Nuclear Physics A$$3 (1993) 585c-588c N U C L EAR North-Holland, Amsterdam PHYSICS A Elastic and Inelastic Scattering from 3H and 3He W.J. Briscoe a, D.B. Barlowb, B.L. Bermana, R.W. Caressa, K.S. Dhugaa, S.N. Dragic a, S.J. Greene c, D. Isenhower d, D. Knowlesa, D. Maceka, S.K. Matthews a A. Mokhtari a, B.M.K. Nefkensb, N.J. Nicholasa, C. Pillaib, J. W. Price b, M.E. Sadlerd, Ivo Slaus e, I. Supek e, M.F. Tarag na aCenter for NuclearStudies and Department of Physics,The GeorgeWashingtonUniversity, Washington, D.C. 20052 bDepartmentof Physics,The University of CaSfomia at Los Angeles,Los Angeles, CaSfomia 90024 cClinton P. AndersonMeson Physics Facility, LANL, Los Alamos,New Mexico 87545 dDepartmentof Physics, Ahilene ChristianUniversity, Abilene,Texas79699 eRuder BoskovicInstitute,Zagreb, Croatia Abstract We have measured the differential cross sections for the scattering of ~-+from 3H and 3He. The do's are normalized to ~+-d elastic scattedng measured under the same experimental conditions. Our newest measurements were performed at incident pion energies from 142 to 256 MeV and angles between 140° and 180 o. The momentum-transfer dependence of the cross sections was measured up to 11 fm -2, making it possible to explore differences in the matter form factors of 31-1 and 3He. 1. Introduction Our program of cross-section measurements for n+-3H and ~+3He elastic scattering in the angular ran¢le between 40 ° and 110° in the region of the AI~ resonance has yielded nte-resting resuts. 1,2 The most =mportant quantt'es measured are the superratio, R, the simple ratios, r 1 and r2, and the paired-unpaired nucleon ratios p+ and p_ (defined below). Deviation from unity beyond the Coulomb correction in R, r 1, and r2 indicates nuclearcharge-symmetry breaking (CSB). QCD implies a small intrinsic violation of charge ~ymmetry (CS) as a consequence of the up-down quark mass difference; this mass difference is responsible for a small CSB component n the N-N interaction via the mechanism of p--m mixing.3 A test of CS is made possible by measuring the superratio R = rl.r~ where r4 - dafn+3HI/da{n-3He) and r9 = da(n-3H)/da(rt+3He~. The superratio provid-es a test i -- • w ~ • . a ~ • of CS independent of the absolute beam ca ibr,~don and of the effic=ency and acceptance of the pion detector FI s also equal to p+-p_, where p+ = da{rc+3HI/da(n+3He) and o = d~(rc-3H)/do(~'3He). If CS is valid, R is equal to unity at "eve@ angle and at'all energies after corrections have been made for e ectromagnetic effects n our experiments these are small. In pion ~cattering on ght nuclei the A resonance plays a major role, s3Decifically the A- in ~" H scattering and the A ++ in ~+3He. Quark-mode ca culations g vea mass difference of about 5 MeV between the A ++ and the A', leading to a value of R ~ 1. 0375-9474/931506.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved.