Pole model for nonlepton and radiative hyperon decay
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MODEL
HYPERON
FOR
NONLEPTON
AND
RADIATIVE
DECAY
A.
G.
Potashev
UDC 539.1.01
Nonlepton and weak radiative decays of hyperons a r e analyzed on the basis of the pole model. In c o n t r a s t with other analyses, the contributions f r o m both baryon and meson poles a r e taken into account. Experimental information on these decays is used to find the p a r a m e t e r s of the effective weak t w o - b a r y o n interaction. 1.
Introduction
There have been s e v e r a l studies of nonlepton decays of hyperons in the pole approximation [1-3]. The p a r a m e t e r s of the t w o - b a r y o n weak interaction have been evaluated under the assumption that all the s t r o n g interaction constants a r e of the same o r d e r of magnitude and that the contributions f r o m the meson poles a r e negligible. In the SU3-invariant pole model for nonlepton decay, the n o n p a r i t y - c o n s e r v i n g part of the decay amplitude is governed completely by the contribution f r o m the K * - m e s o n pole. Sum rules for the amplitudes of nonlepton decays and the decay a s y m m e t r y p a r a m e t e r s have been obtained in this model [4-6]. Below we examine the pole model for nonlepton decay of hyperons with an account of the contributions f r o m both baryon and meson poles. The constants of the strong b a r y o n - m e s o n interactions a r e found f r o m the experimental NN~ constant and f r o m the r e q u i r e m e n t s of SU 3 s y m m e t r y . The p a r a m e t e r s found for the weak t w o - b a r y o n interaction a r e then used to find the r a t e s of the weak radiative decays of hyperons. 2.
Nonlepton
Decays
We consider the following hyperon decays: A -+fl -~- ,~-, y'+ --+ n + ~+, ~+ -->p @ ~,o, E- -~. tt -]- ~-.
(1)
We write the amplitudes for these decays under the assumption that these amplitudes are dominated by the contributions f r o m the A, N, E, K, and K* pole t e r m s (Fig. 1). The v e r t i c e s c o r r e s p o n d i n g to the weak transitions Y ~ N , K*-*:r, and K ~ are r e p r e s e n t e d by the following effective interactions: H ( Y - + N ) = CmpN (ar -k i%bv) Y,
(2)
H (K* + r,) = OmvaK,~F,~O~?~,
(3)
H (K + ,~) = 6rn~ax~.K?~,,
(4)
where G = 10 -7 is a dimensionless constant; mp is the proton m a s s ; a y and b y are dimensionless i n t e r a c tion p a r a m e t e r s c o r r e s p o n d i n g to Y - - N transitions with c o n s e r v e d and nonconserved parity; and aKTr and aK,Tr are dimensionless p a r a m e t e r s c h a r a c t e r i z i n g the magnitudes of the K ~Tr and K*-*lr interactions. We write the amplitude for the A--*p + 7r- decay as Tx = (2~)' ~ (p~ -- pp -- p~) -p(A., q- iT~BA) A
(5)
and we write that for E * , ~ hyperons as T -+'~= (2~) ~~ (p~ - - pN -- p~) N (A +-'~-k iT~B +'~ E,
(6)
S c i e n t i f i c - R e s e a r c h Institute of Nuclear P h y s i c s , S.M. Kirov T o m s k Polytechnical Institute. T r a n s lated f r o m Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 8, pp. 17-22, August, 1969. Original a r t i c l e submitte
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