Journal articles: 'Hard scattering in relativistic heavy ion collisions'

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Kumar for the ALICE Collaboration, Shyam. "Characterising Charm Jet Properties with Azimuthal Correlations of D Mesons and Charged Particles with ALICE at the LHC." Proceedings 10, no. 1 (April 19, 2019): 35. http://dx.doi.org/10.3390/proceedings2019010035.

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Charm quarks are produced via hard parton scattering in ultra-relativistic heavy-ion collisions, hence are ideal probes to study a possible de-confined state of matter, known as Quark Gluon Plasma (QGP). The angular correlation of a meson containing a charm quark with other charged particles in heavy-ion collisions can help in studying the properties of QGP. Similar studies in pp collisions can give insight about the charm production mechanism while in p-Pb collisions could provide essential information to disentangle final-state QGP-induced modifications from effects caused by cold nuclear matter. In this proceedings, the results are presented for p-Pb collisions at s NN = 5.02 TeV and pp collisions at s = 13 TeV, so far the highest available energy at the LHC. The results are compared with Monte Carlo (MC) simulations using PYTHIA and POWHEG event generators and with pp collision results at s = 7 TeV.

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Ray, Robert L., and Alexander M. Jentsch. "Two-particle correlations on transverse momentum: an untapped resource for studying relativistic heavy-ion collision dynamics." EPJ Web of Conferences 235 (2020): 01003. http://dx.doi.org/10.1051/epjconf/202023501003.

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Two-particle correlation projections onto two-dimensional transverse momentum coordinates (pt1, pt2) allow access to properties of the relativistic heavy-ion collision system which are complementary to that studied using angular correlations. Examples include the degree of thermal equilibration and the variance of dynamical fluctuations in hard-scattering processes. Results for minimum-bias Au + Au collisions at √sNN = 200 are presented, with the structures described by two phenomenological models. The correlations structures and extracted physical quantities are then compared to theoretical predictions. Conclusions from these comparisons regarding global equilibration, fluctuations in soft and semi-hard QCD processes, and the effects of the hot, dense collision medium are presented.

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Nouicer, Rachid. "Highlights from PHENIX at RHIC." EPJ Web of Conferences 171 (2018): 01003. http://dx.doi.org/10.1051/epjconf/201817101003.

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Hadrons conveying strange quarks or heavy quarks are essential probes of the hot and dense medium created in relativistic heavy-ion collisions. With hidden strangeness, ϕ meson production and its transport in the nuclear medium have attracted high interest since its discovery. Heavy quark-antiquark pairs, like charmonium and bottomonium mesons, are mainly produced in initial hard scattering processes of partons. While some of the produced pairs form bound quarkonia, the vast majority hadronize into particles carrying open heavy flavor. In this context, the PHENIX collaboration carries out a comprehensive physics program which studies the ϕ meson production, and heavy flavor production in relativistic heavy-ion collisions at RHIC. In recent years, the PHENIX experiment upgraded the detector in installing silicon vertex tracker (VTX) at mid-rapidity region and forward silicon vertex tracker (FVTX) at the forward rapidity region. With these new upgrades, the experiment has collected large data samples, and enhanced the capability of heavy flavor measurements via precision tracking. This paper summarizes the latest PHENIX results concerning ϕ meson, open and closed charm and beauty heavy quark production in relativistic heavy-ion collisions. These results are presented as a function of rapidity, energy and system size, and their interpretation with respect to the current theoretical understanding.

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TANNENBAUM, M. J. "RESULTS FROM PHENIX AT RHIC WITH IMPLICATIONS FOR LHC." International Journal of Modern Physics A 26, no. 32 (December 30, 2011): 5299–335. http://dx.doi.org/10.1142/s0217751x11054966.

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Results from the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) in nucleus–nucleus and proton–proton collisions at c.m. energy [Formula: see text] are presented in the context of the methods of single and two-particle inclusive reactions which were used in the discovery of hard-scattering in p–p collisions at the CERN ISR in the 1970's. These techniques are used at RHIC in A + A collisions because of the huge combinatoric background from the large particle multiplicity. Topics include J/Ψ suppression, jet quenching in the dense medium (sQGP) as observed with π0 at large transverse momentum, thermal photons, collective flow, two-particle correlations, suppression of heavy quarks at large pT and its possible relation to Higgs searches at the LHC. The differences and similarities of the measurements in p–p and A + A collisions are presented. The two discussion sessions which followed the lectures on which this article is based are included at the end.

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Gupta, Rohit, Anjaly Menon, Shubhangi Jain, and Satyajit Jena. "The Theoretical Description of the Transverse Momentum Spectra: A Unified Model." Universe 9, no. 2 (February 20, 2023): 111. http://dx.doi.org/10.3390/universe9020111.

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Analysis of transverse momentum distributions is a useful tool to understand the dynamics of relativistic particles produced in high-energy collisions. Finding a proper distribution function to approximate the spectra is a vastly developing area of research in particle physics. In this work, we have provided a detailed theoretical description of the unified statistical framework in high-energy physics. We have tested the applicability of this framework on experimental data by analyzing the transverse momentum spectra of pion produced in heavy-ion collision at RHIC and LHC. We have also attempted to explain the transverse momentum spectra of charged hadrons formed in pp collision at different energies using the unified statistical framework. This formalism has been proved to nicely explain the spectra of particles produced in soft processes as well as hard scattering processes in a consistent manner.

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Chang, Zilong. "Gluon polarization measurements from longitudinally polarized proton-proton collisions at STAR." Journal of Physics: Conference Series 1643, no. 1 (December 1, 2020): 012184. http://dx.doi.org/10.1088/1742-6596/1643/1/012184.

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Abstract The gluon polarization contribution to the proton spin is an integral part to solve the longstanding proton spin puzzle. At the Relativistic Heavy Ion Collider (RHIC), the STAR experiment has measured jets produced in mid-pseudo-rapidity, |η| < 1.0, and full azimuth, ϕ, from longitudinally polarized pp collisions to study the gluon polarization in the proton. At center of mass energies s = 200 and 510 GeV, jet production is dominated by hard QCD scattering processes such as gluon-gluon (gg) and quark-gluon (qg), thus making the longitudinal double-spin asymmetry (ALL ) sensitive to the gluon polarization. Early STAR inclusive jet ALL results at s = 200 GeV provided the first evidence of the non-zero gluon polarization at momentum fraction x > 0.05. The higher center of mass energy s = 510 GeV allows to explore the gluon polarization as low as x ∼ 0.015. In this talk we will present the recent STAR inclusive jet and dijet ALL results at s = 510 GeV, and discuss the relevant new analysis techniques for the estimation of trigger bias and reconstruction uncertainty, the underlying event correction on the jet energy and its effect on jet ALL . Dijet results are shown for different topologies in regions of pseudo-rapidity, effectively scanning the x-dependence of the gluon polarization.

