Pseudorapidity Distributions Of Particles Research Articles

Charged Particle Pseudorapidity Distributions Measured with the STAR EPD

In 2018, in preparation for the Beam Energy Scan II, the STAR detector was upgraded with the Event Plane Detector (EPD). The instrument enhanced STAR’s capabilities in centrality determination for fluctuation measurements, event plane resolution for flow measurements, and in triggering overall. Due to its fine radial granularity, it can also be utilized to measure pseudorapidity distributions of the produced charged primary particles, in EPD’s pseudorapidity coverage of 2.15<|η|<5.09. As such a measurement cannot be done directly, the response of the detector to the primary particles has to be understood well. The detector response matrix was determined via Monte Carlo simulations, and corrected charged particle pseudorapidity distributions were obtained in Au + Au collisions at the center of mass collision energies sNN = 19.6 and 27.0 GeV using an iterative unfolding procedure. Several systematic checks of the method were also done.

Study of Pseudo-rapidity Distributions of Secondary Particles at High Energies

Study of Pseudo-rapidity Distributions of Secondary Particles at High Energies

Limiting fragmentation in high-energy nuclear collisions at the CERN Large Hadron Collider

The hypothesis of limiting fragmentation (LF) or it is called otherwise recently, as extended longitudinal scaling, is an interesting phenomena in high energy multiparticle production process. This paper discusses about different regions of phase space and their importance in hadron production, giving special emphasis on the fragmentation region. Although it was conjectured as a universal phenomenon in high energy physics, with the advent of higher center-of-mass energies, it has become prudent to analyse and understand the validity of such hypothesis in view of the increasing inelastic nucleon-nucleon cross-section ($\sigma_{\rm in}$). In this work, we revisit the phenomenon of limiting fragmentation for nucleus-nucleus (A+A) collisions in the pseudorapidity distribution of charged particles at various energies. We use energy dependent $\sigma_{\rm in}$ to transform the charged particle pseudorapidity distributions ($dN^{\rm AA}_{ch}/d\eta$) into differential cross-section per unit pseudorapidity ($d\sigma^{\rm AA}/d\eta$) of charged particles and study the phenomenon of LF. We find that in $d\sigma^{\rm AA}/d\eta$ LF seems to be violated at LHC energies while considering the energy dependent $\sigma_{\rm in}$. We also perform a similar study using A Multi-Phase Transport (AMPT) Model with string melting scenario and also find that LF is violated at LHC energies.

Projectile mass and energy dependence of multifractal detrended cross-correlation analysis of pseudorapidity space and azimuthal space in high energy nuclear collisions

This paper studies the cross-correlation between the pseudorapidity and azimuthal distributions of the shower particles emitted in [Formula: see text]S-AgBr interactions at 200[Formula: see text]GeV and [Formula: see text]O-AgBr interactions at 60[Formula: see text]GeV applying Multifractal detrended cross-correlation analysis (MF-DXA) methodology. The cross-correlation between the pseudorapidity ([Formula: see text]) space and the azimuthal ([Formula: see text]) space is found to exhibit multifractality in case of both the interactions. The results obtained from the analysis of the experimental data were compared with those obtained for the randomly shuffled data for both the interactions, and the results revealed that the multifractality is due to the presence of long-range correlations. The study clearly indicates that the strength of the cross-correlation depends on both the projectile mass and energy.

Search for Excited Muons at the Future SPPC-based Muon--Proton Colliders

We have investigated the production potential of the spin-1/2 excited muons, predicted by the preonic models, at the four SPPC (Super Proton-Proton Collider)-based muon-proton colliders in different center-of-mass energies. For the signal process \mu p\rightarrow\mu^{\star}X\rightarrow\mu\gamma X, the production cross-section and the decay width values of the excited muons have been calculated. The pseudorapidity and transverse momentum distributions of the final state particles of muons and photons have been obtained to be determine the kinematical cuts best suited for discovery of the excited muons. By applying these cuts we have gotten the discovery, observation and exclusion mass limits of the excited muons for two compositeness scale values. It is shown that the discovery limits on the excited muons in case the compositeness scale equals to 100 TeV are 2.7, 3.9, 3.1 and 6.7 TeV for center-of-mass energies of 10.3, 14.2, 14.6 and 20.2 TeV, respectively.

