus solve eq. (20) with =
U1jk’Ik)= U~irOflS(k~Ik)+ v~(k’ik),
(41)
Vj~(k~Ik)=1r2f’(k~IVik~PL(cos9kk,)d(cos9kk,),
(42)
=
(2ir)
fd3d3’ e’~~VC(rIr’) e~”
2ir
(~ L
2ir
~(2L
+ 1)V~PL(cos0))
(43)
L
2
_LZ,,
Ae [p(q)—cosqR~~1],
q
2=k2+k’2—2kk’cos0, q *
=
LPOTI’ automatically switches off the Coulomb potential in those cases.
(44) (45)
116
RH. Landau
/
Pion and kaon elas0c scattering
where p(q) is the nuclear charge from factor. Note that regardless of the nuclear shape,
15(r).
the
subtraction in eq. (44) removes the singularity normally present in V~(k’ I k) since (46)
_q2~)~q4~..•.
p(q)~l
In generating the Coulomb potential LPOYI’ has the option of using a realistic form factor in eq. (44), or a uniform sphere of radius R~.In the latter case Psphere(’/)
3 sin qR~ 2 R cos qR~ qR~ q( 2
=
(47)
—
and R~(* R~~1 of eq. (44)) should be chosen as (48)
R(,=~r2)
to give the same rms size as a more realistic distribution. When eventually the wave equation (20) is solved for the complex irA phase shift i~, effectively we have determined the irA wave function for r R~~1 [15] (section 2.4 discusses wavefunctions). The nuclear phase shift in the presence of the Coulomb force, 87~, is determined by matching the inner solution into 6NC shifted Coulomb waves at Rcut: NC tan~1[F,G0]+[F,F0] tan~L = [i~, G] + tan 81[G0, G]
df [f,g]=g——f—. dr
dg dr
(49)
Here F(F0) and G(G0) are the regular and irregular Coulomb wave functions [19] evaluated at the Coulomb parameter, 2 c (A — I \ Z,rZA !.cA(kO) y=Z,,ZA hc e v 7,~ A 137.036 k0 (50)
)
The (A 1)/A factor corrects for the scaling present in the KMT presentation. The scattering amplitude now consists of a point (charge) Coulomb term and a nuclear-Coulomb term, the latter including corrections for the finite size of the charge distribution: 1(9) +fNC(0). (51) —
f(9)
fP
j~Pt(o)
=
2
—
exp(2io 0—
y
In sin 9/2),
(52)
2k0 sin 0/2 9)
~
=
(2L
+
1) e2mn,{e2871
1
—
I] P 1(cos 9).
fNC(
0 L~-0
(53)
2” factor is removed from both fCN and fNC(9). In LPOTT the actual computation, the unobservable also has two options in which the eConiomb potential is not added to the nuclear potential as in (41) but instead an approximate correction is added to the final amplitude. These options are useful for calculating pure nuclear total cross sections, charge exchange scattering via the subtraction technique, eqs. (38)—(40), or for increasing the speed of explorative calculations. In both cases the finite size of the charge distribution is included by multiplying the point Coulomb amplitude by the actual nuclear form factor p(q) before adding this amplitude to the pure nuclear one:
f(o)
~fPi(9)p(q)
+~
~
(2L + 1)[e25’— lJP 1(cos 9),
0
L—0
(54)
/ Pion and kaon elastic scattering
R.H. Landau
f(9) _f~Pl(9)p(q)+~1
~ (2L 0 L=0
117
+ l)[e2b0Le2~— l]PL(cos 9).
(55)
In practice, eqs. (54) and (55) tend to give very similar results and only differ significantly from the exact procedure (5l)—(53) for heavy nuclei or low energies. 2.4. Form of the first-order potential In the impulse and factorization approximation, the first-order optical potential defined by (10), (15) and (16) is
(k~IUdIk) A- l [KfIt~(~)Ii)Zp~
(q)
=
ia(&
X
+
(fIt~(w)Ii)Np~a
1te1(q)~
(56)
12~)(k~IusIk)A- l[(fIt~P(~)lj)zpP (q) + io.(12 x 12’)(flt(~)li>Np~1n(q)], (57) =
where
Ii)=Ik,
If)=Ik’, p0—q), q=k’—k.
i’0)’
(58)
Po is an “optimal” choice [3,4,6] for the momentum of the struck nucleon, Po
(59)
—k/A+[(A—l)/2A]q.
In addition to optimizing the factorization approximation, this choice leads to 4 momentum conservation in both the irN and irA systems for all diagonal, lkI Ik’I, elements in the optical potential, since then =
1p0—qI=1p01.
(60)
The matter and spin form factors available in LPOTT are described in section 2.5, the computation of the two body t matrix in the irA corn is described in section 2.6. Their partial wave expansions are: p(k’
—
k)
(fIt~Ii)
=
=
(61)
~ p1(k’ I k)Pt(cos ~k’k), /=0
B1’~(k’Ik)P1(cos~k’k),
(62)
~ B~(k’Ik)P/’(cos9k~k),
(63)
~ /1=0
~fIt~Ii)=
ti=0
where the B’s follow the code of table 1. When these expansions are inserted into (56) and (57), there results the partial wave expansion of the full optical potential, (13) and (14) with (64)
2,
u~(k’1k)
=
A
1 ti=ot=0 ~ (NB~P~atteri + ZB1p~aiteri)(c~L)
—
u~(k’Ik)=A—
I
~
{NB~~p~ 1~1+ ~
+
1) +L(L± i)—l(l+ 1)~
tt=0 1=0
(65) where C~)j0’~is a Clebsch Gordon coefficient.
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R. H. Landau
/
Pion and kaon elastic scattering
—
Table I Partial wave code for (BN(NL), BNUC) and (BNF, BNUCF) the nonflip and spin flip (F) n~/K~ nucleon amplitudes eq. (l08)’~ NL index
L,,N
Target
(Ret, IM t)
1,2 3,4 5,6 7, 8 9,10 11, 12 13, 14 15, 16 17, 18 19, 20
0(S) 0(S) 1(P) 1(P) 2(D) 2(D) 3 (F) 3 (F) 4(G) 4 (G)
p n p n p n p n p n
Re,lrn Re,lm Re,lrn Re, Irn Re.lrn Re, Im Re, Im Re, Im Re, Im Re, Im
~ For a ?7, amplitude.
or K°projectile the storage is the same, subroutine OPTP then uses the isospin relations of (107) for the needed
Eq. (17) can now be used to determine UL ± and then the wave equation (20) can be solved numerically. This procedure is discussed in section 3.1. ,
2.5. Nuclear form factors 2.5.1. Harmonic oscillator density The nuclear proton and neutron matter densities have the form
~(r) =
a
=
~(o)[ 1 + a(r/acm)21 exp[
~/~5= ~3(2 + 5a)/2(2 + 3a)a~h,
(Z— 2)/3,
p(q)
=
p,(k’Ik)
[1
—
exp[
~
[i
_q2a~~/4]
[exp(—x)/(2
+ 3a)] [(2 2+k’2)a~ z=~kk’a~h, x=~(k 5, =
(66)
_r2/a~h],
+
3a
—
—
(Z
—
2
)(qa~~)2]exp[
2ax)(21+ l)i1(z)
—
q2a
5/4j
+ 2azli1_ (z) +
(67a)
(I + l)i1~(z)], (67b) (68)
where p1 is defined in (61) and i1 is the modified spherical Bessel function of the first kind. 2C The sizedata parameters for neutrons and protons are fm. inputIn parameters. A fit [20] (66) tothe e —‘ scattering yielded [20] (acm, aCh)If~l (1.66, 1.71) some applications we of removed finite proton size from this fit p(r) since it is included in the two body t matrices: =
2 aCh + 4(0.76 fm)2 5+ a~ ~ + ~
a~
=
(69)
—
=
(70)
A more modern fit [21] gives (acm, ach)= (1.56 fm, 156 fm)12(.. 3C calculations we have included the possibility that the For ‘
P1/2
(71) neutron has a different size parameter
/ Pion and kaon elastic scattering
R.H. Landau
w than the
ach
119
of (66):
p~atter(q) (N_ 1
2a~h/4) +
1±~
=
(qacm)2~exp( -q
1
-
~
exp( - q2w2/4),
(72)
p~°~ (73)
1~=4(l/N)[l— (qw)2/6]exp[_q2w2/4].
The 1/N factor in (73) gets cancelled by the N factor in eq. (57), and the 1/3 factor arises from the spin-angle function for a p wave neutron For densities other than these Gaussian forms, pL(k’ I k) is calculated by a numerical projection of the form factor: ‘~.
1 fd(coso)P~(coso)p(q=Vk2+k/2_2kk~coso).
(74)
2.5.2. Modified Wood Saxon density (75)
g5(r)=po(I+wr2/a~h)/{l+exp[(r_ach)/acm]).
The p1(k’ I k) are calculated via a two step procedure. First we calculate I k,,,) by direct Fourier 2km (forpi(km calcium ~max 691 MeV the transform for afor kmwhich whichp(q) yields a large momentum transfer ~max MeV): largest q value is measured and for Pb ~max =
=
pi(km 1km)
=
~
=
4ir(21 + l)j~r2drp(r)j,(kmr)j,(kmr)
(an arbitrary ~S(r) could be used here). Then (74) is used with p(q) calculated with pt(km ~p,(k~Ik~)P
I km):
qqmax,
(77a)
~lmax’
(77b)
1(l_q
/=0
p(qmax)exp[ =
2/2k~),
(76)
5 x 1O~MeV,
—
(q2
aPh
=
—
q~ax)/a],
2.77
X
q>
iO’~MeV.
2.5.3. 4He p,(k I k’) is calculated via (76) using the fit of Frosch et al. [21] p~atter(q)= ~~iauer(~)
=
[i
—
(a~~q2)6]exp[ _a~q2/4J /f~’(x),
(78)
with the proton charge form factor as in ref. [22]: f~~’(x) 1/(l =
+
q2/l8.2 fm_2)2.
(ach, acm) are read in, with our standard values being (1.362, 0.316) fm.
*
We thank A.W. Thomas for the 1/3.
(79)
/
RH. Landau
120
2.5.4.