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Maldonado-Gonzalez, Julio Cesar, Alejandro Ayala, Isabel Dominguez, and Maria Elena Tejeda-Yeomans. "QGP hydrodynamical study using energy-momentum in-medium deposition by an extended source." EPJ Web of Conferences 172 (2018): 08003. http://dx.doi.org/10.1051/epjconf/201817208003.

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The quark-gluon plasma (QGP) is created under extreme conditions, such as the ones prevailing in heavy ion collisions. The characterization of the QGP can be done using high-pT probes such as the partons that are created through hard scatterings in the fireball. These fast-moving partons lose energy and momentum along their traveled path through the medium. The parton deposition of energy-momentum creates an in-medium disturbance that can be described using approximations within relativistic hydrodynamics in a defined regime of the QGP evolution. Based on earlier research in this field, we study the use of extended sources that depend on the location of the parton-jet in the initial stages of the QGP evolution. We explore this approach as a way to complement the current numerical landscape of hydrodynamical QGP studies and to eventually generate initial conditions that can be used as input of hydrodynamical numerical simulations.

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Wolschin, Georg. "Aspects of Relativistic Heavy-Ion Collisions." Universe 6, no. 5 (April 30, 2020): 61. http://dx.doi.org/10.3390/universe6050061.

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The rapid thermalization of quarks and gluons in the initial stages of relativistic heavy-ion collisions is treated using analytic solutions of a nonlinear diffusion equation with schematic initial conditions, and for gluons with boundary conditions at the singularity. On a similarly short time scale of t ≤ 1 fm/c, the stopping of baryons is accounted for through a QCD-inspired approach based on the parton distribution functions of valence quarks, and gluons. Charged-hadron production is considered phenomenologically using a linear relativistic diffusion model with two fragmentation sources, and a central gluonic source that rises with ln 3 ( s N N ) . The limiting-fragmentation conjecture that agrees with data at energies reached at the Relativistic Heavy-Ion Collider (RHIC) is found to be consistent with Large Hadron Collider (LHC) data for Pb-Pb at s N N = 2.76 and 5.02 TeV. Quarkonia are used as hard probes for the properties of the quark-gluon plasma (QGP) through a comparison of theoretical predictions with recent CMS, ALICE and LHCb data for Pb-Pb and p-Pb collisions.

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ALBERICO, W. M., A. BERAUDO, A. DE PACE, A. MOLINARI, M. MONTENO, M. NARDI, and F. PRINO. "LANGEVIN DYNAMICS OF HEAVY FLAVORS IN RELATIVISTIC HEAVY-ION COLLISIONS." International Journal of Modern Physics E 20, no. 07 (July 2011): 1623–28. http://dx.doi.org/10.1142/s0218301311019982.

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We study the stochastic dynamics of c and b quarks, produced in hard initial processes, in the hot medium created after the collision of two relativistic heavy ions. This is done through the numerical solution of the relativistic Langevin equation. The latter requires the knowledge of the friction and diffusion coefficients, whose microscopic evaluation is performed treating separately the contribution of soft and hard collisions. The evolution of the background medium is described by ideal/viscous hydrodynamics. Below the critical temperature the heavy quarks are converted into hadrons, whose semileptonic decays provide single-electron spectra to be compared with the current experimental data measured at RHIC. We focus on the nuclear modification factor RAA and on the elliptic-flow coefficient v2, getting, for sufficiently large pT, a reasonable agreement.

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Steffen, Frank D., and Markus H. Thoma. "Hard thermal photon production in relativistic heavy ion collisions." Physics Letters B 510, no. 1-4 (June 2001): 98–106. http://dx.doi.org/10.1016/s0370-2693(01)00525-1.

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Gao, Jian-Hua. "Global Polarization Theory Overview." EPJ Web of Conferences 259 (2022): 02003. http://dx.doi.org/10.1051/epjconf/202225902003.

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We give a brief overview about theory development of spin polarization in relativistic heavy ion collisions, which includes how the polarization could be generated by single scattering, what the polarization could be in equilibrium, how to address some recent puzzles in spin polarization in heavy ion collisions and how much progress we have made in spin hydrodynamics and spin kinetic theory. We will also discuss the possible helicity polarization in relativistic heavy ion collisions.

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SCHENKE, BJÖRN, SANGYONG JEON, and CHARLES GALE. "MONTE-CARLO SIMULATION OF HEAVY-ION COLLISIONS." International Journal of Modern Physics E 20, no. 07 (July 2011): 1588–93. http://dx.doi.org/10.1142/s0218301311019921.

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Results from the Modular Algorithm for Relativistic Treatment of heavy IoN Interactions (MARTINI) are presented. This comprehensive event generator for the hard and penetrating probes in high energy nucleus-nucleus collisions employs a time evolution model for the soft background, PYTHIA 8.1 and the McGill-AMY parton evolution scheme including radiative as well as elastic processes. It generates full event configurations in the high pT region, allowing to perform the same processing as with experimental data, such as multi-particle correlation analyses and full jet reconstruction.

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GUBSER, STEVEN S. "HEAVY ION COLLISIONS AND BLACK HOLE DYNAMICS." International Journal of Modern Physics D 17, no. 03n04 (March 2008): 673–78. http://dx.doi.org/10.1142/s0218271808012425.

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Relativistic heavy ion collisions create a strongly coupled quark–gluon plasma. Some of the plasma's properties can be approximately understood in terms of a dual black hole. These properties include shear viscosity, thermalization time, and drag force on heavy quarks. They are hard to calculate from first principles in QCD. Extracting predictions about quark–gluon plasmas from dual black holes mostly involves solving Einstein's equations and classical string equations of motion. AdS/CFT provides a translation from gravitational calculations to gauge theory predictions. The gauge theory to which the predictions apply is [Formula: see text] super-Yang–Mills theory. QCD is different in many respects from super-Yang–Mills, but it seems that its high temperature properties are similar enough for us to make some meaningful comparisons.

