Multinucleon pion absorption on {sup 4}He into the pppn final state
- University of Basel, CH-4056 Basel (Switzerland)
- University of Karlsruhe, D-76128 Karlsruhe (Germany)
- LAMPF, Los Alamos, New Mexico 87545 (United States)
- University of Maryland, College Park, Maryland 20742 (United States)
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
- New Mexico State University, Las Cruces, New Mexico 88003 (United States)
- Old Dominion University, Norfolk, Virginia 23529 (United States)
- Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)
- University of Zagreb, HR-10000 Zagreb (Croatia)
Results from a 4{pi} solid angle measurement of the reaction {pi}{sup +4}He{r_arrow}pppn at incident pion energies of T{sub {pi}{sup +}}= 70, 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the reactions where three nucleons participate, leading to energetic (ppp) or (ppn) final states, and for states where four nucleons are involved (pppn). The two three-nucleon absorption modes were investigated in particular, and an energy dependent isospin ratio of the cross sections of {sigma}{sub ppn}/ {sigma}{sub ppp}=3.6{plus_minus}1.3, 2.6 {plus_minus}0.5, 1.8{plus_minus}0.3, 1.4{plus_minus} 0.2, and 1.8{plus_minus}0.6 was determined from 70 to 330 MeV. The differential cross sections were described by a complete set of eight independent variables and compared to simple cascade and phase space models. From this analysis the contributions from initial state interactions to the multinucleon absorption cross sections were found to be more important at higher pion energies, while those from final state interactions are stronger at lower energies. However, both mechanisms combined were found to account for not more than one-third of the total pppn multinucleon yield. The remaining strength is reasonably well reproduced by phase space models, but shows a dependence on the incident pion{close_quote}s orbital angular momentum. The isospin structure of the (ppp) and (ppn) final states is not understood, nor are some structures in their distributions. The four-nucleon yield (pppn) was found to be weak (1{endash}8{percent} of the total absorption cross section) and shows no evidence for a {open_quotes}double- {Delta}{close_quotes} excitation. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 542706
- Journal Information:
- Physical Review, C, Vol. 56, Issue 4; Other Information: PBD: Oct 1997
- Country of Publication:
- United States
- Language:
- English
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