Improvements in Tests of Long-Range Charge Independence

Abstract

The procedure used to determine the pionnucleon coupling constant g(2) from multi-energy fits to nucleon-nucleon (N-N) scattering data has been shortened without a material loss of accuracy. The g(2) presetting effect is discussed in connection with the limited accuracy of g(2) determinations in general and the possibilities of the "optimized polynomial expansions". The desirability of the Yale graded introduction of one-pion exchange (OPE)-to-"searched" transition energies (E(tr)) is brought out. Corrections for virtual discontinuities in phase-shift-energy dependence at the E(tr) decreased the violation of long-range charge independence (LRCI). The effect of two-pion exchange (TPE) has been calculated on the ps theory as approximately 1 for go(2)(p-p) - go(2)(n-p), go(2) = g(2)/[unk]c; a result consistent with LRCI. Searching all phase parameters including g(2) for both isospin values I in g(2) determinations from n-p data, but with fixed I = 1 non-OPE phases as deduced from p-p data in the base search with frozen g(2), the OPE effect of the neutral pion, pi degrees , was separated from that of the charged pion, pi(c). The g(2) for pi(c) in n-p scattering is determined with much better statistical accuracy than that for pi degrees . The overall n-p value of g(2) is nearly equal to that for pi(c). The results suggest that the distinction between p-p and n-p values of g(2), if present, is in first approximation that arising from the difference between pi degrees -N and pi(c)-N couplings. Some limitations on the validity of the conclusions are mentioned.