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Norbeck, Edwin, Karel Šafařík, and Peter A. Steinberg. "Hard-Scattering Results in Heavy-Ion Collisions at the LHC." Annual Review of Nuclear and Particle Science 64, no. 1 (October 19, 2014): 383–411. http://dx.doi.org/10.1146/annurev-nucl-102912-144532.

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Nattrass, Christine. "Measurements of jets in heavy ion collisions." EPJ Web of Conferences 172 (2018): 05010. http://dx.doi.org/10.1051/epjconf/201817205010.

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The Quark Gluon Plasma (QGP) is created in high energy heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). This medium is transparent to electromagnetic probes but nearly opaque to colored probes. Hard partons produced early in the collision fragment and hadronize into a collimated spray of particles called a jet. The partons lose energy as they traverse the medium, a process called jet quenching. Most of the lost energy is still correlated with the parent parton, contributing to particle production at larger angles and lower momenta relative to the parent parton than in proton-proton collisions. This partonic energy loss can be measured through several observables, each of which give different insights into the degree and mechanism of energy loss. The measurements to date are summarized and the path forward is discussed.

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Vitev, Ivan. "Hard Probes in Heavy Ion Collisions: Current Status and Prospects for Application of QCD Evolution Techniques." International Journal of Modern Physics: Conference Series 37 (January 2015): 1560059. http://dx.doi.org/10.1142/s2010194515600599.

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In the past decade the observation of cross section modification for leading hadrons, heavy flavor and two particle correlations in heavy ion collisions has provided important insights into the dynamics of parton propagation in dense strongly-interacting matter. The development of the theory of reconstructed jets and related experimental measurements have further shed light on the characteristics of in-medium parton showers. So far, experimental results from ultra-relativistic nuclear collisions at RHIC and LHC have been analyzed in the framework of parton energy loss, where the precision of the theoretical predictions cannot be systematically improved. Only recently have higher order calculations and applications of resummation and evolution to heavy ion collisions begun to emerge. Several examples of such advances are discussed in these proceedings.

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Dash, Sadhana, Basanta K. Nandi, Ranjit Nayak, Ashutosh Kumar Pandey, and Priyanka Sett. "Comprehending particle production at RHIC and LHC energies using global measurements." Modern Physics Letters A 32, no. 12 (April 9, 2017): 1750060. http://dx.doi.org/10.1142/s0217732317500602.

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The centrality dependence of the charged-particle multiplicity densities [Formula: see text] and transverse energy densities [Formula: see text] are investigated using the two-component Glauber approach for broad range of energies in heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC). A comprehensive study shows that the data is well-described within the framework of two-component model which includes the contribution of “soft processes” and “hard processes” for different centrality classes and energies. The data at two different energies are compared by means of the ratio of [Formula: see text] (and [Formula: see text]) to see the interplay of energy scaling and relative contribution of hard processes.

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Bravina, Larissa, Yurii Kvasiuk, Sergey Sivoklokov, Oleksandr Vitiuk, and Evgeny Zabrodin. "Directed Flow in Microscopic Models in Relativistic A+A Collisions." Universe 5, no. 3 (March 5, 2019): 69. http://dx.doi.org/10.3390/universe5030069.

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Evolution of directed flow of charged particles produced in relativistic heavy-ion collisions at energies 4 ≤ s ≤ 19.6 GeV is considered within two microscopic transport models, ultra-relativistic quantum molecular dynamics (UrQMD) and quark-gluon string model (QGSM). In both models, the directed flow of protons changes its sign at midrapidity from antiflow to normal flow with decreasing energy of collisions, whereas the flows of mesons and antiprotons remain antiflow-oriented. For lighter colliding systems, such as Cu+Cu or S+S, changing of the proton directed flow occurs at lower bombarding energies and for more central topologies compared to a heavy Au+Au system. The differences can be explained by dissimilar production zones of different hadrons and by the influence of spectators. Directed flows of most abundant hadronic species at midrapidity are found to be formed within t = 10–12 fm/c after the beginning of nuclear collision. The influence of hard and soft mean-field potentials on the directed flow is also studied.

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ROLAND, CHRISTOF, GÁBOR I. VERES, and KRISZTIÁN KRAJCZÁR. "SIMULATION OF JET QUENCHING OBSERVABLES IN HEAVY ION COLLISIONS AT THE LHC." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 1937–42. http://dx.doi.org/10.1142/s0218301307007258.

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Large transverse momentum jets provide unique tools to study dense QCD matter in high-energy heavy-ion collisions. Results from RHIC on suppression of high transverse momentum particles in Au + Au collisions indicate a significant energy loss of leading partons in the dense and strongly interacting matter formed in these collisions. The LHC will collide Pb ions at [Formula: see text], where the cross section of hard scattering will increase dramatically. Large production rates, the large acceptance of the CMS calorimeters and tracking system, combined with the capability of triggering on jets, will extend the transverse momentum reach of charged particle spectra and nuclear modification factors up to pT > 200 GeV / c .

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Pari, Sharareh Mehrabi, Kurosh Javidan, and Fatemeh Taghavi Shahri. "Viscosity to entropy ratio of QGP in relativistic heavy ion collision: Hard thermal loop corrections." International Journal of Modern Physics E 25, no. 06 (June 2016): 1650040. http://dx.doi.org/10.1142/s0218301316500403.

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In this work, we report on our computation results for the best value of the shear viscosity to entropy ratio of quark–gluon plasma produced in the relativistic Au–Au collisions at [Formula: see text][Formula: see text]GeV. Time evolution of heavy quarks distribution functions is calculated by solving the Fokker–Planck evolution equation using the new technique: Iterative Laplace transform method. We compute the drag and diffusion coefficients by considering the hard thermal loop corrections and also temperature dependence running strong coupling, up to complete interactions of leading order.

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HUMANIC, THOMAS J. "HANBURY-BROWN–TWISS INTERFEROMETRY WITH IDENTICAL BOSONS IN RELATIVISTIC HEAVY ION COLLISIONS: COMPARISONS WITH HADRONIC SCATTERING MODELS." International Journal of Modern Physics E 15, no. 01 (February 2006): 197–236. http://dx.doi.org/10.1142/s0218301306003977.

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Identical boson Hanbury-Brown–Twiss interferometry as applied to relativistic heavy-ion collisions is reviewed. Emphasis is placed on the use of hadronic scattering models to interpret the physical significance of experimental results. Interferometric studies with center-of-mass energies from <1 GeV/nucleon up to 5500 GeV/nucleon are considered.

