Results of high-transverse-momentum charged-hadron production in 400-GeV/c proton-proton and proton-deuteron collisions and 800-GeV/c proton-proton collisions are presented. The transverse-momentum range of the data is from 5.2 to 9.0 GeV/c for the 400-GeV/c collisions and from 3.6 to 11.0 GeV/c for the 800-GeV/c collisions; the data are centered around 90° in the proton-nucleon center-of-momentum system. Single-pion invariant cross sections and particle ratios were measured at both energies. The results are compared to previous experiments and the Lund model.
We present high-statistics results on the reactions a+p→c+X where a and c can be any of π±, K±, p, or p¯. The data were taken at 100 and 175 GeV/c incident momenta using the Fermilab Single-Arm Spectrometer operated over the kinematic range 0.2<x<1.0 and pt<~1.0 GeV/c. Investigating the x dependence of the data, we find agreement with a quark-parton picture, namely the cross sections have a power-law behavior in 1−x independent of pbeam and pt.
Full angular distributions of the polarization parameter in elastic K+p scattering at 1.37, 1.45, 1.60, 1.71, 1.80, 1.89, 2.11, and 2.31 GeV/c are presented. These data were obtained in an experiment at the Zero Gradient Synchrotron using a polarized proton target with arrays of scintillation and Čerenkov counters to detect the scattered particles.
We report results from a study of Λ0 polarization in the exclusive reaction pp→pf(Λ0K+) at 800−GeV/c. We observe a dependence of the polarization on the Λ0K+ invariant mass with large (+71%) positive polarization at small mass (1.63−GeV/c2) and large (−43%) negative polarization at large mass (2.75−GeV/c2). This observation confirms the result of the CERN ISR R608 experiment and extends the range over which the effect is observed. The strong dependence of the polarization on the Λ0K+ invariant mass suggests that the origin of the polarization is closely related to the production dynamics of the diffractively produced Λ0K+ system.
We report measurements of the ratios K+π+, pπ+, K−π−, p¯π−, π−π+, K−K+, and p¯p for hadrons with 0.19<xt<0.62 produced in p−Be and p−W collisions at s=38.8 GeV. The K+π+ ratio at high xt gives the fragmentation-function ratio DuK+Duπ+ at high z. The high-xt K−π− ratio gives an upper limit for DdK−Ddπ− at high z. The pt dependence of pπ+ suggests that scattered constituent diquarks are the primary source of protons with pt<6 GeV/c. We also present species correlations in high-mass h+h− pairs. Strong K+K− and pp¯ correlations were observed.
Measurements of correlations of nearly back-to-back hadrons produced at a large transverse momentum in s=38.8 GeV proton-proton collisions are presented and compared to previous results with a beryllium target. The correlations of identified unlike-sign hadron pairs in ratio to the correlation for all unlike-sign pairs are compared with predictions of the Lund model. These predictions differ from the data.
We derive cross-sections for the inclusive productiion in p̄p interactions at 100 GeV /c of π 0 , K S 0 and Λ 0 Λ 0 of 91.5±5.7 mb, 5.2±0.4 mb and 4.8±0.4 mb respectively, which are all higher than pp cross-sections at energy. We find indications that these differences can be attributed to “annihilation” processes.
We report evidence for the Cabibbo-suppressed decay of the charm baryon Λ c + into the final state pK − K + . The analysis is performed on data collected by high energy photoproduction experiment E687 during the 1990–1991 Fermilab fixed target run. The branching ratio of the decay Λ c + → pK − K + relative to the non-suppressed Λ c + → pK − π + is measured to be BR( pK − K + / pK − π + ) = 0.096 ± 0.029 ± 0.010. The upper limit of the decay into pø relative to the inclusive pK − K + decay is measured to be BR( pø / pK − K + < 58% at the 90% confidence level.
The decay Λb0→J/ψ Λ is observed in 110 pb−1 of pp¯ collisions taken at s=1.8 TeV. These data are used to measure a Λb0 mass of 5621±4(stat)±3(syst) MeV/c2, and a mass difference between the Λb0 and the B0 of 340±5(stat)±1(syst) MeV/c2. The production cross-section times branching fraction for the decay Λb0→J/ψ Λ relative to that for the decay B0→J/ψ KS0 has been measured to be 0.27±0.12(stat)±0.05(syst).
We report a measurement of the ratios of the decay rates of the B~+, B~0 and B~0_s mesons into exclusive final states containing a J/psi meson. The final states were selected from 19.6 pb~{-1} of p-pbar collisions recorded by the Collider Detector at Fermilab. These data are interpreted to determine the bquark fragmentation fractions f_u, f_d and f_s. We also determine the branching fractions for the decay modes B~+ --> J/psi K~+, B~+ --> J/psi K~*(892)~+, B~0 --> J/psi K~0, B~0 --> J/psi K~*(892)~0 and B_s~0 --> J/psi phi(1020). We discuss the implications of these measurements to B meson decay models.
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