Charged Particle Pseudorapidity Research Articles

Revisiting the centrality definition and observable centrality dependence of relativistic heavy-ion collisions in PACIAE model

We improve the centrality definition in impact parameter in PACIAE model responding the fact reported by the ALICE, ATLAS, and CMS collaborations that the maximum impact parameter in heavy ion collisions should be extended to 20 fm. Meanwhile the PACIAE program is updated to a new version of PACIAE 2.2.2 with convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in one unified program version. The new impact parameter definition together with the optical Glauber model calculated impact parameter bin, Npart, and Ncoll in proton-nucleus and nucleus-nucleus collisions at relativistic energies are consistent with the improved MC-Glauber model ones within the error bar. The charged-particle pseudorapidity and the transverse momentum distributions in Pb-Pb collisions at sNN=5.02 TeV simulated by PACIAE 2.2.2 well reproduce the ALICE experimental data. New version program summaryProgram Title: PACIAE version 2.2.2CPC Library link to program files:https://doi.org/10.17632/w3g68dj4d9.4Licensing provisions: CC By 4.0Programming language: FORTRANJournal reference of previous version: Comput. Phys. Commun. 224 (2018) 417Does the new version supersede the previous version?: YesReasons for the new version: Recently ALICE, ATLAS and CMS collaborations reported that the maximum impact parameter bmax should be extended to 20 fm in the nuclear-nuclear collisions at relativistic energies. The impact parameter formula in PACIAE model has to be improved correspondingly. Meanwhile the PACIAE model is updated to PACIAE 2.2.2 with the convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in one unified program version.Summary of revisions: The impact parameter b in PACIAE model is calculated by geometrical model ofb=c×bmax, where c refers to the centrality percentile and bmax is assumed to bebmax=RA+RB+f×d. In above equation RA (RB) is the radius of nuclear A (B), d=0.546 fm describes the tail of the nuclear density profile. Originally, the coefficient f is set to be equal to 2 and 1 for nucleus-nucleus and proton-nucleus collisions, respectively. Now they are assumed to be equal to 4 and 2, respectively. Meanwhile, the PACIAE model is updated to the version of PACIAE 2.2.2 with the convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in a unified program version.Nature of problem: The ALICE, ATLAS and CMS collaborations reported that the maximum impact parameter, bmax, in heavy-ion collisions at relativistic energies should be extended to 20 fm where the interaction is really approaching to zero. The impact parameter centrality determination in heavy-ion collisions at relativistic energies has to be revised accordingly in the PACIAE model.Solution method: A new f coefficient sets in the impact parameter formula in PACIAE model, sequentially the new b bin corresponding to a given centrality percentile bin is introduced in the new version of PACIAE 2.2.2.

Distributions of the Transverse Momentum and Pseudorapidity of Charged Particles in pp Collisions at 0.9 TeV

We have studied the charged particles spectra for the pseudorapidity region of ∣η∣ < 2.5, the multiplicity of charged particles, its dependence on pT as well as on η and the relation between average pT and charged particles multiplicity in pp collisions at √s = 0.9 TeV. For simulations, we have used the EPOS-LHC, EPOS-1.99, QGSJETII-04, and SIBYLL-2.3c models and compared their predictions with the experimental data of ATLAS experiment. For the pT distribution, predictions of the Sibyll-2.3c are matching with the experimental data in a region of 0.5 GeV/c < pT < 0.8 GeV/c and EPOS-1.99 model results are near to the experimental data for 0.5 GeV/c < pT < 1.5 GeV/c. For the case of average pT, EPOS-LHC, and Sibyll-2.3c predictions are closer to the experimental data. For the pseudorapidity charged particle density distributions, QGSJETII-04 model predictions are better describing the experimental data.

Study of Pseudorapidity and Transverse-Momentum Distributions of Charged Particles in pp Interactions at √s = 13 TeV Using Hadron Production Models

Pseudorapidity (η) and Transverse momentum (pT) distributions of charged particles produced in proton-proton (pp) collisions at √s = 13 TeV are studied. Transverse momentum distributions of charged particles are considered in the Pseudorapidity region of |η| < 0.8 and in the transverse momentum range of 0 < pT < 20 GeV/c. EPOS1.99, EPOS-LHC and QGSJETII-04 models are used to perform simulations. In order to check the validity of simulations performed using these Monte-Carlo event generators, the results are compared to the measurements of ALICE experiment at the LHC CERN. For the pT distribution, the EPOS1.99 and QGSJET underpredict the experimental data while the EPOS-LHC model reproduced the distribution very well. EPOS-LHC model describes the experimental data very well as compared to the other two models for the ratio of pT spectra of charged particles at √s = 13 TeV to 7 TeV. EPOS-LHC also describes the pseudorapidity distribution very well while the EPOS 1.99 and QGSJETII-04 underpredict and overpredict the distribution respectively.

Soft QCD in ATLAS: Minimum bias and diffraction studies

We present measurements of charged particle production in proton-proton collisions at centre-of-mass energies of √s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. Events were collected using a single-arm minimum bias trigger, charged tracks are measured with high precision in the inner tracking system. Minimum bias analysis uses data samples at all three energies, while diffractive events are studied using a sample of events at √s = 7 TeV. To study diffractive interactions, the events that have hits on exactly one side of the ATLAS detector were selected. The charged particle multiplicity, pseudorapidity and transverse momentum spectra are analyzed and compared to the predictions by various Monte Carlo models.

