The polarization of the recoil proton in π+p and π−p elastic scattering using a liquid-hydrogen target has been measured for backward angles at 547 and 625 MeV/c. The scattered pion and recoil proton were detected in coincidence using the large-acceptance spectrometer to detect and analyze the momentum of the pions and the JANUS polarimeter to identify and measure the polarization of the protons. Results from this experiment agree with other measurements of the recoil polarization, with analyzing-power data previously taken by this group, and with predictions of partial-wave analyses.
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The p¯4He annihilation cross section averaged over the interval 40–50 MeV/ c has been measured using a streamer chamber in a magnetic field. The measured value is 1342±250 mb. It agrees with a behaviour like 1/ p of the annihilation cross section. Our result has been obtained at the lowest momentum achieved till now in measurements of antiproton annihilation in flight.
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The longitudinal and transverse momentum distributions of protons and π±-mesons, produced and pp interactions at close energy (22-24 GeV), are compared. The existence of a difference between these (P<1.2 GeV/c in laboratory system) and for mesons accompaying them, is shown. The observed difference increases with increasing the multiplicity of charged particles. For π+ mesons it increases with decreasing the momentum of accompaying protons. These effects do not practically exist for π- mesons
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We present results on the photoproduction of 10 000 charmed particles from the 108 recorded triggers of Fermilab experiment E691. The total cross section for the photoproduction of D0 and D+ particles (and antiparticles) for xF>0.2 is measured to be 3.88±0.06±0.40 μb/Be nucleus at 〈Eγ〉=145 GeV. We have also measured the relative production of different charmed particles, their pT2 and xF distributions, and the energy dependence of the total charm cross section. The mean pT2 is 1.16±0.04 GeV2/c2 and the ratio of charm cross sections at 200 and 100 GeV is 1.96±0.24. Results of fits to the xF distribution are also reported.
D0/AD0 cross section from K-PI+/K+PI- decay mode.
D+/D- cross section from K-2PI+/K+2PI- decay mode.
D*+/D*- cross section from D0<K-PI+>PI+ + CC decay mode.
We present the results of a study of muon pairs with invariant masses greater than 4.05 GeV/c2 produced in high-energy pion-nucleon interactions. The production cross section together with the inferred pion and nucleon structure functions are reported and compared with other experiments and with QCD predictions. The transverse-momentum distributions are also presented. Finally, the full angular distribution in cosθ and φ is given as a function of mass, Feynman x, and transverse momentum. Longitudinal photon polarization is seen in the lower portion of the mass range at high xπ. This result is compared with a higher-twist model.
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Interacting beam cross-section.
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The transverse-momentum spectra of lambdas (Λ0, Λ¯0) produced in the central region has been measured in p¯p collisions at s=1.8 TeV at the Fermilab Collider. We find that the average transverse momentum of the lambdas increases more rapidly with center-of-mass energy than that of charged particles, and the ratio of lambdas to charged particles increases as a function of center-of-mass energy.
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Using the ARGUS detector at the DORIS II storage ring at DESY, we have observed a charmed meson of mass (2455±3±5) MeV/c2, decaying to D + π − . The natural width of this state is determined to be (15 +13+5 −10−10 ) MeV c 2 . The fragmentation function is hard, as expected for a leading charmed particle from nonresonant e + e − annihilation. Analysis of the decay angular distribution supports the hypothesis that the observed state is an L =1 excited charmed meson with spin-parity 2 + .
Corrected to zero momentum using fragmentation function of Peterson et al., PR D29 (83) 105.
Data read from graph.
Results on the reaction γγ → π + π − π 0 π 0 are presented. There is clear evidence for correlated ϱ + ϱ − production. The cross section is much lower than for γγ → ϱ 0 ϱ 0 .
Results using 3 parameter fit (rho+ rho-, rho+- pi+- pi0, and non-resonant 4pi) to data.
Results using 2 parameter fit (rho+ rho-, and non-resonant 4pi) to data.
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