H. Ahrar

Multiparticle production in π−-emulsion collisions at 340 GeV/c

Abstract Experimental results on π − -emulsion interactions at 340 GeV/ c are presented. The dependence of R on the target mass is studied in the light of constituent quark models. A universal relation for the 〈 N s 〉 dependence on 〈 N ch 〉 and 〈 ν A 〉 is obtained. Systematics of shower multiplicity distributions are also studied and a new scaling function for integral probability distributions of shower tracks is worked out.

Production of Clusters and Heavy Clusters in Nucleon-Nucleon Interactions at 400 GeV/c

In the present paper an attempt has been made to study the production of heavy clusters using the rapidity-interval method proposed by Adamovich et al. among hadrons produced in 400 GeV / pN and p-emulsion collisions. The results show someweak evidence for the production of heavy clusters at 400 GeV. The study of two particle rapidity-gap distributions gives an indication for strong short-range correlation and weak long range correlation at 400 GeV pN interaction.

Study of Cluster Formation in 340 GeV/c–Em Interactions

Cluster production in 340 GeV/c pion-emulsion interactions, using the method of rapidity-gap correlations, has been studied. The particles are found to be more strongly correlated in the forward region of the rapidity space. The size of clusters does not depend on the target size. The rapidity width and maximum rapidity-gap length distributions are also studied.

Nuclear Interactions at 340 GeV/c π − -Emulsion Interactions

In the present work we report some new data on charged particle multiplicity and pseudorapidity distributions of shower particles produced in pion-emulsion collisions at 340 GeV/c. Some of the results are compared with the data from proton-nucleus interactions at 400 GeV/c. From the study of pseudorapidity distributions of charged shower particles, it is noticed that the maxima of η-distributions shifts towards smaller values of η with increasing n g . Bi-modality in the η-distributions is observed for all n g -intervals at 340 GeV/c. There is no tendency of appreciable change in the dispersions of η-distributions with increasing n s , n g or N h , except in the region of small values of n g and N h . Forward-backward correlation has also been investigated.

Characteristics of Pseudorapidity and Rapidity-Gap Distributions at 50 and 400 GeV/c

Some results on pseudorapidity distributions and rapidity-gap distributions of shower particles produced in pion-nucleus and proton-nucleus collisions at 50 and 400 GeV are presented and discussed. Study of the rapidity distributions reveals that the projectile fragmentation is mass independent and the target fragmentation depends upon the target mass. From the rapidity-gap distributions, we find an evidence for short-range correlations which indicates that the secondary particles are produced via cluster formation and the contribution of the long-range correlations is quite small.

Neutral charm production in 400 GeV proton-emulsion interactions

A search has been carried out for neutral charm production in 5,108 proton-emulsion interactions at 400 GeV/c. Nine charm candidates have been observed in our fiducial volume which extends from 100 μm-1,000 μm in the forward cone. One of these is a 4-prong and the others are 2-prong events with opening angle>10 mrad and momenta of both decay tracks>150 MeV/c. Search for associated charm decays was made in an extended fiducial volume around the primary stars of these nine candidates. This yielded two neutral 2-prong events, one associated with the 4-prong and the other with a 2-prong candidate. All unassociated candidates are consistent with being backgrounds due toKs, Λ decays, neutral interactions and γ conversions whereas the background to associated events is negligible. Based on the two associated decays the inclusive cross section forD0, −0 production is determined as 27±20 μb/nucleon. Detailed measurements on the 4-prong candidate lead to the identification of one decay track as an electron and another as a kaon. This is interpreted as a semi-leptonic, Cabbibo favouredD0/D−0 decay.

On Medium Energy Protons Emitted in High Energy Hadron-Nucleus Collisions

A statistics of 1252 protons has been used to investigate the various characteristics of protons emitted with energies between (30-400) MeV in the interactions of 24 GeV/c protons and 50 GeV/c π--mesons with emulsion nuclei. The characteristics of the emitted protons have been found to exhibit no dependence on the nature and energy of the incident particles. Thus the study of different features of protons has been carried out using the combined data from the two experiments.

Formation of Clusters in 340 GeV/c π- Emulsion Interactions

New data from 340 GeV/ c π - -emulsion interactions are analyzed to investigate the cluster formation and their dependences with the target size and multiplicity. The data show significant dependence of the rapidity-gap distributions on the multiplicity. The multiplicity of clusters does not depend on the target size.

Charged charm production in proton-emulsion interactions at 400 GeV/c

A study of charged charm production is made at 400 GeV incident energy of protons in nuclear emulsion. A total of 7005 primary stars have been scrutinized to look for charm particle decays in the forward cone within a decay distance of 100–1,000 μm (3,056 stars) and 100–2,000 μm (3,949 stars). In all 10 charm candidates decaying to 3 charged particles plus neutrals have been observed. Background due to secondary interactions for events of such topology is estimated to be ≈3. Background due to strange particle decays is estimated to be negligible. The rest of the events are attributed toΛc+ andD± decays. This leads to a value of 91±35 μb/nucleon for the total charged charm production cross section. Using production cross section forD± from other experiments we obtainΛc+ production cross section as 62±27 μb/nucleon. Two cases of pair production of charm have been seen.