J. Maillard

ExperimentalJ/ψ hadronic production from 150 to 280 GeV/c

A detailed study ofJ/ψ hadronic production has been performed in a high statistics experiment (more than 1.5 106J/ψ observed in their dimuon decay mode). Data have been taken with incident π±,K±,p±, on hydrogen and platinum targets, at 150, 200 and 280 GeV/c. We find from the observed nuclear dependance of the cross sections, that about 18% of theJ/ψ are produced diffractively. Using known structure functions of the quarks in the nucleon and in the pion, we derive estimations for the gluon structure functions.

Experimental Determination of the pi Meson Structure Functions by the Drell-Yan Mechanism

We have studied high statistics samples of dimuon events (∼35,000) produced from π± on platinum target in the mass interval 4.2≦Mμμ≦8.5 GeV at 150, 200 and 280 GeV/c. The π structure function is obtained by a fit ofd2σ/dx1dx2 to π+ and π− data. At 200 GeV, the simultaneous use of π+ and π− data allows a separate determination of the valence and sea structure functions of the π. Furthermore, the 150 and 280 GeV data allow an accurate determination of the shape of the valence structure function and give an estimate of its evolution betweenQ2=25 and 50 GeV2.

Evidence for ψψ production in π− interactions at 150 and 280 GeV/c

From the analysis of multimuon events produced by π− interactions at 150 and 280 GeV/c in the NA3 spectrometer, we present evidence for the production of two J/ψ mesons in the same interaction (13 events seen, for an expected background of about 0.2 events). Some possible production mechanisms are described and an estimation of the cross section is given.

Measurement of the K−π− structure function ratio using the Drell-Yan process

Abstract The first measurement of the kaon to pion structure function ratio has beenperformed in a high integrated luminosity experiment studying the production of massive muon pairs. The ratio u K u π clearly deviates from 1 for values of x1 > 0.7. A theoretical model comparison is also briefly discussed.

Angular distributions in the dimuon hadronic production at 150 GeV/c

From π- interactions at 150 GeV/c on a heavy target, we present the final analysis of the dimuon decay angular distribution in the mass interval 4.5–8.5 GeV/c2. Results are presented and discussed in various reference frames and are also given in terms of the density matrix elements. Finally the possible contribution of higher-twist effects at largex1 is discussed; we find that our data are not compatible with higher twist contributions as proposed by the Berger and Brodsky Model.

Drell-Yan events from 400 GeV/c protons: determination of the K-factor in a large kinematical domain

We present the analysis of ∼30,000 high mass dimuons (Mμμ>4.5 GeV/c2) produced in 400 GeV/c proton-platinum interactions. A determination of theK-factor is given for different values ofxF andMμμ, and its variations are compared to QCD predictions. The proton structure functions derived from these events are compared to the values obtained in deep inelastic lepton scattering.

Experimental determination of the antiproton structure function by the Drell-Yan mechanism

Abstract We present results on the measurement of the Drell-Yan absolute cross section and of the shape of the nucleon structure functions by the analysis of massive dimuon events produced by antiprotons at 150 GeV and by protons at 150 and 200 GeV. Good agreement is found with the results of the neutrino deep inelastic scattering (DIS) experiments, for the shape of the valence structure function. The measured cross section however, when compared to the model predictions assuming the DIS nucleon structure function exhibits a normalization factor K = 2.3 ± 0.4.

Measurement of the transverse momentum of dimuons produced by hadronic interactions at 150, 200 and 280 GeV/c

Abstract We have studied the transverse momentum of dimuons in the mass interval 4.1 to 8.5 GeV/c2 produced on hydrogen and platinum targets by different hadrons. For incident π−, we give a model independent parametrisation of the data and compare our results to QCD perturbative calculations. First order diagrams predict a transverse momentum s dependence smaller than the observed value.

Upper Limits on Beauty Meson Production in

From events with two like-sign muons, or with three or four muons, observed in the NA3 spectrometer with 280 GeV/c incoming π− beam, we deduce upper limits on the production of beauty meson pairs BB. We use the leptonic branching ratios of B meson measured at CESR storage rings, and assume that no nuclear effects occur in the platinum target. We find σ(BB) < 2 nb/nucleon for centrally produced BB < 10 nb/nucleon for a diffractive production. These values are one order of magnitude lower than previously published limits. As a consequence, the ψψ events observed in our experiment cannot come from BB decays.

\pi^-

We present here the analysis of low mass dimuon events (1.8 < Mμμ < 2.6 GeV/c2) produced by positive and negative pion and proton beams at 200 GeV/c. Using the difference between the π- and the π+ cross sections, and comparing to the Drell-Yan model, we find a K-factor of 2.47 ± 0.5. Only about 12 of the events can be attributed to the Drell-Yan mechanism. If the remaining events are attributed to muonic decays of D mesons we findan upper limit for the cross section of charmed meson production.