P. Negus

Production of high transverse momentum prompt photons and neutral pions in proton-proton interactions at 280 GeV/c

The inclusive cross sections for production of prompt photons and π0s by 280 GeV/c protons incident on a liquid hydrogen target, have been measured forpT in the range 4.0 to 6.5 GeV/c and for |xF|<0.45. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed. Phenomenological fits to the π0 and prompt photon cross sections are given.

High transverse momentum prompt photon production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for prompt photon production by π− and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and FeynmanxF ranges covered are 4.0<pT<7.0GeV/c and −0.45<xF<0.55 respectively. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed.

A study of inclusive Λ, > Σ0 and Σ(1385) production in K−p interactions at 8.25 GeV/c

Abstract Inclusive Λ production has been studied in K−p interactions at 8.25 GeV/c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K∗. In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.

Double prompt photon production at high transverse momentum byπ− on protons at 280 GeV/c

A search for pairs of highpT prompt photons produced in hydrogen by a 280 GeV/c incidentπ- beam has been carried out using a fine-grained electromagnetic calorimeter and the Omega spectrometer at the CERN SPS. Clear evidence for the existence of such events is found with a six standard deviation signal forpT>3.0 GeV/c. The cross-sections are consistent with beyond leading order QCD calculations. A discussion on the determination of αs is also presented.

Observation of a narrow hyperon state of mass 3.17 GeV

Abstract We present evidence for a narrow Y∗ with a mass of 3.17 GeV and a width ⩽ 20 MeV decaying to ΣKK + pions, ΛKK + pions and ΞK + pions. The data come from two high statistics K−p bubble chamber experiments with a sensitivity of ≈100 eV/μb at 8.25 GeV/c and ≈ 45 eV/μb at 6.5 GeV/c.

Study of the reaction K−p→φφΛ at 8.25 GeV/c

Abstract In a high statistics bubble chamber study the reaction K − p → φφΛ is detected with a cross section of 0.7±0.2 μ b. The ratio of φφ production in K − and π − induced reactions is found to be ∼5; this is about ten times smaller than the ratio for the corresponding single φ production reactions.

Intrinsic transverse momentum in the π−p→γγX reaction at 280 GeV/c

Abstract The correlation between the two high transverse momentum (pt2.75 GeV/c) photons of the reaction π−p→γγX is studied at the beam momentum of 280 GeV/c. QCD calculations beyond leading logarithms are not sufficient to explain the width of the distributions and the effects due to intrinsic transverse momentum of the incident partons are discussed.

A 1152 channel timing system for an electromagnetic calorimeter readout

Abstract A 1152 channel timing system used with a large electromagnetic calorimeter is described. Analysis of the timing information from the vertical and horizontal elements of the calorimeter yielded values for the position coordinates of the showers. This information was used to resolve ambiguities in the pattern recognition arising from multiple showers. A resolution of better than 0.25 ns for all channels was achieved. The calibration methods employed to maintain this resolution over several years are discussed.

High transverse momentum π0 production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for π0 production by π− and π+ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and FeynmanxF ranges covered are 4.0<pT<7.0 GeV/c and −0.45<xF<0.6 respectively. The data are compared with leading order QCD calculations.

A partial wave analysis of thef′ region in the reaction\(K^ - p \to K\bar K\Lambda ^0 \) at 8.25 GeV/c

AbstractA partial wave analysis of theK