Heavy ion collisions and cosmology
Floerchinger, Stefan
2015-01-01
There are interesting parallels between the physics of heavy ion collisions and cosmology. Both systems are out-of-equilibrium and relativistic fluid dynamics plays an important role for their theoretical description. From a comparison one can draw interesting conclusions for both sides. For heavy ion physics it could be rewarding to attempt a theoretical description of fluid perturbations similar to cosmological perturbation theory. In the context of late time cosmology, it could be interesting to study dissipative properties such as shear and bulk viscosity and corresponding relaxation times in more detail. Knowledge and experience from heavy ion physics could help to constrain the microscopic properties of dark matter from observational knowledge of the cosmological fluid properties.
Timescales in heavy ion collisions
Lisa, Mike
2016-01-01
The study of high energy collisions between heavy nuclei is a field unto itself, distinct from nuclear and particle physics. A defining aspect of heavy ion physics is the importance of a bulk, self-interacting system with a rich space-time substructure. I focus on the issue of timescales in heavy ion collisions, starting with proof from low-energy collisions that femtoscopy can, indeed, measure very long timescales. I then discuss the relativistic case, where detailed measurements over three orders of magnitude in energy reveal a timescale increase that might be due to a first-order phase transition. I discuss also consistency in evolution timescales as determined from traditional longitudinal sizes and a novel analysis using shape information.
International Nuclear Information System (INIS)
The status of research into collisions of nuclei at high energy is reviewed. Reactions and products are classified, and spectator matter is discussed. Then the thermalization of participant matter is considered at some length. Finally, disintegration of the hot matter is addressed. A = 20 and 40 projectiles of 250 to 1050 MeV/A are employed to illustrate the major points. 44 references, 10 figures
Central collisions of heavy ions
International Nuclear Information System (INIS)
This report describes the activities of the Heavy Ion Physics Group at the University of California, Riverside from October 1, 1991 to September 30, 1992. During this period, the program focused on particle production at AGS energies, and correlation studies at the Bevalac in nucleus-nucleus central collisions. As part of the PHENIX collaboration, contributions were made to the Preliminary Conceptual Design Report (pCDR), and work on a RHIC silicon microstrip detector R ampersand D project was performed
System size in relativistic heavy ion collisions
Institute of Scientific and Technical Information of China (English)
WANG Yang-Yang; ZHAO Lin-Jie; YUAN Zhong-Sheng; ZHANG Dan-Dan; FANG Wei; XU Ming-Mei
2011-01-01
System size is more than a geometrical quantity in relativistic heavy ion collisions; it is closely related to evolution process,i.e.a different system size corresponds to a different evolution process,and whether QGP is produced depends on the system size.We propose that the system size should be under the same level when comparing the measurements from different colliding nuclei.The equivalence of the peripheral collisions of Au-Au and the central collisions of smaller nuclei is studied using the Monte Carlo method.Comparing the transverse overlapping area of the colliding nuclei,the number of participant nucleons and the number of nucleon-nucleon binary collisions in various colliding nuclei,we give an estimate of the correspondence in system size.This is helpful in the experimental comparison of the measurements from different colliding nuclei.
RELATIVISTIC HEAVY ION COLLISIONS: EXPERIMENT
Energy Technology Data Exchange (ETDEWEB)
Friedlander, Erwin M.; Heckman, Harry H.
1982-04-01
Relativistic heavy ion physics began as a 'no man's land' between particle and nuclear physics, with both sides frowning upon it as 'unclean', because on one hand, hadronic interactions and particle production cloud nuclear structure effects, while on the other, the baryonic environment complicates the interpretation of production experiments. They have attempted to review here the experimental evidence on RHI collisions from the point of view that it represents a new endeavor in the understanding of strong interaction physics. Such an approach appears increasingly justified; first, by the accumulation of data and observations of new features of hadronic interactions that could not have been detected outside a baryonic environment; second, by the maturation of the field owing to the advances made over the past several years in experimental inquiries on particle production by RHI, including pions, kaons, hyperons, and searches for antiprotons; and third, by the steady and progressive increase in the energy and mass ranges of light nuclear beams that have become available to the experiment; indeed the energy range has widened from the {approx} 0.2 to 2 AGeV at the Bevalac to {approx}4 AGeV at Dubna and recently, to the quantum jump in energies to {approx} 1000 equivalent AGeV at the CERN PS-ISR. Accompanying these expansions in the energy frontier are the immediate prospects for very heavy ion beams at the Bevalac up to, and including, 1 AGeV {sup 238}U, thereby extending the 'mass frontier' to its ultimate extent.
Cosmology and elementary particles. Heavy ion collisions
International Nuclear Information System (INIS)
These school lectures were centered around two principal subjects: first tried to show how cosmology and particle physics are deeply related more and more nowadays. Second one was around heavy ion collisions and their relations with quark matter
Holographic heavy ion collisions with baryon charge
Casalderrey-Solana, Jorge; van der Schee, Wilke; Triana, Miquel
2016-01-01
We numerically simulate collisions of charged shockwaves in Einstein-Maxwell theory in anti-de Sitter space as a toy model of heavy ion collisions with non-zero baryon charge. The stress tensor and the baryon current become well described by charged hydrodynamics at roughly the same time. The effect of the charge density on generic observables is typically no larger than 15\\%. %The rapidity profile of the charge is wider than the profile of the local energy density. We find significant stopping of the baryon charge and compare our results with those in heavy ion collision experiments.
Theory of heavy ion collisions. Annual progress report
International Nuclear Information System (INIS)
It is demonstrated clearly that macroscopic models account for many of the observed features of heavy ion collisions. During this phase of the program major steps have been taken toward a better understanding of fusion excitation function, strongly damped collisions, the emission of nucleons at intermediate energies, heavy ion collisions and pions in relativistic heavy ion collisions
Searching for $\\Xi_{cc}^+$ in Relativistic Heavy Ion Collisions
Zhao, Jiaxin; Zhuang, Pengfei
2016-01-01
We study the doubly charmed baryon $\\Xi_{cc}^+$ in high energy nuclear collisions. We solve the three-body Schroedinger equation with relativistic correction and calculate the $\\Xi_{cc}^+$ yield and transverse momentum distribution via coalescence mechanism. For $\\Xi_{cc}^+$ production in central Pb+Pb collisions at LHC energy, the yield is extremely enhanced, and the production cross section per binary collision is one order of magnitude larger than that in p+p collisions. This indicates that, it is most probable to discover $\\Xi_{cc}^+$ in heavy ion collisions and its discovery can be considered as a probe of the quark-luon plasma formation.
Quarkonium production in heavy-ion collisions
Directory of Open Access Journals (Sweden)
Arnaldi Roberta
2014-03-01
Full Text Available The production of quarkonium states plays a crucial role among the probes to investigate the formation of the plasma of quarks and gluons (QGP in heavy-ion collisions. A review of the charmonium and bottomonium production, mainly focussing on the latest results from the LHC experiments, is presented.
Positron spectroscopy after heavy ion collisions
International Nuclear Information System (INIS)
The author reviews the theoretical and experimental results on positron production in heavy ion collisions. After a discussion of the quasi-atomic picture, the possible observation of the axion, and the inverse Bhabha scattering, the positron spectrometer EPOS of the GSI Darmstadt is described. Thereafter the experimental results are presented. (HSI)
Relativistic Hydrodynamics for Heavy-Ion Collisions
Ollitrault, Jean-Yves
2008-01-01
Relativistic hydrodynamics is essential to our current understanding of nucleus-nucleus collisions at ultrarelativistic energies (current experiments at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN Large Hadron Collider). This is an introduction to relativistic hydrodynamics for graduate students. It includes a detailed…
Color screening in relativistic heavy ion collisions
International Nuclear Information System (INIS)
We calculate the color screening length in a non-equilibrated gluon gas formed by interacting minijets in relativistic heavy-ion collisions. We show that the screening length is too short at CERN LHC collider energy to permit the formation of independent flux-tubes or strings. The prediction for RHIC energies is somewhat ambiguous. (orig.)
Sigma meson in heavy ion collision
International Nuclear Information System (INIS)
We want to present a short theoretical prediction of the behaviour of the sigma meson in heavy ion collisions. It is considered that the sigma meson is a pion-pion correlation, resulting from the decay of the N*(1440) resonance. There will be presented some QMD simulations. (authors)
Recent results on relativistic heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Munhoz, Marcelo [Universidade de Sao Paulo (IF/USP), Sao Paulo, SP (Brazil). Inst. de Fisica
2013-07-01
Full text: The study of relativistic heavy ion collisions is a very important tool in order to understand the strong interaction described by QCD. The formation of the Quark-Gluon Plasma and the study of its properties is a very challenging quest. The Large Hadron Collider (LHC) from CERN (European Organization for Nuclear Research) generates ultra-relativistic Pb + Pb collisions at the TeV scale inaugurating a new era for such studies. Three experiments, ATLAS, CMS and ALICE are able to measure the products of such collisions. In special, the ALICE experiment was designed specifically for the study of heavy ion collisions. In this presentation, I'll discuss the latest results that shed light in the QGP understanding. (author)
Jets in Heavy Ion Collisions with CMS
Salur, Sevil
2016-01-01
Jet physics in heavy ion collisions is a rich field which has been rapidly evolving since the first observations of medium interactions at RHIC through back-to-back hadron correlations and at LHC via reconstructed jets. In order to completely characterize the final state via jet-medium interactions and distinguish between competing energy loss mechanisms complementary and robust jet observables are investigated. Latest developments of jet finding techniques and their applications to heavy ion environments are discussed with an emphasis given on experimental results from CMS experiment.
Jets In Heavy Ion Collisions with CMS
Salur, Sevil
2016-08-01
Jet physics in heavy ion collisions is a rich field which has been rapidly evolving since the first observations of medium interactions at RHIC through back-to-back hadron correlations and at LHC via reconstructed jets. In order to completely characterize the final state via jet-medium interactions and distinguish between competing energy loss mechanisms, complementary and robust jet observables are investigated. Latest developments of jet finding techniques and their applications to heavy ion environments are discussed with an emphasis given on experimental results from CMS experiment.