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Blau, Dmitry, and Dmitri Peresunko. "Direct Photon Production in Heavy-Ion Collisions: Theory and Experiment." Particles 6, no. 1 (January 30, 2023): 173–87. http://dx.doi.org/10.3390/particles6010009.

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Direct photons provide a possibility to test properties of hot matter created in proton–proton (pp), proton–nucleus (p–A) or nucleus–nucleus (A–A) collisions. As they are created in charged particles’ scatterings and freely escape the hot region, they provide a tool to test all stages of the collision: the scattering of the partons of incoming nucleons, pre-equilibrium evolution and collective expansion of hot quark–gluon matter created in nucleus–nucleus collisions. Comparing direct photon production in pp, p–A and A–A collisions, one can check the scaling with the number of binary collisions expected at a high transverse momentum range and obtain insight into the hot and cold hadronic matter properties with soft photons. The collective elliptic flow of direct photons is a unique possibility to trace the collective flow formation and space–time evolution of the fireball. We review the experimental results on direct photon production in pp, p–A and A–A collisions at the Super Proton Synchroton (SPS), the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) energies and discuss an agreement of theoretical predictions with measurements. Finally, we present predictions of direct photon spectra and collective flow for lower energy collisions expected at the Nuclotron-based Ion Collider fAcility (NICA) and the Facility for Antiproton and Ion Research (FAIR).

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RENK, THORSTEN. "YaJEM — A MONTE CARLO CODE FOR IN-MEDIUM SHOWER EVOLUTION." International Journal of Modern Physics E 20, no. 07 (July 2011): 1594–99. http://dx.doi.org/10.1142/s0218301311019933.

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High transverse momentum (PT) QCD scattering processes are regarded as a valuable tool to study the medium produced in heavy-ion collisions, as due to uncertainty arguments their cross section should be calculable independent of medium properties whereas the medium then modifies only the final state partons emerging from a hard vertex. With the heavy-ion physics program at the CERN LHC imminent, the attention of high PT physics in heavy ion collisions is shifting from the observation of hard single hadrons to fully reconstructed jets. However, the presence of a background medium at low PT complicates jet-finding as compared to p - p collisions. Monte-Carlo (MC) codes designed to simulate the evolution of parton showers evolving into hadron jets are valuable tools to understand the complicated interplay between the medium modification of the jet and the bias introduced by a specific jet-finding scheme. However, such codes also use a set of approximations which needs to be tested against the better understood single high PT hadron observables. In this paper, I review the ideas underlying the MC code YaJEM (Yet another Jet Energy-loss Model) and present some of the results obtained with the code.

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on behalf of ALICE collaboration, Preeti Dhankher. "Multiplicity Dependence of Heavy-Flavour Hadron Decay Electron Production in Collisions at √sNN = 8.16 Measured with ALICE at the LHC." Proceedings 10, no. 1 (April 15, 2019): 28. http://dx.doi.org/10.3390/proceedings2019010028.

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A Large Ion Collider Experiment (ALICE) at the Large Hadron collider (LHC) is a heavy-ion dedicated experiment designed to study nuclear matter at extreme condition of high temperature and high density at which quarks are deconfined and give rise to a new state of matter known as Quark Gluon Plasma (QGP). Heavy flavours (charm and beauty), are produced in the initial stages of hadronic collisions in hard scattering processes and therefore are effective probes to study the QGP. In this contribution, recent measurements of the production of electrons from heavy-flavour hadron decays, their nuclear modification factor and the self-normalised yield measured up to 14 in collisions at √sNN = 8.16 TeV collected in LHC Run2 in 2016 are presented.

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SAKAGUCHI, TAKAO. "SYSTEM SIZE AND ENERGY DEPENDENCE OF HIGH pT HADRON PRODUCTION MEASURED WITH PHENIX EXPERIMENT AT RHIC." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 2166–73. http://dx.doi.org/10.1142/s0218301307007635.

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PHENIX has measured high transverse momentum (pT) identified hadrons in different collision species and energies in the last five RHIC runs. The systematic study of the high PT hadron production provides an idea on interaction of hard scattered partons and the matter created in relativistic heavy ion collision. The η/π0 ratio is measured in Au + Au collisions, which gives a hint on the system thermalization and particle production. A future measurement of hadron and photon measurement is discussed.

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Steffen, Frank D., and Markus H. Thoma. "Erratum to: “Hard thermal photon production in relativistic heavy ion collisions” [Phys. Lett. B 510 (2001) 98]." Physics Letters B 660, no. 5 (March 2008): 604–6. http://dx.doi.org/10.1016/j.physletb.2007.11.020.

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Foka, Panagiota, and Małgorzata Anna Janik. "An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: Hard probes." Reviews in Physics 1 (November 2016): 172–94. http://dx.doi.org/10.1016/j.revip.2016.11.001.

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LIPPERT, THOMAS, JOACHIM THIEL, NORBERT GRÜN, and WERNER SCHEID. "COHERENCE AND INCOHERENCE IN THE PHOTON AND DILEPTON PRODUCTION BY BREMSSTRAHLUNG IN RELATIVISTIC HEAVY-ION COLLISIONS." International Journal of Modern Physics A 06, no. 29 (December 10, 1991): 5249–69. http://dx.doi.org/10.1142/s0217751x9100246x.

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Due to the strong collective deceleration during the initial stage of relativistic heavy-ion collisions, the nuclear matter irradiates real and virtual bremsstrahlung. We describe the process of bremsstrahlung emission in the framework of a semiclassical model in order to study coherence and incoherence effects in the production process. Guided by the intuitive notation of shock fronts being formed between the incident nuclei, we use a simple parametrization of the nuclear current density. The photon spectrum is studied up to photon energies of 300 MeV. In particular, a gradual transition from the coherent production process of low-energy photons to the incoherent one for hard photons is demonstrated. For heavy collision systems coherence effects in the photon spectra dominate, showing characteristic structures arising from shock fronts. The dilepton spectrum is described in first-order perturbation theory. Generally, dileptons are found to be produced incoherently. Only in the case of dielectron production with small invariant pair masses do moderate coherence effects survive.

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Okawa, Hideki. "Status and Performance of sPHENIX Experiment." EPJ Web of Conferences 276 (2023): 05004. http://dx.doi.org/10.1051/epjconf/202327605004.

