B. Heck

The axial field spectrometer at the CERN ISR

Abstract The axial field spectrometer is being exploited in a wide-ranging programme to study pp and p p -collisions which are characterized by a large transverse momentum. A specially shaped magnet together with an “imaging” drift chamber is used for efficient detection and momentum analysis of high multiplicity events at interaction rates of up to 5 × 106 s. Particle identification is accomplished over 1 sr; an uranium/scintillator hadron calorimeter will cover more than 8 sr in 1982 to provide an unbiased energy measurement.

Direct evidence for the emergence of jets in events triggered on large transverse energy in pp collisions at s = 63 GeV

We present data obtained from a 1.7 sr hadron calorimeter, triggered on transverse energy, in pp collisions at s=63 GeV at the CERN-ISR. From the change in the distribution of energy in the calorimeter, we extract the cross section for two-constituent hard scattering for pT between 6 and 14 GeV at y = 0. The decrease of this jet cross section over this pT range is consistent with exp (−bpT), with b = (1.02 ± 0.09) GeV−1. The slope and normalization of the cross section agree well with a QCD motivated Monte Carlo model. The ratio between jet and single particle cross sections [dσJET/dpT)/(dσπ0/dpT)]| y = 0 changes from about 200 at 6 GeV to about 1500 at 14 GeV.

Bose-Einstein correlations in αα, pp and pp interactions

Abstract Bose-Einstein correlations between pions produced in the central region of rapidity in αα, pp and p p interactions have been studied at the ISR. The parameters r and τ c -often interpreted as the radius and depth of the π-emitting region - are found to be independent of incident particle type but to depend on the mean charged multiplicity. In high multiplicity events, the pions appear to originate from a larger space-time region.

A measurement of the inclusive cross section of charged pions at very high transverse momenta

Abstract The inclusive cross sections for the production of high transverse momentum π + and π − mesons in proton-proton interactions have been measured at the highest ISR energy √ s = 63 GeV and at a c.m. production angle of 50°. The cross sections for π + and π − mesons are compared as a function of transverse momentum. It is shown that the inclusive cross section of π − mesons decreases faster than the π + cross section. particle σ ( π ± )/ σ (charged particles) are presented as a function of transverse momentum.

Further evidence for jet production from the charged particles produced in pp collisions at triggered on large transverse energy

Abstract The detailed shape of events triggered by a 1.7 sr hadron calorimeter is studied using charged track information in the Axial Field Spectrometer at the CERN ISR. With increasing transverse energy (ET) a large fraction of the events are seen to have a limited transverse momentum relative to the trigger direction. A comparison of the circularity of the events with a prediction of a QCD-motivated Monte Carlo model shows that at high ET the events originate predominantly from two-constituent scattering.

The dominance of jets at large transverse energy in a full-azimuth hadron calorimeter at ISR energies

Abstract Events with a large transverse energy in a calorimeter with full azimuthal coverage and |y|

Inclusive vector-meson production in the central region of pp collisions at √s = 63 GeV

Production of ϱ0, K∗0, K∗0, and φ have been measured in proton-proton collisions at the CERN Intersecting Storage Rings (ISR) at low pT in the central region. The transverse mass spectra are well described by exp (−aμT), with a = −6.4±0.2 GeV−1. The cross sections for dσ/dy|y=0are 6.5±0.8±1.2 mb for ϱ0, 1.9±0.3±0.3 mb for K∗), 1.9±03±03 mb for K∗0, and 60.±0.12±0.13 mb for φ, where the first error is statistical and the second is sytematic.

Antibaryon production in the central region at the ISR

Using annihilation in a calorimeter as a trigger on antiprotons, we have measured the relative production cross sections of p, Λ and Ξ at y∼0 in the transverse momentum range 1 to 2 GeV/c in pp collisions at √s=63 GeV. We investigate correlations between the antibaryons and associated produced particles, and find evidence for local baryon number conservation.

Multiplicity distributions in p-α and α-α collisions in the CERN ISR

Abstract Measurements of charged particle multiplicity distributions in the central rapidity region in p-p and p-α, and α-α collisions are reported. They are better fitted to the “wounded nucleon” than to the “gluon string” model. The average transverse momenta, for all three reactions, are identical (and almost independent of multiplicity) up to very high multiplicities.

The jet cross section in pp interactions at √s = 45 GeV and its √s dependence

Abstract The differential cross section for production of jets in pp interactions at y = 0 and p T from 6–12 GeV/ c has been measured at √ s = 45 GeV at the CERN Intersecting Storage Rings and compared with a previous measurement at √ s = 63 GeV. The data were obtained using a 2.1 sr hadron calorimeter which was triggered on transverse energy. The energy dependence of the jet cross section is well described by (1− x T ) m p T − n , with m = 10.6±1.0 and n = 5.3±0.2. The results are in good agreement with predictions obtained from a QCD-motivated model.