Pion and kaon elastic scattering
tHe(3H) p~aiter(q)
=
F~~(3He)/f~P(q),
(80)
p~atter(q)
=
J~
(81)
3H)/f~(q), 6(
p~, 1~(q)42Fmaa(3He) +~-~f~5(3He)_f-~-1~(3H)].
(82)
=
p~~(q)=
~[
3He)
-
31~6(He) +
Fmag(
2~7931~N’
fin”
(83)
~1~h(~H)J,
913l~N’
~
~p”
Realistic. For 3He we use the analytic forms for the charge and magnetic form factors which McCarthy et al. [23] fit to their electron scattering data: ‘~h,mag(F1e)= exp[ _a2q2]
—
ac=(0.675 ±0.008) fm;
b2q2 exp[
_c2q2]
+d
exp[
—
((q
—
(84a)
q)/p)2]
bj(0.366 ±0.025) fm;
c~=(0.836±O.O32)fm; dc=(~6.78±0.83)Xl0~3•
90±0.l6) fm’; p~=(O. bm=(0.456 ±0.029) fm;
q 0=(3.98 ±0.09) fm’; am =(0.654±0.024) fm; cm
=
(0.821 ±0.053) fm;
dm
=
(84b)
0.
[(am, bm, cm) are read in as (ACHP, ACMP, WSP), the other input sizes being reserved for the p2 poten-
tial.] For the 3H charge form factor we use the actual data points of Collard et al. [23] for q2
8 fm2, for 8 fm2
16 fm”2 we assume a continuous Gaussian drop off. Since McMillan’s wavefunctions fit f~(3He)(for which there are large q2 data) fairly well in the range 8 fm2
3
F~
6(He) =
3He)
2
2
exp~—a~~pq
=
exp[ _a~~~q2], exp[ _a~~pq2] =
(85
,
(86) (87)
.
Fmag(
2.5.5.
2~j —
deuterium
p~aiter(q)
=
P~aiter =
[tan
‘q/2a + tan 1q/2b —2 tan ‘q/(a
(a, b) = 0.464, 2.404) fm~ read in as (ACHP, ACMP).
+
b)]/[q(~
+
—
~)],
(88)
RH. Landau
/ Pion and kaon elastic scattering
121
2.6. Two body T matrices 2.6.1. Kinematic transformation The off-energy-shell projectile nucleon (irN) t matrices in eqs. (56)—(65), Bf’~and B~/’ are in the irA corn and need to be determined for all possible values of k and k’. We relate them to off-shell t ‘s in the irN com, (K’It(c~)IK),via the transformation “,
(fIt~’li)
(k’,p~It(~a)Ik,po) ~y(sc’It(c~)~K), A—i 2A q,
(89)
=
k POA+
(90a) (90b)
y=[E,,(K).ç(ic’)EN(K)EN(K’)/E,~(k)E~(k’)Efl(p
0)Efl(p~)]
The 2-body momenta states Ii) and If)~
ic
and
(k 4’po)~,\2 \(~,
s~~(k, q) (,,
=
s
0~1~~ii. q1
=
K’
(90c)
1/2
are calculated by evaluating incoming and outgoing corn energy %/~ for
[ E,~(k)+ EN(
2,
(91)
Po)] 2_ (k +p0)
— ~
and then using either the “magic vector” (AAY) covariant prescription: IC
Q
=
—
[
Q.K/K0( K0
K= (K0, K)
+
K, 2Q
=
k—p0
[E,~(k) +EN( Po)’ k +p0]
=
—
[(m~
ic’sc
=
—
m~)/s~~] K,
(93)
cos 9,~,
(94)
sc’ic
or the “historical” one based on the Mandelstam invariants: =
{
s0~~— (m,, + mN)I [s~0~t
2 (~c~ — ~
—
(m,, —
mN)]
(95) (96a)
~
=
t
=
(k~ k,~) cos9,,N=E,,(ic’)E,~(K)—E,~(k)E,,(k’)+kk’ cos —
~C’KK’K
(96b)
9,rA~
Both prescriptions agree on the magnit~ideof the irN corn momentum ac and ic’, but the angle mappings (94) and (96b) differ slightly, with the AAY prescription preferred since then Icos °~NI Icos 9,~ 1 for all k’ and k. LPOTT also permits examination of other prescriptions; e.g. “no angle transformations” (97) or no off-energy-shell variation, Sc
sc’
=
=
Sc0
=
Ic rn( k
(98a)
0, q0), q0=k~—k0,
(98b)
q~ 2k~(1 cos 9,,A).
(98c)
=
—
Note, that regardless of the prescription, y, IKI, IC and Pa depend on the irA scattering angle. Since LPOTT also computes spin flip scattering it is necessary to transform 0K X sc’ on sin =
*
Called BNUC(1) and BNUCF(I) in LPO1T with I given by the code in table 1.
~
We
R. H. Landau
122
/
Pion and kaon elastic scattering
use (94) and (96b) and ignore any precession of the spin induced by the reference frame transformation. The irN subenergy cZ~ in (89) is chosen according to one of three prescriptions, all of which produce an c~ which varies with scattering angle. The first is the two body corn energy for on shell scattering, =
c~o = s0(k0, q0)
E,,(k0) +EN(po)]
=[
(k0 + p0).
2_
(99a)
and the second is the two body com energy for off-shell scattering: (99b) The third choice w30 is a relativistic version of the three body energy [6—8]in which the “active” nucleon has momentum p +p0 and the (A I) nucleon core has mornentump, —
P= —k—p0--p, =
=
(k~+ kA
—
P)~=
[
E,,(k0) + E4(k0)
—
E4 -
( P)
2, —
(100) (101)
JE~2_ p
After substituting for p ~2
A—i A
)
0 (90a), we make the approximation 2q2 A—l\ A
2~ 2
)
2
4+PF+~
(A—l\2 A ) qk,
(102)
withpF = 174 MeV being a “surface value” for the Fermi momentump, and EB, the core—nucleon binding energy, (p2/2m + VNC), an input parameter. We also have built into LPO1T the option of simply shifting the subenergy by an inputted amount ~ 2 after c~is determined by one of the above procedures, ~‘~‘
(103a) Likewise, the irA channel energy, E(k) in (5) or (20) can be shifted. (lo3b) 2.6.2. Partial wave expansion and phase shifts (two body) In the LPOTIF conventions, the spin 0 0 4 two body t matrix in the irN corn for isospin state I,
(ic’It’(c~)Iic)= (It~Fl)+ io.(i~ x ~‘)(It~I),
(104)
is expanded as a sum over eigenchannels of orbital angular momentum I’ and total angular momentum j=l’±
4:
(K’lt~F(~)lk) = ~[(l’
+ l)(K’It+
+ l’( K’It~(~)IK)J P
(~)IK)
1.(cos 9~.), (K’It~)JK)
=
~
[(~‘~tJ.~ (~)k) -
(K’It
(~)IK)]P~~(cos O~.).
(lOSa) (105b)
This 2is factor. the same convention usedthe foron-shell the irA eigenchannel t matrices, inamplitudes eqs. (10), (15) and (16),toexcept for ancomplex overall Correspondingly, are related the 2-body I/2ir shifts via the analogy to eq. (22a) and (21b): phase (scolt.
2p’~), 1Iico)
=
([exp(2i~).1)
—
1] /2i)/( —2ir
(106a) (lO6b)
R. H. Landau
/ Pion and kaon elastic scattering
123
Table 2 Eigen channel (1 2i 2j) code for (T, TX), (Re wave, Im wave) NWAVE
PION
KAON
(a)
channel
channel
1 2 3 4 5 6 7 8 9 10 11 12 13 14
S31 P31 P33 SIl P11 P13 D33 D35 F35 F37 D13 D15 FIS F17
SlI P11 P13 SOl P01 P03 D13 D15 F15 D03 D05 F05 — —
The eigenchannels a = (I’, 2j, 21) included in LPOTT are tabulated in table 2. The meson—neutron, proton amplitudes needed to construct the optical potential are given by linear combinations of the isospin apmlitudes: t”’’)
=
(107a)
3”2,
t”~ = t
t~’~= tt’
=
t~°~ = t~°~ =
4t3/2
+
4t1~2,
4t3~2+ 4j1/2
(107b) (t~’~+
=
t’~P)/2,
(lo7d)
t~~=tK~~=t1,
4(t’
1K*n = tK°p =
(lO7c)
(lO7e)
+ t°).
If this isospin decomposition is combined with the partial wave decomposition in (105), we obtain the complete relation between eigenchannel and physical pion—nucleon amplitudes (here written in terms of j=l’± 4):
2Pl.(cos9,,N),
(lO8a)
t~wp= l,=0 ~ ~ ~ (j+4)t,~” j~/’±
t,=0
=
~
(1±
~
2(j
4)[4t]”~+ 4t)/2] Pl.(cos9~N),
—
l’)t]”2P,~(cos~
(lO8b) (108c)
i,.-1 t~~= ~~
~
2(j_l~)[/2+4t)/2]P,~(cos9~N).
(108d)
This is the same conventions used in (62) and (63) and coded in table 1. The K’~’N amplitudes are obtained
/
R. H. Landau
124
Pion and kaon elastic scattering
from (108) with the replacements ti”2 4
4
—÷4
(lO9a) (109b) (lO9c)
t~
—s4
.
ir~n K~n ir~p K4’p Since ic’, sc, c~,cos 0,rN (9~N 9,~)all depend on cos 9~~A(9~A 9kk) in a rather complicated way, we do the cos 9~rA partial wave analysis of (f 1t~~NIi), (62)—(63), by a simple, numerical projection: ~,
B,(k’ 1k)
=
2l~+ f’d(cos
BF/(k’Ik)= 2/ (I
(9A)ItNF(a(9~A))lK(9~A))P/(cos
~A)Y(~A)(K
~A)’
1)Jd(cosO~A)Ysin9~A sin 9~N(K’ItF(~)lK)P(cos 9~4).
