Yields for J/psi production in Cu+Cu collisions at sqrt (s_NN)= 200 GeV have been measured by the PHENIX experiment over the rapidity range |y| < 2.2 at transverse momenta from 0 to beyond 5 GeV/c. The invariant yield is obtained as a function of rapidity, transverse momentum and collision centrality, and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data provide greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, providing a key constraint that is needed for disentangling cold and hot nuclear matter effects.
J/psi-->e+e- invariant yield in Cu+Cu collisions as a function of p_T at mid-rapidity for the 0-20 centrality range. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
J/PSI yield versus transverse momentum PT, at mid rapidity : -0.35<y<0.35, for a centrality range of 0-20%.
J/psi-->e+e- invariant yield in Cu+Cu collisions as a function of p_T at mid-rapidity for the 20-40 centrality range. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
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 found 122 charmed-particle decays among 3855 neutrino interactions located in the fiducial volume of a hybrid emulsion spectrometer installed in the Fermilab wide-band neutrino beam. We obtain an average relative charmed-particle production cross section of σ(ν μ → c μ − ) σ(ν μ →μ − ) =4.9 −0.6 +0.7 % , at an average neutrino energy of 22 GeV. We also obtain a production rate of σ(ν μ → c c ν μ ) σ(ν μ →ν μ ) =0.13 −0.11 +0.31 % , if we assume that there was an undetected muon, a limit of σ(ν μ → c c μ − ) σ(ν μ → c μ − )<3% (90% CL ) can be obtained. Other cross section ratios and limits are also presented.
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We report on the first observation of neutrino induced production of muon pairs in the electromagnetic field of a nucleus. The data has been obtained using the CHARM II detector exposed to the CERN wideband neutrino and antineutrino beams. A clear signal of 55 ± 16 events is seen in a sample of dimuons of opposite charge without visible recoil at the vertex. The cross section is determined and found to be in agreement with the standard model prediction.
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In a sample of 670 000 charged-current neutrino events, 101 μ−μ− events have been observed, with 30 GeV<Eν<600 GeV and Pμ>9 GeV/c for both muons. After background subtraction, 18.5±13.9 events remain, yielding a prompt rate of (5.5±4.1)×10−5 per charged-current event. A sample of 124 000 antineutrino events yields 15 μ+μ+ events, giving 6.4±4.2 events after background subtraction and a prompt rate of (1.0±0.7)×10−4 per charged-current event. The numbers and kinematic distributions of these events are consistent with standard model sources.
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The production of ${\rm J}/\psi$ and
The J/PSI production cross sections, per target nucleon, times the di-muon branching ratio for the two data samples.
The PSI(3685) production cross sections, per target nucleon, times the di-muon branching ratio for the two data samples.
J/PSI production cross section times the di-muon branching ratio for the BEtarget as a function of the Feynman X bin.
We have measured the production of massive muon pairs in hadronic collisions at the CERN Super Proton Synchrotron (SPS). A clear signal of production of the ϒ resonance by π + of 200 GeV/ c and π − of 200 and 280 GeV/ c on a platinum target is observed.
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We report on a measurement of coherent single charged pion production in neutrino-nucleus scattering. The analysis is based on data taken with the CHARM II detector in beams of muon-neutrinos and -antineutrinos. The event numbers amount to N ( μ − π ) = 748 and N ( μ + π ) = 631. Cross sections and their dependence on the neutrino energy are determined. The results are in agreement with the predictions of models based on the PCAC hypothesis.
Visible cross section for production of pions with energy > 5 GeV.
Visible cross section for production of pions with energy > 5 GeV.
Total cross section from data corrected using the Rein-Sehgal model.
Neutral strange particle production in\(\bar v\) Ne charged current interactions is studied using the bubble chamber BEBC, exposed to the CERN SPS antineutrino wide band beam. From a sample of 1191 neutral strange particles, the inclusive production rates are determined to be (15.7±0.8)% forK0 mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for\(\bar \Lambda \) and (0.6±0.3)% for Σ0 hyperons. The inclusive production properties ofK0 mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane.
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We have performed in the NA3 experiment the study of high mass dimuon production by a hadronic unseparated beam on hydrogen and platinum targets. The comparison of the production cross‐section for proton and antiproton together with the differential cross‐section dσ/dx allows us to compare the data with a production mechanism involving quark‐antiquark and gluon‐gluon interactions. The cosΘ* distribution of the same J/ψ data have also been analysed and results will be presented. Finally we have observed T production from 150 GeV/c incident pions.
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