Single production of the excited muons at the SPPC-based ultimate p collider

Single production potential of the excited muons at the SPPC-based ultimate muon-proton collider with center-of-mass energy of 116.6 TeV was analyzed. We calculated the production cross-sections and the decay widths of the excited muons with the process of µp → µ*X → γµX . We obtained the normalized transverse momentum and pseudorapidity distributions of the final-state particles to attain the kinematical cuts for the discovery of the excited muons. With these cuts, we determined the mass limits. It was shown that the discovery limits on the mass of the excited muons are 19.6 and 10.1 TeV for λ = mµ* and λ = 50 TeV, respectively.

Energy and centrality dependent study of deconfinement phase transition in a color string percolation approach at RHIC energies

We take the experimental data for transverse momentum spectra of identified charged hadrons in different centrality classes for nucleus-nucleus (A+A) collisions at various Relativistic Heavy-Ion Collider (RHIC) energies measured by the STAR collaboration. We analyse these data in the framework of color string percolation model (CSPM) in order to extract various percolation parameters at different centralities at RHIC energies to study the effect of collision geometry and collision energy. We use these parameters to study the centrality dependent behaviour of initial temperature of the percolation cluster, energy density, average transverse momentum, shear viscosity to entropy density ratio ($\eta/s$) and trace anomaly for different energies at RHIC from $\sqrt{s_{\rm NN}}$ = 19.6 to 200 GeV. These observables are found to strongly depend on centrality at various collision energies. The critical percolation density, which is related to the deconfinement phase transition is achieved in the most central nucleus-nucleus collisions, while it fails in the peripheral collisions. A universal scaling is observed in color suppression factor and initial temperatures when studied as a function of charged particle pseudorapidity distribution scaled by nuclear overlap area at RHIC energies. The minimum of $\eta/s$ is observed in the most central collisions at $\sqrt{s_{\rm NN}}$ = 130 and 200 GeV.

Universal freezeout condition for charged hadrons in a hybrid approach

Hadronic freezeout during the evolution of the medium created in heavy-ion collisions is an important phenomena. It is quite useful to find a universal freezeout condition for each and every nuclear collisions. In this article, we have constructed a hybrid model to calculate the ratio of transverse energy to total mean multiplicity $E_{T} /N_{ch}$, since this ratio can possibly act as a freezeout condition in heavy-ion collision experiments. Present hybrid model blends two approaches : Tsallis statistics and wounded quark approach. Recently, Tsallis statistics has been reliably used to obtain the transverse momentum distribution of charged hadrons produced in relativistic ion collisions. On the other side it has been shown that the pseudorapidity distribution of charged hadrons can be calculated satisfactorily using the wounded quark model (WQM). We have used this hybrid model to calculate the transverse energy density distributions, $dE_{T}/d\eta$ at midrapidity using charged particle pseudorapidity distributions, $dN_{ch}/d\eta$ and mean transverse momentum $\langle p_{T} \rangle$ in various type of nuclear collisions. We found that present hybrid model satisfactorily explains the experimental data whether other models fail to reproduce the data at central and at peripheral collisions simultaneously. Finally, ratio of transverse energy to total mean multiplicity, $E_{T} /N_{ch}$ has been computed within hybrid model and compared with the available experimental data at RHIC and LHC energies. We observed no explicit dependence of $E_{T} /N_{ch}$ on energy as well as centrality and thus it can definitely act as a freezeout criteria.

Description of charged particle pseudorapidity distributions in Pb+Pb collisions with Tsallis thermodynamics

The centrality dependence of pseudorapidity distributions for charged particles produced in Au+Au collisions at $\sqrt{s_{NN}}=130$ GeV and 200 GeV at RHIC, and in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at LHC are investigated in the fireball model, assuming that the rapidity axis is populated with fireballs following one distribution function. We assume that the particles in the fireball fulfill the Tsallis distribution. The theoretical results are compared with the experimental measurements and a good agreement is found. Using these results, the pseudorapidity distributions of charged particles produced in Pb+Pb central collisions at $\sqrt{s_{NN}}=5.02$ TeV and 10 TeV are predicted.

Unified Hydrodynamics and Pseudorapidity Distributions of Charged Particles Produced in Heavy Ion Collisions at Low Energies at RHIC**Supported by the Shanghai Key Lab of Modern Optical System.

In the context of unified hydrodynamics, we discuss the pseudorapidity distributions of the charged particles produced in Au-Au and Cu-Cu collisions at the low RHIC energies of and 22.4 GeV, respectively. It is found that the unified hydrodynamics alone can give a good description to the experimental measurements. This is different from the collisions at the maximum RHIC energy of GeV or at LHC energy of TeV, in which the leading particles must be taken into account so that we can properly explain the experimental observations.