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sPHENIX is a state-of-the-art experiment at the Relativistic Heavy Ion Collider. Hard probes are to be measured in p+p, p+Au and Au+Au collisions to understand the properties of the quark-gluon plasma. sPHENIX covers a wide range of physics programs: jet correlations and substructure, upsilon spectroscopy, open heavy flavor and cold quantum chromodynamics. It provides unique opportunities in the low transverse momentum region and also offer kinematic overlap with the Large Hadron Collider experiments. In these proceedings, the scientific mission of sPHENIX, detector design and key performance parameters are described, and expected projections of some measurements under consideration are presented.

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LIU, WEI, CHE MING KO, and BEN-WEI ZHANG. "JET CONVERSIONS IN QGP AND SUPPRESSION OF IDENTIFIED HADRONS." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 1930–36. http://dx.doi.org/10.1142/s021830130700726x.

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A gluon or quark jet traversing through a quark-gluon plasma can be converted into a quark or gluon jet through scatterings with thermal partons. Their conversion rates due to two-body elastic and inelastic scattering as well as scatterings involving gluon radiation are evaluated in the lowest order in Quantum Chromodynamics (QCD). Including both energy loss and conversions of quark and gluon jets in the expanding quark-gluon plasma produced in relativistic heavy ion collisions, we find a net conversion of quark jets to gluon jets. This reduces the difference between the nuclear modification factors for quark and gluon jets in central heavy ion collisions and thus enhances the p/π+ and [Formula: see text] ratios at high transverse momentum. Using the larger QCD coupling constant from lattice QCD calculations than that given by the perturbative QCD further enhances the net quark to gluon jet conversion rate, leading to a closer similarity between these ratios at high transverse momentum in central Au + Au collisions at [Formula: see text] and in p + p collisions at same energy as observed in experiments.

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HARRIS, JOHN W. "EVIDENCE FOR A QUARK-GLUON PLASMA AT RHIC." International Journal of Modern Physics E 16, no. 03 (April 2007): 643–59. http://dx.doi.org/10.1142/s0218301307006186.

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This presentation is given in honor of Walter Greiner's 70th birthday, in recognition of the pioneering work of his "Frankfurt School" and their contributions to the field of heavy ion physics. Ultra-relativistic collisions of heavy nuclei at the Relativistic Heavy Ion Collider (RHIC) form an extremely hot system at energy densities greater than 5 GeV/fm3, where normal hadrons cannot exist. Upon rapid cooling of the system to a temperature T ~ 175 MeV and vanishingly small baryo-chemical potential, hadrons coalesce from quarks at the quark-hadron phase boundary predicted by lattice QCD. A large amount of collective (elliptic) flow at the quark level provides evidence for strong pressure gradients in the initial partonic stage of the collision when the system is dense and highly interacting prior to coalescence into hadrons. The suppression of both light (u,d,s) and heavy (c,b) hadrons at large transverse momenta, that form from fragmentation of hard-scattered partons, and the quenching of di-jets provide evidence for extremely large energy loss of partons as they attempt to propagate through the dense, strongly-coupled, colored medium created at RHIC.

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Pitonyak, Daniel, Koichi Kanazawa, Yuji Koike, and Andreas Metz. "Transverse Single-Spin Asymmetries in Proton-Proton Collisions Within Collinear Factorization." International Journal of Modern Physics: Conference Series 37 (January 2015): 1560033. http://dx.doi.org/10.1142/s2010194515600332.

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We provide a new analysis within collinear factorization of transverse single-spin asymmetries (TSSAs) in high transverse momentum charged and neutral pion production in pp collisions at the Relativistic Heavy Ion Collider (RHIC). This study incorporates the so-called twist-3 fragmentation term and shows that one can describe RHIC data through this mechanism. Moreover, by fixing other non-perturbative inputs through extractions of transverse momentum dependent functions in e+e- → h1h2X and semi-inclusive deep-inelastic scattering (SIDIS), we provide for the first time a consistency between certain spin/azimuthal asymmetries in all three reactions (i.e., pp, e+e-, and SIDIS).

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KO, CHE MING. "JET CONVERSIONS IN QUARK-GLUON PLASMA." International Journal of Modern Physics E 20, no. 07 (July 2011): 1641–45. http://dx.doi.org/10.1142/s0218301311020010.

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In addition to loosing energy, a quark or gluon jet traversing through a quark-gluon plasma can also be converted to a gluon or quark jet through scattering with the thermal quarks and gluons. Their conversion rates due to two-body elastic [Formula: see text] and inelastic [Formula: see text] scattering have been evaluated in the lowest order in QCD. Including both energy loss and conversions of quark and gluon jets in the expanding quark-gluon plasma produced in relativistic heavy ion collisions, a net conversion of quark jets to gluon jets has been found. This reduces the difference between the nuclear modification factors for quark and gluon jets in heavy ion collisions and thus enhances the ratios of high transverse momentum protons and antiprotons to pions that are produced from the fragmentation of these jets. To account for the observed similar ratios in central Au + Au and p + p collisions at same energy requires, however, a much larger net quark to gluon jet conversion rate than that given by the lowest-order QCD, indicating the importance of higher-order processes and the strongly coupling nature of the quark-gluon plasma in describing the propagation of jets in the quark-gluon plasma.

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Moriggi, Lucas, and Magno Machado. "Nuclear Modification Factor in Small System Collisions within Perturbative QCD including Thermal Effects." Physics 4, no. 3 (July 18, 2022): 787–99. http://dx.doi.org/10.3390/physics4030050.

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In this paper, the nuclear modification factors, RxA, are investigated for pion production in small system collisions, measured by PHENIX experiment at RHIC (Relativistic Heavy Ion Collider). The theoretical framework is the parton transverse momentum kT-factorization formalism for hard processes at small momentum fraction, x. Evidence for collective expansion and thermal effects for pions, produced at equilibrium, is studied based on phenomenological parametrization of blast-wave type in the relaxation time approximation. The dependencies on the centrality and on the projectile species are discussed in terms of the behavior of Cronin peak and the suppression of RxA at large transverse momentum, pT. The multiplicity of produced particles, which is sensitive to the soft sector of the spectra, is also included in the present analysis.

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Dolejší, Jiří, Wojciech Florkowski, and Jörg Hüfner. "Critical scattering at the chiral phase transition and low-pT enhancement of mesons in ultra-relativistic heavy-ion collisions." Physics Letters B 349, no. 1-2 (April 1995): 18–22. http://dx.doi.org/10.1016/0370-2693(95)00254-i.

