Pseudorapidity Distributions Research Articles

Mathematical modelling for pseudorapidity distribution of hadron-hadron collisions

The modelling of proton-proton collisions at high energies using both group method data handling (GMDH) and gene expression programming (GEP) approaches is investigated over a wide range of center-of-mass energy (from \( \sqrt{s} = 23.6\) GeV to 7 TeV). We have used GMDH and GEP models to obtain two different mathematical formulae expressing the complex relation of the charged-particle pseudorapidity distribution \((\frac{d N_{ch}}{d \eta})\) of proton-proton interactions as a function of the center-of-mass energy \((\sqrt{s})\) in a simple explicit form. We have used the obtained formulae to simulate and predict \( \frac{d N_{ch}}{d \eta}\). Predictions are made at \( \sqrt{s}= 10\) TeV and 14 TeV. Compared to the available experimental data and to some widely used Monte Carlo generators (PYTHIA, PHOJET, and QGSM models), it is found that our models can accurately simulate and predict the charged-particle pseudorapidity distribution of proton-proton collisions.

Charged Particle, Photon Multiplicity, and Transverse Energy Production in High-Energy Heavy-Ion Collisions

We review the charged particle and photon multiplicities and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons, and the transverse energy measurement.

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.

Characteristics of disintegration of different emulsion nuclei by relativistic 28Si nuclei at 3.7 A GeV

An analysis of the data based on 924 inelastic interaction events induced by 28Si nuclei in a nuclear emulsion is presented. The nuclear fragmentation process is studied by analysing the total charge (Q) distribution of the projectile spectators for different emulsion target groups along with the comparison of Monte Carlo Glauber model results. Probability distributions for total disintegrated events as a function of different projectile masses are shown and compared with cascade evaporation model results at same energy per nucleon. Further, mean multiplicities of different charged secondaries for different classes of events are presented and for each event, variation of mean multiplicities as a function of total charge (Q) is also presented. The pseudorapidity distributions and normalized pseudorapidity distributions of the produced charged particles in nucleus–nucleus collisions at 3.7 A GeV are analysed for total disintegration (TD) as well as minimum-bias events.

Measurement of pseudorapidity distributions of charged particles in proton–proton collisions at $$\sqrt{s} = 8$$ s = 8 TeV by the CMS and TOTEM experiments

Pseudorapidity ( $$\eta $$ ) distributions of charged particles produced in proton–proton collisions at a centre-of-mass energy of 8 $$~\text {TeV}$$ are measured in the ranges $$|\eta | < 2.2$$ and $$5.3 < |\eta | < 6.4$$ covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of $$\mathcal {L} = 45$$ $$~\upmu {\mathrm {b}}^{-1}$$ . Measurements are presented for three event categories. The most inclusive category is sensitive to 91–96 % of the total inelastic proton–proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. The data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions.

Role of quarks in hadroproduction in high energy collisions

A qualitative model for hadroproduction in high energy collisions considering two components (“thermal” and “hard”) to hadroproduction is proposed. Inclusive pseudorapidity distributions, dσ/dη, and transverse momentum spectra, d2σ/(dηdpT2), measured by different collaborations are considered in terms of this model. The shapes of the pseudorapidity distributions agree with that one can expect from the qualitative picture introduced. The model is used to provide predictions for the LHC. Data up to a centre-of-mass energy of 7 TeV are well described and predictions for higher energies await new data. Finally, the differences between charged particle spectra produced in inclusive and diffractive events are discussed and the absence of the “thermal” component in the latter is observed.

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.

Pseudorapidity distributions of charged particles produced in p–p collisions at center-of-mass energies from 23.6 GeV to 900 GeV

In p–p collisions there are two leading particles, one in the projectile and the other in the target fragmentation region. In this paper we show that, just like in nucleus–nucleus collisions, the revised Landau hydrodynamic model alone does not provide a good enough description of the measured pseudorapidity distributions of charged particles produced in p–p collisions. Only after the leading particles are taken into account can the experimental data be properly matched with the theoretical model in the entire available energy region from [Formula: see text] to 900 GeV.

Studies of dijet and photon-jet properties in pp, pPb, and PbPb collisions with CMS

Abstract Studies of dijet and photon-jet properties in pPb collisions are of great importance for establishing a QCD baseline for hadronic interactions with cold nuclear matter. Dijet and photon-jet production has been measured in pPb collisions at a nucleon–nucleon center-of-mass energy of 5.02 TeV. The transverse momentum balance and azimuthal angle correlations are studied in both dijet and photon-jet channels, leading to the observation that there is no significant modification, which allows these systems to be used as tools to probe the nuclear modifications of the parton distribution functions (PDFs). In the dijet system, pseudorapidity distributions are studied as a function of the transverse energy in the forward calorimeters ( E T HF ). The mean value of the dijet pseudorapidity is found to change monotonically with increasing E T HF , indicating a correlation between the energy emitted at large pseudorapidity and the longitudinal motion of the dijet frame. The pseudorapidity distribution of the dijet system is compared with next-to-leading-order perturbative QCD predictions obtained from both nucleon and nuclear PDFs, and the data more closely match the latter. In addition to the studies of initial state, the photon-jet measurements related to quenching in PbPb are updated to have a more precise pp reference based on the 2013 LHC run at 2.76 TeV.