Study of the peculiarities of multiparticle production via event-by-event analysis in asymmetric nucleus-nucleus interactions

In this work the study on the peculiarities of multiparticle production in interactions of asymmetric nuclei to search for unusual features of such interactions, is performed. A research of long-range and short-range multiparticle correlations in the pseudorapidity distribution of secondary particles on the basis of analysis of individual interactions of nuclei of 197 Au at energy 10.7 AGeV with photoemulsion nuclei, is carried out. Events with long-range multiparticle correlations (LC), short-range multiparticle correlations (SC) and mixed type (MT) in pseudorapidity distribution of secondary particles, are selected by the Hurst method in accordance with Hurst curve behavior. These types have significantly different characteristics. At first, they have different fragmentation parameters. Events of LC type are processes of full destruction of the projectile nucleus, in which multicharge fragments are absent. In events of mixed type several multicharge fragments of projectile nucleus are discovered. Secondly, these two types have significantly different multiplicity distribution. The mean multiplicity of LC type events is significantly more than in mixed type events. On the basis of research of the dependence of multiplicity versus target-nuclei fragments number for events of various types it is revealed, that the most considerable multiparticle correlations are observed in interactions of the mixed type, which correspond to the central collisions of gold nuclei and nuclei of CNO-group, i.e. nuclei with strongly asymmetric volume, nuclear mass, charge, etc. Such events are characterised by full destruction of the target-nucleus and the disintegration of the projectile-nucleus on several multi-charged fragments.

Excited Muon Searches at the FCC-Based Muon-Hadron Colliders

We study the excited muon production at the FCC-based muon-hadron colliders. We give the excited muon decay widths and production cross-sections. We deal with the μp→μ⋆q→μγq process and plot the transverse momentum and normalized pseudorapidity distributions of final state particles to define the kinematical cuts best suited for discovery. By using these cuts, we get the mass limits for excited muons. It is shown that the discovery limits obtained on the mass of μ⋆ are 2.2, 5.8, and 7.5 TeV for muon energies of 63, 750, and 1500 GeV, respectively.

Centrality dependence of low-pT and high-pT particle production in proton–lead collisions with ATLAS

Measurements of the centrality dependence of low-pT and high-pT particle production in proton-lead collisions at the LHC can provide unique insight into the dynamics of soft and hard scattering processes and the initial state of ultra-relativistic nuclear collisions. Recent results have shown that both soft and hard processes may be significantly influenced by event-to-event fluctuations (variations) in the structure of the proton. In this proceedings, the latest measurements of the centrality dependence of charged particle, and Z boson production with the ATLAS detector at the LHC are used to explore these questions. In particular, the sensitivity of the charged particle pseudorapidity distribution in proton–lead collisions to the choice of centrality variable is discussed. Separately, to address recent measurements of the correlation between the initial-state hard scattering kinematics in dijet events and forward transverse energy in proton-proton collisions will be presented.

Extracting squared speed-of-sound parameter from asymmetric nuclear collisions at high energies

We apply the Landau hydrodynamic model in leading target/projectile nucleons and target/projectile cylinders in the multisource thermal model respectively, in asymmetric nuclear collisions. Each leading nucleon source or cylinder source is regarded as an energy reservoir to emit or produce particles and can be described by the Landau hydrodynamic model. The pseudorapidity distribution of final-state particles is in fact a sum of four Gaussian functions which correspond to the contributions of the leading target nucleons, target cylinder, projectile cylinder and leading projectile nucleons, respectively, in accordance with their central rapidities from low to high value. Based on the descriptions of the pseudorapidity distributions of final-state particles produced in proton-emulsion, deuteron-gold and gold-emulsion collisions, the squared speed-of-sound parameters for the four sources in asymmetric nuclear collisions have been extracted and shown to be approximately the same within the statistical error.

Inclusive photon production at forward rapidities in pp collisions at LHC energies with the ALICE experiment

Measurements of multiplicity and pseudorapidity distributions of particles produced in pp collisions are important for the study of particle production mechanisms and to obtain baseline distributions to be compared with those from heavy-ion collisions. The inclusive photon measurements (dominated by π0 decays) are complementary to the charged particle measurements. The present work focuses on the forward rapidity region with comparisons to different models such as PYTHIA and PHOJET.We report the measurements of multiplicity and pseudorapidity distributions of inclusive photons using the ALICE Photon Multiplicity Detector (PMD) at forward rapidities (2.3 < η < 3.9) in pp collisions at = 0.9, 2.76 and 7 TeV. It is observed that the photon multiplicity distributions are well described by negative binomial distributions (NBD). Multiplicity distributions are studied in terms of KNO variables for each energy. It is shown that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and power law dependence. The results are compared to different model predictions. These models reproduce experimental results at lower energy while they are not accurate at higher energies.

