Total cross sections of π+ and π− mesons on protons and deuterons have been measured in a transmission experiment to relative accuracies of ±0.2% over the laboratory momentum range 0.46-2.67 GeV/c. The systematic error is estimated to be about ±0.5% over most of the range, increasing to about ±2% near both ends. Data have been obtained at momentum intervals of 25-50 MeV/c with a momentum resolution of ±0.6%. No new structure is observed in the π±p total cross sections, but results differ in several details from previous experiments. From 1-2 GeV/c, where systematic erros are the smallest, the total cross section of π− mesons on deuterons is found to be consistently higher than that of π+ mesons by (1.3±0.3)%; about half of this difference may be understood in terms of Coulomb-barrier effects. The πd and πN total cross sections are used to check the validity of the Glauber theory. Substantial disagreements (up to 2 mb) are observed, and the conclusion is drawn that the Glauber theory is inadequate in this momentum range.
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We report measurements of the polarization parameters in π+p and π−p elastic scattering at an incident momentum of 100 GeV/c. The results cover the range 0.18<~−t<~1.4 GeV2 and are in agreement with current Regge-model predictions.
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The π − p→K 0 λ polarization has been measured at 5 GeV/ c in the range 0<− t <1.4 (GeV/ c ) 2 . The polarization is small for − t ⪅0.4 (GeV/ c ) 2 , becoming negative at the higher values of − t .
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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.
The production of the f 0 (1270) has been studied in the reaction π − p → π + π − n at 12 and 15 GeV/ c in the momentum transfer range 0.02 to 0.80 GeV 2 . Differential and total cross sections for the reaction π − p → f 0 n have been determined. The f 0 decay density matrix elements have been evaluated requiring all the matrix eigenvalues to be non-negative. The relative unnatural and natural parity exchange contributions to the f 0 production have been studied. The results are compared with a Regge exchange model formulated in terms of the pion and A 2 exchanges including cut contributions.
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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.
Evidence for the backward production of the B(1235) meson in the final state π+p→pfπ+ω at 11.46 GeV/c with σ(|u′|<1.5 GeV2)=1.28±0.26 μb is presented. When nucleon exchange is assumed to dominate, estimates for the SU(3) mixing parameter FD as well as the B coupling to the nucleon-antinucleon are given. Some indication of a narrow enhancement at M(π+ω)≃1.03 GeV/c2 is seen, but confirmation of this as a resonant state is not yet possible.
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The reaction π − p → ω n has been studied at 8 and 12 GeV / c incident momenta with the CERN Omega spectrometer using a neutron time of flight trigger. The differential cross sections and the ω-decay density matrix elements are presented as functions of the momentum transfer squared − t in the range of 0.02 to 0.80 GeV 2 . The data are used to evaluate the intercept and slope of both the natural and unnatural parity exchange trajectories. Regge exchange amplitude factorisation tests involving the reaction π N → ω N are investigated.
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We present results of a hybrid-bubble-chamber experiment examining the reaction π+p→π+pK+K− at an incident momentum of 11.46 GeV/c. The total cross section for this channel is determined to be 87.2±6.4 μb. A partial-wave analysis of the K+π+K− system reveals no unambiguous evidence of resonant activity, although mass enhancements are noted in the JP=0− κ¯K+ (S wave), JP=2− fπ (S wave), and JP=2−, K¯*0(892)K+ (P wave). This is the first published report of the relative phases of the waves seen in this reaction. We comment on the influence this channel may have on A1 and A3 production.
NOTE ERROR IN ABSTRACT IS +- 6.4 BUT TEXT QUOTES +- 9.3. FIGURE LOOKS CLOSER TO +- 6.4.
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The reaction π−p→X−p, X−→ηπ−, η→γγ has been studied in an optical spark-chamber experiment at the Argonne ZGS (Zero Gradient Synchrotron) at a beam momentum of 6.0 GeV/c and with 0.27≤|t|≤0.42 (GeV/c)2. The ηπ mass spectrum contains about 1400 events in the mass range 0.80<M(ηπ)<1.55 GeV/c2, and is dominated by approximately 1000 events of the type A2−→ηπ−. No structure is discernible within the A2 mass spectrum for an experimental resolution of 7.1 MeV/c2 [16.7 MeV/c2 FWHM (full width at half maximum)]. A single D-wave Breit-Wigner distribution fits the data with a high confidence level, yielding for the A2 the parameters M0=1.323±0.003 GeV/c2 and Γ0=0.108±0.009 GeV/c2. The angular distribution of the decay A2−→ηπ− is analyzed and the resultant density matrix elements have the values ρ11=0.45±0.02, ρ1−1=0.45±0.04, and ρ00=0.09±0.04. All other elements are consistent with zero. Finally, the missing-mass spectrum in the region of the A2 is presented. A signal of 230 events above background per 5-MeV/c2 interval is observed at the A2 peak, with a signal to background ratio of greater than 1:1. A single D-wave Breit-Wigner distribution together with a quadratic background fits the data well, with the parameters for the A2 being M0=1.324±0.003 GeV/c2 and Γ0=0.104±0.009 GeV/c2. Both A2 mass spectra are incompatible with the dipole shape.
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THIS FIT ASSUMES ALL OTHER DENSITY MATRIX ELEMENTS (RHO(2M) AND RE(RHO(10))) ARE ZERO SINCE THEY ARE QUITE CONSISTENT WITH ZERO IN A FULL FIT. QUOTED ERRORS INCLUDE SYSTEMATIC ERRORS, WHILE STATISTICAL FITTING ERRORS ARE SHOWN SEPARATELY.
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