Collinear processes in the quark model

Collinear processes in the quark model

ANNALS OF 44, 35-56 PHYSICS: Collinear (1967) Processes in the Quark Model Yu. M. MALYUTA Physics A quark Institute model of the of had...

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ANNALS

OF

44, 35-56

PHYSICS:

Collinear

(1967)

Processes

in the

Quark

Model

Yu. M. MALYUTA Physics

A quark

Institute

model

of the

of hadrons

SU(3) Relations are found of meson and baryon ential cross sections

x

Ukrainian

Academy

is proposed,

SU(3)

x

...

based

X SU(3)

of Sciences,

Kiev,

on the collinear (Zj + 1

U.S.S.R.

group

cofactors).

within the framework of this model for the partial widths resonances, as well as relations for the total and differof a number of elastic and inelastic scattering processes. I.

INTRODUCTION

In a number of recent researches (I)-( 4) many predictions have been made concerning collinear processeswithin the framework of collinear groups SU( 6), and SU(3) X SU(3). Unfortunately, some of these predictions have been in gross disagreement with the experimental data (5). The disagreement is, apparently, due to the violation of collinear symmetries by unitarity (6). In the hope of obtaining better predictions Lipkin proposed a new approach to the description of collinear processesbased on an “independent quark model” (7). By means of this approach it became possible to obtain relations which are not predicted by collinear symmetries, but which are in good agreement with experiment. Thus, the new approach proclaimed the idea of “symmetry without symmetry” ( 7). In the present paper we propose a quark model of hadrons based on the collinear group SU(3) x SU(3) x . . * X SU( 3) (2j + 1 cofactors), (1) where each cofactor correspondsto a definite helicity state.’ For the description of collinear processeswithin the framework of group (I), the impulse approximation (IO), ( 11) , well known in nuclear physics, is applied. In the quark language the impulse approximation is formulated as follows: the hadron-hadron scattering amplitude is equal to the sum of the amplitudes for scattering of each quark in the incident hadron by each quark in the target hadron. This approximation actually permits us to go beyond the framework of group (1) and leads to the relations that follow from “symmetry without symmetry”. 1 The group (1) is the subgroup of U[3(2j formation along the z-direction. The group for the description of hadron shell structure

+ l)] which commutes with a Lorentz U[3(2j + l)] was proposed in papers in the jj coupling scheme. 35

trans(8), (9)

36

MALYUTA

TABLE su (3) 8

I Multiplicity

Y, I 1, FS

Ull&

U21z3

-1, $8

II. HADRON

U3Ql U&l

DECAYS

In this section we shall obtain the branching ratios for different decay modesof mesons and baryons. Let us consider the two-particle partial decay of some hadron Hk+HiHj, (2) which can proceed through several isotopic channels. The partial width of the resonancein the LJ state is given by (12) :

(3)

COLLINEAR

PROCESSES

TABLE E’, I

IN

THE

QUARK

MODEL

37

II Multiplicity

1, N

where M is the massof the resonance,Pouti s the magnitude of the spatial momentum of the produced particles in the rest system of the resonance, and (Hk 1HiHi) is the vertex part for the decay (2). To find the relations between the vertex parts (Hk 1HiHi) we apply impulse

35

YALYUl’A

FIG.

approximation.

We restrict

1

ourselves to an investigation

of the decays

COLLINEAR

PROCESSES

IN

FIG.

THE

QUARK

MODEL

39

2

for which the relative widths have been experimentally checked (13). Using Tables I and II, it is not difficult to construct diagrams contributing to the vertex parts (Hk 1HiHi) in the impulse approximation. These diagrams are pre-

40

MALTUTA

sented in Figs. 1-3, for meson decays,’ and in Figs. 4-10, for baryon decays.2 Denoting the topologically equivalent diagrams by the same parameters and applying formula (3), it is possible to compute the relative widths of the resonances. The results of the computations for meson resonances are given in Table IV, and for baryon resonances in Table V (the symbol I’0 denotes the relative width, uncorrected for the phase-space ( 2PoUt) 2L+1/M2). The results which are in good or satisfactory agreement with the experimental data (1s) are marked with asterisks. 2 Since the hadrons involved in the processes under consideration belong of different groups (l), it is necessary to refer to the common subgroup of SU(3) x @‘J. (where J, is the spin component in the direction of motion; parameter). Then the basic quark triplets of the group (1) may be written in

to multiplets these groups cp is the real the form

where (u1u2u3) is a unitary triplet and a,, is a helicity singlet. The graphic notations quarks are given in Table III (where B is the baryon number, Y is the hypercharge, is the isospin). The v-lines, demonstrating conservation of helicity, are omitted drawings. The numerals near the diagrams mark the number of equivalent diagrams.

of the and I in the

COLLINEAR

PROCESSES

III.

