We have measured the inclusive production of J ψ in 16 and 22 GeV π − copper collisions in a wide aperture magnetic spectrometer. The cross section per Cu nucleus for x > 0 corrected for branching ratio is 64 ± 38 nb at 16 GeV and 196 ± 38 nb at 22 GeV. As threshold is approached, the mean values of the Feynman x distribution increase and the cross section for J ψ production drops steeply. This can be understood in terms of the quark-fusion model where the antiquark content of the pion makes an increasingly significant contribution as M 2 s increases.
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We present data on dimuon production by 16 GeV π + and π − beams on a Cu target. From the data we evaluate, for π − N collisions, the fraction of dimuon events that originate from the annihilation process q q ̄ → μ + μ − . Using this information the experimentally determined cross section for the process q q ̄ → μ + μ − is observed to be in agreement with the Drell-Yan model over a wide range of incident energies. The observed deviations from exact scaling are of the order predicted by QCD calculations for the Q 2 -dependence of the nucleon and the pion structure function.
CROSS SECTIONS ARE PER COPPER NUCLEUS.
CROSS SECTIONS ARE PER COPPER NUCLEUS.
We have studied backward baryon and meson production in π−p→pπ+π−π− at 8.0 GeV/c using a streamer chamber triggered by the detection of a fast forward proton. Our data sample (1227 events) displays prominent N*ρ and N*f quasi-two-body production. These states are investigated with regard to the peripheral nature of the production mechanism and sequential decay of the excited baryon and meson systems. The quasi-two-body production of N*ρ and N*f intermediate states is consistent with u-channel proton exchange as the dominant production mechanism. In the π+π−π− mass distribution we observe a 3- to 4- standard-deviation enhancement at M3π=1897±17 MeV/c2 with full width at half maximum = 110 ± 82 MeV/c2, but find no but find no evidence for backward A1 or A2 production. We observe Δ++(1232) production in the pπ+ effective mass distribution.
THESE VALUES ASSUME ONLY RHO(11) IS NON-ZERO. VALUES FOR OTHER RHO(MM) ARE QUOTED IN PAPER. SIG ERRORS INCLUDE OVER-ALL NORMALIZATION UNCERTAINTY, BUT NO BACKGROUND CORRECTIONS HAVE BEEN MADE.
STATISTICAL ERRORS ONLY, NO BACKGROUND CORRECTION.
STATISTICAL ERRORS ONLY, NO BACKGROUND CORRECTION.
A measurement of the strong coupling constant α S is presented using hadronic events produced in e + e − annihilations at s =58.0 GeV from the AMY detector at TRISTAN. The measurement is based on comparisons of the distributions of thrust, heavy jet mass, total jet broadening, wide jet broadening, and energy-energy correlations with QCD calculations resummed up to next-to-leading-logarithms matched with the O ( α S 2 ) perturbative calculation. Combining the results of the individual evaluations, we find α S (58 GeV )=0.132±0.006 .
No description provided.
The photon structure function F 2 γ has been measured at an average Q 2 value of 6.8 GeV 2 using data collected by the AMY detector at the TRISTAN e + e − collider. The measured F 2 γ is compared with several QCD-based parton density models.
No description provided.
A study of e + e − annihilations into final states containing a single energetic photon with no accompanying particles is made at a center of mass energy of 57.8 GeV. The measured cross section is consistent with expectations from standard model processes and is used to set limits on the masses of the scalar electron and photino particles predicted by supersymmetry theories. If the photino is assumed to be massless, the 90% confidence level lower limit on the mass of the degenerate scalar electron is 65.5 GeV. If the results of all the single photon experiments are combined, this lower limit increases to 79.3 GeV.
No description provided.
The inclusive cross section for the production of charmed D<sup loc="post">∗±</sup> mesons in two-photon processes is measured with the AMY detector at the TRISTAN e<sup loc="post">+</sup>e<sup loc="post">−</sup> collider. D<sup loc="post">∗±</sup> mesons are identified from the distribution of charged-particle transverse momenta relative to the jet axis. A data sample corresponding to an integrated luminosity of 176 pb<sup loc="post">−1</sup> at a center-of-mass energy of 58 GeV is used to determine a cross section σ(e<sup loc="post">+</sup>e<sup loc="post">−</sup> → e<sup loc="post">+</sup>e<sup loc="post">−</sup>D<sup loc="post">∗±</sup>X) = 270 ± 49(stat) ± 38(syst) pb. The results are compared with theoretical expectations based on the Vector Meson Dominance, direct quark-parton model, and resolved photon processes.
No description provided.
Reduced acceptance region to compare with the TOPAZ results.
The forward-backward asymmetry in e + e − → b b at s = 57.9 GeV and the b-quark branching ratio to muons have been measured using neural networks. Unlike previous methods for measuring the b b forward-backward asymmetry where the estimated background from c -quark decays and other sources are subtracted, here events are categorized as either b b or non- b b events by neural networks based on event-by-event characteristics. The determined asymmetry is −0.429 ± 0.044 (stat) ± 0.047 (sys) and is consistent with the prediction of the standard model. The measured B B mixing parameter is 0.136 ± 0.037 (stat) ± 0.040 (sys) ± 0.002 (model) and the measured b-quark branching ratio to muons is 0.122 ± 0.006 (stat) ± 0.007 (sys).
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We present a study of the third moment of the inclusive momentum distribution of particles within jets produced by e + e - annihilation at TRISTAN. In this analysis, the QCD coupling strength α s is determined by fits to the prediction of the Next-to-Leading Logarithm Parton-Shower model. The measured value of α s (57.9 GeV ) = 0.134 -0.005 +0.006 .
No description provided.
Using 773 muons found in hadronic events from 142 pb−1 of data at a c.m. energy of 57.8 GeV, we extract the cross section and forward-backward charge asymmetry for the e+e−→bb¯ process, and the heavy quark fragmentation function parameters for the Peterson model. For the analysis of the e+e−→bb¯ process, we use a method in which the behavior of the c quark and lighter quarks is assumed, with only that of the b quark left indeterminate. The cross section and asymmetry for e+e−→bb¯ are found to be Rb = 0.57 ± 0.06(stat) ± 0.08(syst) and Ab = −0.59 ± 0.09 ± 0.09, respectively. They are consistent with the standard model predictions. For the study of the fragmentation function we use the variable 〈xE〉, the fraction of the beam energy carried by the heavy hadrons. We obtain 〈xE〉c=0.56−0.05−0.03+0.04+0.03 and 〈xE〉b=0.65−0.04−0.06+0.06+0.05, respectively. These are in good agreement with previously measured values.
No description provided.
No description provided.
Here X=E(hadron)/E(beam).