Studies of dijet pseudorapidity distributions and transverse momentum balance in pPb collisions at [formula omitted

Dijet production has been measured in pPb collisions at a nucleon–nucleon center-of-mass energy of 5.02 TeV. A data sample corresponding to an integrated luminosity of 35 nb−1 was collected using the Compact Muon Solenoid detector at the Large Hadron Collider. The dijet transverse momentum balance and pseudorapidity distributions are studied as a function of the transverse energy in the forward calorimeters (ETHF[|η|>4]). For pPb collisions, the dijet transverse momentum ratio is comparable to the same quantities obtained from a simulated pp reference and insensitive to ETHF[|η|>4]. In contrast, the distribution of the dijet pseudorapidity is changing with increasing ETHF[|η|>4], indicating a correlation between the energy emitted at large pseudorapidity and the longitudinal motion of the dijet frame. The observed pseudorapidity distribution of the dijet system in minimum bias pPb collisions is consistent with next-to-leading-order perturbative QCD predictions from nuclear parton distribution functions.

Measurement of the centrality dependence of charged particle pseudorapidity distribution in proton–lead collisions at sNN=5.02TeV with the ATLAS detector

Multiplicity distributions of charged particles as a function of pseudorapidity dNch/dη have been measured by the ATLAS Collaboration in p + Pb collisions at sNN=5.02TeV at the LHC. The multiplicity of charged particles was measured in |η|<2.7 using combinations of correlated space points into tracklets in the Pixel detector. These measurements are presented as a function of the centrality of the collision defined by forward energy deposited in 3.1<η<4.9 and three Glauber type Monte-Carlo simulations of the collisions. The measured multiplicity distributions have similar shapes as the ones measured at RHIC in d + Au collisions.

Particle production and long-range correlations in p+Pb collisions with the ATLAS detector

The ATLAS experiment at the LHC has measured the centrality dependence of charged particle pseudorapidity distribution, charged particle spectra, and the two-particle correlations in p+Pb collisions at a nucleon-nucleon centre-of-mass energy of sqrt(s_NN)=5.02TeV. Charged particles were measured over |eta|<2.7 using the ATLAS detector tracking system. The p+Pb collision centrality was characterized by the total transverse energy deposited over the interval 3.2<eta<4.9 in the direction of the Pb-beam. Three different calculations of the number of participating nucleons, have been carried out using a standard Glauber initial state model as well as two Glauber-Gribov extensions. Charged particle multiplicities per participant pair, and the normalised charged particle spectra are found to vary in shape with eta and also with the model, pointing to the importance of the fluctuating nature of nucleon-nucleon collisions in the modelling of the initial state of p+Pb collisions. The two particle correlation exhibits flow-like modulations for all centrality intervals and particle p_T.

Pseudorapidity distributions of the produced charged particles in nucleus-nucleus collisions at low energies at the BNL relativistic heavy ion collider

The revised Landau hydrodynamic model is used to discuss the pseudorapidity distributions of the produced charged particles in Au+Au and Cu+Cu collisions at energies of √sNN = 19.6 and 22.4 GeV respectively at the BNL Relativistic Heavy Ion Collider. It is found that the revised Landau hydrodynamic model alone can give a good description of the experimental measurements. This is different from the result with the same collisions but at the maximum energy of √sNN = 200 GeV, where in addition to the revised Landau hydrodynamic model, the effects of leading particles have to be taken into account in order to explain the experimental observations. This can be attributed to the different degrees of transparency of participants at the different incident energies.

Multifractal detrended fluctuation analysis of pseudorapidity and azimuthal distribution of pions emitted in high energy nuclear collisions

In this paper multifractal analysis of fluctuation pattern of pions emitted in 32 S-AgBr and 16 O-AgBr interactions at 200 GeV and 60 GeV, respectively, is performed in the framework of multifractal detrended fluctuation analysis (MFDFA). The pseudorapidity and azimuthal distributions exhibit multifractal scaling properties at both energies. The variation of multifractal width with energy is also studied. The study reveals a dependence of multifractal width on energy in pseudorapidity space while no such dependence is observed in azimuthal space.

