Pseudorapidity Interval Research Articles

Investigation of freezeout parameters and other thermodynamic quantities with changing pseudorapidity at 0.9 TeV in pp collisions

Abstract The charged particles in different pseudorapidity intervals are analyzed by the thermodynamically consistent Tsallis pareto type function at 0.9 TeV in proton-proton collisions. We extracted the effective temperature $T$ and the non-extensive parameter $q$. The former decreases while the later increases towards the forward pseudorapidities. Using $T$ and $q$ obtained from the Tsallis pareto type function, we calculated the particle density $n$, energy density $\varepsilon$, pressure $P$ and squared speed of sound $c^2_s$ at kinetic freezeout. All these quantities are larger at mid-rapidity and decrease towards the forward pseudorapdity regions.

Multiplicity and event-scale dependent flow and jet fragmentation in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV and in p–Pb collisions at sNN\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s_{\ extrm{NN}}} $$\\end{document} = 5.02 TeV

Long- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV and p–Pb collisions at sNN\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s_{\ extrm{NN}}} $$\\end{document} = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle ∆φ and pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum interval 1 < pT< 4 GeV/c. Flow coefficients are extracted for the long-range correlations (1.6 < |∆η| < 1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events.

Optimizing the Parton Showers in PYTHIA8 for Xe–Xe collision at 5.44 TeV

We present the doubly differential invariant yield of primary charged particles [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text] in Xe–Xe collisions at [Formula: see text] = 5.44 TeV, as a function of [Formula: see text] in kinematic region of [Formula: see text] and for the pseudorapidity interval of [Formula: see text] by using PYTHIA8 tuned to different Parton Showers like Simple Showers (Time-Like, Space-Like), DIRE and VINCIA Showers. The predictions of hard and soft QCD processes of Parton Showers are then compared with the ALICE data at different centrality classes of 0–5%, 50–60% and 70–80%. The observed deviations are connected with the kinematics involved and are mostly due to the color coherence and soft gluon emission from parton pairs. As PYTHIA8 does not take into account the Cronin effect, thus the deviation at low [Formula: see text] is due to Cronin effect. The nuclear modification factor is constructed and it is observed that the signal is less than unity or suppression is seen which is coming from Parton Showers.

Vector meson photoproduction in UPCs with FoCal

We discuss the physics prospects of photon-induced measurements using the high-granularity FoCal detector to be installed at the ALICE experiment, covering the pseudorapidity interval 3.4 ≤ η ≤ 5.8. This new detector, scheduled to be in operation from Run 4, will explore the small Bjorken-x physics region in an unprecedented way. In this region the gluon ,saturation phenomenon is expected to be dominant. Combined with the rest of the ALICE subdetectors, including the zero degree calorimenters, FoCal will serve to reconstruct in a model-independent way the measured photoproduction cross sections for vectors mesons in a wide range of photon-target energies, down to x values of about 7 × 10−6 and 2 × 10−6 in ultra-peripheral photon–proton and photon–lead collisions, respectively.

Elucidating the jet cross-section in pp and pPb collisions at sNN = 5.02TeV

In this paper, we present the charged particles jet cross-section study in [Formula: see text] and [Formula: see text] collisions at [Formula: see text],TeV using PYTHIA8 (PYTHIA8.186 and PYTHIA8.306) and HIJING 2.0 models, in kinematic range of [Formula: see text],GeV/c for [Formula: see text] collisions and [Formula: see text],GeV/c for [Formula: see text] collisions. The jets are reconstructed for [Formula: see text], 0.3, 0.4 and 0.6 for the pseudorapidity interval of [Formula: see text] 0.9-R. The jets algorithms: cell jet and slow jet inside PYTHIA8.186 and anti-[Formula: see text] algorithm using HIJING 2.0 have been used for Monte Carlo simulations. The simulation results are then compared with measurements of the ALICE experiment. It is observed that all models’ predictions are lower than experimental data up to [Formula: see text],GeV/c; after that, the Monte Carlo study of Cell and slow jet satisfies the experimental data. The CR tunes could not explain the ALICE data at high [Formula: see text] values due to nonperturbative QCD effects. We have also calculated the nuclear modification factor [Formula: see text], and no clear suppression has been seen in the case of [Formula: see text] collisions. The results from the models indicate that the QGP is not formed and that the cold nuclear matter effect exists in pPb collisions.

