S. K. Tuli

Some general characteristics of 28Si-emulsion interactions at 4.5 GeV/c per nucleon

Abstract We present our observations on the salient features of the interactions produced by 28Si nuclei of 4.5 GeV/c per nucleon in photographic emulsions. The results on the inelastic mean-free path and interaction cross section are presented and compared with the predictions of a geometrical model. Measurements on the multiplicity distribution, mean multiplicities, multiplicity correlations and multiplicity scaling of charged secondary particles are studied. A comparison with other available data at same/nearby incident momentum per nucleon from proton-nucleus and carbon-nucleus collisions is presented in order to examine the dependence on the projectile mass.

Central collisions of 28Si with Ag(Br) nuclei

Abstract This paper presents data on multiplicity and pseudorapidity distributions of hadrons from central collisions of 28 Si with Ag(Br) targets at 4.5 GeV c per nucleon. These events exhibit approximate pseudorapidity distribution scaling in their target as well as in the projectile rest frames. The average pseudorapidity 〈gh〉 is examined as a function of grey particle multiplicity, n g and the effect of intranuclear collisions is discussed. A rough estimation of the energy density has been made from the data of this experiment. Also, a comparison with data from collisions induced by lighter nuclei at the same momentum per nucleon is presented in order to trace the dependence on the projectile mass.

Electron production by 4.0 GeV/c π+p interactions

Abstract We have investigated electron production in 4.0 GeV/ c π + pinteractions. Limits to direct electron pair production are measured and an example of ϱ 0 or ω 0 decay to e + e − is observed. The ratio of the number of singly produced electrons to the total number of charged pions is less than 6 × 10 -5 (at the 95% confidence level).

On the parametrization of hadron-nucleus multiplicity distributions

Abstract A new parametrization for the hadron-nucleus multiplicity distributions is proposed and compared with pion-nucleus and proton-nucleus data with the same values of parameters. We believe that these parameters have their origin in basic quark-gluon interactions. We further illustrate this by evaluating the value of these parameters with the help of QCD.

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.

Gamma and π0 production by 4 GeV/cπ+p interactions

Abstract Inclusive data for the production of γ rays and π 0 are presented from an experiment with a 4 GeV/ c π + beam, using a track-sensitive target. The results are compared with data at other energies and with π + and π − distributions.

Some general properties of projectile fragments in 40Ar interactions in nuclear emulsions at 1.8 A GeV

An analysis of projectile fragments has been performed using 40Ar-emulsion interactions at 1.8 A GeV. The interaction mean free path of 40Ar nuclei was obtained on the basis of 4600 events which enabled one to calculate the total inelastic cross section. Correlations between the multiplicity of different charged particles were studied extensively to get an insight into the reaction mechanism. The average number of interacting nucleons of the projectile was calculated and compared with results from other experiments. Events with projectile fragments were divided into various reaction channels and several parameters like average emission angle and target particle multiplicities were studied as a function of target mass in different reaction channels. The projectile fragmentation properties were found to be independent of the target for peripheral collisions.

Emission of projectile helium fragments in 14N interactions at 2.1 GeV/nucleon: A test of factorization and limiting fragmentation

Abstract An analysis of projectile helium fragments has been performed from the point of view of testing the factorization and limiting fragmentation hypothesis. An event-by-event examination of 923 interactions of 14 N in emulsion at 2.1 GeV per nucleon has been made for target identification. Events with projectile fragments have been divided into various reaction channels according to the multiplicity of He nuclei. The multiplicity distribution, angular structure and other properties of the projectile He fragments have been investigated to see the dependence on different targets and target excitation. The properties of He fragments emitted from the projectile have been found to remain independent of target in peripheral collision processes. The target and projectile breakup properties have been analysed in terms of the collision geometry. Gaussian distributions have been fitted to the projected angular distribution data for He fragments at various intervals of impact parameter and in different reaction channels. The properties of emitted He nuclei exhibit characteristic features of factorization and limiting fragmentation.

On fragmentation characteristics of relativistic 14N projectiles

Abstract An analysis of multiply-charged projectile fragments has been performed from the point of view of fragmentation characteristics using a statistics of 916 fragments comprising over 923 interactions of 14 N in emulsion at 2.1 GeV per nucleon. The number of interacting nucleons has been investigated in the light of the prediction of the participant-spectator model. The momentum of projectile fragments has been measured directly. Gaussian distributions have been fitted to the projected angular distributions as well as momentum distributions for multiply-charged projectile fragments at various intervals of impact parameter and in different reaction channels. Relativistic Maxwell-Boltzmann distributions have been fitted to the emission angles of He fragments, emitted in the collision with varius targets, to investigate the emission characteristics of relativistic projectile fragments.

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.