Studies of dijet transverse momentum balance and pseudorapidity distributions in pPb collisions at $$\sqrt{s_{\mathrm{NN}}} = 5.02$$ s NN = 5.02 $$\,\text {TeV}$$ TeV

Dijet production has been measured in $$\mathrm {p}\mathrm {Pb}$$ collisions at a nucleon–nucleon centre-of-mass energy of 5.02 $$\,\text {TeV}$$ . A data sample corresponding to an integrated luminosity of 35 $${{\,\text {nb}^{{-1}}}} $$ was collected using the Compact Muon Solenoid detector at the Large Hadron Collider. The dijet transverse momentum balance, azimuthal angle correlations, and pseudorapidity distributions are studied as a function of the transverse energy in the forward calorimeters ( $$E_\mathrm {T}^{4<|\eta |<\mathrm {5.2}} $$ ). For $$\mathrm {p}\mathrm {Pb}$$ collisions, the dijet transverse momentum ratio and the width of the distribution of dijet azimuthal angle difference are comparable to the same quantities obtained from a simulated $$\mathrm {p}\mathrm {p}$$ reference and insensitive to $$E_\mathrm {T}^{4<|\eta |<\mathrm {5.2}} $$ . In contrast, the mean value of the dijet pseudorapidity is found to change monotonically with increasing $$E_\mathrm {T}^{4<|\eta |<\mathrm {5.2}} $$ , indicating a correlation between the energy emitted at large pseudorapidity and the longitudinal motion of the dijet frame. The pseudorapidity distribution of the dijet system in minimum bias $$\mathrm {p}\mathrm {Pb}$$ collisions is compared with next-to-leading-order perturbative QCD predictions obtained from both nucleon and nuclear parton distribution functions, and the data more closely match the latter.

Verification of the model of a collision of a 800-GeV proton with an emulsion-nucleus tube

The production of quark-gluon plasma is discussed within the hydrodynamic theory of multiparticle hadron production in head-on collisions of nucleons with nucleons and nuclei. In searches for collisions of a proton with a tube of a track-emulsion nucleus, the use of parametrically invariant quantities is proposed. An experimental verification of statistical models involving qualitatively different pseudorapidity distributions of weakly ionizing secondary particles is performed. The results of this verification are discussed.

Hadron collider potential for excited bosons search

The e+e− and μ+μ− dilepton final states are the most clear channels for a new heavy neutral resonance search. Their advantage is that usually in the region of expected heavy-mass resonance peak the main irreducible background, from the Standard Model Drell-Yan process, contributes two orders of magnitude smaller than the signal. In this paper we consider the future prospects for search for the excited neutral Z*-bosons. The bosons can be observed as a Breit-Wigner resonance peak in the dilepton invariant mass distributions in the same way as the well-known extra gauge Z′ bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow to distinguish them from the other heavy neutral resonances. At present only the ATLAS Collaboration has looked for such new excitations at the Large Hadron Collider and has published its results for 7 TeV collision energy. After successful comparison of our evaluation with these official results we present our estimations for the discovery potential and the exclusion limits on the Z*-boson search in pp collisions at higher centre-of-mass energies and different luminosities. In particular, LHC Run 2 can discover Z*-boson with its mass up to 5.3 TeV, while the High Luminosity LHC can extend that reach to 6.2 TeV. The High Energy LHC (with collision energy of 33 TeV) will be able to probe two times heavier resonance masses at the same integrated luminosities.

Centrality dependence of charged particle production in proton–lead collisions measured by ATLAS

The ATLAS experiment at the LHC has measured the centrality dependence of charged particle pseudorapidity distributions, d N ch / d η , in p + Pb collisions at a nucleon–nucleon center-of-mass energy of s NN = 5.02 TeV . Charged particles were reconstructed over | η | < 2.7 using the ATLAS pixel detector. The proton–lead collision centrality was characterized by the total transverse energy measured over the pseudorapidity interval 3.1 < η < 4.9 in the direction of the lead beam. Three different calculations of the number of participants, N part , have been carried out using a standard Glauber model as well as two Glauber–Gribov extensions, providing results pointing to the importance of the fluctuating nature of nucleon–nucleon collisions in the modeling of the initial state of p + Pb collisions.

Particle production in relativisticpp(p¯)andAAcollisions at RHIC and LHC energies with Tsallis statistics using the two-cylindrical multisource thermal model

An improved Tsallis statistics is implemented in a multisource thermal model to describe systematically pseudorapidity spectra of charged particles produced in relativistic nucleon-nucleon ($pp$ or $p\overline{p}$) collisions at various collision energies and in relativistic nucleus-nucleus ($AA$) collisions at different energies with different centralities. The results with Tsallis statistics using the two-cylindrical multisource thermal model are in good agreement with the experimental data measured at RHIC and LHC energies. It is found that the rapidity shifts of longitudinal sources increase linearly with collision energies and centralities in the framework. According to the laws, we also give a prediction of the pseudorapidity distributions in $pp$($\overline{p}$) collisions at higher energies.

Jets and high pT hadrons in CMS

Abstract We present the recent experimental results on jets and high p T hadrons measured by the CMS Collaboration using various observables: jet and high p T charged hadron yields, dijet imbalance, jet shapes and fragmentation functions. The measurements of dijet p T and pseudorapidity distributions in pPb collisions using the data delivered by LHC at early 2013 are also presented.