(I
lOa)
(lIOb)
A strikingly important consequence [2] of the “angle transformation”, (2.6.1 plus (109), (110)) is that a partial wave amplitude in the irA com, B1, will contain contributions from all irN com partial waves amplitudes, t~,.To incorporate this mapping more accurately, the B’s and BF’s are computed for more 1’ values than the t.,.’s. 2.6.3. Relation of off-to on-shell t matrices
A key ingredient in the LPT optical potential is a separable potential model to determine the off-shell matrix in each irN eigenchannel a: 2D~(c~), (Ill) (sc’Itn(cZ)Isc) = g~(K’)g~(Sc)/2ir ~ (112) —
The 2ir2 factor in (111), not present in refs. [12—14], is needed to match the LPOTT convention(106). K, K’ and c~can now vary independently. Above the elastic threshold, the off-shell behavior can be expressed as a simple product: (K’Ita(~[ScO1)IK)I~>n~+n, = g~(~)g~(K) (KOltn(~[KO])IKO). ga
(113)
(~~
0)
Below threshold (~< m,~+ mN) the t matrices become pure real and LPOT’T makes use of tabulated Fredholm determinants Da to extrapolate via,(lll). Yet, a consistent set of low energy c’s, Da’S and ge’s must be used for a smooth and accurate extrapolation; for this purpose LPOTT contains the RSL t’s [24] and the matching Coronis—Landau (CL) [12] g ‘s and D ‘s. Recently, there have been a number of potential (g’s) published and applied: LPT [2] used the (now obsolete) LT and LMM potentials [14] which both provided essentially identical irA scattering; Thomas and Landau [6—8]used the Thomas potentials [13] (see below) with the original Salomon phases; and Landau [25] most recently applied the CL potentials [12] at very low energy. Since the latter two potentials are available in LPOTT, we describe their unique characteristics. The Thomas potentials gTH and corresponding t matrices are fit to only s and p waves and furthermore have a structure different from the LT, LMM and CL ones. In order to use (113) for the above-threshold, off-shell behavior, we have defined —
1/2 (T)(
‘~_
g~ ~P,
ir
mN(E,,(p)+EN(p))
2
EN(p)(E,,(p)+mN)
(TI’J)(
g~ ~p
R. H. Landau
/ Pion and kaon elastic scattering
and tabulated them. Below threshold (111) is used, but only after the nonrelativistic nucleon kinematics a
~
1
125
are computed and tabulated with
Da’S
dpp2g~,T~(p)2
— J(00
0
(115)
Since at the very lowest energies the phase shifts fit by Thomas are not exactly the same as those now contained in LPOT’F (the RSL fit [24]), g(I~~I) should not be used in LPOTT below 30 MeV. The CL model uses the recent RSL phases and contains a D~11which produces both a pole in at the nucleon mass and a sign change in at E0 = 1210.7 MeV: 2g~(p)
D~
1 co—mN EO—mN 2 11(co)=—E0—t3 + E0—c~ ~
2
dpp
ç°°
mN—E,T(p)—EN(p)
dpp2g~(p)
,-°°
lrJo ~+iEE,~(p)EN(pY (116)
There is also the option with the CL potentials of using a D~11in which the pole at mN has been subtracted: D~11(~i)=D~11(~)— (~3—mN)3DpII/&~iI~.,...m.
(117)
Finally, two nonmicroscopic off-shell behaviors are available in LPOTT: the “constant behavior”:
(iC’Ita((.~)ISc)= (ScOIta(C~O)IICO),
(118)
and the “local laplacian” model (generalized to D and F waves): (.c’ItIIc)
=
a+
b(ic’
—
‘c) + c(ic’
—
ic) +
d(K’ — ,c).
(119)
Here, a, b, c and d are related to the on-shell amplitudes in a rather complicated way, for example, if tF = tD = 0, then (119) implies [26] ts + t~(sc’2+ 1c2)/2Ksc’, b = t~/2icsc’. (120) —
a=
The Kisslinger potential has an off-shell behavior too divergent for the kernel of (18) to be compact and cannot be used meaningfully in p space. Of course, it is always possible to insert phenomenological off-shell cut-off functions, but then one may as well use a more microscopic and consistent separable model. 2.6.4. Inclusion of the Pauli exclusion For a separable irN potential it is possible with LPOTT to replace the irN t matrix by a G matrix in which intermediate nucleon states lie without the Fermi sea. We do this in the angle-averaged approximation for s and p waves by adding a “correction” term to Thomas’s Fredholm determinant El,, in (111) and (115): D~’-~+D,,+~D.~’, =
f”fdpp2g~(p){l f
(121) —
Q
2/2mN
0(P, p))/[ c~+ i
Pr
0,
~=
2
—p~I1/4~Pp,
[(~P +p) mj.
mN/(mN +
—
mN},
(122)
E,,(p) —p
~‘P+p
Q0= 1,
—
I~F—pl>pr’ otherwise,
150MeV/c), (123)
R. H. Landau
126
/
Pion and kaon elastic scattering
Since P depends on the irA off-shell momenta and scattering angle: p2 = ( Po + k)2 ~(k2 + k’2 + 2k.k’),
(124)
the integrations in (122) are rather lengthy since they are done for all k and k’. N. B. To perserve consistency, only the Thomas potentials can be used in (122)
error may result for other
—
g ‘5. 2.6.5. Fermi averaging “folding” In principle, LPOTT could easily be used to evaluate the ground state expectation value of the optical potential operator [6], ‘-
(k’(Ujk) + A- 1 ~fd3p~*(
(125)
p-q)(f~t~(co)Ii)~~(p).
The order-of-magnitude or more increase in running time has not permitted this, however, and various approximations are made. The most extreme is the factorization approximation of eqs. (56) and (57). In practice we usually use a “folding” approximation to (125) [2,4,6]: (k’jU(k)
in which we integrate only the energy, the irN corn, =
c3( p)2
s( p)
=
(fIt~(co)li),
(A - l)p(q)fd3p[ ~~(P)I2/A}
—
to,
fd~p~[l~( p)12/AI
(K(
(flt(w)pi) when the t matrices
are first calculated in
p)It.,( ~( p))~(p)),
(127)
(128)
m~— m~ + E,~(PIab)EN( p) —2 P’abP’
K(p)
=
P~b
(icO/mN)[E,,(sco)+EN(ico)].
[s(p)
dependence of
(126)
—
(ma + mN)2][s(p)
—
(ma —
mN)2]
(129)
/4s(p),
(130)
The formulas used for [~~I~~(p)I2]/A are from the harmonic oscillator shell model: AP 1~(p), 2
A
Ei~~
=
4P1~(p)+(A—4)P1~(p), ~ + 12P1~+ (A 16)[Pid + p2~]/2,
4A16,
4P1~+12PIP+24(Pld+P2S)/2+(A—40)PIf,
40A48,
—
2),
P1~(p)
=
A4,
N exp(
—
(pa)
4 exp(
P
—
2exp(
P 2~= 2N( pa) (pa)2)/l5, N
=
—
16
A
40,
(131)
(pa)2)/3,
a3/ir3”2,
1~(p)= 4N(pa)
2exp(_ (pa)2)/2, 4(pa)2) 6exp( (pa)2)/l05.
P 2~(p)= 3N(1
—
P
—
2~(p)
=
8N( pa)
(132)
R.H. Landau
/ Pion and kaon elastic scattering
127
2.7. Annihilation potential Annihilation (true absorption) of pions can be included with a second order potential [6,8]: (k’lUt2~(E0)Ik)=
4irA(A
—
—
~) {~0~0~ ~
2~.ç~(2iT)
g~(sc0)
k~cos okk.}P(k
c0(k0) g~~)
+
k),
(133)
0,a1)=(648,289)MeV/c,
(134)
—
g~ (‘ce) 2,(a g~(Sc)=S~/(ct~+Sc2), gp(Sc)=SpSc/(a~-~-K2)
2(q) =fe4~~p2(r)d3r.
(135)
~
For the harmonic oscillator density of (66), + a(12
—
q2a2)/8 + a2(15
xexp(_q2a2/8)/[ir3/2a3(l
—
4q2a2 + q~a~/l6)/l6]
(136)
+~a)221/~],
whereas for the Wood—Saxon shapes, LPOTT calculates momentum and is calculated from (95) with
?( q) numerically.
iç~ in
(133) is the irNN corn
2. (137) 0) +ED(2k0/A)] 2_ k~(l 2/A) The partial wave decomposition of U~2~ is computed numerically via (42) and (43). At present, LPOTF calculates the isoscalar annihilation strengths B 0 and C0 from ir + d pp total cross sections [6], and prints out these values. Future modifications will employ the more microscopic (isobar) model 3He. of Yoo and Landau [27] which will also provide a spin and isospin dependence as needed e.g. for S,,D
=
[E~(k
—
—~
—
3. Nwnerical techniques 3.1. Solution of Lippmann—Schwinger equation by matrix inversion
We reduce eq. (20) to a set of linear equations. First, we execute the principal value prescription by subtracting an integral of zero value (the Haftel—Tabakin [28] procedure): 2
ç~O
R(k Ik)U(k Ik)+—J
p2U(k’Ip)R(plk) dp Ea(kO)+EA(kO)~Ea(P)~EA(P)
—k~U(k’Ik
2)/2~t(k 0)R(k0Ik) 0)
(k~—p
(138) (for clarity we drop the L ±).Next, the nonsingular integral is approximated as a W1-weighted grid of N appropriately chosen points k1 (see GAUSS, section 4): R(k’ 1k)
U(k’ 1k)
+~ ~
wj[ k~U(k’ik~)R(k~ik’) ko2U(k~iko)R(koik)J —
sum
over a
(139)
R.H. Landau
128
/
Pion and kaon elastic scattering
Now we define the (N + l)th (NI) grid point as k0, kN±l=kNI=ko,
(140)
and combine the Green’s function and weight into a D0: 2 2 W,k Do(k/)=_E(k)E(k)~ 1=l,N,
(l4la)
Do(kNl)= —~k~2~t(k 0)~ k~—k~
(l4lb)
An equivalent form of (139) for k’ and k on the grid of points is thus R(k1Ik1)=U(k,Ik1)—~U(k1Ik,)D0(k,)R(k,Ik1)
(142)
R(k,Ik,)+~U(k1Ik1)D0(k,)R(k1Ik1)=U(k,Ik1).
(143)
or
This is the desired set of linear equations which can now be solved [F][R]
=
by
matrix inversion, (144)
[U],
(145) F(k1,k1)=~1~+U(k,,k~)D0(k1),
(146a)
[F]=[1]—[UG].