Viscous photons in relativistic heavy ion collisions
Dion, Maxime; Schenke, Bjoern; Young, Clint; Jeon, Sangyong; Gale, Charles
2011-01-01
Theoretical studies of the production of real photons in relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are performed. The space-time evolution of the colliding system is modelled using MUSIC, a 3+1D relativistic hydrodynamic simulation. The inclusive spectrum and its azimuthal angular anisotropy are studied separately, and the relative contributions of the different photon sources are highlighted. It is shown that the photon v_2 coefficient is especially sensitive to the details of the microscopic dynamics like the equation of state, the ratio of shear viscosity over entropy density, eta/s, and to the morphology of the initial state.
Quark Recombination in Heavy Ion Collisions
Fries, Rainer J.(Cyclotron Institute, Department of Physics & Astronomy, Texas A&M University, College Station, TX, 77843-3366, USA)
2011-01-01
Data on high energy nuclear collisions collected at the Relativistic Heavy Ion Collider over the past decade have provided convincing evidence that hadronization is quite different in hot nuclear environments compared to p+p collisions. In particular, the data suggest that we see traces of quark degrees of freedom in elliptic flow, with the implication that collective flow is generated on the parton level and is transfered to hadrons through a simple recombination step. In this contribution w...
Some properties of the central heavy ion collisions
Wazir, Z; Khan, E U; Haseeb, Mahnaz Q; Ajaz, M; Khan, K H
2009-01-01
Some experimental results are discussed in connection with the properties of the central heavy ion collisions. These experiments indicate the regime changes and saturation at some values of the centrality. This phenomenon is considered to be a signal of the percolation cluster formation in heavy ion collisions at high energies. Keywords: heavy ion collisions, theoretical models, centrality, phase transition.
Chiral Magnetic Effect in Heavy Ion Collisions
Liao, Jinfeng
2016-01-01
The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. It is of fundamental importance to search for the CME in experiments. The heavy ion collisions provide a unique environment where a hot chiral-symmetric quark-gluon plasma is created, gluonic topological fluctuations generate chirality imbalance, and very strong magnetic fields $|\\vec{\\bf B}|\\sim m_\\pi^2$ are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. In this contribution we give a brief overview on the status of such efforts.
International Nuclear Information System (INIS)
During the work on which this Thesis is based, the significant role of the Fusion-Fission Asymmetric mechanism in light heavy ion collisions (ANC ≤ 60) has been emphasized. The Spin Dis-alignment in the oblate-oblate system has supplied evidence for the first time for the Butterfly mode in a resonant-like reaction. These two aspects, one macroscopic and the other more closely related to microscopic effects are certainly different from a conceptual point of view but are quite complementary for a global understanding of dinuclear systems. In the first part, inclusive and exclusive measurements of the 35Cl + 12C and 35Cl + 24Mg reaction have been performed at 8 MeV/nucleon in the Saclay experiment. These measurements have permitted us to verify the origin of products which have given rise of the asymmetric fusion-fission mechanism and which have demonstrated that the three-body process in this energy range is very weak. In the second part the 28Si + 28Si reaction has been performed at the resonance energy Elab> = 111.6 MeV at Strasbourg with the Eurogam phase II multi-detector array and VIVITRON accelerator. An angular momentum Jπ 38+ for inelastic and mutual channels of the 28Si + 28Si exit channel has been measured and has supplied evidence for a spin dis-alignment which has been interpreted in the framework of a molecular model by Butterfly motion. The spectroscopic study of 32S nucleus, has revealed the occurrence of a new γ-ray transition 0+(8507.8 keV) → 21+(2230.2 keV). (author)
Dissipative heavy-ion collisions
International Nuclear Information System (INIS)
This report is a compilation of lecture notes of a series of lectures held at Argonne National Laboratory in October and November 1984. The lectures are a discussion of dissipative phenomena as observed in collisions of atomic nuclei. The model is based on a system which has initially zero temperature and the initial energy is kinetic and binding energy. Collisions excite the nuclei, and outgoing fragments or the compound system deexcite before they are detected. Brownian motion is used to introduce the concept of dissipation. The master equation and the Fokker-Planck equation are derived. 73 refs., 59 figs
Vorticity in heavy-ion collisions
Deng, Wei-Tian; Huang, Xu-Guang
2016-06-01
We study the event-by-event generation of flow vorticity in the BNL Relativistic Heavy Ion Collider Au +Au collisions and CERN Large Hadron Collider Pb +Pb collisions by using the hijing model. Different definitions of the vorticity field and velocity field are considered. A variety of properties of the vorticity are explored, including the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction, and the time evolution. In addition, the spatial distribution of the flow helicity is also studied.
Glueballs in Peripheral Heavy-Ion Collisions
A.A. Natale
1995-01-01
We estimate the cross-section for glueball production in peripheral heavy-ion collisions through two-photon and double-Pomeron exchange, at energies that will be available at RHIC and LHC. Glueballs will be produced at large rates, opening the possibility to study decays with very small branching ratios. In particular, we discuss the possibility of observing the subprocess $\\gamma \\gamma (PP) \\rightarrow G \\rightarrow \\gamma \\gamma$.
Nonlinear QED Effects in Heavy Ion Collisions
Klein, Spencer R.
2000-01-01
Peripheral collisions of relativistic heavy ions uniquely probe many aspects of QED. Examples include $e^+e^-$ pair production and nuclear excitation in strong fields. After discussing these reactions, I will draw parallels between $\\gamma\\to e^+e^-$ and $\\gamma\\to q\\bar q$ and consider partly hadronic reactions. The scattered $q\\bar q$ pairs are a prolific source of vector mesons, which demonstrate many quantum effects. The two ions are a two-source interferometer, demonstrating interference...
Pionic instabilities in high-energy heavy ion collisions
International Nuclear Information System (INIS)
The study of heavy ion reactions includes the determination of whether pionic instabilities can exist at the densities and excitation energies expected in heavy ion collisions, the calculation of growth rates of unstable pion modes, and the determination of the effect such instabilities would have on the dynamics in heavy ion collisions. 14 references
Viscous photons in relativistic heavy ion collisions
Dion, Maxime; Paquet, Jean-François; Schenke, Björn; Young, Clint; Jeon, Sangyong; Gale, Charles
2011-12-01
Theoretical studies of the production of real thermal photons in relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are performed. The space-time evolution of the colliding system is modelled using music, a 3+1D relativistic hydrodynamic simulation, using both its ideal and viscous versions. The inclusive spectrum and its azimuthal angular anisotropy are studied separately, and the relative contributions of the different photon sources are highlighted. It is shown that the photon v2 coefficient is especially sensitive to the details of the microscopic dynamics like the equation of state, the ratio of shear viscosity over entropy density, η/s, and to the morphology of the initial state.
Theory overview of Heavy Ion collisions
Lappi, T
2016-01-01
This presentation discusses some recently active topics in the theoretical interpretation of high energy heavy ion collisions at the LHC and at RHIC. We argue that the standard paradigm for understanding the spacetime evolution of the bulk of the matter produced in the collision is provided by viscous relativistic hydrodynamics, which can be used to systematically extract properties of the QCD medium from experimental results. The initial conditions of this hydrodynamical evolution are increasingly well understood in terms of gluon saturation, and can be quantified using Classical Yang-Mills fields and QCD effective kinetic theory. Hard and electromagnetic probes of the plasma provide additional constraints. A particularly fascinating subject are high multiplicity proton-proton and proton-nucleus collisions, where some of the characteristics previously attributed to only nucleus-nucleus collisions have been observed.
Direct photons in heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Baeuchle, Bjoern
2010-12-13
Direct photon emission from heavy-ion collisions has been calculated and compared to available experimental data. Three different models have been combined to extract direct photons from different environments in a heavy-ion collision: Thermal photons from partonic and hadronic matter have been extracted from relativistic, non-viscous 3+1-dimensional hydrodynamic calculations. Thermal and non-thermal photons from hadronic interactions have been calculated from relativistic transport theory. The impact of different physics assumptions about the thermalized matter has been studied. The models used for the determination of photons from both hydrodynamic and transport calculations have been elucidated and their numerical properties tested. The origin of direct photons, itemised by emission stage, emission time, channel and baryon number density, has been investigated for various systems, as have the transverse momentum spectra and elliptic flow patterns of direct photons. Taking into account the full (vacuum) spectral function of the rho-meson decreases the direct photon emission by approximately 10% at low photon transverse momentum. In all systems that have been considered -- heavy-ion collisions at E{sub lab}=35 AGeV and 158 AGeV, (s{sub NN}){sup 1/2}=62.4 GeV, 130 GeV and 200 GeV -- thermal emission from a system with partonic degrees of freedom is greatly enhanced over that from hadronic systems, while the difference between the direct photon yields from a viscous and a non-viscous hadronic system (transport vs. hydrodynamics) is found to be very small. Predictions for direct photon emission in central U+U-collisions at 35 AGeV have been made. (orig.)
Direct photons in heavy-ion collisions
International Nuclear Information System (INIS)
Direct photon emission from heavy-ion collisions has been calculated and compared to available experimental data. Three different models have been combined to extract direct photons from different environments in a heavy-ion collision: Thermal photons from partonic and hadronic matter have been extracted from relativistic, non-viscous 3+1-dimensional hydrodynamic calculations. Thermal and non-thermal photons from hadronic interactions have been calculated from relativistic transport theory. The impact of different physics assumptions about the thermalized matter has been studied. The models used for the determination of photons from both hydrodynamic and transport calculations have been elucidated and their numerical properties tested. The origin of direct photons, itemised by emission stage, emission time, channel and baryon number density, has been investigated for various systems, as have the transverse momentum spectra and elliptic flow patterns of direct photons. Taking into account the full (vacuum) spectral function of the rho-meson decreases the direct photon emission by approximately 10% at low photon transverse momentum. In all systems that have been considered -- heavy-ion collisions at Elab=35 AGeV and 158 AGeV, (sNN)1/2=62.4 GeV, 130 GeV and 200 GeV -- thermal emission from a system with partonic degrees of freedom is greatly enhanced over that from hadronic systems, while the difference between the direct photon yields from a viscous and a non-viscous hadronic system (transport vs. hydrodynamics) is found to be very small. Predictions for direct photon emission in central U+U-collisions at 35 AGeV have been made. (orig.)
