Upper limits are presented for the differential cross section in the reactions π−p→K+Σ− and π−p→K+Y*−(1385) with small momentum transfer from π− to K+.
EXTRAPOLATED TO T=0 ASSUMING SLOPE IS 5 GEV**-2.
ISOTROPIC ANGULAR DISTRIBUTION ASSUMED IN GIVEN T-RANGE.
Measurements of the differential cross section for the reactions π+p→K+Σ+ and π+p→K+Y*+(1385) are reported at 3.5, 3.75, 4.0, 4.25, 4.5, 4.75, 5.0, 6.0, 10.0, and 14.0 GeV/c. Polarization in π+p→K+Σ+ is also reported at 6.0, 10.0, and 14.0 GeV/c. At small |t|, the cross section for π+p→K+Σ+ is well described by an exponential Aebt with slopes in the range b≈8−10 (GeV/c)−2; for |t|>0.5 (GeV/c)2 this slope decreases considerably. The cross section for π+p→K+Y*+(1385) is well described for |t|>0.2 (GeV/c)2 by a single exponential of slope about half that for π+p→K+Σ+; there is no break near |t|>0.5 (GeV/c)2. We observe a dip in this cross section near t=0. The polarization in π+p→K+Σ+ is consistent with zero for |t|<0.4 (GeV/c)2 and becomes large and positive for larger |t|.
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We present differential cross-section data for the reaction π+p→π+p near 180° in the center-of-mass system at beam momenta between 3.25 GeVc and 10 GeVc.
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In a sample of 108 563 pictures taken with the Fermilab 30-inch hydrogen bubble chamber, exposed to a 360-GeV/c π− beam, we have observed 19 453 interactions in a selected fiducial region. The observed charged multiplicity distribution has been corrected for the effects of scan efficiency, errors in prong count, missed close-in vees, secondary interactions, and neutron stars and for Dalitz pairs. The two-prong events have been corrected for losses at low −t. The total cross section is measured to be 25.25 ± 0.35 mb, and the elastic cross section is 3.61 ± 0.11 mb with an exponential slope of (8.82 ± 0.30) (GeV/c)−2. The average charged-particle multiplicity for inelastic events is 8.73 ± 0.04, and the second moment f2 is measured to be 9.83 ± 0.23.
SYSTEMATIC CORRECTIONS INCLUDED IN ERRORS.
FROM FIT, FORWARD D(SIG)/DT = 31.84 +- 0.68 MB/GEV**2, AND AGREES WITH OPTICAL POINT FROM MEASURED TOTAL CROSS SECTIONS.
A high-mass Δ resonance is observed in several final states from π + p interactions at 10.3 GeV/ c . We obtain fitted mass and width values for this structure of 1871 ± 22 MeV and 205 ± 43 MeV, respectively. The branching ratios for decays to π + p, p π + π 0 , n π + π + and Σ + K + are found to be 0.48 ± 0.15, 0.26 ± 0.07, 0.24 ± 0.07 and 0.03 ± 0.01, respectively. The Δϱ, Δω differential cross sections and the ϱ 0 density matrix elements are examined.
DEL(1950B) (OR DEL(1880B)) FITTED WITH BRIET-WIGNER RESONANCE AND POLYNOMIAL BACKGROUND.
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The major production channels of four-prong final states resulting from π+p interactions at a center-of-mass energy of 4.5 GeV are studied. In addition to total production cross sections, comprehensive listings of partial and resonance production cross sections are also given for each final state of interest. All final states, including nπ+π+π+π−, are found to exhibit copious resonance production.
PARTIAL CROSS SECTIONS FROM PI+ P --> PI+ P PI+ PI-.
PARTIAL CROSS SECTIONS FROM PI+ P --> PI+ P PI+ PI- PI0.
Cross sections, differential cross sections, single and joint spin-density matrix elements are given for the reactions π+p→(ρ0, ω)Δ++ at 10.3 GeV/c. Correlations between the vector-meson and the Δ++ decay angular distributions are observed. A discussion of the results in terms of particle exchange, SU(3) symmetry, quark additivity, and the equal-phase hypothesis is presented. The amplitudes for the process π+p→ρ0Δ++ are extracted by a model-dependent analysis and compared with current theoretical predictions.
P-WAVE BREIT-WIGNER RESONANCES PLUS BACKGROUND USED WITH SLICE TECHNIQUE.
FROM RESONANCE OVERLAP REGION WITH BACKGROUND SUBTRACTED AND NORMALIZED TO TOTAL CROSS SECTION.
FROM RESONANCE OVERLAP REGION WITH BACKGROUND SUBTRACTED AND NORMALIZED TO TOTAL CROSS SECTION.
Inclusive and semi-inclusive cross sections for gp0 production in 100, 200, and 360 GeV/c π−p interactions are presented. Differential cross sections for ρ0 production as functions of c.m. rapidity and transverse momentum are compared with the corresponding differential cross sections for pion production. Effects of various methods of estimating background on the values obtained for ρ0 production cross sections are discussed. About 10% of the final-state charged pions appear to come from ρ0 decay. Thus, while ρ0 production and decay is a significant source of final-state pions, other sources must contribute the majority of the produced pions.
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Inclusive cross sections for π 0 , K s 0 , Λ 0 and Λ 0 production in 100, 200 and 360 GeV /c π − p interactions are presented and compared with data at other energies. Invariant cross sections for γ, K s 0 , Λ 0 and Λ 0 production are presented in terms of Feynman x , the rapidity y , and transverse momentum squared, p T 2 . A comparison of the observed γ spectrum is made with the spectra computed assuming that the π 0 momentum distribution is identical to that of the observed π + or π − .
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Inclusive e+e− production in 17-GeV/c π−p collisions has been measured. An excess of e+e− pairs over those from known sources for 0.1<~mee<~0.6 GeV and x<0.5 was found. No evidence is found for enhancements in specific final states involving electrons and photons or charged particles. The photon multiplicity associated with these pairs is measured.
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