Time variations of the solar-neutrino flux

Nuclear Physics A527 (1991) 679c-682c North-Holland, Amsterdam

TIME VARIATIONS

OF THE SOLAR-NEUTRINO

619c

FLUX

Eugene Kh. AKHMEDOV Kurchatov Institute of Atomic Energy, Moscow 123182, U.S.S.R. Possible causes for the apparent eleven-year variation of the solar-neutrino flux axe considered. For each scenario, consequences axe derived for the chlorine, gallium, ve, boron and vd experiments, the last two experiments being of particular interest because they allow the comparison of the charged-current (CC) and neutral-current (NC) modes. 1.

INTRODUCTION

The solar-neutrino problem is the discrepancy between theory’) and observationG) in the 37C1 experiment of Davis et al., which recently haa been confirmed by the vescattering experiment of the Kamiokande II Collaboration. 3, Besides the too-low flux of solar neutrinos, the 37C1 data have another extremely interesting feature: there seems to be an anti-correlation between the detection rate and the sun-spot number (eleven-year variations). ‘) The Kamiokande II data can neither confirm nor refute these variations; if they exist, they are 5 30% in this experiment.3) Here we assume that this anticorrelation is a real phenomenon and briefly consider its possible causes. More detailed discussion can be found in Ref. [4]. 2.

Tc VARIATIONS

The ‘B-neutrino flux depends crucially on the central temperature of the sun, Tc. A small (- 10%) variation of Tc can reproduce the 37C1 data (see Table 1). However, the Tc-variation hypothesis seems to be in conflict with the Kamiokande II data. 3.

NEUTRINO SPIN PROCESSION

If the electron neutrinos have a sufficiently large magnetic moment, neutrino spin precession in the toroidal magnetic field of the convective zone of the sun will transform a significant fraction of the left-handed ue~‘s into the sterile right-handed V&k Since the magnetic field strength is correlated with the sun-spot number, the observed neutrino flux should anticorrelate with the solar activity.‘) 4.

RESONANT

SPIN-FLAVOR

PRECESSION OF NEUTRINOS

If neutrinos have flavor-off-diagonal (transition) magnetic moments pej, their spins will simultaneously be rotated with their flavor changing under a transverse magnetic field.5) Matter can resonantly amplify such a precession .6) The expected consequences of this scenario are shown in Table 1. The 37C1 and Kamiokande II data can be reconciled with each other provided IE<< 1 and the v’s are Majorana particles. 03759474/91/$03.50 0 1991 - Elsevier Science PublishersB.V. (North-Holland)

E. K Akhmedov

680~

5.

PARAMETRIC

AMPLIFICATION argued ‘1 that

It has been oscillations’)

due to density

of the 37C1 counting

rate.

too high an amplitude 6.

/ Solar-neutrino jlux

OF NEUTRINO

the parametric

enhancement

waves in the sun might This

scenario

of matter-density

OSCILLATIONS

requires

account

(or suppression) for the eleven-year

considerable

parameter

of the Yvariations

stretching

and

variations.

CONCLUSION

Examination of Table 1 shows that the most plausible candidates for the origin of the time variations of the solar-neutrino flux seem to be neutrino spin- and spin-flavor precessions.

Future

experiments

will show whether

these time variations

really occur

and

Conference

on

what their true origin is. REFERENCES 1. J. N. Bahcall 2. R. Davis, J. Schneps 3. Y. Tots&a,

4. E. Kh.

and Astrophysics

et al., eds. (World talk delivered

and Astrophysics Akhmedov,

5. M. B. Voloshin, 6. E. Kh.

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90”,

IAE-5017/l

(1990);

Akhmedov,

D37

Phys.

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June 5 - 11, 1988,

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Yad. Fiz., in press. Sow. Phys. Lett.

JETP

B213

64 (1986)

(1988)

446.

64; C.-S. Lim

1368. B226

and V. A. Chechin, Yad. Fit.

USA,

June 10 - 15, 1990.

599; Phys. (1988)

297.

International

Boston, 1989).

International

Geneva,

and L. B Okun’,

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V. A. Tzarev

26; E. Kh.

88”,

Singapore,

Yad. Fiz. 48 (1988) Phys.

60 (1988)

Thirteenth

at the Fourteenth

and A. Yu. Smirnov,

8. V. K. Ermilova,

of the

Scientific,

M. I. Vysotsky

Akhmedov,

Phys.

“Neutrino

“Neutrino

preprint

and W. J. Marciano, 7. P. I. Krastev

Mod.

Rev.

et al., in Proceedings

Jr.

Physics

Neutrino

Physics

and R. K. Ulrich,

47 (1988)

(1989)

341.

KT. Soob. Fiz. Lebedev Institute 475.

5

variation5

v’s

vek->lJ@

(BIDirac

v,->,,Gr,)

HNajorana

EM-7

ReV)/#BB,

rates

high solar b) neutrino

(f)

or

(-)

to

or

(-1

semiannual

stand

(+)

or

the

suppression

f

(+I b)

factor

aft)

t-1

f-1

(-1

f-J

or

(-)

f-b

‘rzt’

of low-energy

#(SB)/#(eB)maxi

f+)

$MiSSN

or

(+) b)

a1 (t ‘QSStl

(+)

cnn5t

‘SSM’

Qmax

(+)

LX(t)

(-1

NC

+1

04-l

comment

4

*i-i

of

neutrinos

al(t)

.a(t)

X=1: o.01a110.41

;=;:
a(t)

a(t)

seniannual variations at the periods a) variations. Standard SB-neutrino spectrum;

for

or

b)

llB

act)Qmax

vd,

a1 ct’QSStl

b)

a)

a)

cc

QSSn $a(t)C&

$(t’QsSR

(*I

a

+3

f+)

al (t ) Qssn

(+I

(t)+l ’ fiSN

Saft)

ba

4+)

a(t)Qmax

(-)

a(t)Q,,x

Vk

Definitions:

SNU

(unknown) constunt

experiments.

(+I

t4a(t)+0.11

and (-)

slight

f+)

the

solar-neutrino

(2)

(-) (+)

CO.Sal (t)+o.zwl

(+)

or

SNU

(-1

’ ) Qlnm

a(t)Qm,x

-

XQSSM

of the sun.

corresponds

field

max

(;

37c1

XQSSH

E>5-7 NeV)SS,,4 ar is

Q for

Q

(t)+0.9wl

yr.av. (2)

I-)

f9.3a(t)+Sl

(+)

CO.lal

a(t)

spectrum may be distorted.

activity!

due to inner mapnetic

+‘B,

Detection

71Sa

C0.2a(t)+0.f33Qm,,

various

(VTR)

v’s

Exper i ment

I. Paramet(A)Oscillations into active ric resonance states of v os- ’ fB)Oscill ations cillatiinto stwi la on5 states

LResonant spin flavor precession

!.Neutrino spin precession

.T,

icenar io

Table 1