Studies of relativistic heavy ion collisions
International Nuclear Information System (INIS)
This report presents the progress in our program of Relativistic Heavy Ion studies. The first phase of experiments on lepton pairs is almost complete and the results from the initial part of this program are presented in copies of three publications. It appears that the origin of lepton pairs is the annihilation of pions. The evidence for this seems to be the shape of the dilepton mass spectrum, the cross-section as a function of energy which seems to scale with pion production, and the general kinematic behavior of the lepton pairs themselves. We present progress on the development of Ring Imaging Cerenkov counters for dilepton observations in general, and a short report on a high resolution method counter proposal that could be adapted to RHIC counters in general. Publication of results on hyperon polarization with incident polarized proton beams is also presented. These results use the phenomenological approach that could be useful in understanding hyperon production in heavy ion collisions. In this connection, a proposal for studying high density nuclear matter with incident antiprotons is presented. Progress on the TPC detectors developed by the BNL group for heavy ion research is reported, along with recent analysis of polarization with incident silicon beams. Finally, the most recent results on subthreshold antiproton production is presented. These latter results are several orders of magnitude more than expected and they point to some kind of coherent hadronic phenomena even at extremely low energies
Diomega production in relativistic heavy ion collisions
Pal, Subrata; Ko, C. M.; Zhang, Z. Y.
2001-01-01
Using a multiphase transport model, we study the production of a new strange dibaryon (\\Omega\\Omega)_{0+} in dense hadronic matter formed in relativistic heavy ion collisions. The (multi-)strange baryons (\\Xi and \\Omega) are produced by strangeness-exchange reactions between antikaons and hyperons in the pure hadronic phase. The rescattering between the omegas at midrapidity leads to a production probability of \\simeq 3x10^{-7} (\\Omega\\Omega)_{0+} per event at the RHIC energy of \\sqrt s=130A ...
Non abelian hydrodynamics and heavy ion collisions
Calzetta, E.
2014-01-01
The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.
Multifragmentation and dynamics in heavy ion collisions
Indian Academy of Sciences (India)
R Roy
2001-07-01
A midrapidity zone formed in heavy-ion collisions has been investigated through special selections of light particles and intermediate mass fragments detected in the reaction 35Cl on 12C at 43 MeV/nucleon and the reactions 58Ni on 12C, 24Mg, and 197Au at 34.5 MeV/nucleon, and of neutron energy spectra measured in the reaction 35Cl on natTa. Properties of the observables have been examined to characterize the neck-like structure formed between the two reaction partners.
Non abelian hydrodynamics and heavy ion collisions
Calzetta, Esteban
2013-01-01
The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.
HBT in Relativisitic Heavy Ion Collisions
Murray, Michael
2001-01-01
A summary of current interferometry data in relativistic heavy ions is presented. At sqrt{s}=17GeV a sudden increase in the pion source volume is observed for central PbPb collisions. This seems to imply that the pion phase density has reached a limit. The source size of different particles decreases with mass when the transverse velocity is held constant but increases with mass when the transverse mass is held constant. The antiproton source radius is larger than the proton source radius. So...
Study of relativistic heavy ion central collisions
International Nuclear Information System (INIS)
This thesis is devoted to the study of nuclear collisions between a target nucleus and a projectile nucleus, the latter having been accelerated at energies ranging from 100 to 2000 MeV (Mega-Electronvolts) per nucleon. The main goal of this field is the determination of nuclear matter equation of state at high densities and temperatures. This determination requires the study of central collisions only, that is collisions at small impact parameters. The detector ''Diogene'' used at the ''Saturne'' (Saclay, France) accelerator can measure simultaneously the momenta, masses and emission angles of all particles (pions, protons, deuterons ...) emitted in each collision. The pressure effects pre-dicted by the ''intra-nuclear cascade'' model are discussed. The pion (pi meson) production in relativistic heavy ion collisions is reviewed. Finally, we present the results of pion production measurements, using ''Diogene'', in collisions between alpha particles and carbon, copper, or lead target nuclei at 200, 400, 600 and 800 MeV per nucleon. The number of pions per collision is studied in relationship with the proton number. This can be explained in terms of compressional energy. The pion multiplicity distributions and the differential cross-sections are also presented
Holography, Hydrodynamization and Heavy-Ion Collisions
Heller, Michal P
2016-01-01
In the course of the past several years holography has emerged as an ab initio tool in exploring strongly-time-dependent phenomena in gauge theories. These lecture notes overview recent developments in this area driven by phenomenological questions concerning applicability of hydrodynamics under extreme conditions occurring in ultrarelativistic heavy-ion collisions at RHIC and LHC. The topics include equilibration time scales, holographic collisions and hydrodynamization from the point of view of the asymptotic character of the hydrodynamic gradient expansion. The emphasis is put on concepts rather than calculational techniques and particular attention is devoted to present these developments in the context of the most recent advances and some of the open problems.
Bremsstrahlung Pair Production In Relativistic Heavy Ion Collision
Meier, H; Hencken, K.; Trautmann, D.; Baur, G.
1997-01-01
We calculate production of electron- and muon-pairs by the bremsstrahlung process in hadron collisions and compare it with the dominant two-photon process. Results for the total cross section are given for proton-proton and heavy-ion collisions at energies of the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).
Collective Flow and Viscosity in Relativistic Heavy-Ion Collisions
Heinz, U.; Snellings, R.J.M.
2013-01-01
We review collective flow, its anisotropies, and its event-to-event fluctuations in relativistic heavy-ion collisions, as well as the extraction of the specific shear viscosity of quark–gluon plasma from collective flow data collected in heavy-ion collision experiments at RHIC and the LHC. We emphas
Quarkonia at finite temperature in relativistic heavy-ion collisions
Indian Academy of Sciences (India)
Saumen Datta
2015-05-01
The behaviour of quarkonia in relativistic heavy-ion collisions is reviewed. After a detailed discussion of the current theoretical understanding of quarkonia in a static equilibriated plasma, we discuss quarkonia yield from the fireball created in ultrarelativistic heavy-ion collision experiments. We end with a brief discussion of the experimental results and outlook.
Theoretical Concepts for Ultra-Relativistic Heavy Ion Collisions
McLerran, Larry
2009-01-01
Various forms of matter may be produced in ultra-relativistic heavy ion collisions. These are the Quark Gluon Plasma, the Color Glass Condensate, the Glasma and Quarkyonic Matter. A novel effect that may be associated with topological charge fluctuations is the Chiral Magnetic Effect. I explain these concepts and explain how they may be seen in ultra-relativistic heavy ion collisions.
Hadron Production in Heavy Ion Collisions
Energy Technology Data Exchange (ETDEWEB)
Ritter, Hans Georg; Xu, Nu
2009-05-19
Heavy ion collisions are an ideal tool to explore the QCD phase diagram. The goal is to study the equation of state (EOS) and to search for possible in-medium modifications of hadrons. By varying the collision energy a variety of regimes with their specific physics interest can be studied. At energies of a few GeV per nucleon, the regime where experiments were performed first at the Berkeley Bevalac and later at the Schwer-Ionen-Synchrotron (SIS) at GSI in Darmstadt, we study the equation of state of dense nuclear matter and try to identify in-medium modifications of hadrons. Towards higher energies, the regime of the Alternating Gradient Synchrotron (AGS) at the Brookhaven National Laboratory (BNL), the Super-Proton Synchrotron (SPS) at CERN, and the Relativistic Heavy Ion Collider (RHIC) at BNL, we expect to produce a new state of matter, the Quark-Gluon Plasma (QGP). The physics goal is to identify the QGP and to study its properties. By varying the energy, different forms of matter are produced. At low energies we study dense nuclear matter, similar to the type of matter neutron stars are made of. As the energy is increased the main constituents of the matter will change. Baryon excitations will become more prevalent (resonance matter). Eventually we produce deconfined partonic matter that is thought to be in the core of neutron stars and that existed in the early universe. At low energies a great variety of collective effects is observed and a rather good understanding of the particle production has been achieved, especially that of the most abundantly produced pions and kaons. Many observations can be interpreted as time-ordered emission of various particle species. It is possible to determine, albeit model dependent, the equation of state of nuclear matter. We also have seen indications, that the kaon mass, especially the mass of the K{sup +}, might be modified by the medium created in heavy ion collisions. At AGS energies and above, emphasis shifts towards
Electromagnetic probes in heavy-ion collisions
Directory of Open Access Journals (Sweden)
van Hees H.
2015-01-01
Full Text Available Due to their penetrating nature, electromagnetic probes, i.e., lepton-antilepton pairs (dileptons and photons are unique tools to gain insight into the nature of the hot and dense medium of strongly-interacting particles created in relativistic heavy-ion collisions, including hints to the nature of the restoration of chiral symmetry of QCD. Of particular interest are the spectral properties of the electromagnetic current-correlation function of these particles within the dense and/or hot medium. The related theoretical investigations of the in-medium properties of the involved particles in both the partonic and hadronic part of the QCD phase diagram underline the importance of a proper understanding of the properties of various hadron resonances in the medium.
High Gluon Densities in Heavy Ions Collisions
Blaizot, Jean-Paul
2016-01-01
The early stages of heavy ion collisions are dominated by high density systems of gluons that carry each a small fraction $x$ of the momenta of the colliding nucleons. A distinguishing feature of such systems is the phenomenon of "saturation" which tames the expected growth of the gluon density as the energy of the collision increases. The onset of saturation occurs at a particular transverse momentum scale, the "saturation momentum", that emerges dynamically and that marks the onset of non-linear gluon interactions. At high energy, and for large nuclei, the saturation momentum is large compared to the typical hadronic scale, making high density gluons amenable to a description with weak coupling techniques. This paper reviews some of the challenges faced in the study of such dense systems of small $x$ gluons, and of the progress made in addressing them. The focus is on conceptual issues, and the presentation is both pedagogical, and critical. Examples where high gluon density could play a visible role in hea...
Proceedings of the Budapest workshop on relativistic heavy ion collisions
International Nuclear Information System (INIS)
This volume is the Proceedings of the Budapest workshop on relativistic heavy ion collisions held in Budapest, 10-13 Aug, 1992. The topics include experimental heavy ion physics, Bose-Einstein correlations, intermittency, relativistic transport theory, Quark-Gluon Plasma rehadronization, astronuclear physics and cosmology. All contributions were indexed and abstracted. (author)
Status of chemical equilibrium in relativistic heavy-ion collisions
Indian Academy of Sciences (India)
J Cleymans
2003-04-01
Recent work on chemical equilibrium in heavy-ion collisions is reviewed. The energy dependence of thermal parameters is discussed. The centrality dependence of thermal parameters at SPS energies is presented.
