G.W. Van Apeldoorn

Ionization measurements with an HPD in the analysis of pp interactions at 7.3 GeV/c☆

Abstract From the measurement of bubble chamber pictures with an HPD, values for the bubble density of the tracks are obtained that allow separation of protons and pions up to moments of 1.8 GeV/c. These ionization measurements form together with a number of other tests the basis of a reliable automatic decision system which is now used in the analysis of bubble chamber pictures in the Zeeman-Laboratorium.

Study of diffraction dissociation and double resonance production in the final state pp π+π− at 7.2 GeV/c

On 8 K events of the reaction ppπ+π− at 7.23 GeV/c simple selection on angular parameters is performed yielding a sample of events with the typical features of diffraction dissociation. A cross section of 1.22 ± 0.08 mb (in two vertices) and a slope of the t distribution of 12.6 ± 1.0 GeV−2 for −t < 0.1 GeV2 are obtained for the diffraction fraction dissociation p → pπ+π− + c.c. Using an analogous selection procedure, another sample of events is isolated that is characterized by double resonance production. Cross sections for ΔΔ and ΔΔ′ + c.c. production amount to 1.27 ± 0.09 mb and 0.23 ± 0.07 mb respectively. Diffraction dissociation and double resonance production together make up for 87% of the total cross section for the reaction pp → ppπ+π−, which is 3.11 ± 0.13 mb.

Final states with a neutral meson and a π+π− or pp pair in pp interactions at 7.2 GeV/c

Cross sections are reported for pp interactions at 7.2 GeV/c beam momentum yielding one of the mesons ϱ0, ω, ϕ, η or η′; together with a gp+π− pair or a pp pair. Results are compared with data on similar pp interactions at other beam momenta. The angular distributions for the final states with a ϱ0 or ω clearly show a peripheral behaviour. Our results may be understood within the framework of the quark model, but differ from the predictions of the quark rearrangement model. Deviations from ideal mixing of vector mesons are discussed. The energy dependence of ϱ0 and ω production is compared with that of analogous pp and π±p interactions.

Average transverse momentum and the seagull effect

Abstract The average transverse momentum of pions as a function of their longitudinal momentum is studied in a number of reactions produced by 4.25 GeV/ ac negative kaons or by 7.3 GeV/ c antiprotons on protons. The observed seagull effects are attributed to the dominance of different reaction mechanisms at different values of the longitudinal momentum of the pions.

A search for the I peak at 2.60 GeV/c2 in 12 GeV/c pp interactions in the CERN 2 m HBC

In a study of 12 GeV/c pp interactions in the CERN 2 m HBC, we have searched for a narrow K3π state. Contrary to an investigation of 12 GeV/c pp interactions in the CERN BEBC, we find no support for such a state.

The reactionp→Δ(1236)\(\bar \Delta \)(1236) at beam momenta of 7.23 GeV/c and 12.0 GeV/c

The reactionp→Δ(1236)\(\bar \Delta \)(1236) is studied at 7.23 GeV/c and at 12GeV/c in terms of the OPE model of Wolf. Good agreement between the model and experimental data is found for the mass andt distributions whereas for decay angular distributions the agreement is less satisfactory. A modified model, allowing for a spin orbit coupling, gives good agreement also for the angular distribution.

Diffraction dissociation in the final state ppπ+π− at 12 GeV/c

In a study of 4.7 k events of the reaction pp→ppπ+π− at 12 GeV/c a cross section of 0.57±0.04 mb and a slope of the t distribution of 14.8±1.5 GeV/c−2 for −t<0.1 GeV2 are obtained for the diffraction dissociation p→pπ+π−. This slope agrees with the slope of the t distribution for elastic pp scattering. Also the energy behaviour of diffraction dissociation is similar to the energy behaviour of elastic pp scattering. A comparison is made with the analogous reactions in pp interactions.

Automatic measurement of 12 GeV/c p̄p interactions in the CERN 2 m HBC

Abstract We report on the automatic method developed in Amsterdam for the measurement of 125 k pictures of an exposure of 12 GeV/ c p in the CERN 2 m HBC. The method uses an HPD in zero guidance mode. We describe the automatic scan, the measurement and the recovery-system. Results are presented on yields, random and systematic losses, measuring efficiencies and time rates. These results are compared with results of some other measuring methods.