scholarly journals Indication of a Differential Freeze-Out in Proton-Proton and Heavy-Ion Collisions at RHIC and LHC Energies

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Dhananjaya Thakur ◽  
Sushanta Tripathy ◽  
Prakhar Garg ◽  
Raghunath Sahoo ◽  
Jean Cleymans
Keyword(s):  
Radial Flow ◽  
Chemical Potential ◽  
Heavy Ion ◽  
Mass Hierarchy ◽  
Proton Proton ◽  
Ion Collisions ◽  
Tsallis Distribution ◽  
Mass Dependent ◽  
Proton Proton Collisions ◽  
Freeze Out

The experimental data from the RHIC and LHC experiments of invariant pT spectra for most peripheral A+A and p+p collisions are analyzed with Tsallis distributions in different approaches. The information about the freeze-out surface in terms of freeze-out volume, temperature, chemical potential, and radial flow velocity for π+, K+, and p and their antiparticles is obtained. Furthermore, these parameters are studied as a function of the mass of the particles. A mass dependent differential freeze-out is observed which does not seem to distinguish between particles and their antiparticles. Furthermore, a mass-hierarchy in the radial flow is observed, meaning heavier particles suffer lower radial flow. Tsallis distribution function at finite chemical potential is used to study the mass dependence of chemical potential. The peripheral heavy-ion and proton-proton collisions at the same energies seem to be equivalent in terms of the extracted thermodynamic parameters.

scholarly journals Dielectron Production in Proton–Proton Collisions at √s=7 TeV with ALICE

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Sebastian Scheid
Keyword(s):  
Cross Sections ◽  
Mass Range ◽  
Heavy Ion ◽  
Event Generator ◽  
Leading Order ◽  
Proton Proton ◽  
Total Cross Sections ◽  
Proton Collisions ◽  
Ion Collisions ◽  
Proton Proton Collisions

The ALICE Collaboration measured dielectron production as a function of the invariant mass ( m ee ), the pair transverse momentum ( p T , ee ) and the pair distance of closest approach ( DCA ee ) in pp collisions at s = 7 TeV. Prompt and non-prompt dielectron sources can be separated with the DCA ee , which will give the opportunity in heavy-ion collisions to identify thermal radiation from the medium in the intermediate-mass range dominated by contributions from open-charm and beauty hadron decays. The charm and beauty total cross sections are extracted from the data by fitting the spectra with two different MC generators, i.e., PYTHIA a leading order event generator and POWHEG a next-to-leading order event generator. Significant model dependences are observed, reflecting the sensitivity of this measurement to the heavy-flavour production mechanisms.

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 Centrality dependence of thermal freeze-out conditions at LHC in Pb+Pb collisions at sNN = 2.76TeV

2015 ◽  
Vol 30 (33) ◽  
pp. 1550167 ◽  
Author(s):  
Saeed Uddin ◽  
Inam-ul Bashir ◽  
Riyaz Ahmed Bhat ◽  
Waseem Bashir
Keyword(s):  
Experimental Data ◽  
Chemical Potential ◽  
Heavy Ion ◽  
Collective Flow ◽  
Flow Profile ◽  
Alice Experiment ◽  
Ion Collisions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Freeze Out

We have analyzed the available midrapidity [Formula: see text] transverse momentum spectra of identified particles such as protons [Formula: see text], kaons [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] for different centralities of Pb+Pb collisions at the LHC energy [Formula: see text]. We have used our earlier proposed unified statistical thermal freeze-out model. The model incorporates the effect of nuclear transparency in such energetic collisions and the resulting asymmetry in the collective-flow profile along the longitudinal and the transverse directions. Our calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment. The model calculation fits the experimental data for different particle species which provide thermal freeze-out conditions in terms of temperature and collective-flow parameters. The analysis shows a rise in the thermal freeze-out temperature and a mild decrease in the transverse collective-flow velocity as we go from central to the peripheral collisions. The baryon chemical potential is assumed to be nearly zero for the bulk of the matter [Formula: see text], a situation expected in the heavy ion collisions at LHC energies in the Bjorken approach owing to nearly complete nuclear transparency. The contributions from the decay of the heavier resonances are also taken into account in our calculations.

scholarly journals Energy Dependence of Particle Ratios in High Energy Nucleus-Nucleus Collisions: A USTFM Approach

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Inam-ul Bashir ◽  
Rameez Ahmad Parra ◽  
Hamid Nanda ◽  
Saeed Uddin
Keyword(s):  
Particle Production ◽  
Chemical Potential ◽  
Heavy Ion ◽  
High Energy ◽  
Ion Collisions ◽  
System A ◽  
Particle Ratios ◽  
High Degree ◽  
Chemical Freeze ◽  
Freeze Out

We study the identified particle ratios produced at mid-rapidity (y<0.5) in heavy-ion collisions, along with their correlations with the collision energy. We employ our earlier proposed unified statistical thermal freeze-out model (USTFM), which incorporates the effects of both longitudinal and transverse hydrodynamic flow in the hot hadronic system. A fair agreement seen between the experimental data and our model results confirms that the particle production in these collisions is of statistical nature. The variation of the chemical freeze-out temperature and the baryon chemical potential with respect to collision energies is studied. The chemical freeze-out temperature is found to be almost constant beyond the RHIC energy and is found to be close to the QCD predicted phase-transition temperature suggesting that the chemical freeze-out occurs soon after the hadronization takes place. The vanishing value of chemical potential at LHC indicates very high degree of nuclear transparency in the collision.