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Waqas, Muhammad, Fu-Hu Liu, and Zafar Wazir. "Dependence of Temperatures and Kinetic Freeze-Out Volume on Centrality in Au-Au and Pb-Pb Collisions at High Energy." Advances in High Energy Physics 2020 (May 27, 2020): 1–15. http://dx.doi.org/10.1155/2020/8198126.

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Centrality-dependent double-differential transverse momentum spectra of negatively charged particles (π−, K−, and p¯) at the mid(pseudo)rapidity interval in nuclear collisions are analyzed by the standard distribution in terms of multicomponent. The experimental data measured in gold-gold (Au-Au) collisions by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC) and in lead-lead (Pb-Pb) collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) are studied. The effective temperature, initial temperature, kinetic freeze-out temperature, transverse flow velocity, and kinetic freeze-out volume are extracted from the fitting to transverse momentum spectra. We observed that the mentioned five quantities increase with the increase of event centrality due to the fact that the average transverse momentum increases with the increase of event centrality. This renders that larger momentum (energy) transfer and further multiple scattering had happened in central centrality.

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Khabarov, Sergey, Elena Kulish, Vasilisa Lenivenko, Alexander Makankin, Anna Maksymchuk, Vladimir Palichik, Maria Patsyuk, Sergey Vasiliev, Aleksander Vishnevskij, and Nikolay Voytishin. "First glance at the tracking detectors data collected in the first BM@N SRC run." EPJ Web of Conferences 201 (2019): 04002. http://dx.doi.org/10.1051/epjconf/201920104002.

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BM@N (Baryonic Matter at Nuclotron) is the first experiment at the accelerator complex of NICA-Nuclotron at JINR (Dubna). The aim of the experiment is to study collisions of relativistic ion beams of the kinetic energy from 1 to 4.5 AGeV with fixed targets. The last run started a new physics program of BM@N – Short Range Correlations (SRC) studies in light nuclei. The BM@N setup allows detecting of the residual nucleus for the first time. BM@N tracking detectors play a key role in the identification of the nucleus after hard scattering in inverse kinematics. We present the first results of the BM@N tracking detectors using the data collected in spring 2018.

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Taylor, Frank E. "Applications of pT-xR Variables in Describing Inclusive Cross Sections at the LHC." Universe 7, no. 6 (June 9, 2021): 196. http://dx.doi.org/10.3390/universe7060196.

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Invariant inclusive single-particle/jet cross sections in p–p collisions can be factorized in terms of two separable pT dependences, a [pT−s] sector and an [xR−pT−s] sector. Here, we extend our earlier work by analyzing more extensive data to explore various s-dependent attributes and other systematics of inclusive jet, photon and single particle reactions. Approximate power laws in s, pT and xR are found. Physical arguments are given which relate observations to the underlying physics of parton–parton hard scattering and the parton distribution functions in the proton. We show that the A(s,pT) function, introduced in our earlier publication to describe the pT dependence of the inclusive cross section, is directly related to the underlying hard parton–parton scattering for jet production, with little influence from soft physics. In addition to the a function, we introduce another function, the F(s,xR) function that obeys radial scaling for inclusive jets and offers another test of the underlying parton physics. An application to heavy ion physics is given, where we use our variables to determine the transparency of cold nuclear matter to penetrating heavy mesons through the lead nucleus.

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Eliseev, Sergey M., and Bekhzad S. Yuldashev. "Monte Carlo model for neutrino-nucleus interactions: past, present and future." EPJ Web of Conferences 204 (2019): 06013. http://dx.doi.org/10.1051/epjconf/201920406013.

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Quantum Chromodynamics (QCD) is the correct theory of strong interactions. The main direction of investigations in physics of elementary particles and nuclear physics is testing of QCD. QCD predicts that at high energy density there will be a transformation from ordinary nuclear matter to a plasma of free quarks and gluons, the Quark-Gluon Plasma (QGP). In order to reach new knowledge of QCD from the interaction of relativistic heavy ions, one needs directly comparable data sets from systems of various sizes, different energies and different experimental probes. Lepton-nucleus scattering provides a nontrivial possibility to study space-time evolution of jets inside the nuclear matter. Using QCD-inspired time dependent cross sections for pre-hadrons we have introduced a space-time model for propagation and hadronization of quark and gluon jets in the nuclear matter in DIS. The aim of this work is to examine a multiproduction process of charged-current deep inelastic vμ-nucleus and nuclear emulsion scattering and estimate quantitatively the value of the formation time. These studies may help to explain the jet quenching in heavy ion collisions. In conclusion, the role of neutrino generators in modern neutrino experiments with nuclear targets will be discussed.

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Naik, Bharati. "Measurement of azimuthal correlations of D mesons with charged particles in pp collisions at √s=13$\sqrt s = 13$ TeV with ALICE at the LHC." EPJ Web of Conferences 199 (2019): 04002. http://dx.doi.org/10.1051/epjconf/201919904002.

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The ALICE (A Large Ion Collider Experiment) detector at the LHC (Large Hadron Collider) is dedicated to the study of the properties of the hot and dense QCD matter (Quark–Gluon Plasma) produced in the nucleus-nucleus collisions at high energy. Heavy quarks (charm and beauty), having large masses, are produced in the hard-parton scattering in the early stages of the collision. Therefore, they experience the whole evolution of the hot and dense medium, representing an important tool for its characterization. The study of angular correlations between D mesons and charged particles in Pb–Pb collisions gives insight about the energy loss of charm quarks and the medium-induced modification of its fragmentation into jets. Moreover, pp collisions help to understand the production mechanisms, fragmentation and hadronization of charm quarks and acts as a reference for p–Pb and Pb–Pb measurements. In this article, the measurement of azimuthal correlations between D0 meson and charged particles in pp collisions at $\sqrt s = 13$ TeV is presented. The collisional energy dependence of the correlations is extracted from the comparison with the results at $\sqrt s = 7$ TeV. The data are also compared with simulations performed with different event generators.

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HOROWITZ, C. J. "MULTI-MESSENGER OBSERVATIONS OF NEUTRON-RICH MATTER." International Journal of Modern Physics E 20, no. 10 (October 2011): 2077–100. http://dx.doi.org/10.1142/s0218301311020332.

