Pion absorption onHe3atTπ

Abstract

Pion absorption in He was studied at T =62.5 and 82.8 MeV using nucleon-nucleon coincidences, For~+ absorption on proton-neutron pairs the differential cross section is the same as that for n. ++d~p+p except for an increase by a factor of about 1.5. For m absorption on the proton-proton pair, the differential cross section is asymmetric about 90', indicating possible isospin mixing. The total cross sections Op, (m+) are 10.2%0.9 mb and 13.5+1.3 mb at 62.5 and 82.8 MeV and for opp(~) are 0 70%0 07 mb and 0 92+0 10 mb at 62 5 and 82 8 MeV The three body absorption cross sections for m+ and n are found to be comparable to each other and show no strong energy dependence. The three-body absorption cross section 03(m+) is 6.7%2.5 mb and 5.7+2.3 mb and for m, a3(m ) is 8.7+1.4 mb and 6.5+2.0 mb at 62.5 and 82.8 MeV, respectively.

Experimental studies of the quark-gluon structure of nucleons and nuclei and of pion- and proton-nucleus interactions. Progress report, April 1, 1994--March 31, 1997

“…Our results on 3He [67] (Fig. 14) show that the total absorption cross section peaks at lower pion energy than earlier measurements suggested [68,69,70,711 bringing these data more into line with those of 2H and 4He. A large increase in the total absorption cross section from 3He to 4He for several pion energies between 100 MeV and 270 MeV had been previously reported by Baumgartner, et uZ.…”

Total cross sections and analyzing powers for the reactionp+p→p+p+π0near threshold

“…Other estimates for this cross section can be obtained from pion absorption in He (Refs. [55] and [56]). These measurements find that the oo, Sp term is 19+4 pm at 409 MeV and 31+6 pb at 442 MeV.…”

Proton polarization fromπ+absorption inHe3MayTal‐Beck1, Aclander2, Altman3 et al. 1992Phys. Rev. Lett.Self Cite153110View full textAdd to dashboardCite

“…This mechanism masks the N-N correlations. Indeed, cross-section measurements of n + absorption on 3 He and 4 He have shown no sensitivity to short range N-N correlations [3]. This follows from the observation that for all angles o-0r + "<T-pp)^N^a(n + d^pp) ,…”

“…The size of this r=0 p-n pair is smaller than that of the real deuteron due to increased nuclear binding and the density of nucleons in 3 He is twice that of the deuteron [2].…”

“…The polarization of one of the final-state protons in the n"d"-+])p reaction within the 3 He system was measured. The results can be compared with the free process for which this polarization is simply related to the extensively measured analyzing power A^o of the timereversed ^pp-+dn reaction.…”