Differential cross sections for π+p elastic scattering in the momentum region 1.2 to 2.3 GeV/c are presented for the center-of-mass angular range 0.9>cosθ>−0.9. Typically, 50 000 events were obtained at each of 16 momenta using magnetostrictive-readout wire spark chambers to detect the particles scattered from a liquid hydrogen target. The results are compared to those of the CERN-71 phase-shift analysis. The well-known dips at t≅−0.7 (GeV/c)2 and at u′=−0.2 (GeV/c)2 are observed. In addition, structure is seen at constant u′=−1.3 (GeV/c)2. The results of a pion attenuation study in iron are also presented.
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We present here the results of an experiment to study the polarization in p−p elastic scattering at the incident momenta 5.15, 7.00, and 12.33 Ge V/c, at t values ranging between - 0.5 and - 6.5 (GeV/c)2. At each momentum we observe a relative maximum in the polarization around t=−1.8 (GeV/c)2. At 12.33 GeV/c the data exhibit a double zero near t=−2.4 (GeV/c)2 and another relative maximum near t=−2.9 (GeV/c)2. The results are discussed in terms of the Chu-Hendry optical model.
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We present herein the initial results of a large-angle elastic p−p polarization experiment which is now in progress at the Argonne ZGS (Zero-Gradient Synchrotron) accelerator. Data for the incident proton momentum of 5.15 GeVc are presented for 30∘≲θc.m.≲90∘. These results, which extend to t≈−4.0(GeVc)2, represent the first high-statistics p−p polarization measurements for |t| values greater than ∼2.5 (GeVc)2. We observe a minimum in the polarization near t=−0.8(GeVc)2, a smooth increase in the polarization until a maximum is attained near t=−1.8(GeVc)2, and then a monotonic decline in the polarization until the value of zero is reached at θc.m.=90∘. The data are analyzed in terms of an optical model.
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Measurements of π±p, K±p, pp, and p¯p elastic scattering are presented for incident momenta of 3, 3.65, 5, and 6 GeVc and momentum transfers typically 0.03 to 1.8 GeV2. The angle and momentum of the scattered particle were measured with the Argonne Effective Mass Spectrometer for 300 000 events, yielding 930 cross-section values with an uncertainty in absolute normalization of ±4%. Only the K+ and proton data show any significant change in slope of the forward diffraction peak with incident momentum. The particle-antiparticle crossover positions are consistent with no energy dependence, average values being 0.14 ± 0.03, 0.190 ± 0.006, and 0.162 ± 0.004 GeV2 for π' s, K' s, and protons, respectively; these errors reflect both statistics and the ±1.5% uncertainty in particle-antiparticle relative normalization. Differences between particle and antiparticle cross sections isolate interference terms between amplitudes of opposite C parity in the t channel; these differences indicate that the imaginary part of the odd-C nonflip-helicity amplitude has a J0(r(−t)12) structure for −t<0.8 GeV2, as predicted by strong absorption models. The cross-section differences for K± and proton-antiproton are in qualitative agreement with the predictions of ω universality, the agreement improving with increasing energy. The corresponding quark-model predictions relating the π± and K± differences failed by more than a factor of 2. We have combined our π± cross sections with other data to better determine the πN amplitudes in a model-independent way; results of this analysis are presented.
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We present new measurements of the differential cross sections for K − p → K 0 n at 3, 4, 5 and 6 GeV/ c , where we have 248, 538, 761, and 376 events, respectively. Total cross sections are obtained by integrating the differential cross sections. We combine our data with other data from 3 to 15.7 GeV/ c to calculate an effective Regge trajectory for this reaction. Comparisons are made to predictions from exchange degeneracy and SU(3) sum rules.
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We have measured the Λ° polarization in π − p→ K°Λ° at 5 GeV / c , using a data sample of 3709 events. The polarization is positive for small t , passes through zero near t = −0.3 (GeV/ c ) 2 , and becomes large and negative at larger t , consistent with a value of −1.0 for t between −0.7 and −1.6(GeV/ c ) 2 .
THE AUTHORS FEEL THAT THE POLARIZATIONS > 1 IN ABSOLUTE VALUE ARE PROBABLY DUE TO STATISTICS RATHER THAN SYSTEMATIC ERRORS.
We report on an experiment to obtain differential cross sections for K+p elastic scattering in the vicinity of the possible exotic baryon, the Z1*(1900). The differential cross sections are based on typically 70 000 selected events in the angular region −0.9≤cosθc.m.≤0.9 at each of 22 momenta from 0.865 to 2.125 GeV/c. The data are intended for use in partial-wave analysis to search for the Z1*.
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We have measured the differential cross sections for the associated-production reactions π−p→K0Λ0 and π−p→K0Σ0 at 3, 4, 5, and 6 GeV/c, with a total of over 40 000 events. We find that both reactions have exponential forward peaks for −t≲0.4 (GeV/c)2, with no indication of forward-direction flattening or turnover; the slopes of the forward peaks show little if any variation with momentum; and the two cross sections are equal within experimental error from −t=1.2 (GeV/c)2 out to at least −t=2.0 (GeV/c)2.
INTERCEPT AND SLOPE FROM FIT TO D(SIG)/DT (PRESUMABLY FOR -TP < ABOUT 0.4 GEV**2).
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Differential cross sections for π±p, K±p, pp, and p¯p elastic scattering were measured at 3, 3.65, 5, and 6 GeVc for momentum transfers from 0.03 to 1.5 GeV2 using the Argonne effective mass spectrometer. Particular attention was paid to the relative particle-antiparticle normalization. The crossover points are consistent with no energy dependence, average values being 0.14 ± 0.03, 1.190 ± 0.005, and 0.160 ± 0.007 GeV2 for π's, K's, and protons, respectively.
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Differential cross sections for π + p and π − p elastic scattering have been measured with an accuracy of typically ±2% at 10 and 9 energies respectively in the range 88 to 292 MeV of lab kinetic energy.
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