Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility we have studied (p, n) reactions on the light nuclei Li, ' "B,and ' ' C. Double differential cross sections have been measured between Hi, b=0' and 50' in 5' intervals, at E"=186MeV. Contributions of the quasifree reaction in the giant resonance region are estimated. Energy spectra of EL=1 transitions have been extracted using multipole decomposition analysis. The resulting EL=1 spectra are compared with results of photonuclear reactions.Empirical results are also compared with distorted wave impulse approximation calculations. PACS number(s): 25.40.Ep, 27.20.+n, 24.70.+s

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Abstract:The energy dependence of the total cross section for the pp −→ pK + Λ reaction was measured in the threshold region covering the excess energy range up to 7 MeV.Existing model calculations describe the slope of the measured cross sections well, but are too low by a factor of two to three in rate.The data were used for a precise determination of the beam momentum of the COSY-synchrotron.

Threshold measurements of the associated strangeness production reactions pp → pK + Λ and pp → pK + Σ 0 are presented. Although slight differences in the shapes of the excitation functions are observed, the most remarkable feature of the data is that at the same excess energy the total cross section for the Σ 0 production appears to be about a factor of 28 smaller than the one for the Λ particle. It is concluded that strong Σ 0 p final state interactions, and in particular the ΣN → Λp conversion reaction, are the likely cause of the depletion for the yield in the Σ signal. This hypothesis is in line with other experimental evidence in the literature.

The s e l e c t i v i t y and t h e s u r p r i s i n g s i m p l i c i t y of response function f o r spin-isospin t r a n s i t i o n s with t h e (p,n) r e a c t i o n a t intermediate energies has been AL=O t r a n s f e r s f o r 5 4 9 5 6~e t a r g e t s . I n t h e case of used t o study the spin-isospin c o r r e l a t i o n s i n n u c l e i t h e N i i s o t o p e s , a comparison may be made with t h e M1 (see Ref. 1 and o t h e r references within). The zero s p e c t r a obtained from e l e c t r o -e x c i t a t i o n . 3 9 degree s p e c t r a have been used t o o b t a i n t h e AL = 0 The experimental r e s u l t s and a n a l y s i s f o r the response function of n u c l e i while t h e measured2 energy 5 8~i ( p , n ) 5 8~u r e a c t i o n have been published3; t h e dependence of the e f f e c t i v e n u c l e o n n u c l e u s i n t e r a c t i o n a n a l y s i s f o r t h e o t h e r i s o t o p e s is i n progress.r e s u l t i n g from the spin-isospin terms i n the The double d i f f e r e n t i a l c r o s s s e c t i o n of L = 0 nucleonnucleon f o r c e has been employed t o i d e n t i f y t h e s t r e n g t h observed a t ( 3~ = 0' f o r t h e 5 8~i ( p , n ) 5 8~u spin-isospin o r Gamow-Teller strength. Other r e a c t i o n is presented i n Fig. l b and i s compared i n multipoles observed a t higher e x c i t a t i o n energies Fig. l c with the B(M1)C s t r e n g t h reported4 f o r t h e i n d i c a t e a maximum d i f f e r e n t i a l c r o s s s e c t i o n a t 5 8~i ( e , e ' ) reaction. The l o c a t i o n s of known 1+ e x c i t e ds l i g h t l y higher angles and have been i n t e r p r e t e d a s s t a t e s i n A = 58 n u c l e i a r e shown i n Fig. la. (AL = 1, AS = 1) and (AL = 2, AS = 1) e x c i t a t i 0 n s . l *permanent address: C e n t r a l Research I n s t i t u t e f o r W e have obtained 160 MeV (p,n) d a t a on 5 4 * 5 6~e and Physics, Budapest, Hungary.5 8 * 6 0~i and 120 MeV d a t a f o r t h e 5 8~i ( p , n ) 5 8~u r e a c t i o n 1) C. Gaarde e t a l . , Nucl. Phys. A369, 258 (1981).i n order t o study t h e response function of 5 8 * 6 0~i 2) T.N. Taddeucci e t a l . , Phys. Rev. C 25, 1094 (1981).t a r g e t s t o spin-isospin t r a n s i t i o n s characterized with 3) J. Rapaport e t al., Phys. Lett. 119B, 61 (1982). AL = 0, AL = 1 and AL = 2 t r a n s f e r s and t o study t h e 4) R.A. Lindgren e t a l . , Phys. Rev. C 3, 1789 (1976).

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