scholarly journals Understanding the energy dependence of $$B_2$$ in heavy ion collisions: interplay of volume and space-momentum correlations

2021 ◽  
Vol 57 (2) ◽  
Author(s):  
Vincent Gaebel ◽  
Michel Bonne ◽  
Tom Reichert ◽  
Ajdin Burnic ◽  
Paula Hillmann ◽  
...  
Keyword(s):  
Radial Flow ◽  
Transport Model ◽  
Qualitative Change ◽  
Heavy Ion ◽  
Volume Effect ◽  
Quantum Molecular Dynamics ◽  
Proton Proton ◽  
Coalescence Model ◽  
Ion Collisions ◽  
Deuteron Production

AbstractThe deuteron coalescence parameter $$B_2$$ B 2 in proton+proton and nucleus+nucleus collisions in the energy range of $$\sqrt{s_{NN}}=$$ s NN = 900–7000 GeV for proton + proton and $$\sqrt{s_{NN}}=$$ s NN = 2–2760 GeV for nucleus + nucleus collisions is analyzed with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model, supplemented by an event-by-event phase space coalescence model for deuteron and anti-deuteron production. The results are compared to data by the E866, E877, PHENIX, STAR and ALICE experiments. The $$B_2$$ B 2 values are calculated from the final spectra of protons and deuterons. At lower energies, $$\sqrt{s_{NN}}\le 20$$ s NN ≤ 20 GeV, $$B_2$$ B 2 drops drastically with increasing energy. The calculations confirm that this is due to the increasing freeze-out volume reflected in $$B_2\sim 1/V$$ B 2 ∼ 1 / V . At higher energies, $$\sqrt{s_{NN}}\ge 20$$ s NN ≥ 20 GeV, $$B_2$$ B 2 saturates at a constant level. This qualitative change and the vanishing of the volume suppression is shown to be due to the development of strong radial flow with increasing energy. The flow leads to strong space-momentum correlations which counteract the volume effect.

scholarly journals Pair production of magnetic monopoles and stable high-electric-charge objects in proton-proton and heavy-ion collisions

2021 ◽  
Author(s):  
Wen Yi Song ◽  
Wendy Taylor
Keyword(s):  
Electric Charge ◽  
Cross Sections ◽  
Heavy Ion Collisions ◽  
Production Cross ◽  
Heavy Ion ◽  
Magnetic Monopoles ◽  
Proton Proton ◽  
Proton Collisions ◽  
Ion Collisions ◽  
Proton Proton Collisions

Abstract We describe pair-production models of spin-0 and spin-½ magnetic monopoles and high-electric-charge objects in proton-proton and heavy-ion collisions, considering both the Drell-Yan and the photon-fusion processes. In particular, we extend the Drell-Yan production model of spin-½ high-electric-charge objects to include Z0-boson exchange for proton-proton collisions. Furthermore, we explore spin-½ and, for the first time, spin-0 production in ultraperipheral heavy-ion collisions. With matrix element calculations and equivalent photon fluxes implemented in MadGraph5_aMC@NLO, we present leading-order production cross sections of these mechanisms in √s = 14 TeV proton-proton collisions and √sNN = 5.5 TeV ultraperipheral lead-lead collisions at the LHC. While the mass range accessible in ultraperipheral lead-lead collisions is much lower than that in proton-proton collisions, we find that the theoretical production cross sections are significantly enhanced in the former for masses below 82 GeV.

Radial flow and differential freeze-out in proton-proton collisions at $\sqrt{s} = 7$s=7 TeV at the LHC

2019 ◽  
Vol 55 (1) ◽  
Author(s):  
Arvind Khuntia ◽  
Himanshu Sharma ◽  
Swatantra Kumar Tiwari ◽  
Raghunath Sahoo ◽  
Jean Cleymans
Keyword(s):  
Radial Flow ◽  
Proton Proton ◽  
Proton Collisions ◽  
Proton Proton Collisions ◽  
Freeze Out

scholarly journals Jet charge in heavy-ion collisions

2020 ◽  
Vol 235 ◽  
pp. 05004
Author(s):  
Hai Tao Li
Keyword(s):  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Jet Quenching ◽  
Effective Theory ◽  
Proton Proton ◽  
Ion Collisions ◽  
Soft Collinear Effective Theory ◽  
Flavor Tagging ◽  
Proton Proton Collisions

Jet quenching effects have been widely used to study the properties of strongly-interacting matter, quark-gluon plasma, in heavy-ion collisions. Flavor tagging in heavy-ion collisions plays an important role to reveal the medium parton showers for quark and gluon evolution. Combining with kinematic information, the average jet charge can be used to separate the contribution of different jet flavors, which is defined as the momentum- weighted sum of the charges of hadrons inside a given jet. Using soft-collinear effective theory with medium interactions, we investigate the factorization of the jet charge in QCD medium. We provide predictions for jet charge distributions and their modifications compared to the ones in proton-proton collisions.

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