(146b)
To avoid dealing with complex matrices, the real and imaginary parts of R and U are separated and the number of linear equations is doubled from N 1 to N2 2( N + 1), =
R=R’+iR’,
U=U”+iU’,
(147)
R~ (N2\ U~ (N2\_ UrD0 —U’D0 R~ /N2\ 2 R’ R’ U’ U’D0 UrD0 (N2) The matrices U and F are stored as a linear array with the algorithm,
(148)
Ut(k,Ik~)= U~=U~=U[(j— l)N2+i], i,j= l,Nl,
(149a)
~
=
UNI+ 1] = U[(j—
l)N2
+ i+
Nh,
(l49b)
l)Nl +:].
(l49c) 2 (the 2 for J L ±4).The present U and are dimensioned U(M, and F(M)ofwhere (2N1) version of F LPOTT has M 4356, so 2) a maximum 32 gridMpoints is possible. A change in the dimension statement would permit more grid points. At any one time, the U and F matrices only for one L value are stored in the memory. The values for all L values are stored on tape 7 and read in as needed. k—F[(k
=
=
=
R.H. Landau / Pion and kaon elastic scattering
129
3.2. Coordinate space wavefunction The basis of our procedure is similar to that described in PIPIT [17]. LPOTT will produce a deck (file) which can be used to calculate the irA wavefunction (possible with spin too) separately from running LPOTF if the subroutine WAVFN, COULFN and SPBESL are used. Our notation is that of Rodberg and Thaler [20], ~~r)=~U,(r)it(2l+ e’~
(J,(r)
—
.
-j~-— sin(.&r
—
l)P,(cos9),
y ln(2kr)
—
l~-+
(150)
(151)
~L + &L).
After converting our standing wave conventions to outgoing waves, rearranging our F matrix to give the conventional Moller operators, renormalizing the A /( A 1) factors present in the KMT procedure, and using Coulomb waves (if one of the “exact” Coulomb procedures is chosen), the Moller wave operator evaluated on our grid of points is —
QT(k
1, k1)
=
A
1
—
~
+AQR(
k1, k1)
T’(kNI, kNI)1 (
NI’
(152)
NI
F,~,”is determined by the matrix inversion in (145) and T’/R’ is the ratio before Coulomb matching. The wavefunction for 1 ‘Store (number of t ‘s calculated) is =
—~-—{cos~LFL(kr)+sin8LGL(kr)),r>Rcut U,(r)=
(153a)
NI
(t
~ Jt(1Cm~~)12T(1CN+I, km)ZL,
r < Rcut,
(l53b)
m= I NI
ZL
=
kR
(cos s~LFL(kRCUl)+ sin ~LGL(kRcut))/ ~ J/(kmRCUt)QT(kN+ I’ km). cut
For I>
‘Store
(153c)
m=1
the Born approximation should be used, (154)
U,(r)=FL(kr)/kr.
The Coulomb wavefunction routine RCWFN by Barnett et al. [30] is used to calculate the FL’s and GL’s.
4. Description of subroutines In section 4.1 we tabulate and identify all subroutines in the order of their listing. In Figs. 1—8 we give flowcharts with equation number references for the MAIN program and the most important subroutines, OPTP, TNUC, TNUCTH, TNOFF, TPICM, RHOKFF and FFACT. In section 4.2 we describe the storage in COMMON’s and of the potential matrix on TAPE 7. 4.1. Subroutine tabulation
1. MAIN 2. BESLIA
R- and T-matrix via matrix inversion in momentum space. exp( z) times spherical Bessel function of argument iz, (68). —
)>
RH. Landau / Pion and kaon elastic scattering
130
MAIN LPQ~T Pie
LiOTT
~ t~~4-3~_~.( ~NP?INPUT ~
1515(t
I
~)
~
-~
(5)-(~Il1)
~
L~OPlN
L~e~co~*bI j(s~ ~4~(r), D(E)
I
0’)
LPUMI
~l~ I I L~
çLPLM )~LPJ’MX>~
I
I
N5f’INI
H~0TI
~‘~1
_____
_____
_-~~--~H’fr)J >(N6FIN-?,-~-~---~ ~ 4.
1—
__ 1L tL”
~-~
?
fr’~-~~I~—-—-N 4iaç(~ (~) ITi~-iP’4~I Y _______
C.~JC[1]L~L),
~
I
H
____
~)
I
~66x-?)-~ L~
~
~
u
I~’t~r~I ~
j~J
~
.~ti.c*ecTLt~~1t1 ~
N5flN—N5~tNtI
Fig. I. Flowchart of main program LPOTT.
3. 4. 5 6. 7. 8. 9. 10.
CGC2 FFMHE3 FFHE3 FHE3Gs FMMM FFPN FFCHE3 LEGPOL LAGRNG
2,(65). Clebsch—Gordon coefficient squared, Analytic fit of McCarthy et al. to the (C0I~’2”3) 3He magnetic form factor, (84a). Assembly of charge and magnetic form factors for 3He and 3He. Interpolation on McMillan’s tn-nucleon form factors. Dipole fit to the proton’s charge form factor (79). Analytic fit of McCarthy et al. to the 3He charge form factor, (84a). Legendre polynomials up to order 50 (15). Simultaneous Lagrange interpolation on an entire matrix (R. Landau’s modification of IBM SSP routine).
/
RH. Landau
Pion and kaon elastic scattering
131
oPrP 1~J5
(~aII ~
MAIN 7~J
I
I
~
I
P~ TA?~~
N
~PUM.I
I
ii~izI ~
I ________
~~I4~I4~(I2)
,L.
(
~)J
(l~5)
C.~ft~vrnOPrP
__________
L
I
~ fixed)
Call p~Hor~rFI /(WP~)Nsv~aIILj
J
4
_____
I
VCo~IL(Wft~)I
I
VArWP.)I
(4~)
TN Li C.
j
_ _______
~ ~
~
I
___________ ___________
I
ii
S~ipfiva~h 1~PE
I
T~wfbl1e4’T
(Ø~)_________
L.PLJt~I
____________
4
C~I~I Ca~ ,,~,
I
L~LJM41
L~f~~M
___
LG~) Ui.ai~(k/i~’)
~)
I.~~(~~/k) j—1~— ~
____
Y~p~~N ___
[~&r I ___________
CaIITNUCTH
________
_____ 1211 1’ l{r2.Iz~1I
jz-NPr~
~L1
-11 • 1
Fig. 2. Flowchart of OPTP.
11. RHOOFR 12. RHOK 13. SPBESL 14. TNCM 15. TNUC
~NLiC.$~
______
(iio~)
________
1
~ri~
Fig. 3. Flowchart of TNUC.
Unnormalized coordinate space nuclear densities of Fermi or HO type, (75), (66). Numerical Fourier transformation of a coordinate space density into a form factor, (75b). Spherical Bessel function of the first kind, (75b). Calls appropriate subroutine for projectile—nucleon t matrix, i.e. TPICM or TKCM. Kinematically maps the two body t matrix from the 7rN to irA corn and does a numerical partial wave decomposition to find BNUC, (89)—(90), (110).
R. H. Landau / Pion and kaon elastic scattering
132
TI’JU CT H
W ~o
(~Th I
~
I
TNOFF-
1~ (~)
~
4~r ~)
NW~Y~>
/‘~Call~
~NU?J
N
I~rh~~fr
~
I
~
__________
I~
KI~’fy5wS
________________ __________
~
N
I C”)(~)
~
~
—< NIrTY(5) _________
~
I
I I
I
9 bNbNr
20. FFACT 21. MINV
I
4
I______
I
~ (Ill)
~
I
‘~)1~) JI
(Ill)
I ~.<
(“i)
____________
I
°(~)
E~b(~J1
NlrY(~n>~L,_ I LOCAL. (jl’~)
T~sI
~~olO9 ,J,o
I ~
,~< I ~~/~0~I
.
jTN1JC(~~~~ ~ I~4
TFOLD VCOUL VC OPTP
wirrr&~>~J~N~
____________
~
l~N~Ift)\~
I
~
~
~
~
16. 17. 18. 19.
I
______________
IE-~I
Fig. 4. Flowchart of TNUCTH.
A4~h1NsIQM4
________________
I?>±~_~
[
<____________
(~)(9~
NIFTYC5)2?~
________
I
(102)
______
2~.~CL4)
L Call MIXUP
Fig. 5. Flowchart of TNOFF.
Folds (Fermi averages) 2 body I matrices, (127). Partial wave decomposition of cut-off Coulomb potential, (42). Coulomb potential in momentum space, (44), (47). Assembly and storage of the optical potential from t matrices and form factors, (64)—(65). Form factor as a function of momentum transfer, (77). Matrix inversion.
)
R.H. Landau / Pion and kaon elastic scattering
133
TPIC..W~ ~ZG(6~ilar4w TKCM) (~ll
f~
I~~NGM (TNO~
‘Jr
~)
(_I~CaII Jr ~
________
b~4~al~~’ ~
___________
N
(ICC.)
~
N
________
I~ti:~] J.(~b))] (toG) ~ ( CakuLa~To’. 1 t~ ____
Ta
_______
1
‘~
~.
____
~C~allMIXUP ________
f
Pr~tT~.
~~A)(Ne~
‘~_____
_______
j
I
I
I
LNI~rY~ Cø1IiWXUP
I 9~~)
Fig. 6. Flowchart of TPLCM.
22. 23. 24. 25. 26. 27. 28.
PIMIX MIXUP PLPRME RHOKFF TPICM TPIRSL TNOFF
29. LOGPLT 30. TNUCTH 31. VABS 32. WAVFN 33. PAUL! INTGL QAV 34. G
Combine eigenchannel amplitudes into ir ±p and ir ±n amplitudes (107)—( 108). Calls pion, kaon or nucleon mixup. Derivative of Legendre polynomial, (14). Partial wave decomposition of form factor via projection, (76). Calculates and stores on-shell irN eigenchannel amplitude from phase shifts, (106). irN phases from Rowe, Salomon and Landau fit. Off-shell two body amplitudes from on-shell amplitudes in the two body corn; fixed K, K’, ~ all L, (lll)—(l20). Sernilogarithmic printer plotting routine; (adapted by RHL). Angle-dependent 2-body t matrix in the meson—nucleus corn. The code is given in table 3. Partial wave decomposition of the annihilation (“ true absorption”) potential, (42). Coordinate space wave function from F’ matrix, (153). Modification terms for irN denominator arising from Pauli blocking (121 )—( 124) (A.W. Thomas, author). Thomas’s separable potential for PAUL!.