Phenomenology of Heavy Flavors in Ultrarelativistic Heavy-Ion Collisions
Isayev, A A
2010-01-01
Some recent experimental results obtained in collisions of heavy nuclei ($\\sqrt{s}=200$ GeV) at BNL Relativistic Heavy-Ion Collider (RHIC) are discussed. The probes of dense matter created in heavy-ion collision by quarkonia, $D$ and $B$ mesons containing heavy charm and beauty quarks are considered. The centrality, rapidity and transverse momentum dependences of the nuclear modification factor and elliptic flow coefficient are presented and their possible theoretical interpretation is provided.
Mach cones in viscous heavy-ion collisions
Bouras, I.; Betz, B.; Z. Xu; Greiner, C.(Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany)
2014-01-01
The formation of Mach cones is studied in a full $(3+1)$-dimensional setup of ultrarelativistic heavy-ion collisions, considering a transverse and longitudinal expanding medium at Relativistic Heavy-Ion Collider energies. For smooth initial conditions and central collisions the jet-medium interaction is investigated using high-energy jets and various values of the ratio of shear viscosity over entropy density, $\\eta/s$. For small viscosities, the formation of Mach cones is proven, whereas for...
Experimental results on charge fluctuations in heavy-ion collisions
Mishra, D K; Netrakanti, P K; Pant, L M; Mohanty, A K
2016-01-01
We present a subset of experimental results on charge fluctuation from the heavy-ion collisions to search for phase transition and location of critical point in the QCD phase diagram. Measurements from the heavy-ion experiments at the SPS and RHIC energies observe that total charge fluctuations increase from central to peripheral collisions. The net-charge fluctuations in terms of dynamical fluctuation measure $\
Classical gluon production amplitude in heavy-ion collisions
Chirilli Giovanni Antonio
2016-01-01
The distribution of quarks and gluons produced in the initial stages of nuclear collisions, known as the initial condition of the Quark-Gluon Plasma formation, is the fundamental building block of heavy-ion theory. I will present the scattering amplitude, beyond the leading order, of the classical gluon produced in heavy-ion collisions. The result is obtained in the framework of saturation physics and Wilson lines formalism.
Classical gluon production amplitude in heavy-ion collisions
Directory of Open Access Journals (Sweden)
Chirilli Giovanni Antonio
2016-01-01
Full Text Available The distribution of quarks and gluons produced in the initial stages of nuclear collisions, known as the initial condition of the Quark-Gluon Plasma formation, is the fundamental building block of heavy-ion theory. I will present the scattering amplitude, beyond the leading order, of the classical gluon produced in heavy-ion collisions. The result is obtained in the framework of saturation physics and Wilson lines formalism.
Classical gluon production amplitude in heavy-ion collisions
Chirilli, Giovanni Antonio
2016-03-01
The distribution of quarks and gluons produced in the initial stages of nuclear collisions, known as the initial condition of the Quark-Gluon Plasma formation, is the fundamental building block of heavy-ion theory. I will present the scattering amplitude, beyond the leading order, of the classical gluon produced in heavy-ion collisions. The result is obtained in the framework of saturation physics and Wilson lines formalism.
Lambda-Lambda Correlation in Relativistic Heavy Ion Collisions
Morita Kenji; Furumoto Takenori; Ohnishi Akira
2015-01-01
We investigate Λ − Λ correlation function in relativistic heavy ion collisions to extract their interaction. Using an expanding source model for heavy ion collisions, we disentangle effects of collective expansion and those of the interaction at low relative momenta. Then, we discuss the influence of the feed-down correction for Σ0 decay and indicate the possible existence of a residual correlation at high relative momenta. Consequently, the present STAR data suggest a weakly attractive inter...
String theory and relativistic heavy ion collisions
Friess, Joshua J.
It has long been known that string theory describes not only quantum gravity, but also gauge theories with a high degree of supersymmetry. Said gauge theories also have a large number of colors in a regime with a large effective coupling constant that does not depend on energy scale. Supersymmetry is broken in nature, if it is present at all, however the gauge theory described by string theory shares many common features with QCD at temperatures above the quark deconfinement transition. It is generally though not entirely accepted that collisions of gold nuclei at the Relativistic Heavy Ion Collider (RHIC) produce a thermalized Quark-Gluon Plasma (QGP) at temperatures distinctly above the transition temperature as determined from lattice simulations. Hence, we might hope that a string theoretic description of gauge dynamics can elucidate some otherwise intractable physics of the strongly coupled plasma. Here we use string theory to calculate the outgoing energy flux from a RHIC process called "jet quenching", in which a high-momentum quark or gluon traverses a large distance in the QGP. Our setup is in the context of the highly supersymmetric string dual gauge theory, but we nevertheless find that the gross features of the resulting stress-energy tensor match reasonably well with experimental data. We will furthermore discuss the technology behind computations of the leading-order corrections to gauge theory observables that are uniquely string-induced, and we will describe a potential solution to string theory that could resolve a number of discrepancies between the traditional highly supersymmetric setup and QCD---in particular, a significant reduction in the amount of supersymmetry, and a finite effective coupling that is still greater than unity but does depend on energy scale.
Skyrme tensor force in heavy ion collisions
Stevenson, P. D.; Suckling, E. B.; Fracasso, S.; Barton, M. C.; Umar, A. S.
2016-05-01
Background: It is generally acknowledged that the time-dependent Hartree-Fock (TDHF) method provides a useful foundation for a fully microscopic many-body theory of low-energy heavy ion reactions. The TDHF method is also known in nuclear physics in the small-amplitude domain, where it provides a useful description of collective states, and is based on the mean-field formalism, which has been a relatively successful approximation to the nuclear many-body problem. Currently, the TDHF theory is being widely used in the study of fusion excitation functions, fission, and deep-inelastic scattering of heavy mass systems, while providing a natural foundation for many other studies. Purpose: With the advancement of computational power it is now possible to undertake TDHF calculations without any symmetry assumptions and incorporate the major strides made by the nuclear structure community in improving the energy density functionals used in these calculations. In particular, time-odd and tensor terms in these functionals are naturally present during the dynamical evolution, while being absent or minimally important for most static calculations. The parameters of these terms are determined by the requirement of Galilean invariance or local gauge invariance but their significance for the reaction dynamics have not been fully studied. This work addresses this question with emphasis on the tensor force. Method: The full version of the Skyrme force, including terms arising only from the Skyrme tensor force, is applied to the study of collisions within a completely symmetry-unrestricted TDHF implementation. Results: We examine the effect on upper fusion thresholds with and without the tensor force terms and find an effect on the fusion threshold energy of the order several MeV. Details of the distribution of the energy within terms in the energy density functional are also discussed. Conclusions: Terms in the energy density functional linked to the tensor force can play a non
CERN achievements in relativistic heavy ion collisions
Directory of Open Access Journals (Sweden)
Bruno Giuseppe Eugenio
2015-01-01
Full Text Available Twenty years after a Letter of Intent by the GSI and LBL groups for the “Study of particle production and target fragmentation in central 20Ne on Pb reactions, at 12 GeV per nucleon energy of the CERN PS external beam" [1], based on the results found by the NA45/CERES, NA49, NA50, and WA97/NA57 experiments at the SPS, CERN announced compelling evidence for the formation of a new state of matter in heavyion collisions at CERN-SPS energies [2]. Some of the experiments were indeed the 2nd or 3rd generation successors of the apparatuses originally proposed by the GSI-LBL collaboration. Actually, the CERN ion program initiated at the SPS with the acceleration of oxygen ions at 60 and 200 GeV/nucleon only in 1986, and continued with sulphur ions at 200 GeV/nucleon up to 1993. The rest is history: lead-ion beams at 160 GeV/nucleon became available at the SPS in 1994; the LHC accelerated and collided lead beams at a center of mass energy per nucleon pair √sNN = 2.76 TeV in 2010. Heavy ion physics is definitely in the future program of CERN: ALICE will operate a major upgrade of its detectors during the second long shutdown of the LHC, in 2018-2019, and the associated physics program will span the third and fourth LHC runs, till late 2020s.
Dissipative processes in light heavy ion collisions
International Nuclear Information System (INIS)
The deep inelastic processes in light heavy ion collisions were systematically studied in the reactions 19 F(111.4, 125, 136.9 MeV) + 12 C, 27 Al, and 27 Al(140.14 MeV) + 12 C, 27 Al using the experimental device DRACULA mounted at LNS-Catania. ΔE - E identification, continuous measurements of energy and angle, mass identification by time-of-flight and γ-multiplicity measurements have been performed for the main reaction products. The double differential cross sections, as a function of different experimental observables, show similar trends with those observed for much heavier systems. Thus, a complete dynamics, from quasielastic to complete dissipation regime, is evidenced even in the case of such light systems and microscopic models could be described. The variance of the charge distribution and the amount of energy dissipated per exchanged nucleon for light systems follow the same type of correlations as medium and heavy systems which have been explained within very simple hypotheses. The interaction time, estimated from the experimental angular distributions for different windows of total kinetic energy, varies from some units of 10-23 sec up to the order of 10-21 sec, showing the presence of fast and slow processes relative to the transit time value of ∼ 5·10-22 sec. The increasing value of the interaction time, represented as a function of the atomic number (Z) and total kinetic energy loss, shows that isotopes with atomic numbers farther from the projectile corresponding value can be populated. Thus, integrated angular distributions usually presented in the literature, becoming flatter with increasing number of transferred nucleons, reflect the necessity of a larger interaction time in order to reach products very different from the projectile. For the same degree of inelasticity of the reaction, the estimated mean lifetime is roughly the same for every atomic number value in the exit channel. This suggests a diffusion-type process. After describing
Probing the hardest branching of jets in heavy ion collisions
Chien, Yang-Ting
2016-01-01
We present the first calculation of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet in heavy ion collisions. These observables are directly sensitive to the hardest branching in the process of jet formation and are, therefore, ideal for studying the early stage of the in-medium parton shower evolution. The modification of the momentum sharing and angular separation distributions in lead-lead relative to proton-proton collisions is evaluated using the leading-order medium-induced splitting functions obtained in the framework of soft-collinear effective theory with Glauber gluon interactions. Qualitative and in most cases quantitative agreement between theory and preliminary CMS measurements suggests that the parton shower in heavy ion collisions can be dramatically modified early in the branching history. We propose a new measurement which will illuminate the angular distribution of the hardest branching within jets in heavy ion collisions.
