Experimental Study of Inclusive Pion Double Charge Exchange Reactions in the delta Resonance Region

摘要

An extensive experimental investigation of the inclusive pion double charge exchange (DCX) process has been carried out with pion energies in the region of delta (1232) excitation. The reactions exp 16 O( pi exp + , pi exp - )X and exp 40 Ca( pi exp + , pi exp - )X were studied with pion beam kinetic energies of 120, 150, 180, 210, 240 and 270 MeV. With negative pions, the reactions exp 16 O( pi exp - , pi exp + )X and exp 40 Ca( pi exp - , pi exp + )X were observed with incident beam energies of 180, 210 and 240 MeV. In addition, some exploratory measurements were performed with carbon and lead targets with 180 MeV pions. At each energy, outgoing pion spectra were measured at three to five angles in the range 25 exp 0 to 130 exp 0 . These spectrometer-based measurements featured an almost complete coverage of the outgoing pion spectrum, from 15 MeV to the maximum energy for inclusive DCX (typically 30 MeV below the beam energy). This coverage allowed a reliable integration of the spectra so that angular distributions and total cross sections for inclusive DCX could be obtained. The spectra exhibit a large degree of similarity over the range of energies, targets, and scattering angles investigated. DCX is of interest because, by charge conservation alone, at least two nucleons in a nucleus must participate in the reaction. It is thus a natural way to study multiple scattering, which is potentially an important part of pion-nucleus reactions. The data are discussed qualitatively in the context of a double quasi-free scattering mechanism, by comparing the results with a simple two step Fermi Gas model. A simple cascade model of pion-nucleus reactions is also developed and compared with the DCX data. 60 references. (ERA citation 09:019388)