Coincidence measurements of the (π+,π0p) reaction atTπ+=165 MeV

Abstract

We report coincidence measurements of the ({pi}{sup +},{pi}{sup 0}{ital p}) reaction at a beam energy of {ital T}{sub {pi}}{sup +}=165 MeV. The neutral pions were detected by the LAMPF {pi}{sup 0} spectrometer and the protons by an array of plastic-scintillator telescopes. The resulting energy resolution for the determination of the excitation energy of the residual nucleus was about 10 MeV. Measurements were performed on {sup 16}O at laboratory angles {theta}{sub {pi}}{sup 0}=70{degree}, 80{degree}, 110{degree}, and 130{degree}. The cross section is predominantly quasifree. Its angular dependence follows the trend of the free single-charge-exchange cross section at back angles and is somewhat suppressed relative to this at more forward angles. Events corresponding to removal of {ital p}-shell nucleons were identified by their {pi}{sup 0} and {ital p} energies. The {pi}{sup 0} energy spectra for such events are compared to similar pion energy spectra for the {sup 16}O({pi}{sup {plus minus}},{pi}{sup {plus minus}}{ital p}) reactions; the cross-section ratios are consistent with ratios calculated from isospin coupling alone. {pi}{sup 0} energy spectra are also compared to predictions of {Delta}-hole model calculations; the calculations for events in which protons are detected at the conjugate quasifree angle underestimate the ({pi}{sup +},{pi}{sup 0}{ital p}) cross sections by 30--55more » %. At {theta}{sub {pi}}{sup 0}=110{degree} the ({pi}{sup +},{pi}{sup 0}{ital p}) reaction was also studied on Fe, Sn, and Pb. No significant {ital A} dependence of the cross section was observed.« less