J.G. Rushbrooke

Multiplicity distributions in different pseudorapidity intervals at a CMS energy of 540 GeV

Abstract 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.

Charged particle multiplicity distributions at 200 and 900 GeV c.m. energy

Multiplicity distributions of charged particles produced in non single-diffractive collisions between protons and antiprotons at centre of mass energies of 200 and 900 GeV are presented. The data were recorded in the UA5 streamer chambers at the CERN Collider, which was operated in a pulsed mode between the two energies. A new method to correct for acceptance limitations and inefficiencies based on the principle of maximum entropy has been used. Multiplicity distributions in full phase space and in intervals of pseudorapidity are presented in tabular form. The violation of KNO scaling in full phase space found by the UA5 group at an energy of 546 GeV is confirmed also at 200 and 900 GeV. The shape of the 900 GeV distribution in full phase space is narrower in the peak region than at 200 GeV but exhibits a pronounced high multiplicity tail. The negative binomial distribution fits data at 200 GeV in all pseudorapidity intervals and in small intervals at 900 GeV. In large intervals at 900 GeV, however, the negative binomial distribution. Fits to the partially coherent laser distribution are also presented as well as comparisons with predictions of the Dual Parton, the Fritiof and the Pythia models.

A new empirical regularity for multiplicity distributions in place of KNO scaling

Abstract Charged particle multiplicity distributions for the inelastic, non-single-diffractive component of p p reactions at 540 GeV CMS energy and of pp reactions above about 10 GeV are shown to be remarkably well described by a negative binomial distribution at each energy. The two parameters of the distribution depend on energy in a regular manner, which affords the possibility of predicting multiplicity distributions at high energies not yet experimentally available. In this description there is a complete absence of any tendency to approach asymptotic KNO scaling below 540 GeV. The approximate scaling in the CM energy range 10–62 GeV is shown, in this framework, to be accidental.

Scaling violations in multiplicity distributions at 200 and 900 GeV

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 s0.13 dependence.

Performance of a scintillating fibre detector for the UA2 upgrade

Abstract A large scintillating fibre detector for the UA2 experiment at the CERN p p Collider is under construction. It will be used for tracking and electron identification. The performance of a full scale test module containing 960 fibres of 2.1 m length and 1 mm diameter is described.

First results on complete events from pp collisions at the cm energy of 540 GeV.

Abstract First results from the UA5 detector on charged particle production at √s = 540 GeV in the pseudorapidity range ∣ν∣

Particle multiplicities in pp interactions at √s=540 GeV

Abstract We present the charged multiplicity distribution in p p interactions at √ s =540 GeV. Moments of the distribution are given, and compared with KNO scaling predictions. An estimate of the particle composition at collider energies is also made.

Production of photons and search for Centauro events at the SPS collider

Abstract The pseudorapidity distribution of photons produced in pp interactions at s =540 GeV has been measured and compared with that of charged particles. The correlation between photon and charged-particle production has been studied. A search amongst high multiplicity events for any having the properties of the Centauro events reported in cosmic-ray experiments has revealed no candidates in a sample of 3600 inelastic events.

Kaon Production in

Abstract 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 p p 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|

\bar{p} p

Abstract First results from UA5 on charged particle multiplicities from p p interactions at √s = 540 GeV are presented. A value of 27.4 ± 2.0 is obtained for the mean charged multiplicity 〈nch〉 of produced hadrons. This excludes an s 1 4 behaviour of 〈nch〉 in going from ISR to Collider energies, but is not in disagreement with an extrapolation using a quadratic fit in ln s to previous lower energy data up to ISR energies.