Perturbed stationary state approach to nuclear heavy ion collision
International Nuclear Information System (INIS)
In order to treat the nuclear heavy ion collision at low energy, the perturbed stationary state method developed in the atomic collision is extended so as to include the coupling between the internal state and the angular part of the relative motion. It is shown that this method provides a simple interpretation for the molecular resonances observed in the scatterings of 12C + 12C, 12C + 16O and 16O + 16O, and for the induced rotation mechanism during the collision between heavy ions. Also given is the detailed study for the applicability of the perturbation treatment of this method. (author)
$\\eta$ Production in Peripheral Heavy-Ion Collisions
Schramm, Alec J.; Reeves, Daniel H.
1995-01-01
We estimate the impact parameter dependence of the production cross section for $\\eta_c$ and $\\eta_b$ mesons in peripheral heavy-ion collisions collisions. Total and elastic $\\gamma\\gamma$ cross sections are calculated in an equivalent photon approximation.
Physics Opportunities in Ultraperipheral Heavy Ion Collisions at LHC
Baur, G.
2001-01-01
Due to coherence, there are strong electromagnetic fields of short duration in very peripheral heavy ion collisions. They give rise to photon-photon and photon-nucleus collisions with high flux. Photon-photon and photon-hadron physics at various invariant mass scales are discussed.
Photoproduction of top in peripheral heavy ion collisions
Klein, S R; Vogt, R; Klein, Spencer R.; Nystrand, Joakim; Vogt, Ramona
2001-01-01
In relativistic heavy ion collisions, top quarks can be produced by photon-gluon fusion when a photon from the Weizs\\"acker-Williams virtual photon field of one nucleus interacts with a gluon in the other nucleus. Photoproduction with heavy ions at the Large Hadron Collider (LHC) will be the first accessible non-hadronic top production channel. We calculate the $t \\bar t$ photoproduction cross sections, pair mass and top quark rapidity distributions in peripheral heavy ion collisions. The cross sections are sensitive to the top quark charge and the large-$Q^2$ gluon distribution in the nucleus. We find a cross section of 94 pb in calcium-calcium collisions, leading to 490 pairs in a one month LHC run. We also find $p$Pb and $p$Ca cross sections of 5.8 and 3.4 pb respectively, resulting in 15 and 88 $t\\bar t$ pairs per month.
Soft vs Hard: Particle Production in High-Energy Heavy-Ion Collisions
Mishra, Aditya Nath; Pareek, Pooja; Behera, Nirbhay K; Sahoo, Raghunath; Nandi, Basanta K
2015-01-01
The centrality dependence of pseudorapidity density of charged particles and transverse energy is studied for a wide range of collision energies for heavy-ion collisions at midrapidity. A two-component model approach has been adopted to quantify the soft and hard components of particle production, coming from nucleon participants and binary nucleon-nucleon collisions, respectively. Within experimental uncertainties, the hard component contributing to the particle production has been found to be nearly independent of collisions energy from RHIC to LHC. The suppression of high-$p_{\\rm T}$ hadrons and jets in the medium created in heavy-ion collisions seem to play a role in the nearly independent collision energy behavior of hard components in particle production. We also use MC event generators, like HIJING and AMPT to study the possible effects of the suppression of high $p_{T}$ partons inside the medium and the effect of the threshold momentum for minijets, contributing to hard scattering processes.
Hydrodynamics in heavy-ion collisions: recent developments
Jaiswal, Amaresh
2016-01-01
Relativistic hydrodynamics has been quite successful in explaining the collective behaviour of the QCD matter produced in high energy heavy-ion collisions at RHIC and LHC. We briefly review the latest developments in the hydrodynamical modeling of relativistic heavy-ion collisions. Essential ingredients of the model such as the hydrodynamic evolution equations, dissipation, initial conditions, equation of state, and freeze-out process are reviewed. We discuss observable quantities such as particle spectra and anisotropic flow as well as the event-by-event fluctuations of these quantities. We also discuss the extraction of transport coefficients of the hot and dense QCD matter from the experimental data of collective flow.
Complexified boost invariance and holographic heavy ion collisions
Gubser, Steven S
2015-01-01
At strong coupling holographic studies have shown that heavy ion collisions do not obey normal boost invariance. Here we study a modified boost invariance through a complex shift in time, and show that this leads to surprisingly good agreement with numerical holographic computations. When including perturbations the agreement becomes even better, both in the hydrodynamic and the far-from-equilibrium regime. One of the main advantages is an analytic formulation of the stress-energy tensor of the longitudinal dynamics of holographic heavy ion collisions.
Imaging of granular sources in high energy heavy ion collisions
Yang, Zhi-Tao; Zhang, Wei-Ning; Huo, Lei; Zhang, Jing-Bo
2008-01-01
We investigate the source imaging for a granular pion-emitting source model in high energy heavy ion collisions. The two-pion source functions of the granular sources exhibit a two-tiered structure. Using a parametrized formula of granular two-pion source function, we examine the two-tiered structure of the source functions for the imaging data of Au+Au collisions at Alternating Gradient Synchrotron (AGS) and Relativistic Heavy Ion Collider (RHIC). We find that the imaging technique introduce...
Lambda-Lambda Correlation in Relativistic Heavy Ion Collisions
Directory of Open Access Journals (Sweden)
Morita Kenji
2015-01-01
Full Text Available We investigate Λ − Λ correlation function in relativistic heavy ion collisions to extract their interaction. Using an expanding source model for heavy ion collisions, we disentangle effects of collective expansion and those of the interaction at low relative momenta. Then, we discuss the influence of the feed-down correction for Σ0 decay and indicate the possible existence of a residual correlation at high relative momenta. Consequently, the present STAR data suggest a weakly attractive interaction for the ΛΛ pairs which is represented by the scattering length, 1/a0 < −0.8 fm−1.
Universal behavior of charged particle production in heavy ion collisions
Phobos Collaboration; Steinberg, Peter A.; Back, B. B.; Baker, M. D.; Barton, D. S.; Betts, R. R.; Ballintijn, M.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; Garcia, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Michałowski, J.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tang, J.-L.; Teng, R.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wadsworth, B.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.
2003-03-01
The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at sqrt(s_NN) = 19.6, 130 and 200 GeV. Two kinds of universal behavior are observed in charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/pbar-p and e+e- data. N_tot/(N_part/2) in nuclear collisions at high energy scales with sqrt(s) in a similar way as N_tot in e+e- collisions and has a very weak centrality dependence. This feature may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions.
Hadronic Resonances in Heavy-Ion Collisions at ALICE
Directory of Open Access Journals (Sweden)
Knospea A. G.
2012-11-01
Full Text Available Modifications to the masses and widths of hadronic resonances in heavy-ion collisions could be a sign of chiral symmetry restoration. Uncorrected spectra, masses, and widths of the ϕ(1020 and K*(8920 resonances have been measured in Pb–Pb collisions at √sNN = 2.76 TeV using the ALICE detector. These measurements are presented and compared to resonances in other collision systems.
Hadronic Resonances in Heavy-Ion Collisions at ALICE
Knospe, A G
2012-01-01
Modifications to the masses and widths of hadronic resonances in heavy-ion collisions could be a sign of chiral symmetry restoration. Uncorrected spectra, masses, and widths of the phi(1020) and K*(892)0 resonances have been measured in Pb-Pb collisions at 2.76 TeV using the ALICE detector. These measurements are presented and compared to resonances in other collision systems.
Rotating quark-gluon plasma in relativistic heavy ion collisions
Jiang, Yin; Liao, Jinfeng
2016-01-01
We study the rotational collective motion of the quark-gluon plasma in relativistic heavy ion collisions using the widely-adopted AMPT (A Multi-Phase Transport) model. The global angular momentum, the average vorticity carried by the quark-gluon plasma, and the locally defined vorticity fields are computed for Au+Au collisions, with detailed information of their time evolution, spatial distribution, as well as the dependence on beam energy and collision centrality.
Statistical multifragmentation features of midvelocity source in semiperipheral heavy-ion collisions
Casini, G.; Piantelli, S.; Maurenzig, P. R.; Olmi, A.; Botvina, A. S.
2009-01-01
Some characteristics of midvelocity emissions in semiperipheral heavy-ion collisions at Fermi energies are discussed in the framework of a multifragmenting scenario. We report on binary dissipative collisions of 93Nb + 93Nb at 38AMeV in which we measured an abundant emission of particles and fragments not originated from the usual evaporative decay of hot primary fragments. We checked the compatibility of these emissions with the multifragmentation of a source which forms in the overlap regio...
Soft electromagnetic radiations from relativistic heavy ion collisions
International Nuclear Information System (INIS)
Photons and dileptons have long been considered as excellent probes of quark-gluon plasma (QGP) expected to be formed in relativistic heavy ion collisions. To evaluate soft photons and dileptons from quark matter as well as soft photon approximation (SPA) is applied. The estimations of soft electromagnetic radiations that exists in the literature have certain discrepancies and efforts were made to correct them
Reconstruction of the Proton Source in Relativistic Heavy Ion Collisions
Polleri, Alberto; Mattiello, Raffaele; Mishustin, Igor; Bondorf, Jakob
1999-01-01
We describe a direct method to reconstruct the transverse proton source formed in a relativistic heavy ion collision, making use of experimentally measured proton and deuteron spectra and assuming that deuterons are formed via two-nucleon coalescence. We show that an ambiguity with respect to the source temperature still persists and we indicate a possible solution to the problem.
What is the temperature in heavy ion collisions?
Biro, T. S.; Purcsel, G.; Muller, B.
2004-01-01
We consider the Tsallis distribution as the source of the apparent slope of one-particle spectra in heavy-ion collisions and investigate the equation of state of this special quark matter in the framework of non-extensive thermodynamics.
Coherent Pion Pairs from Heavy-Ion Collisions
Pratt, Scott; Haglin, Kevin
1996-01-01
The degree to which a nucleus can act as a source for coherent pion pairs is investigated for intermediate-energy heavy-ion collisions. Creation through both isovector and isoscalar channels is considered. Two experimental signals are proposed for evidence of two-pion coherent production, two-pion enhancement and the focusing of outgoing pions along the beam axis.