Pseudorapidity window size dependence of multiplicity fluctuations in high-energy collisions with system size and beam energies

An investigation of the critical behavior of strongly interacting quantum chromodynamics (QCD) matter has been performed by analyzing fluctuation observables on event-by-event (ebe) basis measured in high-energy collision experiments. The fluctuation analysis is performed using nuclear interactions at different target sizes and at different colliding beam energies as a function of varying width of pseudorapidity interval. For the sake of comparison, ebe multiplicity fluctuations in hadronic and heavy ion collisions (p–H, p–A and A–B) are studied within the framework of the Lund Monte Carlo-based FRITIOF model. Charged particle multiplicity and the variance of the multiplicity distribution are estimated for the interactions involving different target sizes and beam momenta, i.e., p–H, p–CNO, p–AgBr at 200 A GeV/c and [Formula: see text]O–AgBr collisions at 14.6 A, 60 A and 200 A GeV/c. Further, multiplicity fluctuations are quantified in terms of intensive quantity, the scaled variances [Formula: see text] and the strongly intensive quantity [Formula: see text] derived from the charged particle multiplicity and the width of the multiplicity distribution. Strongly intensive quantity [Formula: see text] is a quantity of great significance to extract information about short- and long-range multiplicity correlations. Furthermore, the collision centrality and centrality bin width-dependent behavior of the multiplicity fluctuation have been examined in the framework of Lund Monte Carlo-based FRITIOF model. Results based on the fluctuation analysis carried out in this study are interpreted in terms of dynamics of collision process and the possibility of related QCD phase transition.

Modeling of charged-particle multiplicity and transverse-momentum distributions in pp collisions using a DNN

A machine learning technique is used to fit multiplicity distributions in high energy proton-proton collisions and applied to make predictions for collisions at higher energies. The method is tested with Monte Carlo event generators. Charged-particle multiplicity and transverse-momentum distributions within different pseudorapidity intervals in proton-proton collisions were simulated using the PYTHIA event generator for center of mass energies sqrt{s}= 0.9, 2.36, 2.76, 5, 7, 8, 13 TeV for model training and validation and at 10, 20, 27, 50, 100 and 150 TeV for model predictions. Comparisons are made in order to ensure the model reproduces the relation between input variables and output distributions for the charged particle multiplicity and transverse-momentum. The multiplicity and transverse-momentum distributions are described and predicted very well, not only in the case of the trained but also in the case of untrained energy values. The study proposes a way to predict multiplicity distributions at a new energy by extrapolating the information inherent in the lower energy data. Using real data instead of Monte Carlo, as measured at the LHC, the technique has the potential to project the multiplicity distributions for different intervals at very high collision energies, e.g. 27 TeV or 100 TeV for the upgraded HE-LHC and FCC-hh respectively, using only data collected at the LHC, i.e. at center of mass energies from 0.9 up to 13 TeV.

Measurement of the nuclear modification factor for muons from charm and bottom hadrons in Pb+Pb collisions at 5.02 TeV with the ATLAS detector

Heavy-flavour hadron production provides information about the transport properties and microscopic structure of the quark–gluon plasma created in ultra-relativistic heavy-ion collisions. A measurement of the muons from semileptonic decays of charm and bottom hadrons produced in Pb+Pb and pp collisions at a nucleon–nucleon centre-of-mass energy of 5.02 TeV with the ATLAS detector at the Large Hadron Collider is presented. The Pb+Pb data were collected in 2015 and 2018 with sampled integrated luminosities of 208μb−1 and 38μb−1, respectively, and pp data with a sampled integrated luminosity of 1.17pb−1 were collected in 2017. Muons from heavy-flavour semileptonic decays are separated from the light-flavour hadronic background using the momentum imbalance between the inner detector and muon spectrometer measurements, and muons originating from charm and bottom decays are further separated via the muon track's transverse impact parameter. Differential yields in Pb+Pb collisions and differential cross sections in pp collisions for such muons are measured as a function of muon transverse momentum from 4 GeV to 30 GeV in the absolute pseudorapidity interval |η|<2. Nuclear modification factors for charm and bottom muons are presented as a function of muon transverse momentum in intervals of Pb+Pb collision centrality. The bottom muon results are the most precise measurement of b quark nuclear modification at low transverse momentum where reconstruction of B hadrons is challenging. The measured nuclear modification factors quantify a significant suppression of the yields of muons from decays of charm and bottom hadrons, with stronger effects for muons from charm hadron decays.

