Measurement of the Recoil Proton Polarization in Elasticπ−pScattering atTπ=

Abstract

We report here results for the recoil proton polarization in negative pion-proton elastic scattering as measured with a carbon plate spark chamber. The results for positive pion scattering have been already published. 1 The experimental setup was described in reference 1. In the second part of the present paper will also be given preliminary results of a calibration run, made to verify the values adopted for the analyzing power of the chamber. 7r"7? polarization results.-(a) 410 MeV. Table I gives the results based on 20 000 elastic scattering events. The polarization has been computed by the maximum-likelihood method. The given value is that which maximizes the product 2 i = l Figure 1 shows the horizontal and vertical asymmetries obtained for each angular position of the chamber, and the average polarization.(b) 492 MeV. For this energy, about 25 000 elastic events were selected. The results are given in Table II and Fig. 2.At both energies the vertical asymmetries are consistent with zero and the measurements made with the chamber at right and at left of the beam are in good agreement.Check of the analyzing power of the chamber.-The polarization in the proton-carbon elastic scattering at 220 MeV is known with high accuracy from measurements at Rochester. 3 The test was made with incident protons of this energy using an experimental setup similar to that for the pion-proton measurement. The hydrogen target was replaced by a carbon plate 1.7 cm thick. The chamber was placed at llc5° relative to the incident beam and triggered for each proton interacting in the target Table I. Polarization for T 7r = 410 MeV. We give, for each interval of 0.1 in the cosine of the pion scattering angle in the cm. system, the polarization as measured with the chamber at the right and at the left of the incident beam, and the average polarization. The error is statistical only and corresponds to the root mean square of the likelihood curve. Left position PolarizationRight position

Scattering ofπ−Mesons in the Momentum Range 0.643-2.14 GeV/cfrom a Polarized Proton Target

“…3. The figure also shows the results of Bareyre et a/., 11 Chamberlain et a/., 13 Duke et al,u and Suwa et a/. 6 There is, in general, good agreement between these earlier measurements and the present work.…”

“…It is interesting that seven of the nine new resonances proposed by Donnachie et al 17 fall within this range as well as several of those more firmly established. In fact, over the total range of this experiment all partial waves up to Z=3, and in both isotopic spin states, resonate at least once, if all the resonances listed by Donnachie et al 11 are included. In view of this, it is also interesting that above 0.9 GeV/c all the coefficients, at least up to Z> 6 , show a similar pattern of behavior, and there are no striking differences between the odd-and even-order coefficients such as would be expected if only a few well-separated resonant states were present in this region of momentum.…”

“…16 P.Bareyre, C. Bricman, and G. Villet, Phvs. Letters 18, 342, (1965); P Bareyre, C. Bricman, and. G. Villet, Phys.…”

Phase-shift analysis of ?+ p-scattering in the energy region from 194 to 600 MeV

“…The procedures for interpolation of cross sections and polarizations as well as for excluding unreliable experimental points were performed automatically on the basis of the LNPI bank of data on nN scattering. In the PSA we made use of all the data on a(O) and P(O) obtained in LNPI [1,2] as well as of the results published in [11][12][13][14][15][16][17][18][19]. In Ref.…”