Direct hadron production in ultrarelativistic heavy ion collisions
Peressounko, D. Yu.; Pokrovsky, Yu. E.
1997-01-01
Hadrons emitted by the pre-surface layer of quark-gluon plasma (QGP) before phase transition into hadronic gas are considered as possible source of direct information about QGP. It is shown that these hadrons dominate at soft p_t if QGP is created in ultrarelativistic heavy ion collisions.
Elliptic and Triangular flow in asymmetric heavy-ion collisions
Haque, Md Rihan; Mohanty, Bedangadas
2011-01-01
We present a study of the elliptic (v2) and triangular (v3) flow and their corresponding eccentricity fluctuations for asymmetric (Au+Ag, Au+Cu and Au+Si) collisions at \\sqrt_NN = 200 GeV. These are compared to the corresponding results from symmetric (Au+Au and Cu+Cu) collisions at the same energy. The study which is carried out using a multi-phase transport (AMPT) model shows that triangularity (\\epsilon_3), fluctuations in triangularity and v3 do not show much variation for the different colliding ion sizes studied. However the eccentricity (\\epsilon_2), fluctuations in eccentricity and v2 shows a strong dependence on colliding ion size for a given number of participating nucleons. Our study thus indicates that asymmetric heavy-ion collisions could be used to constrain models dealing with flow fluctuations in heavy-ion collisions.
Pseudorapidity correlations in heavy ion collisions from viscous fluid dynamics
Monnai, Akihiko; Schenke, Björn
2016-01-01
We demonstrate by explicit calculations in 3+1 dimensional viscous relativistic fluid dynamics how two-particle pseudorapidity correlation functions in heavy ion collisions at the LHC and RHIC depend on the number of particle producing sources and the transport properties of the produced medium. In particular, we present results for the Legendre coefficients of the two-particle pseudorapidity correlation function, an,m, in Pb+Pb collisions at 2760 GeV and Au+Au collisions at 200 GeV from viscous hydrodynamics with three dimensionally fluctuating initial conditions. Our results suggest that the an,m provide important constraints on initial state fluctuations in heavy ion collisions.
Directed flow in ultrarelativistic heavy-ion collisions
Bozek, Piotr; Wyskiel, Iwona
2010-01-01
We study the generation of directed flow in the hydrodynamic expansion of the hot matter formed in ultrarelativistic heavy-ion collisions at 200GeV. The experimentally observed negative directed flow in a wide range of central pseudorapidities isreproduced assuming that the fireball is tilted away from the collision axis. The tilt of the source is consistent with a preferential emission in the forward/backward hemisphere from forward/backward participating nucleons. The model reproduces the e...
Electromagnetic processes in relativistic heavy ion collisions
International Nuclear Information System (INIS)
A study of the processes generated by the electromagnetic interaction in relativistic nuclear, and atomic collisions is presented. Very strong electromagnetic fields for a very short time are present in distant collisions with no nuclear contact. Such fields can also lead to interesting effects, which are discussed here. (orig.)
Jets and Vector Bosons in Heavy Ion Collisions
De La Cruz, Begona
2013-01-01
This paper reviews experimental results on jets and electroweak boson (photon, W and Z) production in heavy-ion collisions, from the CMS and ATLAS detectors, using data collected during 2011 PbPb run and pp data collected at an equivalent energy. By comparing the two collision systems, the energy loss of the partons propagating through the medium produced in PbPb collisions can be studied. Its characterization is done using dijet events and isolated photon-jet pairs. Since the electroweak gauge bosons do not participate in the strong interaction, and are thus unmodified by the nuclear medium, they serve as clean probes of the initial state in the collision.
Vorticity in Heavy-Ion Collisions
Deng, Wei-Tian
2016-01-01
We study the event-by-event generation of flow vorticity in RHIC Au + Au collisions and LHC Pb + Pb collisions by using the HIJING model. Different definitions of the vorticity field and velocity field are considered. A variety of properties of the vorticity are explored, including the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction, and the time evolution. In addition, the spatial distribution of the flow helicity is also studied.
Particle-production mechanism in relativistic heavy-ion collisions
Bush, B W; Brian W Bush
1994-01-01
We discuss the production of particles in relativistic heavy-ion collisions through the mechanism of massive bremsstrahlung, in which massive mesons are emitted during rapid nucleon acceleration. This mechanism is described within the framework of classical hadrodynamics for extended nucleons, corresponding to nucleons of finite size interacting with massive meson fields. This new theory provides a natural covariant microscopic approach to relativistic heavy-ion collisions that includes automatically spacetime nonlocality and retardation, nonequilibrium phenomena, interactions among all nucleons, and particle production. Inclusion of the finite nucleon size cures the difficulties with preacceleration and runaway solutions that have plagued the classical theory of self-interacting point particles. For the soft reactions that dominate nucleon-nucleon collisions, a significant fraction of the incident center-of-mass energy is radiated through massive bremsstrahlung. In the present version of the theory, this rad...
International Nuclear Information System (INIS)
Relative double differential cross sections for electron emission in collisions of Iq+ and Xeq+ projectile ions incidence on H2 and He targets are presented for observation angles of 0 degree to 60 degree with respect to the beam. The measurements were performed over a wide range of projectile velocities (0.6 to 3.6 MeV/amu) and charge states (q=7 to 23). As the velocity or charge state of the projectile are decreased, drastic changes in the behavior of the binary encounter peak can be observed. These effects can be attributed to diffraction of the target electrons by the non-Coulomb potential of the clothed projectile ion. A theoretical treatment of the double differential cross sections has been developed where the binary encounter electrons are treated within the impulse approximation as the elastic scattering of quasi-free target electrons by the screened potential of the projectile ion
Pion correlations in relativistic heavy ion collisions at Heavy Ion Spectrometer Systems (HISS)
International Nuclear Information System (INIS)
This thesis contains the setup, analysis and results of experiment E684H ''Multi-Pion Correlations in Relativistic Heavy Ion Collisions''. The goals of the original proposal were: (1) To initiate the use of the HISS facility in the study of central Relativistic Heavy Ion Collisions (RHIC). (2) To perform a second generation experiment for the detailed study of the pion source in RHIC. The first generation experiments, implied by the second goal above, refer to pion correlation studies which the Riverside group had performed at the LBL streamer chamber. The major advantage offered by moving the pion correlation studies to HISS is that, being an electronic detector system, as opposed to the Streamer Chamber which is a visual detector, one can greatly increase the statistics for a study of this sort. An additional advantage is that once one has written the necessary detector and physics analysis code to do a particular type of study, the study may be extended to investigate the systematics, with much less effort and in a relatively short time. This paper discusses the Physics motivation for this experiment, the experimental setup and detectors used, the pion correlation analysis, the results, and the conclusions possible future directions for pion studies at HISS. If one is not interested in all the details of the experiment, I believe that by reading the sections on intensity interferometry, the section the fitting of the correlation function and the systematic corrections applied, and the results section, one will get a fairly complete synopsis of the experiment
Charmonia and open charm production in heavy ion collisions
Gonin, Michel
2005-01-01
The production of heavy flavours in heavy ion collisions has been of great interest since the prediction of Matsui and Satz regarding quarkonium suppression in the quark gluon plasma due to color screening mechanisms. The NA50 collaboration has produced the first charmonia measurements in heavy ion collisions which show evidence for strong and anomalous suppressions in central Pb-Pb collisions. For the suppression of bound state quark-antiquark pairs to be a plasma signature, the production of these quarks inside the cold nucleus should first be well known. Differences in the relative yield of heavy flavour between nucleon-nucleon an nucleon-nucleus collisions probes cold nuclear matter effects such as the modifications of the gluon distribution functions or parton energy loss. The gluon-gluon fusion represents the dominant mechanism for the production of quarkonia studied by the heavy ion experiments. The purpose of this presentation is to highlight the latest results from the CERN-SPS and Fermilab fixed tar...
Electromagnetic excitation of 136Xe in relativistic heavy ion collisions
International Nuclear Information System (INIS)
In the framework of the experimental program at the accelerator facilities SIS/ESR at the Society for Heavy Ion Research in Darmstadt a detector system for relativistic neutrons was developed, constructed, and applied in first experiments. An essential research aim is the study of collective states after electromagnetic excitation in relativistic heavy ion collisions. In peripheral collisions high-energy virtual photons are exchanged. This leads to the excitation of giant resonances, especially of the giant dipole and quadrupole resonance. An essential decay channel of giant resonances in heavy nuclei is the emission of neutrons, followed by the emission of γ radiation below the particle threshold. These decay channels were studied with the detector system developed by the LAND collaboration. A first experiment on the electromagnetic excitation was performed with a 136Xe beam at an energy of 700 MeV/u and Pb respectively C targets. (orig./HSI)
Magnetohydrodynamics and charged currents in heavy ion collisions
International Nuclear Information System (INIS)
The hot QCD matter produced in any heavy ion collision with a nonzero impact parameter is produced within a strong magnetic field. We study the imprint the magnetic fields produced in non-central heavy ion collisions leave on the azimuthal distributions and correlations of the produced charged hadrons. The magnetic field is time-dependent and the medium is expanding, which leads to the induction of charged currents due to the combination of Faraday and Hall effects. We find that these currents result in a charge-dependent directed flow v1 that is odd in rapidity and odd under charge exchange. It can be detected by measuring correlations between the directed flow of charged hadrons at different rapidities, 〈v1±(y1)v1±(y2)〉
The Decoherence Time in High Energy Heavy Ion Collisions
Müller, B; Muller, Berndt; Schafer, Andreas
2006-01-01
We calculate the decoherence time of the ground state wave function of a nucleus in a high energy heavy ion collision. We define this time as the decay time of the ratio Tr D^2 / (Tr D)^2 of traces of the density matrix D. We find that this time is smaller or equal to 1/Q_s, where the saturation scale Q_s is defined within the color glass condensate model of parton saturation. Our result supports the notion that the extremely rapid entropy production deduced for the early stage of heavy ion collisions at collider energies is to a large extent caused by the decoherence of the initial-state wave functions.
