New data are presented on charged particle pseudorapidity distributions for inelastic events produced at c.m. energies\(\sqrt s \)=200 and 900 GeV. The data were obtained at the CERN antiproton-proton Collider operated in a new pulsed mode. The rise of the central density ρ(0) at energies up to\(\sqrt s \)=900 GeV has been studied. A new form of central region scaling is found involving the densityρn(0) for charged multiplicityn, namely that the scaled central densityρn(0)/ρ(0) expressed as a function ofz=n/〈n〉 is independent ofs. Scaling in the fragmentation region holds to 10–20%, and the small amount of scalebreaking observed here could be accommodated within the framework suggested by Wdowcyk and Wolfendale to account for both accelerator and cosmic ray data.
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Cross-sections for diffractive particle production and pseudorapidity distributions of the decay products of diffractive states are presented. The data were obtained with the UA 5 streamer chamber detector at the CERNpp Collider operated in a new pulsed mode yieldingpp interactions at c.m. energies of 900 and 200 GeV. Data recorded with a special trigger designed to select a sample of events enriched in single-diffractive interactions clearly favour apt-limited fragmentation of diffractive states. The cross-section for single-diffractive particle production ϊ was found to be 7.8±0.5±1.1 mb at 900 GeV and 4.8±0.5±0.8 mb at 200 GeV (first error statistical, second systematic). From the pseudorapidity distribution of diffractive states we deduce the average number of charged particles to be 6.5±1.0 at 900 GeV and 4.1±1.1 at 200 GeV. Furthermore we report on our estimates for the cross-section of double-diffractive particle production at both Collider energies.
Single diffractive cross sections.
Average number of single diffractive charged particles.
Estimate of the double diffractive cross sections.
New data are presented on charged particle multiplicity distributions for non single-diffractive events produced at CM energies s = 200 and 900 GeV . The data were obtained at the CERN antiproton-proton collider operated in a new pulsed mode. The multiplicity distributions are very well described by a negative binomial distribution. The highest energy data show no sign of approaching scaling, confirming our earlier results on the breaking of KNO scaling. The energy variation of the average charged multiplicity can be fitted to a quadratic in ln s or a s 0.13 dependence.
Figure gives uncorrected multiplicity distributions. Here we give the corrected distributions. Data supplied by D. Ward.
Results for multiplicity moments based on negative binomial fit to corrected data. Errors reflect both statistical and systematic effects. Results from earlier data at 546 Gev cm energy are also given.
C moments for corrected data where CQ=<N**Q>/<N>**Q.
Results are presented on two-jet and three-jet cross sections, measured in the UA1 experiment at the CERN Super Proton Synchrotron (SPS) pp̄ Collider, at the highest available subprocess cms energies ( s ̂ >150 GeV ). Precise measurements of the two-jet angular distribution are consistent with previous results but show significant scale-breaking effects. The three-jet Dalitz plot and the three-jet angular distributions show evidence for final- and initial-state bremsstrahlung processes, in agreement with the leading-order QCD predictions. A comparison of the yield of wide-angle three-jet events with the yield of two-jet events at smaller scattering angles gives for the strong interaction coupling constant: α s ( K 3J K 2J )=0.16±0.02±0.03 at Q 2 ≈4000 GeV 2 , where the factor K 3J K 2J may plausibly be assumed to be close to unity.
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Using the UA5 detector, the inclusive central production of Ks0 and K± mesons has been measured in non-single-diffractive interactions at the CERN SPS Collider at a c.m. energy of 540 GeV. The average transverse momentum is found to be 〈pT〉 = 0.57±0.03 GeV/c in the rapidity range |y|<2.5, which is an increase of about 30% over the top ISR energy. The K/π ratio has increased from about 8% at ISR energies to 9.5±0.9±0.7% (the last error is systematic) at 540 GeV. The average number of Ks0 per non-single-diffractive event is 1.1±0.1 and the inclusive inelastic cross section is estimated at 49±5 mb.
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Multiplicity distributions of charged particles for inelastic, non single-diffractive events in proton-antiproton collisions at a centre of mass energy of 540 GeV are presented for various pseudorapidity (Δη) intervals. The widths of the multiplicity distributions, scaled to their means, increase as Δη is made smaller, and the deviation from a Poisson distribution becomes progressively more pronounced. It is found that the data are remarkably well described by a negative binomial distribution. The parameters of the distributions vary smoothly with the size of the acceptance interval.
Data for full phase space.
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We report the observation of 21 dimuon events at the CERN p p Collider with the UA1 detector. The events range in invariant dimuon mass from 2 to 22 GeV / c 2 . The properties of these events are given. The bulk of the events are consistent with heavy-flavour production (mainly b b ) with a few candidates for Drell-Yan production. There remain a few events which are difficult to interpret in terms of these processes, in particular two events with isolated, like-sign muons.
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Inclusive particle production cross-sections have been measured at the\(Sp\bar pS\) collider using the UA2 detector in various ranges of transverse momentum (PT) and pseudo-rapidity (η). Cross-section measurements are presented forπ0 production (PT≦15 GeV/c, |η|≦0.85 andPT≦40 GeV/c, 1.0≦|η|≦1.8), for η meson production (3≦PT≦6 GeV/c, |η|≦0.85) and for charged particle production (PT≦10 GeV/c, 1.0≦|η|≦1.8). Results are compared with the predictions of QCD calculations.
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We report evidence for the production of the charged D ∗ mesons in pp̄ collisions at s = 540 GeV . The search was confined to the charged particle fragments of hadronic jets, which are expected to be predominantly gluon jets in this experiment. The fragmentation function and production rate for D ∗ in jets of average transverse momentum of 28 GeV/ c are given.
THE D*'S ARE CONSIDERED AS ARISING ONLY FROM FRAGMENTATION OF HADRONIC JETS ('GLUON' JETS). HERE THE <PT> OF THE JET IS AROUND 28 GEV THE DEFINITION OF Z IS P(D*).P(JET)/(P(JET))**2.
Jet production properties at s = 540 GeV have been measured in the UA2 detector at the CERN p p Collider. Results on the total transverse momentum of the jet system, on the parton density in the nucleon (structure function) and on the two-jet angular distributions are reported. The data are compared with QCD predictions and extrapolations from lower energy experiments.
DISTRIBUTION OF THE SCATTERING ANGLE OF THE 2-JET AXIS IN THE 2-JET COM FRAME WITH A NORMALISATION FIXED AT 1 FOR COS(THETA*) = 0.
STRUCTURE FUNCTION IS DEFINED AS F(X) WHERE D3(SIG)/DX1/DX2/DCOS(THETA) = (F(X1)/X1)*(F(X2)/X2)*D(SIG)/DCOS(THETA).
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