Study QGP through the Correlation Function with Pb-Pb Collisions at

This paper focuses on repeating and verifying the predecessor’s work. We briefly describe our dataset from CMS and then provide information about the Glauber Model built with python. Then, the correlation function of our data and different orders of its Fourier decomposition are presented to verify the former discussion. With the correlation function, we will show the fluctuation of the directed and elliptic flow caused by the non-flow, which comes from the intractable strong interaction during the evolution of the QGP. Based on the assumption that the non-flow contribution is ignorable in large relative pseudorapidity interval, (|Δη|), we separate the non-flow contribution from the elliptic flow. Finally, we provide a detailed derivation of the Fourier decomposition of correlation and discuss their physical meaning, absent in general paperwork.

Hard color-singlet exchange in dijet events in proton-proton collisions at s=13 TeV

Events where the two leading jets are separated by a pseudorapidity interval devoid of particle activity, known as jet-gap-jet events, are studied in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The signature is expected from hard color-singlet exchange. Each of the highest transverse momentum ($p_\mathrm{T}$) jets must have $p_\mathrm{T}^\text{jet}$ $\gt$ 40 GeV and pseudorapidity 1.4 $\lt$ $|\eta^\text{jet}|$ $\lt$ 4.7, with $\eta^\text{jet1} \eta^\text{jet2}$ $\lt$ 0, where $\text{jet1}$ and $\text{jet2}$ are the leading and subleading jets in $p_\mathrm{T}$, respectively. The analysis is based on data collected by the CMS and TOTEM experiments during a low luminosity, high-$\beta^*$ run at the CERN LHC in 2015, with an integrated luminosity of 0.66 pb$^{-1}$. Events with a low number of charged particles with $p_\mathrm{T}$ $\gt$ 0.2 GeV in the interval $|\eta|$ $\lt$ 1 between the jets are observed in excess of calculations that assume only color-exchange. The fraction of events produced via color-singlet exchange, $f_\text{CSE}$, is measured as a function of $p_\mathrm{T}^\text{jet2}$, the pseudorapidity difference between the two leading jets, and the azimuthal angular separation between the two leading jets. The fraction $f_\text{CSE}$ has values of 0.4-1.0%. The results are compared with previous measurements and with predictions from perturbative quantum chromodynamics. In addition, the first study of jet-gap-jet events detected in association with an intact proton using a subsample of events with an integrated luminosity of 0.40 pb$^{-1}$ is presented. The intact protons are detected with the Roman pot detectors of the TOTEM experiment. The $f_\text{CSE}$ in this sample is 2.91 $\pm$ 0.70 (stat) $^{+1.08}_{-1.01}$ (syst) times larger than that for inclusive dijet production in dijets with similar kinematics.

Study of transverse momentum and nuclear modification factors distribution of charged particles produced in pp and Pb–Pb collisions at s NN = 2.76TeV and 5.02TeV

We have studied transverse momentum distributions of charged particles produced in pp and Pb–Pb collisions at [Formula: see text] TeV and 5.02 TeV in the pseudorapidity interval [Formula: see text] and transverse momentum range [Formula: see text][Formula: see text]GeV/[Formula: see text]. We simulated data using EPOS-LHC, EPOS-1.99 and QGSJETII-04 models. The simulation data is compared with the ALICE experimental data values at [Formula: see text] TeV and 5.02 TeV for pp and most central Pb–Pb collisions. It has been observed that, EPOS-LHC and QGSJETII-04 models explain the experimental results for pp collision at [Formula: see text] TeV and 5.02 TeV. The behavior of nuclear modification factors has been studied. The simulation codes of all three models EPOS-LHC, EPOS-1.99 and QGSJETII-04 overestimate the experimental results at low transverse momentum interval: [Formula: see text] GeV/[Formula: see text], for Pb–Pb collisions at [Formula: see text] TeV and 5.02 TeV. However, only EPOS-LHC model can explain the experimental data at high transverse momentum in the range: [Formula: see text] GeV/[Formula: see text]. EPOS-1.99 and QGSJETII-04 underestimate in the region of Cronin effect and cannot give satisfactory estimates for the [Formula: see text] values for which [Formula: see text] demonstrates stronger suppression because of the collective parton effect. It can be inferred that these effects are not taken into account in EPOS-1.99 and QGSJETII-04 models. These models, however, satisfactorily explain the ALICE experimental data in the ranges of [Formula: see text] for which nuclear modification factor [Formula: see text] shows rising trend.