R. H. Landau / Pion and kaon elastic scattering
134
FfACT ~ ~HO~WN VCOUL ~
P~HQKFf
.~.
4,2 C~fl
F-FH~~ (~).(s~)
A 20
y
~JIifl
--.--*.-
____
4 ~(I~CALL~yN~
I
F-rMHr~ I I
I
N
_____
I F~MMM
I
~
I
~
~
I
I-
~:
~
(17b)
I )o
RCWFN TKCM TKPMAR KMIXUP GAUSS2 GAUSS 40. BLOCK DATA
I ~ll r?AGT
~)tMoK(~l~,)
I
~
____
~
2 3
4 5
6 7
8
(VA.)
4~(~)
I
I
____
(m)
__________
(ia’)
Fig. 8. Flowchart of RHOKFF.
Coulomb wavefunctions routine of ref. [19]. Calculation and storage of K + N amplitudes (M. Paez, author). The Martin analysis of K~’N phase shifts (M. Paez, author). Combine eigenchannel amplitudes into K~p and K~n amplitudes. Scaled Gaussian—Legendre integration points (S. Pieper, programmer). Three nucleon wave function data of McMillan.
Table 3 Code for T~~N(9): TOFTH(I) I
L~ I
T
_________
Fig. 7. Flowchart of FFACT.
35. 36. 37. 38. 39.
~ll I
I
FF~PN
Re/Im
N
Re Im Re Im Re Im Re Im
p p n n p p n n
n, p
Spin flip X X X X
I VT
R.H. Landau / Pion and kaon elastic scattering
135
4.2. Storage LPOTT uses labelled COMMON blocks and EQUIVALENCE’s to transmit variables among subroutines and to save memory space. Consequently, care is required before changes are made to variable storage.
4.2.1. COMMON blocks 1) /NLSPFL/ (length = 8712) MEMBERS - BIAS NAME (LENGTH) 0 1850 3276 4777
GIN ECMDEN AIMW NECMS
(1400) (25) (1400) (1)
1400 1875 4676 4778
KAPG (100) FMN (1) AKAPD (100) DUMMY(3934)
1500 DENOM (350) 1876 REW (1400) 4776 NKAPGS (1)
This is the largest COMMON block (length 8712 words in MAIN) and contains variables for the nonlocal separable potential, g(p) and folding. GIN (14, 100) and KAPG (100) are the inputted g,,(sc) and K of eq. (111), a the eigenchannel label (1—14) of table 2, and 100 values for K are possible (actual number = NKAPGS). DENOM (14, 25) and ECMDEN (25) are the tabulated Da(~) and 25tZ”s of (lll)—(1l2), whereas FMN is used in the subtraction, (117) of the P11 pole from the Coronis—Landau potential. REW(14, 100), AIMW (14, 100) and AKAPD(100) are used to store the real and imaginary parts of the 2-body t matrices (SCøItaIIC0), (106a), for the 14 eigenchannels a, and a possible 100 values for AKAPD (actual number = NECMS). The rest of /NLSPFL/ in MAIN is filled with a DUMMY variable so that there will be room for the EQUIVALENCE of GIN to U (see section 4.2.2). =
2) /SEC2/ (128) MEMBERS - BIAS NAME (LENGTH) 0 56 100 103 106
BNUC BNF XBARC XN NWAVES
(20) 20 BN (16) 72 RETIJ (1) 101 XI (1) 104 NZ (1) 107 NIFTY
(16) (14) (1) (1) (20)
36 86 102 105 127
BNUCF (20) IMTIJ(l4) XPI(l) NES(l) NA(1)
This is the key information-transmitting block. [BNUC(20), BN(l6)] and [BNUCF(20), BNF(16)] are the physical, meson—nucleon, off-shell [nonflip] and [spin-flip] I matrices, B~’~’, in the [ir-nucleus, ir-nucleon] reference frames, respectively, eqs. (62), (63) and (108). The 16 and 20 correspond to the NL index of table 1. RETIJ( 14) and IMTIJ( 14) are the real and imaginary parts of the corresponding eigenchannel amplitudes, (sc’~çIK), (106) and (Ill). The 14 corresponds to the a index. XBARC = ,tlc = 197.3289, XI ir = 3.141593, XPI = projectile mass = (139.578, 493.668), XN is the average nucleon mass XN
=
~-[Nzx938.2s6+
(NA-NZ)x939.55].
NZ, NES, NWAVES, NIFTY and NA are input parameters (see fig. 2). 3) /SEC4/ The input parameters for the nuclear matter and spin distributions (see section 4.2).
(155)
R. H. Landau
136
/
Pion and kaon elastic scattering
4) /SEC6/ Input sizes for “exact” Coulomb procedures used in VCOUL and VC. 5) /ABSP/ S and P wave strengths of absorptive potential for pions as used in VABS. 6) /ENPAUL/, /ENQAV/ Internal transmission of data among PAUL!, INTGL, QAV for Pauli blocking computation. 7) /MMM/
Transmission of 3N wavefunction information in BLOCK DATA to FMMM. 8) /SEC5/ RHO(4, 50) (and DRHO) are the IMAX (~ 50) amplitudes present in the partial wave decompositioin of the nuclear form factor, eq. (61), for a fixed value of KP = k’ and K = k. The “4” indicates the densities:
3
—
proton matter p(q),
2 — neutron matter p(q),
—
proton matter ~( q),
4
—
156
neutron matter ~( q).
RHO contains the final amplitudes used in OPTP, DRHO is used for intermediate éalculations. 4.2.2. EQUIVALENCE in MAIN Class — GIN, length = 8712, MEMBER: BIAS 0 0 0 12 43 60 84 108 144 180 1500 1876 3849 4776
NAME DSIG U REUL X2 X5 X6 X8 X10 Xl3 X16 DENCM REW DFLIP NKAPGS
(LENGTH) (95) (8712) (50) (12) (12) (12) (12) (12) (12) (12) (350) (1400) (95) (0)
0 0 24 50 72 89 120 156 192 1850 3276 3949
Y Xl X3 YY X7 X86 Xll Xl4 Xl7 ECMDEN AIMW POLAR 4777 NECMS
(50) 0 CHART (12) 0 H (12) 36 X4 (50) 50 AIMUL (12) 77 X76 (1) 96 X9 (12) 132 Xl2 (12) 168 Xl5 (12) 1400 KAPG (25) 1875 FMN (1400) 3749 DNOF (61) 4676 AKAPD (0) 4778 DUMMY
(3721) (240) (12) (50) (1) (12) (12) (12) (100)
(0) (95) (100) (3934)
The EQUIVALENCE statement in MAIN is a built-in overlaying device. First, the memory allocated to COMMON/NLSPFL/ is used to store the Hollerith information which explains the NIFTY codes (H(12,20), Xl, X2, X3,...). Then, after OPTP calculates and stores on TAPE 7 the potential matrix elements for all L, k’ and k, /NLSPFL/ is used to store the (complex) potential matrix UJL±I/2(k’,k), eq. (149), (U(4356,2)) for all (k’, k) but only one L. /NLSPFL/ is then reused for each L value. After all the T’s have been calculated, /NLSPFL/ is used to store variables needed to calculate differential cross sections and polarizations (Y, YY, DSIG, DNOF, DFLIP, POLAR). Then it is used in producing the printer plots by LOGPLT (CHART) and finally in setting up the coordinate space wave functions (REUL, AIMUL).
R.H. Landau
/
Pion and kaon elastic scattering
Table 4 Changes for IBM OLD no.
Change
NEW no.