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At very high densities, electrons react with protons to form neutron-rich matter. This material is central to many fundamental questions in nuclear physics and astrophysics. Moreover, neutron-rich matter is being studied with an extraordinary variety of new tools such as Facility for Rare Isotope Beams (FRIB) and the Laser Interferometer Gravitational Wave Observatory (LIGO). We describe the Lead Radius Experiment (PREX) that uses parity violating electron scattering to measure the neutron radius in 208Pb. This has important implications for neutron stars and their crusts. We discuss X-ray observations of neutron star radii. These also have important implications for neutron-rich matter. Gravitational waves (GW) open a new window on neutron-rich matter. They come from sources such as neutron star mergers, rotating neutron star mountains, and collective r-mode oscillations. Using large scale molecular dynamics simulations, we find neutron star crust to be very strong. It can support mountains on rotating neutron stars large enough to generate detectable gravitational waves. Finally, neutrinos from core collapse supernovae (SN) provide another, qualitatively different probe of neutron-rich matter. Neutrinos escape from the surface of last scattering known as the neutrino-sphere. This is a low density warm gas of neutron-rich matter. Neutrino-sphere conditions can be simulated in the laboratory with heavy ion collisions. Observations of neutrinos can probe nucleosyntheses in SN. Simulations of SN depend on the equation of state (EOS) of neutron-rich matter. We discuss a new EOS based on virial and relativistic mean field calculations. We believe that combing astronomical observations using photons, GW, and neutrinos, with laboratory experiments on nuclei, heavy ion collisions, and radioactive beams will fundamentally advance our knowledge of compact objects in the heavens, the dense phases of QCD, the origin of the elements, and of neutron-rich matter.

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Roman, Veronica. "Direct Photons at the PHENIX Experiment: From Large to Small Systems." Proceedings 10, no. 1 (April 17, 2019): 32. http://dx.doi.org/10.3390/proceedings2019010032.

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Direct photons are a unique probe to study the properties of the medium created in heavy ion collisions. Low transverse momentum ( p T ) direct photons are of special interest since thermal photons are supposed to be dominant, while at high p T direct photons come from initial hard scattering (pQCD). PHENIX has observed a large excess of direct photon yield as well as large azimuthal anisotropy at low p T in Au+Au collisions at the c.m.s energy per nucleon pair s N N = 200 GeV. The mechanism to produce a large direct photon yield with a large elliptic anisotropy ( v 2 ) is not well understood yet. PHENIX has made systematic measurements of direct photons with different collision energies and system configurations. It has been found that direct photon yield d N γ / d η is proportional to charge particle multiplicity ( d N c h / d η ) 1 . 25 . This behavior holds for beam energies measured both at RHIC and at the LHC in large systems. This scaling suggests that there is a transition from p+p to A+A system which could be understood with the analysis of smaller systems like p+Au and d+Au.

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Felfli, Zineb, and Alfred Z. Msezane. "Negative Ion Formation in Low-Energy Electron Collisions with the Actinide Atoms Th, Pa, U, Np and Pu." Applied Physics Research 11, no. 1 (January 29, 2019): 52. http://dx.doi.org/10.5539/apr.v11n1p52.

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Here we investigate ground and metastable negative ion formation in low-energy electron collisions with the actinide atoms Th, Pa, U, Np and Pu through the elastic total cross sections (TCSs) calculations. For these atoms, the presence of two or more open d- and f- subshell electrons presents a formidable computational task for conventional theoretical methods, making it difficult to interpret the calculated results. Our robust Regge pole methodology which embeds the crucial electron correlations and the vital core-polarization interaction is used for the calculations. These are the major physical effects mostly responsible for stable negative ion formation in low-energy electron scattering from complex heavy systems. We find that the TCSs are characterized generally by Ramsauer-Townsend minima, shape resonances and dramatically sharp resonances manifesting ground and metastable negative ion formation during the collisions. The extracted from the ground states TCSs anionic binding energies (BEs) are found to be 3.09eV, 2.98eV, 3.03eV, 3.06eV and 3.25eV for Th, Pa, U, Np and Pu, respectively. Interestingly, an additional polarization-induced metastable TCS with anionic BE value of 1.22eV is generated in Pu due to the size effect. We also found that our excited states anionic BEs for several of these atoms compare well with the existing theoretical electron affinities including those calculated using the relativistic configuration-interaction method. We conclude that the existing theoretical calculations tend to identify incorrectly the BEs of the resultant excited anionic states with the electron affinities of the investigated actinide atoms; this demonstrates the great need for experimental verification and unambiguous determination of their electron affinities.

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Larionov, Alexei, and Mark Strikman. "Color Transparency and Hadron Formation Effects in High-Energy Reactions on Nuclei." Particles 3, no. 1 (January 17, 2020): 24–38. http://dx.doi.org/10.3390/particles3010004.

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An incoming or outgoing hadron in a hard collision with large momentum transfer gets squeezed in the transverse direction to its momentum. In the case of nuclear targets, this leads to the reduced interaction of such hadrons with surrounding nucleons which is known as color transparency (CT). The identification of CT in exclusive processes on nuclear targets is of significant interest not only by itself but also due to the fact that CT is a necessary condition for the applicability of factorization for the description of the corresponding elementary process. In this paper we discuss the semiexclusive processes A ( e , e ′ π + ) , A ( π − , l − l + ) and A ( γ , π − p ) . Since CT is closely related to hadron formation mechanism, the reduced interaction of ’pre-hadrons’ with nucleons is a common feature of generic high-energy inclusive processes on nuclear targets, such as hadron attenuation in deep inelastic scattering (DIS). We will discuss the novel way to study hadron formation via slow neutron production induced by a hard photon interaction with a nucleus. Finally, the opportunity to study hadron formation effects in heavy-ion collisions in the NICA regime will be considered.

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Li, Bao-An, and Lie-Wen Chen. "Neutron–proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions." Modern Physics Letters A 30, no. 13 (April 13, 2015): 1530010. http://dx.doi.org/10.1142/s0217732315300104.

