scholarly journals A Baseline Study of the Event-Shape and Multiplicity Dependence of Chemical Freeze-Out Parameters in Proton-Proton Collisions at \( {\sqrt{s}} \) = 13 TeV Using PYTHIA8

Physics ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 679-694
Author(s):  
Rutuparna Rath ◽  
Arvind Khuntia ◽  
Sushanta Tripathy ◽  
Raghunath Sahoo
Keyword(s):  
High Energy ◽  
Monte Carlo Event ◽  
Event Generator ◽  
Particle Multiplicity ◽  
Event Shape ◽  
Charged Particle Multiplicity ◽  
Pp Collisions ◽  
Proton Proton ◽  
Chemical Freeze ◽  
Freeze Out

The event-shape and multiplicity dependence of the chemical freeze-out temperature (Tch), freeze-out radius (R), and strangeness saturation factor (γs) are obtained by studying the particle yields from the PYTHIA8 Monte Carlo event generator in proton-proton (pp) collisions at the centre-of-mass s = 13 TeV. Spherocity is one of the transverse event-shape techniques to distinguish jetty and isotropic events in high-energy collisions and helps in looking into various observables in a more differential manner. In this study, spherocity classes are divided into three categories, namely (i) spherocity integrated, (ii) isotropic, and (iii) jetty. The chemical freeze-out parameters are extracted using a statistical thermal model as a function of the spherocity class and charged particle multiplicity in the canonical, strangeness canonical, and grand canonical ensembles. A clear observation of the multiplicity and spherocity class dependence of Tch, R, and γs is observed. A final state multiplicity, Nch≥ 30 in the forward multiplicity acceptance of the ALICE detector appears to be a thermodynamic limit, where the freeze-out parameters become almost independent of the ensembles. This study plays an important role in understanding the particle production mechanism in high-multiplicity pp collisions at the Large Hadron Collider (LHC) energies in view of a finite hadronic phase lifetime in small systems.

scholarly journals Freeze-Out Parameters in Heavy-Ion Collisions at AGS, SPS, RHIC, and LHC Energies

2015 ◽  
Vol 2015 ◽  
pp. 1-20 ◽  
Author(s):  
Sandeep Chatterjee ◽  
Sabita Das ◽  
Lokesh Kumar ◽  
D. Mishra ◽  
Bedangadas Mohanty ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
High Energy ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Ion Collisions ◽  
Momentum Distributions ◽  
Chemical Freeze ◽  
Freeze Out

We review the chemical and kinetic freeze-out conditions in high energy heavy-ion collisions for AGS, SPS, RHIC, and LHC energies. Chemical freeze-out parameters are obtained using produced particle yields in central collisions while the corresponding kinetic freeze-out parameters are obtained using transverse momentum distributions of produced particles. For chemical freeze-out, different freeze-out scenarios are discussed such as single and double/flavor dependent freeze-out surfaces. Kinetic freeze-out parameters are obtained by doing hydrodynamic inspired blast wave fit to the transverse momentum distributions. The beam energy and centrality dependence of transverse energy per charged particle multiplicity are studied to address the constant energy per particle freeze-out criteria in heavy-ion collisions.

scholarly journals Event Shape and Multiplicity Dependence of Freeze-Out Scenario and System Thermodynamics in Proton+Proton Collisions at s = 13   TeV Using PYTHIA8

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Sushanta Tripathy ◽  
Ashish Bisht ◽  
Raghunath Sahoo ◽  
Arvind Khuntia ◽  
Malavika Panikkassery Salvan
Keyword(s):  
Charged Particle ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Event Generator ◽  
Particle Multiplicity ◽  
Event Shape ◽  
Charged Particle Multiplicity ◽  
Pp Collisions ◽  
Alice Experiment ◽  
Nonextensive Statistics

Recent observations of QGP-like conditions in high-multiplicity pp collisions from ALICE experiment at the LHC warrant an introspection whether to use pp collisions as a baseline measurement to characterize heavy-ion collisions for the possible formation of a Quark-Gluon Plasma. A double differential study of the particle spectra and thermodynamics of the produced system as a function of charged-particle multiplicity and transverse spherocity in pp collisions would shed light on the underlying event dynamics. Transverse spherocity, one of the event shape observables, allows to separate the events in terms of jetty and isotropic events. We analyse the identified particle transverse momentum ( p T ) spectra as a function of charged-particle multiplicity and transverse spherocity using Tsallis nonextensive statistics and Boltzmann-Gibbs Blast-Wave (BGBW) model in pp collisions at s = 13   TeV using PYTHIA8 event generator. The extracted parameters such as temperature ( T ), radial flow ( β ), and nonextensive parameter ( q ) are shown as a function of charged-particle multiplicity for different spherocity classes. We observe that the isotropic events approach thermal equilibrium while the jetty ones remain far from equilibrium. We argue that, while studying the QGP-like conditions in small systems, one should separate the isotropic events from the spherocity-integrated events, as the production dynamics are different.