ELASTIC

IN

THE

QUARK

MODEL

41

SCATTERING

Let us apply impulse approximation to obtain the Johnson-Treiman relations (14) and someother relations for elastic scattering crosssectionswhich agree very well with the experimental data. We shall consider the following forward-scattering reactions: K+p + K+p,

K+n + K+n,

K-p + K-p,

K-n -+ K-n,

42

MALYUTA

Trip 4 a+p,

r-p

* r-p,

PP 4 PPY

pn. -+ pn,

PP 4 15P,

pn4pn.

(4)

Using Tables I and II, it is not difikult to construct diagrams contributing to the amplitudes of elastic scattering (4). These diagrams are presented in Figs. 11-15 (see footnote 2). We can now express all the scattering amplitudes (4) in terms of three parameters :

COLLINEAR

PROCESSES

IN

FIG.

THE

QUARK

6

= 6a + 3b, (K+n 1K+n)

= 6a + 3b,

{K-p

1 K-p)

= 6a + 3b + 2c,

(K-n

1K-n)

= 6a + 3b + c,

{r’p

[ ?r+p) = 6u + c,

(r-p

1x-p)

= 6u + 25

MODEL

43

44

MALYUTA

FIG.

7

(mJI PP>= 9% (P I P> = 9% (FPI l?P)= 9u + (@L] pn>= 9a +

56, 4c,

COLLINEAR

PROCESSES

IN

FIG.

where parameters

(a is the scattering vertices

THE

MODEL

45

8

a denote the diagrams with

contribution),

QUARK

parameters

vertices

a + b denote the diagrams with

MALYUTA

Fra.9

(b is the correction

due to unitary

symmetry

breaking),

and parameters

a + c

COLLINEAR

PROCESSES

IN

THE

QUARK

MODEL

47

FIQ. 10

(c is the annihilation contribution).

According to the optical theorem, a similar

4s

MALYUTA

TABLE QlMk

R

1

TABLE Decay

III

LJ

I

IV ro

1* 1* 1* 1* 12 3* 2* 1* 1*

TABLE Decay

LJ

D 312 DSlZ F 512 F 5/z P 512 F5/2 P 3/2 P 3/2 D 3/2 0312 h/2 P 312 0512 D 512 0512 D5/2 P612 D 312 D 312 & 12

Notation

r

rexp

1 1 1 0.03 1 0.29 0.56 1 0.14

30 38 60 40 91 5.5 3.6 50 50

V I-0

1 1 1 1 1 0 2 1 1 4 2 2 1 4 4 2 2 4 3 3

r

1* 1.94* 1* 0.64 0.22* 0* 1 2.13 1* 3.30* 3.08 0.35 1* 2.97 0.39* 2.43 0.11* 1 0.99 1.24

relp

29 56 75 9 15 1 10 90 15 30 5 30 60 3 10 16 10 65 5 25

COLLINEAR

PROCESSES

K+p -

K+p

K+~L-

K+n

IN

THE

QUARK

MODEL

49

dependence on the parameters will hold for total cross sections. Excluding parameters a, b, c, we obtain the following relations for the total cross sections:3 >$u( K+p)

- a(Kp)]

u(K+p) u(m) 42%)

- &P)

= u(K+n)

- u(Kn)

(5a)

= &rip)

- u(7r-p),

(5b)

= u(K+n),

(6)

= dP)>

(7)

= Men)

- dpn)l

(8a)

3 ReMions (5a, b) are the Johnson-Treiman relations (14). Relations (6) and (7) were obtained by Lipkin (7) within the framework of an independent quark model. Relations @a, b) were obtained by Freund (15) from universality and 8(E) invariance.

50

MALYUTA

K-p e

K-p

K-n-+

K-n

FIG.

12

= 5[a( F-p) = 5b(PP)

- a(a+p)] - dl?n)l.

These relations are very well satisfied experimentally 18 BeV/c kinetic energy of the incident hadron. IV.

INELASTIC

(8b)

(16)

(SC) from

6 BeV/c

to

SCATTERING

Let us apply impulse approximation to obtain the relations for inelastic scattering differential cross sections in the forward and backward direction. We restrict ourselves to an investigation of the reactions K+p -+ K*‘A++,

K-p

4

Eon,

K-p

K-p

4

a*X*-,

-+ n--z*+,

COLLINEAR

PROCESSES

IN

THE

QUARK

MODEL

51

e x

Tr+p-Tr+p

2

*s-+-.-“ssr-,

FIG.

13

K-p * a+~-,

K-p + K”Eo,

K-p + K+Z-,

K-p + K*+e-,

r+p + K*+Z+,

(9)

n--p + K+Z-,

for which the crosssections da/dQ( 0”) and da/dQ( 180”) have been experimentally checked (5). Using Tables I and II, it is not difficult to construct diagrams contributing to the amplitudes of inelastic scattering (9). These diagrams are presented in Fig. 16 and 17 (see footnote 2). Denoting the topologically nonequivalent diagrams by different parameters, we obtain the following expressionsfor the scattering amplitudes (9) : (K+p 1K*‘A++)

= &u,

(K-p 1Z?“n) = 2b,

52

MALYUTA

PP'PP

P"-P"

FIQ.