Pseudorapidity distributions of charged particles as a function of mid- and forward rapidity multiplicities in pp collisions at sqrt{s}\xa0=\xa05.02, 7 and 13 TeV

The multiplicity dependence of the pseudorapidity density of charged particles in proton–proton (pp) collisions at centre-of-mass energies sqrt{s}~=~5.02, 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range (|eta | < 1.5). Results are presented for inelastic events having at least one charged particle produced in the pseudorapidity interval |eta |<1. The multiplicity dependence of the pseudorapidity density of charged particles is measured with mid- and forward rapidity multiplicity estimators, the latter being less affected by autocorrelations. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented. The results can be used to constrain models for particle production as a function of multiplicity in pp collisions.

Investigation of centrality dependence of dynamical fluctuations in narrow pseudo-rapidity interval on event-by-event basis

A detailed study of centrality dependence of event-by-event fluctuations of maximum particle density of the produced particles in narrow pseudo-rapidity interval in terms of the scaled variance [Formula: see text] has been carried out for [Formula: see text]O-emulsion interactions at 4.5[Formula: see text]AGeV/[Formula: see text]. Depending on the values of the total charges or sum of the charges of noninteracting projectile fragments, event samples were classified into four centrality classes. Presence of event-by-event fluctuations of maximum particle density is reflected in the multiparticle production process for different centrality classes. The event-by-event fluctuations are found to decrease with the increase of pseudo-rapidity interval. The event-by-event fluctuations are found to decrease with decreasing centrality of collisions. A comparison with the analyzed results of the total disintegration events has also been carried out. Experimental analysis results have been compared with those obtained from the analysis of Monte Carlo simulated (MC-RAND) events in order to extract the dynamical fluctuations.

Event-by-event fluctuations of maximum particle density with respect to the width of the pseudo-rapidity interval at a few A GeV/c

A detailed study of event-by-event fluctuations of maximum particle density of the produced particles with respect to the width of the pseudo-rapidity interval in terms of the scaled variance ω has been carried out for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5 A GeV/c. For all the interactions the values of scaled variance are found to be greater than one indicating the presence of strong event-by-event fluctuations of maximum particle density values in the multiparticle production process. The event-by-event fluctuations are found to decrease with the increase of the width of the pseudo-rapidity interval. Experimental analysis has been compared with the results obtained from the analysis of events simulated by generating random numbers (MC-RAND) and the Ultra-Relativistic Quantum Molecular Dynamics (UrQMD) model. MC-RAND events show significantly less event-by-event fluctuations in comparison to the experimental data. The UrQMD model also failed to reproduce the experimental results. Comparison of our analysis with the outcome of other analysed emulsion data has also been presented.

Higher harmonic non-linear flow modes of charged hadrons in Pb-Pb collisions at sqrt{s_{mathrm{NN}}} = 5.02 TeV

Anisotropic flow coefficients, vn, non-linear flow mode coefficients, χn,mk, and correlations among different symmetry planes, ρn,mk are measured in Pb-Pb collisions at sqrt{s_{mathrm{NN}}} = 5.02 TeV. Results obtained with multi-particle correlations are reported for the transverse momentum interval 0.2 < pT< 5.0 GeV/c within the pseudorapidity interval 0.4 < |η| < 0.8 as a function of collision centrality. The vn coefficients and χn,mk and ρn,mk are presented up to the ninth and seventh harmonic order, respectively. Calculations suggest that the correlations measured in different symmetry planes and the non-linear flow mode coefficients are dependent on the shear and bulk viscosity to entropy ratios of the medium created in heavy-ion collisions. The comparison between these measurements and those at lower energies and calculations from hydrodynamic models places strong constraints on the initial conditions and transport properties of the system.

Study of Forward-Backward Multiplicity Fluctuations and Correlations with Pseudorapidity

Multiplicity fluctuations in two separated pseudorapidity intervals are studied in terms of strongly intensive variables. This work presents results obtained in the MC model with quark-gluon strings as objects extended in pseudorapidity space and acting as particle emitting sources. The string interactions are implemented within the discrete model of local string fusion. Strings of fluctuating length in pseudorapidity are considered in order to estimate the non-critical background of fluctuations. The results on the dependence of strongly intensive observables on the width of acceptance windows, on the pseudorapidity separation between them and on the string density qualitatively describe the available data from the NA61/SHINE and ALICE experiments.