scholarly journals Measurement of the average very forward energy as a function of the track multiplicity at central pseudorapidities in proton-proton collisions at $$\sqrt{s}=13\,\text {TeV} $$

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
High Energy ◽  
Monte Carlo Event ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Centre Of Mass ◽  
Proton Proton ◽  
Proton Collisions ◽  
Forward Energy ◽  
Proton Proton Collisions

Abstract The average total energy as well as its hadronic and electromagnetic components are measured with the CMS detector at pseudorapidities $$-6.6<\eta <-5.2$$-6.6<η<-5.2 in proton-proton collisions at a centre-of-mass energy $$\sqrt{s}=13\,\text {TeV} $$s=13TeV. The results are presented as a function of the charged particle multiplicity in the region $$|\eta |<2$$|η|<2. This measurement is sensitive to correlations induced by the underlying event structure over a very wide pseudorapidity region. The predictions of Monte Carlo event generators commonly used in collider experiments and ultra-high energy cosmic ray physics are compared to the data. All generators considered overestimate the fraction of energy going into hadrons.

scholarly journals Study of charged-particle multiplicity fluctuations in pp collisions with Monte Carlo event generators at the LHC

2020 ◽  
Vol 29 (09) ◽  
pp. 2050074
Author(s):  
E. Shokr ◽  
A. H. El-Farrash ◽  
A. De Roeck ◽  
M. A. Mahmoud
Keyword(s):  
Charged Particle ◽  
Particle Production ◽  
Local Density ◽  
Particle Density ◽  
Hadron Collider ◽  
Center Of Mass ◽  
Monte Carlo Event ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Proton Proton

Proton–Proton ([Formula: see text]) collisions at the Large Hadron Collider (LHC) are simulated in order to study events with a high local density of charged particles produced in narrow pseudorapidty windows of [Formula: see text] = 0.1, 0.2, and 0.5. The [Formula: see text] collisions are generated at center of mass energies of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] TeV, i.e., the energies at which the LHC has operated so far, using PYTHIA and HERWIG event generators. We have also studied the average of the maximum charged-particle density versus the event multiplicity for all events, using the different pseudorapidity windows. This study prepares for the multi-particle production background expected in a future search for anomalous high-density multiplicity fluctuations using the LHC data.

Modeling charged-particle multiplicity distributions at LHC

2020 ◽  
Vol 35 (36) ◽  
pp. 2050302
Author(s):  
Amr Radi
Keyword(s):  
High Energy Physics ◽  
Hadron Collider ◽  
Center Of Mass ◽  
Charged Particles ◽  
High Energy ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Proton Proton ◽  
Center Of Mass Energy ◽  
8 Tev

With many applications in high-energy physics, Deep Learning or Deep Neural Network (DNN) has become noticeable and practical in recent years. In this article, a new technique is presented for modeling the charged particles multiplicity distribution [Formula: see text] of Proton-Proton [Formula: see text] collisions using an efficient DNN model. The charged particles multiplicity n, the total center of mass energy [Formula: see text], and the pseudorapidity [Formula: see text] used as input in DNN model and the desired output is [Formula: see text]. DNN was trained to build a function, which studies the relationship between [Formula: see text]. The DNN model showed a high degree of consistency in matching the data distributions. The DNN model is used to predict with [Formula: see text] not included in the training set. The expected [Formula: see text] had effectively merged the experimental data and the values expected indicate a strong agreement with Large Hadron Collider (LHC) for ATLAS measurement at [Formula: see text], 7 and 8 TeV.

Freeze-out scenarios in small systems at RHIC and LHC energies

2020 ◽  
Vol 29 (02) ◽  
pp. 2050006
Author(s):  
Susil Kumar Panda ◽  
Subhasis Samanta ◽  
Ajay Kumar Dash ◽  
Ranbir Singh ◽  
Rita Paikaray ◽  
...  
Keyword(s):  
System Size ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Suppression Factor ◽  
Increase With Increase ◽  
Multiplicity Formula ◽  
Charge Multiplicity ◽  
System Volume ◽  
Chemical Freeze ◽  
Freeze Out