(K-p

(K-p (K-p

1 .R-x*+)

=

a,

14

(K-p

I7r%*-)

= 2c,

I?r+r)

= 2c,

(K-p

1K”Eo) = 2c,

1K+K)

= 2c,

W-P

I K *+E-)

(7r’p 1K*+z+)

= b,

(n-p I K+;r;-)

= 25 = 2c

(a is the exchange scattering contribution, b is the annihilation contribution, and c is the superposit,ion of exchange scattering and annihilation contributions). Excluding parameters a, b, c, we obtain the following relations for the differential

COLLINEAR

cross sections in the forward $

(Ktp

[ K*‘A++)

PROCESSES

IN

and backward = 3g

THE

QUARK

MODEL

53

direction!

(K-p 1=-z*+),

4 The quantities denoted in (10) by the symbols &/dQ are equal to the differential cross sections with an accuracy up to the factors (P,,,/SPi,) exp [- (PM + UB)I t I], where P,,t/sPi, is the phase-space correction (12), and exp (-aH 1 t 1) is the structure factor which is the Fourier transform of the quark wavefunction in the hadron (IO), (11) (Pi, and P,,t are the magnitudes of the spatial momenta of the incoming and outgoing particles in the center-ofmass system, s is the square of the total energy, ( t / is the square of the momentum transfer).

54

MALYUTA

u-p --+Tr+~*-

K-P- lT+tFIG.

g

(I$(

Bz)

= 4%

(&I

16

K*+z+),

I’

(10)

= g (K-p 1E-+x-) = !!.g (K-p ( jy*+z-) = g (K-p ( KoEO) = g (7rp 1 &-f-z->.

\-IT

+p-

K”+ t+

FIG. 17 TABLE

VI

:Process

K+p --) K*OA++ K-P ---) ,-i-f*+ K-p --) rr+iz*K-P --f ?r+zK-p --* K+r K-P + K*QK-p --f KOF

X

2.26 3 2.24 3 2.24 3 2.24 3 2.24 3 2.24 3 3

450 1360 80 37 9 3.5 8 2.5

f f f f f f

60 140 10 10 4 1.8

f

1

0.6 f

0.2

0.5 f 2.5 f

0.3 0.6

55

14 3.5 20 19 22 7 5.2 5.3 2.5

f6 f 1.8 f4 f1.4 f 1.3 f 0.6

?4 % 1 1 1 1 1 1 1 1 1 1 1

56

YALY

A comparison of Table VI, where predictions (10) factors indicated

UTA

relations ( 10) with the experimental data (5) is presented in X is the inverse strength factor that normalizes the data to (the comparison was carried out with an accuracy up to the in footnote 4). ACKNOWLEDGMENT

The author wishes to thank Professor N. N. Bogoliubov RECEIVED:

November

for valuable

discussions.

18, 1966 REFERENCES

J. J. COYNE, S. MESHKOV, D. HORN, M. KUGLER, AND Rev. Letters 16, 373 (1965). 2. D. V. VOLKOV, Nuovo Pimento 40,281 (1965). 3. J. KUPSCH, Nuovo Cimento 40, 287 (1965). 4. H. RUEGG AND D. V. VOLKOV, Nuovo Cimento 43, 84 (1966). 6. J. D. JACKSON, Phys. Rev. Letters 16, 990 (1965). 6. A. SALAM, in “Proceedings of 1965 the Oxford International Conference 1.

J. D. CARTER,

H. J. LIPKIN,

Phys.

on Elementary Particles.” Rutherford High Energy Laboratory, Oxford, England, 1965. 7. H. J. LIPKIN, Lecture Notes, Yalta International School, Yalta, U.S.S.R., April 1966. 8. M. M. MILLER, Phys. Rev. Letters 14,416 (1965). 9. Yu. M. MALYUTA, Nucl. Phys. 74, 625 (1965).

10. G. F. CHEW AND G. C. WICK, Phys. Rev. 85, 636 (1952). 11. G. F. CHEW AND M. L. GOLDBERGER, Phys. Rev. 87,778 (1952). la. K. NISHIJIMA, “Fundamental Particles.” Benjamin, New York, 13. A. H. ROSENFELD, Lecture Notes, Yalta International School,

1964. Yalta, U.S.S.R.,

April

1966. 14. K. JOHNSON AND S. B. TREIMAN, Phys. Rev. Letters 14, 189 (1965). 15. P. G. 0. FREUND, Phys. Rev. Letters 16, 929 (1965). 16. W. GALBRAITH, E. JENKINS, T. KYCIA, B. LEONTIC, R. PHILLIPS, RUBINSTEIN, Phys. Rev. 138, B913 (1965).

A. READ,

AND

R.