Correlation and fluctuations in relativistic nucleus-nucleus collisions

Correlation and fluctuations are now well accepted analysis techniques in heavy-ion collisions at relativistic energies. At the current stage of RHIC exploration, matter in bulk and many of the physics questions about the final stage of collisions are addressed with the help of correlation techniques. In the present work after a general introduction to the underlying formalism to the exotic phenomena of correlation and fluctuations, discussion on various parameters disentangling dynamical fluctuations is presented. Analysis to investigate dynamical fluctuations and correlation is carried out in terms of Fq- and Gq-moments. A study of various other parameters involving multiplicity and pseudorapidity of relativistic charged particles produced in high energy nuclear interactions reveals the presence of correlation and fluctuations in particle production in these collisions. The experimental data on 14.5A GeV/c 28Si-nucleus interactions has been analyzed. A parallel analysis of correlation free data generated using MC-RAND Monte Carlo code, UrQMD data and for the HIJING generated events has also been carried out.

Particle production in nuclear collisions over a broad centrality range from the PHOBOS experiment

The PHOBOS collaboration has studied the pseudorapidity and transverse momentum distributions of charged particles produced in heavy ion collisions. Results from Au+Au collisions at various center-of-mass energies and over a broad range of centrality are presented here. The data are compared to Cu+Cu, p+p and d+Au collisions at corresponding energies and centralities. The data are found to exhibit simple scaling properties such as the observed factorization of collision energy and geometry dependences. The presented data help us distinguish between models of particle production in relativistic heavy ion collisions.

Charged particle multiplicity and pseudorapidity density distributions in 16O, 28Si and 197Au-induced nuclear interactions at 14.6 and 11.6A GeV/c

Pseudorapidity density and multiplicity distributions of charged particles produced in heavy-ion collisions at the BNL AGS have been studied. The multiplicity distributions and pseudorapidity distributions of shower particles in Au-induced interactions are presented and compared with model predictions from RQMD, FRITIOF and VENUS. It is shown that the widths of the pseudorapidity distributions of produced particles in central collisions are independent of the interacting system. The results from EMU01 have been compared, and found to agree, with the results from two other heavy-ion experiments, E802 and E814.

REVIEW OF RAPIDITY DENSITY DISTRIBUTIONS IN HEAVY-ION INDUCED INTERACTIONS AT RELATIVISTIC ENERGIES

Violent interactions among colliding nuclei ultimately provide the suitable conditions for creating new and hitherto unexplored phenomena like color rope and quark-gluon plasma formation. The systemmatics achieved so far in pseudorapidity and density distributions of charged particles emitted from relativistic nucleus-nucleus collisions is reviewed and comparisons to model predictions are made. Data from both emulsion and counter experiments are utilized and the dependence of the angular spectra on projectile energy, centrality measured by means of forward charge or enegy flow, and on the projectile/target masses are reported. For a few central events, energy densities of the hot overlap zone are estimated to be beyond onset of deconfinement phase transition.

Negative binomial distribution fits to multiplicity distributions in restricted δη intervals from central 16O+Cu collisions at 14.6A [formula omitted] and their implication for “intermittency”

Fluctuations in pseudorapidity of charged particles from central (ZCAL) collisions of 16O+Cu at 14.6 A·GeV c have been analyzed by the E802 Collaboration using the method of normalized factorial moments as a function of the interval δη. In agreement with previous measurements, an apparent power-law growth of moments with decreasing interval is observed down to δη ∼ 0.1. Experience with e t distributions suggests that fluctuations of multiplicity and transverse energy can be well described by Gamma or Negative Binomial Distributions (NBD) and excellent fits to NBD were obtained in all δη bins. The k parameter of the NBD fit was found to increase linearly with the δη interval, which due to the well known property of the NBD under convolution, indicates that the multiplicity distributions in adjacent bins of pseudorapidity δη ∼ 0.1 are largely statistically independent.

Some interesting features of relativistic charged particles produced in carbon- and silicon-emulsion interactions at 4.5A GeV/c

This paper essentially deals with new data on the multiplicity of the relativistic charged particles produced in carbon- and silicon-nucleus interactions at 4.5A GeV/c. Analysis has been carried out in terms of pseudorapidity of relativistic charged particles and event-by-event rapidity dispersion. The results indicate that the maxima of theη-spectra shift towards smaller values ofη with increasingNg. The study of the rapidity dispersion of the particles reveals the existence of significant clusterization amongst the final-state particles.

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.

RESULTS FROM THE UA5 EXPERIMENTUA5 Collaboration-Bonn-Brussels-Cambridge-CERN-Stockholm

Resultes are presented from the UA5 experiment at the CERN p[MATH] collider with a c.m. energy [MATH] = 540 GeV. Charged particle pseudorapidity and multiplicity distributions are presented. Results on short and long range correlations are given. The production of strange particles and photons has been measured and a search has been made for the so called Centauro phenomenon.