We study the hadronic yields produced in two small collision systems [Formula: see text] at [Formula: see text][Formula: see text]TeV and [Formula: see text] at [Formula: see text][Formula: see text]TeV, and extracted the chemical freeze-out (CFO) parameters. The CFO parameters are obtained using a hadron resonance gas (HRG) model and in this study present the system size dependence of the parameters. We observe that with the strangeness suppression factor [Formula: see text] included in the model, a single freeze-out scenario can describe hadronic yields for all the centralities of [Formula: see text] collision at [Formula: see text][Formula: see text]TeV, indicating that the strange hadrons have not reached full equilibrium. On the other hand, for small average charged particle multiplicity ([Formula: see text]) bins of [Formula: see text] collision at [Formula: see text][Formula: see text]TeV strangeness is not fully equilibrated whereas strangeness equilibration seems to be reached in large [Formula: see text]. For both the collision systems, no significant system volume dependence of the temperature has been observed. However, in comparable [Formula: see text] values, temperatures are 10–20[Formula: see text]MeV larger for [Formula: see text] collision compared to [Formula: see text] collision. We observe that the volume of the system at the CFO increases with increase of charge multiplicity for both the collisions. The increase is much steeper in [Formula: see text] collision at [Formula: see text][Formula: see text]TeV than [Formula: see text] collision at [Formula: see text][Formula: see text]TeV. Further, we analyze the transverse momentum ([Formula: see text]) spectra of different hadrons produced in [Formula: see text] collision at [Formula: see text][Formula: see text]TeV in a combined freeze-out scenario. We show the [Formula: see text] dependence of freeze-out parameters. It is observed that with [Formula: see text] included in the model, a single freeze-out scheme can describe the [Formula: see text] spectra. For similar [Formula: see text] values, [Formula: see text] in both the collision systems are close to each other and overall values of [Formula: see text] increase with increase of [Formula: see text]. Unlike CFO scenario using the produced hadron yields only, freeze-out temperature in combined scenario of chemical and kinetic freeze-out, obtained from [Formula: see text] spectra, increases with increase of [Formula: see text]. For smaller [Formula: see text] values, the temperature in [Formula: see text] collision at [Formula: see text][Formula: see text]TeV is similar to that of [Formula: see text] collision at [Formula: see text][Formula: see text]TeV. However, temperatures are larger in [Formula: see text] collision than [Formula: see text] collision at larger [Formula: see text] values.

scholarly journals (Anti-)deuteron production in pp collisions at $$\sqrt{s}=13 \ \text {TeV}$$

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
S. Acharya ◽  
◽  
D. Adamová ◽  
A. Adler ◽  
J. Adolfsson ◽  
...  
Keyword(s):  
Charged Particle ◽  
Formation Mechanism ◽  
Bound States ◽  
High Energy ◽  
Light Nuclei ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Pp Collisions ◽  
Alice Experiment ◽  
Deuteron Production

AbstractThe study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of $$\text {(anti-)deuterons}$$ (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at $$\sqrt{s}=13$$ s = 13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity ($${\mathrm {d} N_{ch}/\mathrm {d} \eta } \sim 26$$ d N ch / d η ∼ 26 ) as measured in p–Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p–Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM).

scholarly journals Tsallis Statistics in High Energy Physics: Chemical and Thermal Freeze-Outs

Physics ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 654-664
Author(s):  
Jean Cleymans ◽  
Masimba Wellington Paradza
Keyword(s):  
High Energy Physics ◽  
Chemical Potential ◽  
High Energy ◽  
Pp Collisions ◽  
Proton Proton ◽  
Wide Range ◽  
Relativistic Proton ◽  
System Temperature ◽  
Tsallis Distribution ◽  
Freeze Out

We present an overview of a proposal in relativistic proton-proton (pp) collisions emphasizing the thermal or kinetic freeze-out stage in the framework of the Tsallis distribution. In this paper we take into account the chemical potential present in the Tsallis distribution by following a two step procedure. In the first step we used the redudancy present in the variables such as the system temperature, T, volume, V, Tsallis exponent, q, chemical potential, μ, and performed all fits by effectively setting to zero the chemical potential. In the second step the value q is kept fixed at the value determined in the first step. This way the complete set of variables T,q,V and μ can be determined. The final results show a weak energy dependence in pp collisions at the centre-of-mass energy s=20 TeV to 13 TeV. The chemical potential μ at kinetic freeze-out shows an increase with beam energy. This simplifies the description of the thermal freeze-out stage in pp collisions as the values of T and of the freeze-out radius R remain constant to a good approximation over a wide range of beam energies.

scholarly journals Measurement of J/Ψ production as a function of multiplicity in pp and p-Pb collisions with ALICE

2018 ◽  
Vol 182 ◽  
pp. 02064 ◽  
Author(s):  
Anisa Khatun ◽  
Keyword(s):  
Charged Particle ◽  
Theoretical Model ◽  
Electromagnetic Calorimeter ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Pp Collisions ◽  
Proton Proton ◽  
Model Predictions

The increase of hard probe production as a function of the charged particle multiplicity in proton-proton and proton-lead collisions is considered to be an interesting observable for the study of multiple parton interactions. In the present work, the correlation between J/Ψ production and charged particle multiplicity has been reviewed in pp collisions at √s = 7 and 13 TeV and p-Pb collisions at √sNN = 5.02 TeV at mid- and forward rapidities. The J/√ measurement in pp collisions at √s = 13 TeV using events triggered by the ALICE electromagnetic calorimeter at midrapidity is discussed in this report, too. An increment of the relative J/Ψ yields has been observed as a function of the multiplicity. The results have also been compared to theoretical model predictions.

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