R. Vanderhaghen

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.

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.

ψψ production and limits on beauty meson production from 400 GeV/c protons

Abstract From a study of multimuon events obtained in a high luminosity proton-platinum experiment at 400 GeV/ c , we find 5 ± 4 ψψ events, which correspond to a production cross section σ ( ψψ = 27 ± 10 pb. The observed production is compared to the ψψ events previously found in the same apparatus from incoming π − ; a comparison with QCD predictions is performed, giving a good agreement with expectations from gluon-gluon fusion. Finally, using like-sign dimuon, trimuon and quadrimuon events, we give model-dependent upper limits on beauty meson production: 2 nb/nucleon for central models, 20 nb/nucleon for diffractive production.

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.

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.

Negative hyperon production at high energy

Abstract With a negative hyperon beam which we have constructed at the CERN PS we have measured the production by 24 GeV/ c proton of K − , p , Σ − , and − , with respect to π − production. Measurements were made on a tungsten target under the following conditions: 1. at a fixed angle of 10 mrad for momenta between 13 and 20 GeV/ c , 2. at a fixed momentum of 17.2 GeV/ c for angles between 10 and 40 mrad. Production was studied on three targets (B 4 C, Al, W) at 17.2 GeV/ c and 10 mrad. Photographs of hyperon decays have also been taken in a prototype streamer chamber.