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The neutron–proton effective mass splitting in neutron-rich nucleonic matter reflects the spacetime nonlocality of the isovector nuclear interaction. It affects the neutron/proton ratio during the earlier evolution of the Universe, cooling of proto-neutron stars, structure of rare isotopes and dynamics of heavy-ion collisions. While there is still no consensus on whether the neutron–proton effective mass splitting is negative, zero or positive and how it depends on the density as well as the isospin-asymmetry of the medium, significant progress has been made in recent years in addressing these issues. There are different kinds of nucleon effective masses. In this mini-review, we focus on the total effective masses often used in the non-relativistic description of nuclear dynamics. We first recall the connections among the neutron–proton effective mass splitting, the momentum dependence of the isovector potential and the density dependence of the symmetry energy. We then make a few observations about the progress in calculating the neutron–proton effective mass splitting using various nuclear many-body theories and its effects on the isospin-dependence of in-medium nucleon–nucleon cross-sections. Perhaps, our most reliable knowledge so far about the neutron–proton effective mass splitting at saturation density of nuclear matter comes from optical model analyses of huge sets of nucleon–nucleus scattering data accumulated over the last five decades. The momentum dependence of the symmetry potential from these analyses provide a useful boundary condition at saturation density for calibrating nuclear many-body calculations. Several observables in heavy-ion collisions have been identified as sensitive probes of the neutron–proton effective mass splitting in dense neutron-rich matter based on transport model simulations. We review these observables and comment on the latest experimental findings.

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Sampaio dos Santos, G., G. Gil da Silveira, and M. V. T. Machado. "A study on the isolated photon production in nuclear collisions at the CERN-LHC energies." Journal of Physics G: Nuclear and Particle Physics 49, no. 4 (March 11, 2022): 045005. http://dx.doi.org/10.1088/1361-6471/ac4948.

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Abstract An analysis of prompt photon production in high energy nuclear collisions at the Large Hadron Collider is performed within the parton saturation picture taking into account the updated phenomenological color dipole models. Comparison between ⟨N coll⟩ scaling for hard scattering in heavy-ion collisions and the N part-scaling based on geometric scaling arguments has been done. The predictions are parameter free in the first case whereas a dependence on the constant of proportionality κ between the number of participants and the nuclear saturation scale appears in the second case. This parameter has been analyzed in the prompt photon spectrum at small transverse momentum even though no fitting procedure was performed. Results are confronted with the measurements made by the ALICE, ATLAS, and CMS experiments in terms of photon transverse momentum at different rapidity bins. We show that the prompt photon production exhibits distinct scalings in AA events associated to geometrical properties of the collision and can be properly addressed in the color dipole formalism. Based on the N part-scaling, an analytical parametrization for the invariant cross section is provided and employed to predict the x T-scaling in measurements. For κ of order of unit the theoretical scaling curve correctly describes data in the range x T ⩽ 5 × 10−2.

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Li, Xiaowen, Ze-Fang Jiang, Shanshan Cao, and Jian Deng. "Evolution of global polarization in relativistic heavy-ion collisions within a perturbative approach." European Physical Journal C 83, no. 1 (January 31, 2023). http://dx.doi.org/10.1140/epjc/s10052-023-11257-9.

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AbstractExtremely large angular orbital momentum can be produced in non-central heavy-ion collisions, leading to a strong transverse polarization of partons that scatter through the quark-gluon plasma (QGP) due to spin-orbital coupling. We develop a perturbative approach to describe the formation and spacetime evolution of quark polarization inside the QGP. Polarization from both the initial hard scatterings and interactions with the QGP have been consistently described using the quark-potential scattering approach, which has been coupled to realistic initial condition calculation and the subsequent $$(3+1)$$ ( 3 + 1 ) -dimensional viscous hydrodynamic simulation of the QGP for the first time. Within this improved approach, we have found that different spacetime-rapidity-dependent initial energy density distributions generate different time evolution profiles of the longitudinal flow velocity gradient of the QGP, which further lead to an approximately 15% difference in the final polarization of quarks collected on the hadronization hypersurface of the QGP. Therefore, in addition to the collective flow coefficients, the hyperon polarization may serve as a novel tool to help constrain the initial condition of the hot nuclear matter created in high-energy nuclear collisions.

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d’Enterria, David, and Constantin Loizides. "Progress in the Glauber Model at Collider Energies." Annual Review of Nuclear and Particle Science 71, no. 1 (June 25, 2021). http://dx.doi.org/10.1146/annurev-nucl-102419-060007.

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We review the theoretical and experimental progress in the Glauber model of multiple nucleon and/or parton scatterings after the last 10–15 years of operation with proton and nuclear beams at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider. The main developments and the state of the art of the field are summarized. These encompass measurements of the inclusive inelastic proton and nuclear cross sections, advances in the description of the proton and nuclear density profiles and their fluctuations, inclusion of subnucleonic degrees of freedom, experimental procedures and issues related to the determination of the collision centrality, validation of the binary scaling prescription for hard scattering cross sections, and constraints on transport properties of quark–gluon matter from varying initial-state conditions in relativistic hydrodynamics calculations. These advances confirm the validity and usefulness of the Glauber formalism for quantitative studies of quantum chromodynamics matter produced in high-energy collisions of systems, from protons to uranium nuclei, of vastly different size. Expected final online publication date for the Annual Review of Nuclear and Particle Science, Volume 71 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Zhang, Mengxue, Yang He, Shanshan Cao, and Li Yi. "Effects of the formation time of parton shower on jet quenching in heavy-ion collisions." Chinese Physics C, November 22, 2022. http://dx.doi.org/10.1088/1674-1137/aca4c1.

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Abstract Jet quenching has successfully served as a hard probe to study the properties of the Quark-Gluon Plasma (QGP). As a multi-particle system, jets take time to develop from a highly virtual parton to a group of partons close to mass shells. In this work, we present a systematical study on the effects of this formation time on jet quenching in relativistic nuclear collisions. Jets from initial hard scatterings are simulated with Pythia and their interactions with the QGP are described using a Linear Boltzmann Transport (LBT) model that incorporates both elastic and inelastic scatterings between jet partons and the thermal medium. Three different estimations of the jet formation time are implemented and compared, including instantaneous formation, formation from single splitting and formation from sequential splittings, before which no jet-medium interaction is assumed. We found that deferring the jet-medium interaction with a longer formation time not only affects the overall magnitude of the nuclear modification factor of jets, but also its dependence on the jet transverse momentum.

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De, Somnath. "QCD Back-Scattering Photons in Relativistic Heavy ion Collisions." Proceedings of the Indian National Science Academy 81, no. 1 (February 8, 2015). http://dx.doi.org/10.16943/ptinsa/2015/v81i1/48072.

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Journal articles on the topic 'Hard scattering in relativistic heavy ion collisions'

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