System size dependence of net-charge fluctuation in nucleus-nucleus collisions at FAIR energies

Dynamical net-charge fluctuations are studied in symmetric nuclear collisions of different system size and at two different collision energies that in the near future will be available at the Facility for Antiproton and Ion Research (FAIR). Multiparticle emission data simulated by the ultra-relativistic quantum molecular dynamics (UrQMD) are analyzed for this purpose. Our primary objective is to examine the system size dependence of dynamical fluctuation of conserved charge at typical FAIR conditions. The centrality, pseudorapidity interval size and azimuthal angle interval size dependence of the dynamical fluctuations are studied too. The effects of global charge conservation (GCC) and finite multiplicity bin width correction are taken into account. To a large extent the systematics followed by the dynamical fluctuations at FAIR conditions are found to be a lower energy extrapolation of the observations made in this regard in the Relativistic Heavy-ion Collider (RHIC) experiments.

Influence of the Effects of Color Reconnection and the Formation of Hadronic Jets on the Distribution of Charged Particles over the Transverse Momentum in pp-Collisions at the Energies of the Large Hadron Collider

Dependences of the average transverse momentum of charged particles on rapidity $$y$$ and pseudorapidity $$\eta $$ are obtained, and the influence the effects of color reconnection and the formation of hadronic jets have on these dependences is studied. It is shown that the result depends largely on the interval of which physical quantity (rapidity or pseudorapidity) particle distributions over the transverse momentum are considered. It is important to compare theoretically calculated distributions to experimental data. It is shown in particular that allowing for the kinematic factor which arises in describing the distribution of particles over the transverse momentum in the specified pseudorapidity interval considerably influences the description of experimental data on pp-collisions at energies of $$\sqrt s = 7$$ TeV in the Large Hadron Collider.

Moments of multiplicity distributions using Tsallis statistics in leptonic and hadronic collisions

Moments play a crucial role in investigating the characteristics of charged particle multiplicities in high energy interactions. The success of any model which describes the multiplicity data can be understood well by studying the normalised and factorial moments of that distribution.~The Tsallis model is one of the most successful models which describes the multiplicity spectra, transverse momentum ($p_T$) spectra very precisely in high energy interactions.~In our previous work we have used the Tsallis $q$-statistics to describe the multiplicity distributions in leptonic and hadronic collisions at various energies ranging from 14 GeV to 7 TeV.~In the present study we have extended our analysis for calculating the moments using the Tsallis model for $e^+e^-$ interactions at $\sqrt{s}$ = 91 to 206 GeV from the LEP data and for $pp$ interactions at $\sqrt{s}$ = 0.9 to 7 TeV in various pseudo-rapidity intervals from the CMS data at LHC. By using the Tsallis model we have also calculated the average charged multiplicity and its dependence on energy.~It is found that the moments and the mean multiplicities predicted by the Tsallis model are in good agreement with the experimental values.~We have also predicted the mean multiplicity at $\sqrt{s}$ = 500 GeV for $e^+e^-$ collisions and at $\sqrt{s}$ = 14 TeV for $pp$ collisions in extreme pseudo-rapidity interval, $|\eta|$ $<$ 2.4

Design of the FCC-hh muon detector and trigger system

Abstract The design of a muon detector and first-level muon trigger system for the FCC-hh baseline experiment is presented. The baseline FCC-hh detector configuration with a solenoid magnet system providing a field integral of 18 Tm over a wide pseudorapidity interval and a muon system around the solenoid and the calorimeter system is assumed. In order to identify muons with high momentum resolution one needs to measure the muon incidence angle at the entry point of the muon system with an angular resolution better than 100 μ rad. This precision can be achieved with chambers with two quadruple layers which are separated by a 1.5 m thick spacer structure and contain 15 mm diameter aluminium drift tubes filled with Ar:CO(93:7) at 3 bars absolute pressure. Each drift-tube chamber is combined with a double layer of thin-gap RPC chambers which provide bunch crossing identification with better than 1 ns time resolution, muon trigger seeds, and coordinate measurement along the tubes.