A. Rudge

A search for glueballs and a study of doouble pomeron exchange at the CERN intersecting storage rings

We present results from a study of centrally produced mesons in 3 × 106 events with two small-angle protons at the CERN Intersecting Storage Rings. A high-statistics sample of exclusive pp → ppπ+π− events at √s = 63 GeV has been obtained, where the reaction mechanism is dominated by double pomeron exchange. Scalar or tensor glueballs may be produced by this process. The π+π− mass spectrum has a distinctive structure, and analysis shows that the data are dominantly S-wave up to 1600 MeV. The behaviour of the D-wave provides evidence for a 2++ resonance (M = 1480 ± 50 MeV, Γ = 150 ± 50 MeV) in addition to the f(1270). We also show data on exclusive K+K−, pp, and π+π−π+π− production, and on the analogous reaction αα → ααπ+π− at √s = 126 GeV. Flavour independence is suggested by the observation of approximately equal numbers of K+K− and π+π− pairs for mass above 1 GeV. The mass spectra are also apparently independent of √s (45, 63, 126 GeV) and incident particle type (p, α).

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.

Diffraction dissociation in proton-proton collisions at ISR energies

Data are presented on the reaction pp → pX in the range of four-momentum transfer squared 0.04 0.01. The total diffractive cross section integrated over t and M2/s up to M2/s=0.05 rises by approximately 15% from σdif=6.5±0.2 mb at 550 GeV2 to σdif=7.5±0.3 mb at 3880 GeV2.

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|

A study of exclusive central hadron production at the ISR as a search for gluonium states

Abstract We present first results from a study of the exclusive reaction pp→pπ + π − p at √s=63 GeV with π + and π − produced in the central region. This reaction has been suggested as a method of searching for gluonium states. The π + π − mass distribution shows rapid order of magnitude decreases in cross section at both 1000 MeV/ c 2 and 1500 MeV/ c 2 . Further structure is observed above 2000 MeV/ c 2 .

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.

A comparison of direct photon, π0 in pp and pp interactions at the CERN ISR

Abstract We have measured the production of direct photons, π 0 s, and ηs in p p and pp collisions at √ s =53 GeV in the range 2≈ p T ≈6 GeV/ c for the central rapidity region | y | 0.4. No statistically significant difference between pp and pp interactions is observed.

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.