NEW LINE
1, 2
comments
2C 2c
PROGRAM LPOYF (OUTPUT = 64,TAPEI = 64,TAPE2 = 64,TAPE3 = 64, 1= OUTPUT,TAPE4 = 64,TAPE8 = 64,TAPE7,DEBUG = OUTPUT)
75
insert
76 77
110 120
remove
142-3
COMPLEX * 16 H, X1,X2,X3,X4,X5,X6,X7,X8,X9,Xl0,X1 l,X12, 1 X13,X14,X15,Xl6,X17,X86,X76
112 122
7(,(X16(1),H(l,16)),(X17(1),H(1,17))_______ 7 IOHSIN,KAPO ,IOHSO,NO ANG ,2*1OHUNDEF —, IOHE3B,NO AAY
replace
144
READ(5,730,END = 650) NR,LXMAX
261-2
comments
262c
263c
CALL SECOND (CP) WRITE (6,800)CP
348—9
replace
349
READ (2,860,END
360-1
replace
360
READ (4,870,END__201)ECMDEN(NK),(DENOM(NW,NK),NW =1,14)
378—9
comments
377ç 378C 381C 382ç 412ç
CALL SECOND (CP) WRITE (6,800) CP CALL SECOND (CP) WRITE (6,800) CP IF (LDUM.LE.1) CALL TIME (3,3)
856
AlO
855
710 FORMAT (7H NIFTY(,12,2H)= ,13,lOX,A8,A2)
867
comment
866
ç800 FORMAT (IHO,12X,15H TIME(SECONDS)= ,Fl0.2)
1959
()-~ *
1958
DATA VCOULL,REVABS,IMVABS/150*0.OE+00/
2950
()-.o
2949
DATA SIGL/2*l.,3*-l.,l.,
3028
ABS
3027
IF (CABS(ZSIG(N)).NE.O.) ZSIG(N) = l/ZSIG(N)/TWOPI2
3032
ABS
3031
IF (CABS(ZSIG(N)).NE.O.) ZSIG(N)=l/ZSIG(N)/TWOPI2
4045
comment
4044C
REAL DLOG
4143
DLOG
4142
Y=SUM+ALOG(DUM)*CONST
4388
300
4387 4388ç
IF (ABS(GP).GT.1.OE+70) GO TO 110 NB CHANGED EXPONENT TO 70 FOR IBM
4800
REAL -, REAL*8
4800
IMPLICIT REAL * 8 (A-H, O-Z) REAL*8 XS(NFTS), WTS(NPTS) REAL*8 HH(2) REAL*8 GX(l 18), WT( 118) REAL*8 Xl(52), Wl(59), X2(59), W2(59)
()—
*
382-3 413
4801 4802 4804 4805
*
4897
remove
5037
add after C -
4801 4802 4804 4805
=
180)KAPG(NK),
(GIN(NWAVE,NK),NWAVE = 1,14)
1,1,5*— l.,1./, IX/O/,
SUBROUTINE GAUSS(NPTS,KODE,A,B,XS,WTS) SPECIAL SUB FOR IBM SO LPOTF CAN RUN IN REALs4 WITH GAUSS REAL * 8 DA,DB,DXS(48), DWTS(40) DIMENSION XS(48),WTS(48) DA = A DB = B CALL GAUSS2(NPTS,KODE,DA,DB,DXS,DWTS) DO ION = 1,NPTS XS(N) = DXS(N) 10 WTS(N)= DWTS(N) RETURN END
137
138
RH. Landau
/
Pion and kaon elastic scattering
While it may be fairly simple to remove this EQUIVALENCE statement if problems arise, problems will (ultimately) arise if this statement or some of the variables are changed without proper care. 4.2.3. TAPE 7
As indicated in fig. 2, for each (fixed) value of k and k’ OPTP calculates the potential matrix UL±(k’ k), (17), for a//values of L, and then writes these out on TAPE 7 (NSPIN = 1,2 for J = L ±1/2). This is then repeated for a different set of k and k’ with the matrix U stored in the linear form given by the algorithm (149). Of course when the integral equation (138) is solved we need know U
÷(k’1k) for a fixed L ±and all values of k and k’. A good portion of OPTP concerns itself with skipping records on TAPE 7 keeping L ±fixed and varying k and k’ (except if L> LBorfl, since then ony the on-shell point is needed). In the present version of LPOTF we save considerable time by unFORMATTED READ and WRITE statements for TAPE 7. The user with more (or virtual) memory available may choose to save even more time by storing U( k’ I k) in core. 1
4.3. Running on IBM The present version of LPOTT has been converted to run on the IBM 360/195 at the Rutherford High Energy Physics Laboratory, Didcot, Berks. We find that the single precision IBM version reproduces the phases and cross sections of the test case up to four decimal places. This is sufficient since it matches (or exceeds) the precision of the elementary two body input. The changes made are given in table 4.
5. Running LPOTI’ 5.1. Files
LPOTT uses as many as 8 files for input, output and temporary storage. The run parameters are on TAPE 5 and are changed for each specific calculation desired (the input parameters are described in detail in section 4.2). The other files are: TAPE 1 Tables of irN or KN phase shifts and absorption parameters (see READ statement, card no. 2751 in TPICM and FORMAT 170). The RSL [24] irN and Martin K* N phases [30] have analytic form and are thus built in; the Almehed—Lovelace [31] (DELAL) and CERN theory [32] (DCERN) irN phases are supplied on cards, as are the Watt’s [33] (KNWATI’) K~N phases. Note, if a meson—nucleon amplitude is requested for an energy w less than those tabulated, LPOTT will automatically use one of the built in forms; in many instances the user may choose to “cut off” some of the initial tabulated phases so LPOTT is forced to use the analytic form up to the chosen energy and the tabulated ones beyond that. Note, too, that if the user requests to “fold” the two-body t matrices, LPOTT will insert 25 more entries into the table for energies lower than the first tabulated one in order to guarantee a smooth approach to lower energy. On latter application the user may care to increase NES (see section 5.2.2) to incorporate all the tabulated 1 ‘s. TAPE 2 Tables of irN or KN separable potentials, g,( p )‘s, (111) (see READ statement nos. 346,348 and FORMATS 850,860 in MAIN). The Coronis—Landau [12] potentials GCL and Thomas potentials [13] GTH are supplied.
RH. Landau / Pion and kaon elastic scattering
139
TAPE 3 Tables of meson—nucleon t matrices, (106), produced and then interpolated on by LPOTT (see WRITE statement nos. 2780—2782 and FORMATS 205,200 in TPICM or TKCM). Since for a given set of input phase shifts the two-body t matrices will be the same from run-to-run and different nuclei, computer time (and printer paper) will be saved if this file is permanently stored and then used again on later runs (such as our file TALNF). If the user requests the t matrices to be folded, (127), the folded t matrices will also be written onto TAPE 3 and should be saved for later application (see section 5.2.2). In this case, however, there will be a slight dependence on the nucleus since the momentum distribution, (131 )—( 132), is A-dependent. Consequently, we store these folded I matrices as files TFOLDHE, TFOLDC, etc. The exception to this storage on TAPE 3 occurs when NIFTY(3) 2,3 (see section 5.2.2) in which case off-shell t matrices also are stored on TAPE 3 (section 5.4). =
TAPE 4 Tables of the meson—nucleon Fredholm determinant Da(W) of (111) (see READ statements nos. 357—362 and FORMATS 850,870 in MAIN). As the beam energy falls below 50 MeV, the subthreshold extrapolation required by the three-body energy, (101), is required more often and these D,~’sare then used. We supply D functions for the Thomas potentials [131(DENOMT) and for the Coronis-Landau potentials [12] (DENCL and DENCLP); DENCL has a P11 pole at m,,, (116), whereas DENCLP has it removed via the procedure (117). Meaningful results demand that the separable potential function g,,,(p) on TAPE 3 and the Fredhoim determinant on TAPE 4 be consistent. TAPE 5 The input/run parameters (see section 5.2). TAPE 6 The OUTPUT file for LPOTT, normally routed to a printer with 6 lines to the inch (for standard size 5 cycle semilog printer plots). TAPE 7 The scratch file used by OPTP to store potential matrix during execution. Since this matrix changes with each choice of input parameters, it should not be saved and reused. TAPE 8 When the user requests that coordinate space wavefunctions be calculated, LPOTT will place F~’( k’ I k) (the wave matrix ~L) and other data on TAPE 8. As explained in section 5.3, if these data are saved, they can be used independently to reconstruct the meson—nucleus wavefunction.
5.2. Run parameters (TAPE 5) 5.2.1. FORMATS
Card I NR,LXMAX (4X,14) Card2 E (F10.4) Card 3 NGP, KODE, B, NANG, YMIN1, YMIN2 (14, 13, ElO.2, 14, 2F5.2)
R. H. Landau / Pion and kaon elastic scattering
140
Card 4 ACHP, ACMP, WSP, ACHN, ACMN, WSN, RCOUL, RCUT (8F10.4) Card 5 NZ, NA, (NIFTY(N), N 1, 20) (215, 1X, 212, 811, 1013) Card 6 NES, NWAVES, BOR, BOI, COR, COt (215, 4F10.5) =
5.2.2. Definitions NR switch for meson—nucleus wave equation (18) or Green’s function (4). 1: Schrodinger equation with relativistic kinematics (7), 0: nonrelativistic Schrodinger equation (6), nonrelativistic velocity in Coulomb parameter, <0: nonrelativistic Schrodinger equation (6), relativistic velocity in Coulomb parameter, ~ 4: “approximate” Klein—Gordon equation (9). LXMAX number of ir—A partial waves (L values) to be calculated in (15). Restriction: 25 due to DIMENSION statement in MAIN, yet this can be increased to 45. It is better to overestimate LXMAX somewhat since for L> LBORN (calculated by LPOTT) the Born approximation is used and only the on-shell potential matrix calculated. E meson lab kinetic energy in MeV. Restriction: upper energy of input 2-body phase shifts (2013 MeV for the Almehed—Lovelace irN phases, 2022 MeV for the Martin K~N phases). NGP number of grid points used in solution of integral equation (20), (138) via (139). The Gauss—Legendre integration point routine GAUSS was programmed by S. Pieper. 16 is usually good for a light nucleus — unless iI’(r) is wanted when 24 or 32 may be needed; 24—32 for heavy nuclei. Restriction: The DIMENSION N of U and F in MAIN depends on NGP (N 4 X (NGP + 1)2) with 32 the present maximum. For more grid points, only the DIMENSION in MAIN needs to be changed. KODE,B: KODE (standard 022) is a 3-digit decimal number written as HTU with the digits having the following functions: H 1: a square root singularity is removed from the choice of points at the lower limit of the integral. H 0: no special action. T: (1 to 5) T, A and B determine the interval the points are on. Normally LPOTT sets A k0 and reads =
=
=
=
=
=
=
=
=
in B. However, if B is read in as 0, LPOTT sets A 200 MeV. T 1, the interval is A to B (B may be less than A). T 2 (standard) the interval is 0 to ~ with 50% of the points on (0, A) and 50% on (A, ciz). B is not used. T 3, the interval is — ~ to ~ with 50% of the points on (— A, to A). B is not used. T 4, the interval is B to infinity with 50% of the points on (B, A + 2B). As B 0, the scaling approaches case 2. T 5, the interval is 0 to B with 50% of the points on (0, AB/(A + B)). As B — ~, this scaling approaches case 2. U 0,1,2: Gauss—Legendre points. U 0 requires NGP 2—16 (by 2), 20, 24, 32, or 40 or 48. U means GAUSS will use the next smaller value of NGP contained in GAUSS, if NGP is not available and U 2, changes NGP to the next larger number. U 5 returns equal-spaced poits, Simpson’s rule if NGP odd, rectangular elsewise. NANG Angular step size in degrees for which the differential cross sections over the interval (0°, 180°)are to be computed. <0: use INANGI and plot cross sections on printer plot (— 3 is standard), 0: then NANG set to 3. YMIN1, YMIN2: controls for minimum ordinates (cross sections) on semilog printer plots. 10~’M~I mb/sr: lower limit on 1st plot, 10~YM!N2: for the next two. =
= =
= =
—+
=
=
=
=
=
=
=
=
=
R.H. Landau
/
Pion and kaon elastic scattering
141
