D.J. Holthuizen

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.

On the abundances of the Kμ3 and Ke3 decay modes of positive K mesons

SummaryThe abundances of the Kμ3 and Ke3 decay modes were checked in a large stack ofBirgeet al. (1), using the additional criteria ofAlexanderet al. (2). Our results agree completely with those ofBirgeet al. The weighted average of these and comparable corrected results of others yields a relative abundance of (3.9 ± .5)% for Kμ3 and of (5.1 ± .8)% for Ke3 decay. Available experimental data on the electron spectrum of the Ke3 decay mode are compiled and compared to theoretical calculations byFuruichiet al. (3). No evidence is found for an abnormally short mean free path of the positive secondary pions from Kπ2 decay as previously reported byAlexanderet al. (2).RiassuntoLe abbondanze dei modi di decadimento Kμ3 e Ke3 furono esaminate in un grosso pacco di emulsioni diBirgeet al. (1) usando i criteri addizionali diAlexanderet al. (2). I nostri risultati si accordano perfettamente con quelli diBirgeet al. La media ponderata di questi ed altri risultati corretti per renderli omogenei dà un’abbondanza relativa del (3.9 ± .5)% per i decadimenti Kμ3 e del (5.1 ± .8)% per i Ke3. Si elaborano i dati sperimentali disponibili per lo spettro elettronico del decadimento Ke3 e si confrontano col calcolo teorico diFuruichiet al. (3). Non si trovano prove per un cammino libero medio anormalmente corto dei pioni secondari positivi da decadimento Kπ2, come precedentemente riferito daAlexanderet al. (2).

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.

Research on high energy negative π-mesons in nuclear emulsion

The results from research on high-energy mesons ( pi /sup -/) in nuclear emulsions are discussed. At energies as high as several hundred Mev, the scattering amplitudes for pi mesons were investigated, and at still higher energies the various production processes for pions, K-mesons, and hyperons may be studied. The reaction p + n at the only rea p + p + pi /sup -/ is used to calculate the highest energy of the pi mesons produced in the target by the internal proton beam. Another quantity investigated by area scanning was the mean free path for high-energy pion star production. (B. O. G.)

On the real part of the scattering amplitude of proton-nucleus interactions at 12 GeV/c and 24 GeV/c

SummaryMeasurements have been made of the elastic and inelastic interactions of protons of 12 GeV/c and 24 GeV/c in nuclear emulsion. For this purpose, 500 m tracks of 12 GeV/c and 650 m tracks of 24 GeV/c protons were followed under the microscope. Special recorders were connected to these microscopes in order to show small deflections in the tracks with a large angle magnification. The aim was to investigate the presence of interference between the Coulomb scattering amplitude and the real part of the nuclear scattering amplitude. Three models were used to analyse the experimental results. In all cases an interference term is necessary to obtain a satisfactory fit of the experimental results. The interference between the Coulomb scattering amplitude and the real part of the nuclear scattering amplitude is constructive.RiassuntoSi sono eseguite misure delle interazioni elastiche ed anelastiche di protoni di 12 GeV/o e 24 GeV/o in emulsioni nucleari. A questo scopo si sono seguite al micro-scopio 500 m di tracce di protoni di 12 GeV/c e 650 m di tracce di protoni di 24 GeV/c. Speciali registratori erano collegati a questi microscopi per rilevare piccole deviazioni delle tracce con un ingrandimento grandangolare. Lo scopo era di studiare la presenza di interferenze fra l’ampiezza dello scattering di Coulomb e la parte reale dell’ampiezza dello scattering nucleare. Si sono usati tre modelli per analizzare i risultati sperimentali. In tutti i casi è necessario un termine interferenziale per ottenere un soddisfacente adattamento con i risultati sperimentali. L’interferenza fra l’ampiezza dello scattering di Coulomb e la parte reale dell’ampiezza dello scattering nucleare è costruttiva.

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.