Hard scattering contribution to particle production in high energy heavy-ion collisions
International Nuclear Information System (INIS)
Global observables like the multiplicity of produced charged particles and transverse energy, are the key observables used to characterize the properties of the matter created in heavy-ion collisions. In order to study the dependence of the charged particle density on colliding system, center of mass energy and collision centrality, there have been measurements starting few GeV to TeV energies at LHC. There is a need to understand the particle production contribution coming from the QCD hard processes, which scale with number of binary nucleon-nucleon collisions, Ncoll and soft processes scaling with number of participant nucleons, Npart
Transverse Flow of Kaons in Heavy-Ion Collisions
Institute of Scientific and Technical Information of China (English)
郑玉明; 储自力; FUCHS Christian; FAESSLER Amand; 肖武; 华大平; 阎玉鹏
2002-01-01
The transverse flow of positively charged kaons from heavy-ion collisions at intermediate energy is investigatedwithin the framework of the quantum molecular dynamics model. The calculated results show that the experi-mental data are only consistent with those including the kaon mean-field potential from the chiral Lagrangian.This indicates that the transverse flow pattern of kaons is a useful probe of the kaon potential in a nuclearmedium.
Double meson production in ultraperipheral heavy ion collisions
Goncalves, V. P.; Machado, M. V. T.
2003-01-01
The double meson production in ultraperipheral heavy ions collisions is addressed, focusing on the particular case of rho-J/Psi from two-photon reactions. The cross section at photon level is obtained using distinct parameterizations for the gluon distribution on the light meson. The resulting estimates for the nuclear case are presented and discussed. As a by product, we estimate the double rho production cross section using the Pomeron-exchange factorization relations.
Simultaneous Projectile-Target Excitation in Heavy Ion Collisions
Benesh, C. J.; Friar, J. L.
1994-01-01
We calculate the lowest-order contribution to the cross section for simultaneous excitation of projectile and target nuclei in relativistic heavy ion collisions. This process is, to leading order, non-classical and adds incoherently to the well-studied semi-classical Weizs\\"acker-Williams cross section. While the leading contribution to the cross section is down by only $1/Z_P$ from the semiclassical process, and consequently of potential importance for understanding data from light projectil...
Reaction Cross Section in Heavy-Ion Collisions
Wong, Cheuk-Yin
2012-01-01
Previously a compact formula for total reaction cross section for heavy-ion collisions as a function of energy was obtained by treating the angular momentum $l$ as a continuous variable. The accuracy of the continuum approximation is assessed and corrections are evaluated. The accuracy of the compact equation can be improved by a simple modification, if a higher accuracy is required. Simple rules to determine the barrier heights and the penetration probability for the $l$ partial wave from ex...
BRAHMS collaboration results for relativistic heavy ion collisions
Arsene, I.
2008-12-01
In this work we review very briefly a few of the most important results obtained by the BRAHMS Collaboration on the properties of the collisions of heavy ions at relativistic energies. The discussion is general and aims to illustrate the most important achievements of our collaboration during the RHIC run period with short discussions and references to articles that treat the subjects in more detail.
Azimuthal Correlation of Collective Motion in Relativistic Heavy Ion Collisions
Institute of Scientific and Technical Information of China (English)
HUO Lei; ZHANG Wei-Ning; CHEN Xiang-Jun; TANG Gui-Xin; ZHANG Jing-Bo
2001-01-01
The out-of-plane squeeze-out effect in relativistic heavy ion collisions is used to estimate the reaction plane by performing a modified transverse momentum analysis. A technique for investigating the azimuthal correlation between the out-of-plane squeeze-out and directed in-plane flow is described. A clear signature of the azimuthal correlation is evidenced in the 600 A MeV Au + Au reaction from the quantum molecular dynamic model calculations.
Ionization of helium in relativistic heavy-ion collisions
Barna, Imre Ferenc
2002-01-01
The coupled-channel method is used to calculate single-, and double-ionisation cross sections for helium collisions with heavy ions. For highly charged and slow projectiles where the ratio of the projectile charge divided by the projectile velocity is in the magnitude of unity, non-perturbative methods must be used for proper description of the physical process. As basis functions Slater-like orbitals and regular Coulomb wave packages were taken. The Coulomb wave packages give a satisfacto...
Complexified boost invariance and holographic heavy ion collisions
Gubser, Steven; van der Schee, Wilke
2014-01-01
At strong coupling holographic studies have shown that heavy ion collisions do not obey normal boost invariance. Here we study a modified boost invariance through a complex shift in time, and show that this leads to surprisingly good agreement with numerical holographic computations. When including perturbations the agreement becomes even better, both in the hydrodynamic and the far-from-equilibrium regime. One of the main advantages is an analytic formulation of the stress-energy tensor of t...
Isotope analysis in central heavy ion collisions at intermediate energies
Geraci, E.; Abbondanno, U.; Bardelli, L.; Barlini, S.; Bini, M.; Bruno, M.; Cannata, F.; Casini, G.; Chiari, M.; D'Agostino, M.; de Sanctis, J.; Giussani, A.; Gramegna, F.; Kravchuk, V. L.; Lanchais, A. L.; Marini, P.; Moroni, A.; Nannini, A.; Olmi, A.; Ordine, A.; Pasquali, G.; Piantelli, S.; Poggi, G.; Vannini, G.; Nucl-Ex Collaboration
2007-11-01
Symmetry energy is a key quantity in the study of the equation of state of asymmetric nuclear matter. Heavy ion collisions at low and intermediate energies, performed at Laboratori Nazionali di Legnaro and Laboratori Nazionali del Sud, can be used to extract information on the symmetry energy coefficient Csym, which is currently poorly known but relevant both for astrophysics and for deeper knowledge of the structure of exotic nuclei.
Isotope analysis in central heavy ion collisions at intermediate energies
Geraci, E; Bardelli, L; Barlini, S; Bini, M; Bruno, M; Cannata, F; Casini, G; Chiari, M; D'Agostino, M; De Sanctis, J; Giussani, A; Gramegna, F; Kravchuk, V L; Lanchais, A L; Marini, P; Moroni, A; Nannini, A; Olmi, A; Ordine, A; Pasquali, G; Piantelli, S; Poggi, G; Vannini, G
2006-01-01
Symmetry energy is a key quantity in the study of the equation of state of asymmetric nuclear matter. Heavy ion collisions at low and intermediate energies, performed at Laboratori Nazionali di Legnaro and Laboratori Nazionali del Sud, can be used to extract information on the symmetry energy coefficient Csym, which is currently poorly known but relevant both for astrophysics and for structure of exotic nuclei.
Pion and photon production in heavy ion collisions
David, G.
2009-01-01
Measurement of neutral pions and direct photons are closely connected experimentally, on the other hand they probe quite different aspects of relativistic heavy ion collisions. In this short review of the $\\pi^0$ results from the PHENIX experiment at RHIC our focus is on the $\\phi$-integrated nuclear modification factor, its energy and system size dependence, and the impact of these results on parton energy loss models. We also discuss the current status of high $p_T$ and thermal direct photo...
Effect of correlations on cumulants in heavy-ion collisions
Mishra, D K; Garg, P; Netrakanti, P. K.
2015-01-01
We study the effects of correlations on cumulants and their ratios of net-proton multiplicity distributions which have been measured for central (0\\%-5\\%) Au + Au collisions at the Relativistic Heavy Ion Collider (RHIC). This effect has been studied assuming individual proton and anti-proton distributions as a Poisson or Negative Binomial Distribution (NBD). In-spite of significantly correlated production due to baryon number, electric charge conservation and kinematical correlations of proto...
Cumulants of multiplicity distributions in most central heavy ion collisions
Xu, Hao-jie
2016-01-01
We investigate the statistical expectations for cumulants of (net-conserved) charge distributions in relativistic heavy ion collisions, by including a simple but quantitatively more realistic geometric model, i.e. optical Glauber model. We suggest a new approach for centrality definition in studying of multiplicity fluctuations, which aim at eliminating the uncertainties between experimental measurements and theoretical calculations, as well as redoubling the statistics. We find that the stat...
Fluctuating Glasma initial conditions and flow in heavy ion collisions
Schenke, Bjoern; Tribedy, Prithwish; Venugopalan, Raju
2012-01-01
We compute initial conditions in heavy-ion collisions within the Color Glass Condensate (CGC) framework by combining the impact parameter dependent saturation model (IP-Sat) with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this IP-Glasma description includes quantum fluctuations of color charges on the length-scale determined by the inverse nuclear saturation scale Q_s. The model naturally produces initial energy fluctuation...
Viscous potential flow analysis of peripheral heavy ion collisions
Wang, Du-Juan; Néda, Zoltán; Csernai, Laszlo
2013-01-01
The conditions for the development of a Kelvin-Helmholtz instability (KHI) for the quark-gluon plasma (QGP) flow in a peripheral heavy ion collision is investigated. The projectile and target side particles are separated by an energetically motivated hypothetical surface, characterized with a phenomenological surface tension. In such a view, a classical potential flow approximation is considered and the onset of the KHI is studied. The growth rate of the instability is computed as a function ...
Viscous potential flow analysis of peripheral heavy ion collisions
Wang, D. J.; Néda, Z.; Csernai, L. P.
2013-01-01
The conditions for the development of a Kelvin-Helmholtz Instability (KHI) for the Quark-gluon Plasma (QGP) flow in a peripheral heavy-ion collision is investigated. The projectile and target side particles are separated by an energetically motivated hypothetical surface, characterized with a phenomenological surface tension. In such a view, a classical potential flow approximation is considered and the onset of the KHI is studied. The growth rate of the instability is computed as function of...
Transfer of momentum, mass and charge in heavy ion collisions
International Nuclear Information System (INIS)
A model for the first two phases of heavy ion collisions based on the transport of single nucleons through the window between the two scattering nuclei is described in some detail. It is pointed out that the model can account simultaneously for a large portion of the energy transfer from relative to intrinsic motion and for the observed variances in mass and charge numbers for reaction times up to the order of 10-21 s. (P.L.)
Femtoscopy in heavy ion collisions: Wherefore, whence, and whither?
Lisa, Mike
2005-01-01
I present a brief overview of the wealth of femtoscopic measurements from the past two decades of heavy ion experiments. Essentially every conceivable knob at our disposal has been turned; the response of two-particle correlations to these variations has revealed much about he space-momentum substructure of the hot source created in the collisions. I discuss the present status of the femtoscopic program and questions which remain, and point to new efforts which aim to resolve them.