ACHP, ACMP, WSP: Proton distribution size parameters. NIFTY(16) = 0 : (66) is used, WSP ignored, for A = 3, (85)—(87) is used, NIFTY(16) = 1,2: (75a) is used with w = WSP, NIFTY(16) = 3: (78) is used for 4He, (84) for 3He or 3H (i.e. this is the magnetic sizes), (88) for 2H. The “standard” values are given in the text. ACHN, ACMN, WSN: Neutron distribution size parameters. The same coding as for protons above (future versions will use these parameters for the p2 potential in some cases). RCOUL: The size R in fm of the charged sphere for the Coulomb potential, (47), R~= ~J5/3 Rrms, e.g. RC(C, 0, Ca, Pb)=(2.6, 3.1, 4.65, 8.1) fm. RCUT: Coordinate space cut off radius at which the inner logarithmic derivative (calculated in momentum space) is matched onto ~~-shifted Coulomb waves, (49). NZ: Nuclear charge number. NA: Nuclear mass number. NIFTY: The switches to control the calculation. NIFTY (1) =0: ir~scattering, 1: ir — scattering, 2: ir + scattering and then ir — with same nuclear potential (approximate Coulomb), 3: irk, ir scattering and then charge exchange (CEX) (ir, ir°) or (irk, ir°) (approximate Coulomb), 4: ir0 scattering, 5: proton scattering (not yet available), 6: irk, ir0 scattering and then CEX, 7: K + scattering, 8: K°scattering, 9: neutron scattering (not yet available), — 1: K~,K°scattering and then CEX, —2: p, n scattering and then CEX (not yet available). NIFTY (2) =NIFTY (2) x 5 MeV is the value of the binding energy IEBI in the three body energy (101). NIFTY (2) <0 is possible. NIFTY (3) = 0: no coordinate space wavefunction, I: calculate coordinate space wavefunction and write parameterization on TAPE 8 (see 5.3), 2: calculate wavefunction parametrization and off-shell 2-body matrices; write onto TAPE 8 and TAPE 3, 3: calculate off-shell 2-body t matrices and write onto TAPE 3. NIFTY (4) = 1: separable potential model, (111), for off shell 2-body t matrices, 0: “constant” off shell behavior, (118), 2: local, Laplacian model generalized to D and F waves, (119). NIFTY (5) = 0: scattering angle-dependent subenergy with on-shell 2 body kinematics, W 2B0, (99); 2 body momenta (angle transformation) based on Madelstam invariants, (95)—(96), I: subenergy defined as 2 body “incoming” energy, (91); 2 body momenta from Mandelstam invariants, (95)—(96), 2: subenergy defined as “outgoing” energy, (92); 2 body momenta from Mandeistam invariants, (95)—(96), 5: subenergy defined as 3-body energy, (101); 2 body momenta from Mandelstam invariants, (95)—(96), 7: subenergy defined as 3-body energy (101):
R.H. Landau
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/
Pion and kaon elastic scattering
2 body momenta from magic vector (AAY) prescription, (93)—(94), 9: subenergy defined from on shell 2 body kinematics ~a2BO (99); 2 body momenta from magic vector (AAY) prescription, (93)—(94). NIFTY (6) =0: no spin flip scattering; full multiple scattering series (single scattering term always calculated for R Born TBorn), 1: no spin flip scattering; calculate R matrix up to and including double scattering terms (SS term still calculated), 3: include spin flip scattering; full multiple scattering series (separate SS), 4: Set U 0 as check, 5: No spin flip; use SS term as full R matrix (Rms RBorfl) then (21) for unitarized Tms. NIFTY (7) 0: No pion annihilation (true absorption); all 2 body partial wave amplitudes, 1: No annihilation; only S wave 2 body amplitudes, 2: No annihilation; only S and P wave 2 body amplitudes, 3: Include annihilation: all 2 body amplitudes, 4: Annihilation via Yoo—Landau isobar model: all 2 body amplitudes (not available), 5: Annihilation potential printed but not added to U; only S and P wave amplitudes. NIFTY (8) =0: Do not read in phase shifts (use stored t’s); do not fold t matrices, 1: Do not read in phase shifts (use stored I ‘s); fold t matrices, 2: Read in phase shifts and store t’s on TAPE 3; for setup runs. do not fold t matrices, 3: Read in phase shifts; fold t matrices and store I’s onTAPE 3, 4: Use Martin’s analytic form for K~N phase shifts, do not store ‘s on TAPE 3; do not fold, 5: Use Martin’s analytic form for K~Nphase shifts; fold t matrices and store I’s on TAPE 3. NIFTY (9) =0: No Pauli blocking, 1: Pauli blocking of irN t ‘s (must use Thoma’s potentials). NIFTY (lO)= 0 No Coulomb force, 1: Approximate inclusion of the Coulomb force with amplitude phase modifications (55), 2: Approximate inclusion of the Coulomb force without phase modification, (54), 3: Exact Coulomb via matching with uniform charge sphere, 4: Exact Coulomb via matching with realistic charge distribution. NIFTY (11) Upward shift of ir - (or K ± )—nucleon subenergy in MeV. (12) Upward shift of ,r~(or K°)—nucleonsubenergy in MeV. (13)= Upward shift of .~r (or K°)—nucleuschannel E. (14)= Upward shift of ir~ (or K~)—nucleus channel E. (Negative NIFTY’s are OK). =
=
=
=
= =
R. H. Landau
/
Pion and kaon elastic scattering
143
NIFTY (16)=0: Harmonic oscillator p(q), (67), Harmonic oscillator p2(q), (136), 1: Wood—Saxon p(q), (75), Harmonic oscillator ?( q), (136), 2: Wood—Saxon p(q), (75), Wood—Saxon p2(q), (numerical), 3: Special form factors for 3He, 3H, 4He, 2H. NIFTY (17)=0: KMT optical potential with (A — 1)/A scaling. 1: Watson optical potential, no (A — 1)/A scaling. NES Number of energies for table of two body I matrices. If phase shifts are to be read in, NES should be set equal to the number of energies for which the phases have been tabulated. If t matrices stored on TAPE 3 are to be used, NES should be less than or equal to the number of energies there. NWAVES Number of two body eigen channels; normally 14 for pions and 12 for kaons (see table 2). (BOR, BOI), (COR, COl): The (real, imaginary) parts of the S and P wave strengths respectively of the pion annihilation potential, (133). The units are m~4and m6. If zero (or no) values are read in, LPOTT sets (BOR, BOl) (—0.04, 0.04) m~4,(COR, COI) (0.0, 0.08) m;6. =
=
=
=
5.3. Coordinate space wavefunctions The use of the subroutines WAVFN, COULFN and SPBESL with the data on file TAPE 8 permit coordinate space wavefunctions to be calculated even without the other subroutines of LPOTT. The formulas are given in section 3.2. A different data deck/file on TAPE 8 is needed for each energy and/or potential model and the user should supply his own MAIN (with a COMMON block /NLSPFL/ to transfer data). USAGE: Call WAVFN (NSPWF, LMAXWF, RMEV). NSPWF Number of spin terms, 1 for 0 ® 0, 2 for 0 ® LMAXWF Maximum number of partial waves (1 values) for which wavefunction at this RMEV is needed. If LMAXWF is greater than the number of I values for which 8 have been calculated (LSTORE), WAVFN will return F,(kr)/kr. If the wave matrix was calculated with a Coulomb potential included (“exact”), WAVFN will automatically match and return Coulomb-distorted waves; the user has no choice other than to use a different set of data cards. RMEV r (in fm)/hc. REUL(NSPIN, I) real part of U 1_ 1(r). AIMUL (NSPIN, 1) imaginary part of U, 1(r). =
~.
=
=
=
=
Structure of data deck Card 1: NZ, NA, NIFTY(l-20), E, XGAM (Coulomb parameter) Card 2: ACHP, ACMP, WSP, ACHN, ACMN, WSN, RCOUL, RCUT Card 3: NGP, LSTORE Cards 4—8: KK(1,,..., NGP + I) (the grid points) then for I 1, 2 LSTORE Card 5: 1, NSPIN Card 6: Re RL, Im RL, Re TL, Im TL 12R(i), Re ~R(’) Card 7: Re ~R(D’ Im ~R(l)’ —Im Re ~R(2)’ Im ~R(2), — Im ~R(2), Re ~R(2) =
R. H. Landau / Pion and kaon elastic scattering
144
where RL = on-shell R’ matrix before matching, — I)/2i. TL = on-shell T’ matrix after matching, (i~e2’~
5.4. Output of off-shell 2 body
t
matrices
If NIFTY (3) = 2 or 3, LPOTT will write the off-shell two body t matrices onto TAPE 3. These matrices are in the ~‘rAcom and may be useful in DWIA calculations. This output follows statement label 170 in OPTP and contains identifiers (as in section 5.2) describing the run.
6. Test case and set up The test case if for ir~—‘2C scattering at 50 MeV with the three body subenergy, the AAY angle transformation, the annihilation potential, the exact inclusion of the Coulomb force, the CL irN potential model, the RSL irN phase shifts and unfolded t matrices. The ~rN t matrices were computed and tabulated in a former run (see section 6.2). 6.1. Description of output
First the run parameters of section 5.2 are printed out and explained. Then Tab E,~, ~ and ~ are printed. The do ioop over L(7r — A) then begins with L = 0 and identifies itself; since OPTP is called for the first time, all terms in VL(k’ I k) are calculated and stored, and the half-off-shell (k’ = k 0, k = k1,..., k N,) terms for L = 1 are printed: Re V(total), V(Coulomb), Re V(annihilation) - nonflip + flip, Im V(total), Im V(annihilation) — nonflip + flip. Then the strengths and partial wave decomposition of the annihilation potential are tabulated. At this point the output takes a standard form repeated for all the partial waves. The determination of the FL matrix (146) is printed (N.B. a very large determinant, D>> 1, often occurs when a term in the potential is undefined, check array storage and dimensions). Next are printed the unnormalized, on-shell RL matrix (148), normalized RL and TL matrices (22), and the irA complex phase shift. Note that the symmetry present in the F matrix of (146) and (148) should be present in the four RL matrix elements printed as a check. The amplitudes and phase calculated up to this point may include a cut-off Coulomb potential, but have not been matched to external Coulomb waves. If an “exact” Coulomb procedure is chosen, the amplitudes will be printed out again after the matching (49) (the effect of the Coulomb phase aL on TL is also indicated). Finally, the single scattering or Born approximation to R L and T~,(35) and (36), are printed both before and after Coulomb matching. The above format continues until L = LBORN is reached. After that only the Born approximation results are computed. After all the TL’s and RL’s are calcualted, the differential cross sections2,tare Firstare given in the hentabulated. the first four tabulated irA cornlab, are:and, 0cm, finally, cos °Cm’the da/dQ (full MS), da/dQ (Born), t = (k~— k~,) in the Coulomb modified nuclear amplitude fNc of (53) is tabulated: RefNc(OCm), ImfNc(Ocm), IfNC(°cm)12 The total cross sections (28)—(30) then follow. The printout ends with semilogarithmic printer plots. The first is of da/dQ, the second is of do/dQ (“ +“ points) and da/dQ (Born) as “0” points. k~oni(1T— A)
R. H. Landau / Pion and kaon elastic scattering
145
6.2. Output for spin ~ nucleus and charge exchange The general format is the same as above except that for each L value there are two calculations for J = L ± For L = 0 this is provided as a check since the two should be identical. For spin there is also an extra line added to the differential cross section tabulation at each angle. It contains the spin—nonflip and flip cross sections, first and second terms of (26), for both multiple scattering and single scattering, and then the polarization (27). The printer plotting also gets extended: the first plot contains da/dQ +“ and da/dQ (nonflip without f~1) = “0”, the second da/dQ +“ and da/dQ (spin flip) = “0”, and a ~.
