G. Matthiae

PROTON-NUCLEI CROSS SECTIONS AT 20 Gev

Abstract Measurements of the differential cross section of 20 GeV protons scattered elastically and quasi-elastically by a series of nuclei, ranging from Li to U, are presented. The total and the elastic cross sections are also given. The light nuclei show, at the smallest angles, the characteristic center diffraction peak produced by an absorbing disc; at larger angles the quasi-elastic scattering produced by single nucleons predominates. The heavy nuclei exhibit diffraction rings up to the largest angles explored (≈ 20 mrad). The diffraction patterns are interpreted with an optical model that takes into account the contribution of both the nuclear and the Coulomb interactions. The radii of the heaviest nuclei turn out to be consistently larger than those deduced from electron scattering experiments. The opacity is found to be nearly complete only in the heaviest nuclei. Results at the largest angles measured show that only a small fraction of the nucleons in the nuclei can act as effectively independent scattering centres.

Measurement of the proton-antiproton total and elastic cross sections at the CERN SPS collider

Abstract The proton-antiproton total cross section was measured at the CM energy √s = 546 GeV . The result is σ tot = 61.9± 1.5 mb . The ratio of the elastic to the total cross section is σ e l / σ tot = 0.215±0.005. A comparison to the lower energy data shows that the increase of the total cross section with energy is very close to a log 2 s behaviour.

Low momentum transfer elastic scattering at the CERN proton-antiproton collider

Proton-antiproton elastic scattering was measured at the CM energy √s = 546 GeV in the four-momentum transfer range 0.03<−t<0.32GeV2 For −<0.15GeV2 the data are well described by a simple exponential form exp(bt) with slope parameter b=15.2±0.2GeV−2. This value is significantly larger than the one measured in the region 0.21<−t<0.50 GeV2.

Elastic scattering at the CERN SPS collider up to a four-momentum transfer of 1.55 GeV2

Abstract Proton-antiproton elastic scattering was measured at the center-of-mass energy s =546 GeV in the four-momentum transfer range 0.45⩽−⩽1.55GeV 2 . The shape of the t -distribution is quite different from that observed in proton-proton scattering at the ISR. Rather than a dip-bump structure, a kink is present at − ≈0.9GeV 2 followed by a shoulder. The cross section at the second maximum is more than one order of magnitude higher than at the ISR.

DISCONTINUOUS BEHAVIOUR IN LARGE ANGLE PROTON--PROTON ELASTIC SCATTERING AT HIGH ENERGIES.

Abstract Measurements of elastic proton-proton differential cross sections for angles between 65° and 90° c.m.s. have been made at 8, 9, 10, 11, 14, 15 and 21 GeV/c. The shape of the angular distribution is found to change suddenly between 8 and 11 GeV/c. An interpretation of this discontinuous behaviour in terms of the reactive effects of baryon-antibaryon pair production is proposed.

The cross section of diffraction dissociation at the cern SPS collider

Single diffraction dissociation was measured in the reaction p¯p→p¯X at the centre-of-mass energy √s = 546 GeV. The mass M of the system X was deduced from the pseudorapidity distribution of the observed charged tracks. The cross section of single diffraction dissociation for M2/s⩽0.05isσsd=9.4 ± 0.7 mb. Comparison to the ISR data shows that σsd increases with energy less fast than the total and the elastic cross sections.

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.

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 proton-antiproton elastic and total cross section at a centre-of-mass energy of 540 GeV

Abstract First results on the measurement of the elastic and total cross section at the CERN pp Collider are presented. Combining the measurement of elastic scattering at low momentum transfer with the rate of inelastic interactions, a value of the total cross section of 66 mb with a 10% statistical error was obtained.

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.