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We present new high statistics data on hadron production in photon-photon reactions. The data are analyzed in terms of an electron-photon scattering formalism. The dependence of the total cross section of Q 2 , the four-momentum transfer squared of the scattered electron, and on the mass W of the hadronic system is investigated. The data are compared to predictions from Vector-Meson Dominance and the quark model.
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DEPENDENCE ON VISIBLE HADRONIC INVARIANT MASS.
Data read from graph.
We have measured the production cross section for K s 0 in e + e − annihilation from 3.6 to 5.0 GeV center of mass energy. A substantial increase of the K s 0 yield is observed around 4 GeV in qualitative agreement with the charm hypothesis.
THE DATA GIVEN HERE AT 9.3 GEV AND ABOVE ARE REPORTED IN C. BERGER ET AL., PL 104B, 79 (1981). THE 12.0 AND 30 GEV DATA WERE TAKEN AT PETRA.
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We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.
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Using data onvp and\(\bar vp\) charged current interactions from a bubble chamber experiment with BEBC at CERN, the average multiplicities of charged hadrons and pions are determined as functions ofW2 andQ2. The analysis is based on ∼20000 events with incidentv and ∼10000 events with incident\(\bar v\). In addition to the known dependence of the average multiplicity onW2 a weak dependence onQ2 for fixed intervals ofW is observed. ForW>2 GeV andQ2>0.1 GeV2 the average multiplicity of charged hadrons is well described by〈n〉=a1+a2ln(W2/GeV2)+a3ln(Q2/GeV2) witha1=0.465±0.053,a2=1.211±0.021,a3=0.103±0.014 for thevp anda1=−0.372±0.073,a2=1.245±0.028,a3=0.093±0.015 for the\(\bar vp\) reaction.
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Photopion energy distributions have been measured on 7 Li , 28 Si , 51 V and 93 Nb at θ π = 90° with 200 MeV electron. The logarithmic plot of the distributions shows a break at around 10 MeV of the residual energy. This is not explained by the quasi-free π + production. The (e, π + ) cross sections at θ π = 90° deduced by integrating the energy distribution. The result can be approximated by σ 0 Z 2 3 , where σ 0 is 0.13 times the elementary cross section of H(e, π + ) at θ π = 90°. The quasi-free π + production calculated by the Fermi-gas model with Pauli exclusion principle approximately reproduces the relative dependence on the charge number but its absolute value is about ten times as large as the experimental result. The present result for the charged photopion cross section in the threshold region is in contrast to the case in the Δ-resonance region where the cross section of π + + π − photoproduction is expressed by A 2 3 times the elementary cross sections.
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We present a measurement of the polarization of Antilambda hyperons produced in nu_mu charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same V0 identification procedure and analysis method reported in a previous paper for the case of Lambda hyperons. The Antilambda polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.
Lambdabar polarization in regions of Feynman X (XL).
Lambdabar polarization in regions of the Bjorken scaling variable X.
Inclusive π+ photoproduction below the Δ(1232) resonance has been measured from H, C, Ca, Sn, and Pb at laboratory angles of 51°, 81°, 109°, and 141° using tagged photons and ΔE-E plastic scintillator telescopes with 17-MeV thresholds. Particle identification involved both the determination of differential energy loss and the detection of the μ+ from the π+ decay. Double differential cross sections, angular distributions, and total cross sections were obtained for four incident photon energy bins centered at 184, 194, 204, and 213 MeV. Comparisons are made to both theoretical predictions and previous data sets. Ratios of nuclear cross sections to those obtained from the proton are extracted, and the features of these ratios are discussed. © 1996 The American Physical Society.
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The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
PT RANGE FROM 0 TO INFINITY.
PT RANGE FROM 0 TO INFINITY.
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