The π−+p→π0+n differential cross section at 180° has been measured for 52 values of π− momentum from 1.8 to 6.0 GeV/c using a constant-geometry detection system. The average statistical uncertainty is ∼5% and the systematic uncertainty is ∼10%. The details of the experiment and the data analysis are discussed. The data are compared with those of other experiments with which they are generally in agreement. One set of data disagrees with those presented here and a possible reason for this is discussed. A five-parameter fit of the predictions of a dual-resonance model to our data gave excellent agreement. The differential cross sections at 180° for π±p elastic scattering have been compiled and the moduli and relative phase of the T=12 and T=32 pion-nucleon s- and u-channel amplitudes (|A12|, |A32|, and cosδ) have a minimum at u=0.4 GeV/c and, in the s channel, a corresponding minimum at s=2.2 GeV/c.
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We have determined the pion charge exchange cross section on hydrogen for π ° mesons emitted at 180° by measuring neutron time-of-flight. Using known values of the p-wave phase shifts we have deduced the contribution of the s-wave. We obtain a value for the quantity a 1 − a 3 (in h = c = m =1 units where m is the pion mass) =0.270±0.014 in agreement within the errors with recent theoretical calculations. We also find a value of 114±55 μb / sr for the cross section in the center of mass system for radiative pion capture at 22.6 MeV (gamma ray emitted at 180°).
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Measurements of the polarization parameter of the reactions π − p → π 0 n and π − p → η n at 4.90 and 7.85 GeV/ c and for a squared four-momentum transfer − t ranging from 0.1 to 2.0 (GeV/ c ) 2 have been achieved by using a butanol polarized proton target and detecting only the two γ's from the neutral meson decay. The background due to events involving bound protons has been separately measured and subtracted out. A large positive polarization has been found for the reaction π − p → π 0 n. It is consistent with other pion-nucleon scattering data connected by isospin conservation. The polarization for the reaction π − p → η n is not significantly different from zero within the large experimental errors.
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An experiment designed to study the π−p total neutral cross section and its breakdown into several channels has been performed at eleven incident pion momenta ranging from 654 to 1247 MeV/c. Angular distributions for the charge exchange π0 and for η0 production are given in terms of Legendre-polynomial expansion coefficients. Forward and backward differential cross sections are presented for the charge-exchange channel and comparisons with recent dispersion-relation predictions for the forward cross section are made.
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