V. K. Gupta

Multiplicity in proton-nucleus interactions at 200 GeV/c

Abstract Experimental results on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c proton beam at NAL are presented. It is found that the average charged particle multiplicity 〈n s 〉 = 13.0 ± 0.4, D ≡ (〈n s 2 〉 − 〈n s 〉 2 ) 1 2 = 8.5 ± 0.4 and 〈N h 〉 = 7.3 ± 0.2 . Energy dependence of Rem = 〈ns〉/〈nch〉, where 〈nch〉 is the charged particle multiplicity in pp collisions, is investigated in the range 7.1–8000 GeV/c. Rem attains a constant value of 1.71 ± 0.04 beyond 200 GeV/c and furthermore this value of Rem implies an A dependence RA = A0.13. It is found that even for p-nucleus collisions D increases linearly with 〈ns〉 with about the same slope as for pp collisions.

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett.50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioRem = 〈ns〉/〈nch〉, where 〈nch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,Rem = 1·71 implies an effectiveA-dependence ofRA =A0.18,i.e., a very weak dependence. Predictions ofRem on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.

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.

Characteristics of56Fe-emulsion interactions at 1.7 GeV/A

SummaryGeneral characteristics of56Fe-emulsion interactions at 1.7 GeV/A are discussed. The results on interaction cross-section, mean free path, heavy-prong multiplicity, number of emitted alpha-particles and fragments, etc. are compared with corresponding results from interactions of other projectiles over a wide range of mass (A=1÷56). The results on cross-section are discussed in the light of geometrical models with special emphasis on the overlap parameter. Correlations amongst black, grey, heavy particles emitted from target and the alpha and other projectile fragments are discussed.RiassuntoSi discutono le caratteristiche generali delle interazioni56Fe-emulsione a 1.7 GeV/A. Si confrontano i risultati sulla sezione durto dinterazione, il cammino libero medio, la molteplicità di prong pesanti, il numero di particelle alfa emesse e frammenti ecc. con i risultati corrispondenti da interazioni di altri proiettili in un ampio intervallo di massa (A=1÷56). Si discutono i risultati della sezione durto alla luce di modelli geometrici con enfasi speciale sul parametro di soprapposizione. Si discutono le correlazioni tra particelle nere, grigie e pesanti emesse dal bersaglio e la particella alfa e altri frammenti di proiettile.РезюмеОбсуждаются характеристики взаимодействий56Fe с эмульсией при энергии 1.7 ГэВ/A. Результаты для поперечного сечения взаимодействия, длины свободного пробега, множественности, числа испущенных альфа-частиц и фрагментов и т.д. сравниваются с соответствующими результатами для взаимодействий других налетающих частиц в широком интервале масс (A=1÷56). Результаты для поперечного сечения обсуждаются в свете геометрических моделей, обращая особое внимание на параметр перекрытия. Обсуждаются корреляции между черными, серыми, тяжелыми частицами, испущенными из мишени, и альфа- и другими налетающими фрагментами.

Variation of average charged particle multiplicity inp-nucleus interactions with energy and the two component description of particle production at high energies

Experimental data on average shower particle multiplicity (〈Ns〉) accumulated onp-nucleus interactions in the wide momentum region of 7.1–8000 GeV/c is investigated. It is observed that 〈Ns〉 is represented exceedingly well as a function of (vvS). There are two physical processes which represent the experimental data reasonably well in the two momentum regionsviz 7.1–67.9 GeV/c and 67.9–8000 GeV/c. 〈Ns〉=a(vS)/a+b fits the data in the low momentum region, whereas 〈Ns〉=a +b ln (vvS) fits the experimental data in the high momentum region. The two physical processes are unified and represented by a single equation which is shown to be the consequence of two component theory and collective models.

A study of angular correlations of projectile and target fragments in 1.4 A GeV Kr+Ag(Br) collisions

A sample of high multiplicity quasi-central Kr84+Ag(Br) interactions has beenanalysed in terms of angular correlations between projectile and target fragments. The azimuthal correlation of PFs and TFs suggests the presence of a weak collective (bounce-off) effect. Other observations like, target recoil velocity,F/B ratio of TFs with respect to direction of their source etc. are interpreted in terms of a simple two body quasi-elastic scattering and a modified Maxwell-Boltzmann distribution.

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.

Some observations on the systematics in high-energy p-Nucleus interactions

SummaryAn attempt has been made to study the systematics in shower prong distributions in p-emulsion interactions. These distributions show systematic trends similar to those observed in pp and πp interactions. The p-nucleus data seem to observe the semi-inclusive KNO scaling.RiassuntoSi cerca di studiare la sistematica nelle distrilbuzioni delle tracce degli sciami in interazioni p-emulsione. Queste distribuzioni mostrano andamenti sistematioi simili a quelli osservati in interazioni pp e πp. I dati p-nucleo sembrano seguire la variazione di scala KNO seminolusiva.РезюмеИсследуется систематика в ливневых распределениях при взаимодействиях протонов с эмульсией. Рассмотренные распределения обнаруживают систематическое подобие распределениям, обнаруженным в рр и Лр взаимодействиях. По-видимому, данные для взаимодействий протонов с ядрами обнаруживают полу-инклюзивный KNO-скейлинг.

Inelastic interactions of 9.38 GeV/c deuteron in emulsion

Characteristics of the inelastic interactions of 9.38 GeV/c deuterons with nuclear emulsion nuclei have been studied. These have been compared with nucleon-nucleus interactions at a corresponding momentum. The probability of nucleon stripping in deuteron-nucleus interactions has been observed to be 0.5. The charged particle multiplicity in deuteron-nucleus interactions exhibitA-dependence of the typeAα with α=0.08. The experimental data disagree with KNO scaling.

Search for anomalous interaction mean free paths of charge, 2≦Z≦18 projectile fragments in emulsions exposed to 1.8 A GeV40Ar ions

Abstract40Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,Nh dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level.