An investigation of projectile helium fragments in high-energy nucleus–nucleus interactions

A detailed study on the multiplicity distribution of helium (He) fragments emitted in projectile fragmentation of 22Ne, 28Si, and 32S projectiles on interactions with H, CNO, and AgBr targets in a nuclear emulsion track detector has been presented at an incident momentum of (4.1–4.5) AGeV/c. The percentage of events with He fragments increases with increase in projectile mass for all three targets. Studies of multiplicity moments, dispersion of multiplicity distribution, and the investigation of dynamical fluctuations of the projectile He fragments have also been carried out.

Dependence of the cut-off parameters for the cluster reconstruction on incident momenta

In this work, firstly, we have determined the multiplicities of protons that are involved from projectiles to interactions, and secondly, the mean incident momentum using experimental data on the collisions of proton, helium, oxygen, silicon, and sulfur with the nuclear emulsion at 4.5A GeV/c. We have studied the dependences of clot numbers, number of particles in the clot, rapidity, and the mean azimuthal value on the variable dij, and the dependence of the cluster number on the mean value of the variable dij. Using the “Cone” algorithm for the clustering, we have precisely identified that the cut-off parameter to compose the clusters consisted of s and f tracks produced in (p, He, C, O, Si, S) + Em collisions decreases by the power law with mean values of incident momentum.

An investigation of Renyi entropy in high-energy nucleus–nucleus collisions

A study of Renyi entropy of shower particles has been carried out using 16O, 28Si, and 32S projectiles in interaction with AgBr and CNO target present in nuclear emulsion at an incident momentum of 4.5 AGeV/c. The analysis reveals interesting experimental observations for both groups of targets. A comparison of the experimental results with the results obtained from analyzing the event sample generated by the UrQMD code is also presented. Renyi entropy values increase with the increase of projectile mass. This increase is weaker in case of CNO target. The calculated values of second-order Renyi entropy H2 are shown to vary linearly with the logarithm of average particle multiplicity ln⟨n⟩ for both targets. The dependence of Renyi entropy on the logarithm of average particle multiplicity ln⟨n⟩ indicates the presence of long-range correlation in high-energy nucleus–nucleus interactions. The variation is found to be stronger in the case of experimental events in comparison to the UrQMD simulated events indicating stronger long-range correlation for the experimental data.

Tsallis Statistical Interpretation of Transverse Momentum Spectra in High-EnergypA Collisions

In Tsallis statistics, we investigate charged pion and proton production forpCu andpPb interactions at 3, 8, and 15 GeV/c. Two versions of Tsallis distribution are implemented in a multisource thermal model. A comparison with experimental data of the HARP-CDP group shows that they both can reproduce the transverse momentum spectra, but the improved form gives a better description. It is also found that the difference betweenqandq′is small when the temperatureT = T′for the same incident momentum and angular interval, and the value ofqis greater thanq′in most cases.

Emission of Protons and Charged Pions inp+ Cu andp+ Pb Collisions at 3, 8, and 15 GeV/c

We present an analysis of proton and charged pion transverse momentum spectra ofp+Cuandp+Pbreactions at 3, 8, and 15 GeV/cin the framework of a multisource thermal model. The spectra are compared closely with the experimental data of HARP-CDP at all angular intervals. The result shows that the widths of the particle distributions in bothp+Cuandp+Pbcollisions decrease with increasing the angle for the same incident momentum.

CENTRALITY DEPENDENCE OF NONSTATISTICAL FLUCTUATION IN SINGLE PARTICLE DENSITY DISTRIBUTION IN 32S–Ag/Br INTERACTION AT 200A GeV/c

Nonstatistical fluctuations in the density distribution of shower tracks coming out of 32 S – Ag/Br interaction at an incident momentum of 200A GeV/c, have been characterized by using the intermittency and multifractality techniques. A sample of 32 S – Ag/Br nuclear emulsion events has been partitioned into three subsamples with respect to the shower track multiplicity in such a way that one can roughly estimate the average centrality for each subsample. Thereby, the centrality dependence of a set of relevant intermittency and multifractal issues has been investigated.

Radiation pressure on a dielectric surface

The radiation pressure on an insulating dielectric medium should be calculable from the force acting on the polarization vector P. The well-known force proposed by Gordon (Phys. Rev. A, 8, 14 (1973) disappears in the case of a steady-state plane wave. A new form of force explicitly involving the polarization vector is proposed and applied to determine the partition of the incident momentum among the reflected and transmitted wave, and the dielectric medium. The momentum of electromagnetic wave in a dielectric medium thus found is consistent with the classical relationship, wave momentum flux density = wave intensity/wave velocity.

Study of hadrons emission in 4.5A GeV/c32Sinteractions with emulsion

An experimental study of the forward and backward emission of relativistic and fast hadrons in the interactions of 4.5 A,GeV/c 32S with emulsion was carried out. The study supports the conclusion that a collective mechanism is responsible for the production of particles in the backward hemisphere (which is restricted beyond the kinematics limit). The backward emission of both shower and grey particles can be described by an exponential decay law independent of the projectile size. The experimental results suggest that the backward particles result from the decay of the system in a latter stage of the interaction. While the average multiplicities of the shower particles emitted in the forward hemisphere are strongly dependent on the projectile size and incident momentum, the average values of those emitted into the backward hemisphere are found to be only a function of the target size (i.e., impact parameter). Thus, the backward particle production can be considered as a yield of a highly excited target system, in its rest frame.PACS Nos.: 25.75.–q, 25.75.Dw, 25.75.Gz, 25.75.Ld, 25.70.Mn, 25.70.Pq,41.75.Ak, 41.75.Cn, 29.40.Rg, 07.68.+m

Forward backward studies of 22Ne(28Si)-emulsion interactions at (4.1-4.5) AGeV/c

The characteristics of nucleus–nucleus collisions at high energies are investigated for the interaction of 22Ne and 28Si with emulsion nuclei . The multiplicity and correlations of the forward (θ < 90°) and backward (θ ≥ 90°) secondary particles emitted are calculated according to the modified cascade and modified Fritiof models. The predictions of the two models are compared with experimental data at an incident momentum of (4.1–4.5) GeV/c per nucleon. Both models depend on the Monte Carlo techniques where the modified cascade model implies the superposition of nucleon–nucleon interactions, and the modified Fritiof model utilizes the Regge theory for the description of the cascading process. Comparison with data shows no clear preference of one model over the other. However, the modified Fritiof model seems to be nearer to the experimental data than the modified cascade model.PACS No.: 13.85.–t