Pseudorapidity dependence of short-range correlations from a multi-phase transport model**Supported by GBL31512, Major State Basic Research Devolopment Program of China (2014CB845402), NSFC (11475149, 11175232, 11375251, 11421505, 11221504)

Using a multi-phase transport model (AMPT) that includes both initial partonic and hadronic interactions, we study neighboring bin multiplicity correlations as a function of pseudorapidity in Au+Au collisions at . It is observed that for Au+Au collisions, the short-range correlations of final particles have a trough at central pseudorapidity, while for AuAu collisions, the short-range correlations of final particles have a peak at central pseudorapidity. Our findings indicate that the pseudorapidity dependence of short-range correlations should contain some new physical information, and are not a simple result of the pseudorapidity distribution of final particles. The AMPT results with and without hadronic scattering are compared. It is found that hadron scattering can only increase the short-range correlations to some level, but is not responsible for the different correlation shapes for different energies. Further study shows that the different pseudorapidity dependence of short-range correlations are mainly due to partonic evolution and the following hadronization scheme.

Comparative Multifractal Detrended Fluctuation Analysis of Heavy Ion Interactions at a Few GeV to a Few Hundred GeV

We have studied the multifractality of pion emission process in16O-AgBr interactions at 2.1 AGeV and 60 AGeV,12C-AgBr and 24Mg-AgBr interactions at 4.5 AGeV, and32S-AgBr interactions at 200 AGeV using Multifractal Detrended Fluctuation Analysis (MFDFA) method which is capable of extracting the actual multifractal property filtering out the average trend of fluctuation. The analysis reveals that the pseudorapidity distribution of the shower particles is multifractal in nature for all the interactions; that is, pion production mechanism has inbuilt multiscale self-similarity property. We have employed MFDFA method for randomly generated events for32S-AgBr interactions at 200 AGeV. Comparison of expt. results with those obtained from randomly generated data set reveals that the source of multifractality in our data is the presence of long range correlation. Comparing the results obtained from different interactions, it may be concluded that strength of multifractality decreases with projectile mass for the same projectile energy and for a particular projectile it increases with energy. The values of ordinary Hurst exponent suggest that there is long range correlation present in our data for all the interactions.

Transverse momentum and pseudorapidity distributions of final-state particles and spatial structure pictures of an interacting system in p-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV

The transverse momentum and pseudorapidity distributions of final-state particles produced in proton-lead (p-Pb) collisions at center-of-mass energy per nucleon pair \sqrt{s_{NN}}=5.02 TeV are studied in the framework of a multisource thermal model. Experimental results measured by the ALICE and CMS Collaborations are described by the Tsallis transverse momentum distribution and the two-cylinder pseudorapidity distribution. Based on the parameter values extracted from the transverse momentum and pseudorapidity distributions, some other quantities are extracted. Then, the structure pictures of interacting system at the stage of kinetic freeze-out in some spaces are obtained.

The Evolution-Dominated Hydrodynamics and the Pseudorapidity Distributions in Nucleus-Nucleus Collisions at Low Energies at the BNL Relativistic Heavy Ion Collider

In the context of evolution-dominated hydrodynamics, we discuss the pseudorapidity distributions of the charged particles produced in Au-Au and Cu-Cu collisions at the corresponding energies of √^SNN=19:6 and 22.4 GeV at BNL-RHIC. It is found that the evolution-dominated hydrodynamics alone can give a good description to the experimental measurements. This is di_erent from that in collisions at the maximum energy of √^SNN=200 GeV at BNL-RHIC or at √^SNN=2:76 TeV at CERN-LHC. Where, in addition to evolutiondominated hydrodynamics, the leading particles have to be taken into account in order to adequately explain the experimental observations.

Charged particle production in p+Pb collisions with the ATLAS detector

Abstract We report on the measurements of centrality dependence of the charged particle pseudorapidity distribution and transverse momentum distributions in proton–lead collisions with the ATLAS detector at LHC. The data were collected in 2012 run providing proton–nucleus collisions at s NN = 5.02 TeV . These measurements are expected to contribute to understanding the initial state of the nuclear wave function. The presented results also point to the importance of understanding the fluctuating nature of the nucleon–nucleon collisions.