We present results from a measurement of the differential cross sections for Σ−p, Ξ−p, and π−p elastic scattering at 23 GeV/c. We have collected samples of 6200 Σ−p events, 67 Ξ−p events, and 30 000 π−p events in the interval 0.10<|t|<0.23 (GeV/c)2.
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Significant two-particle correlations of dynamical origin are observed in 200 GeV/c π−p inclusive interactions. This is demonstrated by comparison with kinematic correlations calculated from an independent-particle-emission model. Two distinct correlation types are observed: (a) unlike-particle correlations with correlation length ∼ 1.3 rapidity units independent of azimuthal separation, and (b) like-particle correlations with correlation length ∼ 0.4 rapidity units which are observed only for small azimuthal separations.
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Using new data from 100 GeV c π − interactions, we find the energy dependence of the invariant cross-section in the target fragmentation (central) region to be consistent with an A + Bs − 1 2 (C + Ds − 1 4 ) behavior. The leading particle peak near x = + 1 exhibits a width in x which becomes smaller with increasing energy and an integrated cross section which is approximately energy independent.
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We have measured the multiplicities of pions produced in the collisions of π mesons with neon nuclei at bombarding momenta of 10.5 and 200 GeV/c. The diffractive production of pions is clearly separable. If one excludes the diffractive part, the pion multiplicity obeys the same Koba-Nielsen-Olesen scaling as found previously for π−−p collisions. This fact would seem to indicate the validity of an energy-flux or collective-variable description of the production process. A surprisingly large number of energetic protons (> 1 GeV/c lab momentum) are found to be produced in π-Ne collisions.
Elastic and diffractive events removed.
Momentum spectra for forward Σ− and Ξ− production by protons on beryllium are presented. Σ− production data for two primary proton momenta are compared to test scaling of the invariant cross section. In addition, the observed single-particle momentum distributions are compared with single-particle spectra from other inclusive reactions initiated by protons.
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The differential cross section d σ d t′ for the charge-exchange process π + p → π 0 ( π + p) at 8, 16 and 23 GeV/ c is presented for several regions of the π + p effective mass. It is found that the dip at t ′ ≈ 0.6 (GeV/ c ) 2 which is observed in the Δ(1236) mass band becomes a less pronounced structure in the higher mass regions. However, while the slope of the d σ d t′ distributions in the near-forward direction decreases strongly with increasing π + p mass, there is no evidence that the observed structure moves to higher values of t ′ as the π + p mass increases. These results are consistent with a Regge-exchange picture where the position of the dip is determined by the exchanged trajectory, but are inconsistent with a simple geometrical picture.
TP DEPENDENCE FOR FOUR <PI+ P> MASS INTERVALS.
The differential cross section has been measured for the reaction γ +p→ π o + p at the Bonn 2.5 GeV electron synchrotron in the energy range from 0.55 to 2.2 GeV at a c.m.angle of 120 degrees.
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Results are reported of a study of the hypercharge reactions K − p → ωΛ (la), K − p → φΛ (lb), K − p → φ ∑ o (lc), K − p → ϱ o Λ (ld), K − p → ϱ o ∑ o (le), K − p → ϱ − ∑ + (lf) in a 12 events/ub bubble chamber experiment using K − mesons of 4.25 GeV/ c momentum. Total and differential cross sections are presented as well as the density matrix elements of the peripherally produced vector meson and (except for reaction (1f)) the hyperon polarization. For reactions (1a) and (1b) an amplitude analysis is performed. The mass and the width of the ϱ−, φ− and f-meson have been determined.
FURTHER DATA FROM THIS COLLABORATION ON THESE REACTIONS WITH TEN TIMES BETTER STATISTICS ARE PRESENTED IN M. J. LOSTY ET AL., NP B133, 38 (1978).
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We present evidence for the decay A20→ωπ+π0 with a branching ratio Γ(A2→ωππ)Γ(A2→ρπ)=0.28±0.09 and for the decay ω(1675)→ωπ+π− with a branching ratio Γ(ω(1975)→ωπ+π−)Γ(ω(1675)→ρπ)=0.47±0.18. Evidence is given for an intermediate B(1235)π state in the ω(1675) decay.
FITTED WITH BREIT-WIGNER RESONANCES PLUS BACKGROUND.
BACKGROUND SUBTRACTED TP DISTRIBUTIONS.
p¯p elastic scattering at an incident beam momentum of 2.85 GeV/c is analyzed using 18 412 events. The simple exponential parametrization of the diffraction peak is found to be a poor representation of the data. Two other parametrizations are tried and the estimates of dσdt at t=0 and of the slope of the diffraction peak are found to differ significantly between various parametrizations. It is found that two coherent interfering exponentials are able to represent the differential cross section over the range 0.04≤|t|≤1.8 (GeV/c)2 with a χ2 probability of approximately 40%.
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