Total Cross Sections and Angular Distributions forπ−pCharge Exchange in the Second and Third Resonance Regions

Abstract

We have analyzed data at nine different incident pion energies to study the cross sections and angular distributions in the reaction IT~ +P*TT° + n. The energies span the region of the second (600 MeV) and third (900 MeV) pion-nucleon resonances. The angular distributions indicate very little structure in the 600-MeV region, but in the 900-MeV region give strong evidence for a D 5/2 -F 5/2 interference in the T-\ state. The data reported here were obtained in a spark-chamber exposure at the Brookhaven Cosmotron designed to detect the production of neutral final states arising in n~p collisions. The preliminary charge-exchange angular distributions and cross sections presented herein represent about -| of the data we will obtain when we have scanned all our film.A schematic of the experimental setup is shown in Fig. lo A small liquid hydrogen target, 5 cm in diameter transverse to the beam and 4 cm along the beam, was located inside an anticoincidence shield composed of counters 3 and 5.

Phase-Shift Analysis of Pion-Nucleon Elastic Scattering below 1.6 GeV

“…The data come mainly from bubblechamber experiments with the exception of those concerning the neutral channels given by one counter 41 and two spark-chamber experiments. 26 ' 28 The references of the available data except for the very latest ones can be found in an earlier paper 43 and in Ref. 36.…”

“…28,23 The charge-exchange coefficients C n° of the expansion in Legendre polynomials have larger statistical and systematic errors than in the charged final states. However, their variation with energy is well defined (Fig.…”

Constraints onπNPhase-Shift Analysis f from Angular Distributions of Production Reactions

“…This selection may have led us astray in the case of the 550-MeV charge-exchange cross section where we used the measurement of Bulos et a/. 28 Their cross-section was about 2 mb lower than values quoted by several other authors, so that the reaction cross section plotted in Fig. 1 may be about 10% too high at this energy.…”