D. Decamp

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 cross section for dimuon production and the Drell-Yan model

Abstract We have measured the absolute cross section for dimuon production in hadron collisions at 200 GeV/c in the continuum region M = 4–8.5 GeV. In all the channels studied (pN, p N, π±N and π−H2) the experimental cross section is significantly larger by a factor of 2.3 ± 0.5 than expected from the Drell-Yan model. Furthermore, our proton-nucleon data allow a determination of the nucleon valence structure function which agrees with the deep inelastic lepton scattering data.

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.

A large acceptance spectrometer to study high-mass muon pairs

Abstract This paper gives the outlines of the NA3 large acceptance magnetic spectrometer equipped with multiwire proportional chambers running at the CERN-SPS in an extensive study of the production of high mass muon pairs by hadronic beams. A special feature of this experiment is the powerful and efficient trigger and data acquisition system which allows operation of the spectrometer with intense beams, yielding at the same time low trigger rate and high proportion of good events. Some aspects of the off-line analysis program are also described.

First evidence for upsilon production by pions

Abstract 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.

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.

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.

Direct photon pair production from pions and protons at 200 GeV/c

Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦PT≦6 GeV/c and center-of-mass rapidity −0.4≦y*≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.

Production of low mass dimuons at high transverse momentum: Study of ϱ, ω, π resonances

Abstract We use low mass dimuons (0.35 M μμ ⩽ 2 GeV/ c 2 ) to analyse the production at high transverse momentum ( P T ⩾ 2 GeV/ c ) of the resonances ϱ, ω, π. We have studied the variation of the cross section with the type of incident particle (π, K, p) at 150, 200, 280 GeV/ c and the nuclear effects by comparison of platinum and hydrogen targets. There is no significant difference between the slopes of the transverse momentum distributions with those observed at lower P T (0 P T c ), meanwhile x F -distributions show a leading effect in the production of gf by kaons at these relatively high transverse momenta.