-~
=“
=“
third linear plot containing the polarization is added (+ ‘s for positive P(0), — ‘s for negative). For charge exchange scattering (CEX), first ir then ir (or ~0) and, finally, (ir ir°)results are presented with an approximate Coulomb procedure. After the first two calculations, the subtraction indicated in (38)—(40) is performed, the resulting t matrices are printed, and the differential cross sections tabulated. The total “elastic” cross section should be identified with the total CEX cross section. The plots have the same meaning as before. —‘
—,
6.3. Set up We have written LPOTT such that a good amount of information is printed in tables when the user requests the two body phase shifts to be read in (NIFTY(8) = 2, 3). Although we have found this information to be invaluable when setting up and checking LPOTI’ at a new installation, it would be a waste of time and paper to have it on each run. Consequently, we usually have two, short, set up runs to read in the two body phase shifts and tabulate and store the 1) nonfolded and 2) folded two body t matrices (the t ‘s are tabulated and latter read from STREAM/TAPE 3 see section 5.1): —
1) Input (TAPE 5) for nonfolded t ‘s 1
1
48.6000 2 22 0.20E+05
1.5900 6 12
3—2.00—4.00
1.6600 0101000200
0~0 0
1.5900
0
0
0
0
1.6600
0
0
0
0.0
0
3.0000
7.0000
0
The t matrices on TAPE 3 are then saved as, e.g., the file TALNF, and can be used for any nucleus or model (except “folded”). Input (TAPE 5) for folded t ‘s
2)
1
1
48.60000 2 22
1.5900 6 12
.20E+05
3—2.00—4.00
1.6600 0.0000 0101000300 0 0
0
1.5900 0 0 0
1.6600 0
0
0
0.0000
3.0000
7.0000
0
The t matrices on TAPE 3 are then saved as, e.g., the file TFOLDC. Since the folded t matrices depend somewhat on the nucleus via (126) (131), we store a different file for each nucleus. In later runs, such as the “test case”, these previously computed files are used as input. If needed, the output from these set-up runs will be supplied.
146
R.H. Landau / Pion and kaon elastic scattering
Acknowledgements This program is the offspring of theoretical physics research conducted over a number of years with a number of collaborators. The author is proud to acknowledge their contributions to both the physics and computing. In particular, Dr. S.C. Phatak wrote the original program for solving the momentum space Lippmann—Schwinger equation and its vestiges are still present in MAIN and OPTP; Mr. M. Paez has programmed the kaon subroutines; and Dr. A.W. Thomas wrote the Pauli subroutines. The support and hospitality of TRIUMF/UBC and University of Surrey are also acknowledged, as is continued support from the National Science Foundation and the Research Council of Oregon State University. Finally, Drs. R.C. Barrett, P. Bird and J. Tostevin has been most helpful and cooperative in converting LPOTT to the Rutherford IBM system.
References [I] K.M. Watson, Phys. Rev. 89 (1953) 575. N.C. Francis and K.M. Watson, Phys. Rev. 92 (1953) 291. A.K. Kerman, H. McManus and R.M. Thaler, Ann. Phys. 8 (1959) 551. [2] R.H. Landau, S.C. Phatak and F. Tabakin, Ann. Phys. (N.Y.) 78 (1973) 299. S.C. Phatak, F. Tabakin and R.H. Landau, Phys. Rev. C7 (1973) 1804. [3] R.H. Landau, Ann. Phys. (N.Y.) 92 (1975) 205. [4] RH. Landau, Phys. Rev. C15 (1977) 2127. [5] RH. Landau, LAMPF Workshop on Pion Single Charge Exchange, Los Alamos, NM (Jan. 1979) LASL LA-7892C. [6] R.H. Landau and A.W. Thomas, NucI. Phys. A302 (1978) 461; Phys. Lett. 41B (1976) 361. [7] A.W. Thomas and RH. Landau, Phys. Lett. 77B (1978) 155. [8] A.W. Thomas and R.H. Landau, Phys. Rep. 58 (1980) 121. [9] Y. Alexander and RH. Landau, Phys. Lett. 84B (1979) 292. [10] M. Paez and R.H. Landau, Phys. Rev. C24 (1981) 1120. [11] M. Paez and R.H. Landau, Phys. Rev. C24 (1981) 2689. [12] C. Coronis and RH. Landau, Phys. Rev. C24 (1981) 605. [13] A.W. Thomas, Nucl. Phys. A258 (1976) 417. [14] R.H. Landau and F. Tabakin, Phys. Rev. D5 (1972) 2746. J. Londergan, K. McVoy and E. Moniz, Ann Phys. (N.Y.) 86 (1974)147. [15] C.M. Vincent and S.C. Phatak, Phys. Rev. ClO (1974) 391. [16] T.-S.H. Lee and F. Tabakin, Nucl. Phys. A226 (1974) 253. [17] K.A. Eisenstein and F. Tabakin, Comput. Phys. Commun. 12 (1976) 237. [18] ML. Goldberger and KM. Watson, Collision Theory (Wiley, New York. 1964). [19] A.R. Barnett, D.H. Feng, J.W. Steed and L.J.B. Goldfarb, Comput. Phys. Commun. 8 (1974) 377. [20] H.F. Ehrenberg, R. Hofstadter, U. Meyer-Berkhoat, D.G. Ravenhall and S.E. Sobottka, Phys. Rev. 113 (1959) 666. R.C. Barrett and D.F. Jackson, Nuclear Sizes and Structure (Clarendon, Oxford, 1977). [21] R.F. Frosch, iS. McCarthy, RE. Rand and MR. Yearian, Phys. Rev. 160 (1967) 874. [221 B. Bartoli, F. Felicetti and V.S. Silvestrini, Rev. Nuovo Cimento 2 (1972) 241. [23] J.S. McCarthy, I. Sick, R.R. Whitney and M.R. Yearian, Phys. Rev. Lett. 25 (1970) 884. H. Collard et al., Phys. Rev. 138 (1965) B57. M. McMillan, Phys. Rev. C3 (1971) 1702. [24] G. Rowe, M. Salomon and R.H. Landau, Phys. Rev. C18 (1978) 584. M. Salomon, TRIUMF report TRI-74-2 (original version of RSL fit). [25] R.H. Landau, to be published. [26] RH. Landau and F. Tabakin, Nucl. Phys. A231 (1974) 445. [27] K.B. Yoo and RH. Landau, Phys. Rev. C25 (1982) 489. [28] MI. Haftel and F. Tabakin, NucI. Phys. 158 (1970) 1. [29] L.S. Rodberg and R.M. Thaler, Introduction to Quantum Theory of Scattering (Academic Press, New York & London, 1967). [30] B.R. Martin, Nucl. Phys. B94 (1975) 413. [31] S. Almehed and C. Lovelace, NucI. Phys. B40 (1972) 157. [32] D.J. Herdon, A. Barbaro.Galtieri and A.H. Rosenfeld, UCRL-20030 ~rN(1970), CERN Theoretical Fit. [33] S.J. Watts, DV. Bugg, A.A. Carter, M. Coupland, E. Eisenhandler, A. Astburg, G.H. Grayer, A.W. Robertson, T.P. Shah and C. Sutton, Queen Mary and Rutherford Report (1981).
RH. Landau
/
Pion and kaon elastic scattering
TEST RUN OUTPUT 16 22 8. 2SE+95 3-2.98—3.88 NO OF GRID POINTS. 16 1.5598 1.5508 8.8 1.5590 1.5508 0.8 3.9988 7.8808 6 12 9 181795893 8 8 0 0 0 9 0 8 e a HIFTY( 1)— 9 P1+ HIFTYC 2)— 1 s58E SHIFT HIFTY( 3)— 5 NO ~.F. NIFTY( 4)— 1 NLSP—G(P N!FTY( 5>— 7 E38~ AAV NIFTY( 6>. 8 HO SPIW MS NIFTYC 7>— 5 AOS—OLLSP NIFTYC 8>— 8 HO DELIFLD NIFTYC 9>. S NO PAULI HIFTYCIO)— 3 EXACT COUL NtFTY~11). S PIG~PI—~k. OHIFI HIFTY(12>— I PI+~KO SHIFT MIFTYC1]>— S PI-CHANH -. SHI MIFTY~14s I P1+CMANN&L SHIFT HIFTY(15>— 8 NOT USED SHIFT NIFTY(1G) I RNQG.RHO2C NIFTY(17)= I KHT MES.NUAYE8.SIR.0II~CSR~C0I— 59 14 5.9 0.9 8.5 5.9 HES,NUAVES~89R.0SI,C8R~C0I 59 14 —8.14199 0.94898 0.8 0.08008 ,csii,~,* AMASS— l2.0095s*,**s*,I* TPI EPILA~ ECNCSORTS) ICCN PLAO 55.5959
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