Lambda-proton correlations in relativistic heavy ion collisions
Wang, Fuqiang; Pratt, Scott
1999-01-01
The prospect of using lambda-proton correlations to extract source sizes in relativistic heavy ion collisions is investigated. It is found that the strong interaction induces a large peak in the correlation function that provides more sensitive source size measurements than two-proton correlations under some circumstances. The prospect of using lambda-proton correlations to measure the time lag between lambda and proton emissions is also studied.
Lepton interferometry in relativistic heavy ion collisions - a case study
Alam, Jan-e; Mohanty, Bedangadas; Rahaman, A .; Sarkar, Sourav; Sinha, Bikash
2004-01-01
We propose intensity interferometry with identical lepton pairs as an efficient tool for the estimation of the source size of the expanding hot zone produced in relativistic heavy ion collisions. This can act as a complementary method to two photon interferometry. The correlation function of two electrons with the same helicity has been evaluated for RHIC energies. The thermal shift of the rho meson mass has negligible effects on the HBT radii.
Observable consequences of chemical equilibration in energetic heavy ion collisions
Konopka, Jens; Graf, Harald; Stöcker, Horst; Greiner, Walter
2006-01-01
The quantum statistical model (QSM) is used to calculate nuclear fragment distributions in chemical equilibrium. Several observable isotopic effects are predicted for intermediate energy heavy ion collisions. It is demonstrated that particle ratios for different systemsdo not depend on the breakup density-the only free parameter in our model.The importance of entropy measurements is discussed. Specific particle ratios for the system Au-Au are predicted, which can be used to determine the chem...
Deciphering Azimuthal Correlations in Relativistic Heavy-Ion Collisions
Cetner, Tomasz; Grebieszkow, Katarzyna; Mrowczynski, Stanislaw
2010-01-01
We discuss various sources of azimuthal correlations in relativistic heavy-ion collisions. The integral measure Phi is applied to quantify the correlations. We first consider separately the correlations caused by the elliptic flow, resonance decays, jets and transverse momentum conservation. An effect of randomly lost particles is also discussed. Using the PYTHIA and HIJING event generators we produce a sample of events which mimic experimental data. By means of kinematic cuts and particle's ...
Fragment Formation and Phase Transitions in Heavy Ion Collisions
Gaitanos, T.; Wolter, H. H.; Fuchs, C.
2000-01-01
We investigate the thermodynamical properties of nuclear matter in heavy ion collisions, in particular with respect to questions of thermodynamical instability, phase transitions and fragmentation. For this we analyze results of relativistic transport calculations of Au+Au collisons at intermediate energies, separately for spectator and participant matter. On one hand, we determine local thermodynamical variables from the analysis of the local momentum distribution; on the other, we analyze f...
Directory of Open Access Journals (Sweden)
Shusu Shi
2016-01-01
Full Text Available Strange hadrons, especially multistrange hadrons, are good probes for the early partonic stage of heavy ion collisions due to their small hadronic cross sections. In this paper, I give a brief review on the elliptic flow measurements of strange and multistrange hadrons in relativistic heavy ion collisions at Relativistic Heavy Ion Collider (RHIC and Large Hadron Collider (LHC.
Heavy flavour production at CMS in heavy ion collisions
Nguyen, Matthew
2015-01-01
We review recent results relating to beauty production in heavy-ion collisions, in both the closed and open heavy flavor sectors, from the CMS experiment at the LHC. The sequential suppression of the ° states in PbPb collisions is thought to be evidence of the dissociation of quarkonia bound states in deconfined matter. Data from pPb collisions demonstrate that while cold nuclear effects appear to be subdominant in minimum bias collisions, there exists a non-trivial dependence on collision multiplicity that remains to be understood. The suppression of high p T particles in heavy-ion collisions, relative to the expectation from pp collisions, is typically interpreted in terms of energy loss of hard scattered parton in the dense nuclear medium. The flavor dependence of the energy loss may be accessed via measurements of b hadrons and b-tagged jets. Measurement of B mesons, via non-prompt J = y , at relatively low p T indicate a smaller suppression factor than D meson or inclusive charged hadrons. Data on b jet...
Particle Ratios in Heavy-Ion Collisions
Tawfik, A
2005-01-01
In the framework of the statistical models, we calculated different particle ratios in the energy range \\hbox{$3.5$} ratios. We find within the statistical acceptance that the different peaks are located at one value of energy, $\\sqrt{s_{NN}}^{(c)}\\simeq7.5 $GeV. This energy value is corresponding to baryo-chemical potential of $\\mu_B\\simeq0.43 $GeV. We also found that a maximum entropy per particle is allocated at the same collision energy. The saddle-point in the entropy per particle likely refers to the critical endpoint which connects the first-order phase transition with the cross-over.
Chemical Property in Heavy Ion Collisions
Kaneta, M.
K-/K+ and bar{p}/p ratios measured in 158 A\\cdotGeV Pb + Pb collisions are shown as a function of centrality and transverse momentum (Pt). Little significant centrality dependence in neither K-/K+ nor bar{p}/p ratios are observed and they are almost constant as a function of Pt. The chemical freeze-out temperature Tch and the chemical potentials for both light and strange quarks (μq, μs) are extracted by comparing the present data with simple model predictions. The μq, μs and Tch from the NA44 are compared with those obtained from similar analysis of SPS S + A and AGS Si + A data. The chemical freeze-out temperature Tch in CERN energy is higher than thermal freeze-out temperature Tfo which is extracted from transverse momentum distribution of charged hadrons. In AGS energy Tch is close to Tfo.
Heavy Ion Collisions at the LHC - Last Call for Predictions
Energy Technology Data Exchange (ETDEWEB)
Armesto, N; Borghini, N; Jeon, S; Wiedemann, U A; Abreu, S; Akkelin, V; Alam, J; Albacete, J L; Andronic, A; Antonuv, D; Arleo, F; Armesto, N; Arsene, I C; Barnafoldi, G G; Barrette, J; Bauchle, B; Becattini, F; Betz, B; Bleicher, M; Bluhm, M; Boer, D; Bopp, F W; Braun-Munzinger, P; Bravina, L; Busza, W; Cacciari, M; Capella, A; Casalderrey-Solana, J; Chatterjee, R; Chen, L; Cleymans, J; Cole, B A; delValle, Z C; Csernai, L P; Cunqueiro, L; Dainese, A; de Deus, J D; Ding, H; Djordjevic, M; Drescher, H; Dremin, I M; Dumitru, A; El, A; Engel, R; d' Enterria, D; Eskola, K J; Fai, G; Ferreiro, E G; Fries, R J; Frodermann, E; Fujii, H; Gale, C; Gelis, F; Goncalves, V P; Greco, V; Gyulassy, M; van Hees, H; Heinz, U; Honkanen, H; Horowitz, W A; Iancu, E; Ingelman, G; Jalilian-Marian, J; Jeon, S; Kaidalov, A B; Kampfer, B; Kang, Z; Karpenko, I A; Kestin, G; Kharzeev, D; Ko, C M; Koch, B; Kopeliovich, B; Kozlov, M; Kraus, I; Kuznetsova, I; Lee, S H; Lednicky, R; Letessier, J; Levin, E; Li, B; Lin, Z; Liu, H; Liu, W; Loizides, C; Lokhtin, I P; Machado, M T; Malinina, L V; Managadze, A M; Mangano, M L; Mannarelli, M; Manuel, C; Martinez, G; Milhano, J G; Mocsy, A; Molnar, D; Nardi, M; Nayak, J K; Niemi, H; Oeschler, H; Ollitrault, J; Paic, G; Pajares, C; Pantuev, V S; Papp, G; Peressounko, D; Petreczky, P; Petrushanko, S V; Piccinini, F; Pierog, T; Pirner, H J; Porteboeuf, S; Potashnikova, I; Qin, G Y; Qiu, J; Rafelski, J; Rajagopal, K; Ranft, J; Rapp, R; Rasanen, S S; Rathsman, J; Rau, P; Redlich, K; Renk, T; Rezaeian, A H; Rischke, D; Roesler, S; Ruppert, J; Ruuskanen, P V; Salgado, C A; Sapeta, S; Sarcevic, I; Sarkar, S; Sarycheva, L I; Schmidt, I; Shoski, A I; Sinha, B; Sinyukov, Y M; Snigirev, A M; Srivastava, D K; Stachel, J; Stasto, A; Stocker, H; Teplov, C Y; Thews, R L; Torrieri, G; Pop, V T; Triantafyllopoulos, D N; Tuchin, K L; Turbide, S; Tywoniuk, K; Utermann, A; Venugopalan, R; Vitev, I; Vogt, R; Wang, E; Wang, X N; Werner, K; Wessels, E; Wheaton, S; Wicks, S; Wiedemann, U A; Wolschin, G; Xiao, B; Xu, Z; Yasui, S; Zabrodin, E; Zapp, K; Zhang, B
2008-02-25
In August 2006, the CERN Theory Unit announced to restructure its visitor program and to create a 'CERN Theory Institute', where 1-3 month long specific programs can take place. The first such Institute was held from 14 May to 10 June 2007, focusing on 'Heavy Ion Collisions at the LHC - Last Call for Predictions'. It brought together close to 100 scientists working on the theory of ultra-relativistic heavy ion collisions. The aim of this workshop was to review and document the status of expectations and predictions for the heavy ion program at the Large Hadron Collider LHC before its start. LHC will explore heavy ion collisions at {approx} 30 times higher center of mass energy than explored previously at the Relativistic Heavy Ion Collider RHIC. So, on the one hand, the charge of this workshop provided a natural forum for the exchange of the most recent ideas, and allowed to monitor how the understanding of heavy ion collisions has evolved in recent years with the data from RHIC, and with the preparation of the LHC experimental program. On the other hand, the workshop aimed at a documentation which helps to distinguish pre- from post-dictions. An analogous documentation of the 'Last Call for Predictions' [1] was prepared prior to the start of the heavy-ion program at the Relativistic Heavy Ion Collider RHIC, and it proved useful in the subsequent discussion and interpretation of RHIC data. The present write-up is the documentation of predictions for the LHC heavy ion program, received or presented during the CERN TH Institute. The set-up of the CERN TH Institute allowed us to aim for the wide-most coverage of predictions. There were more than 100 presentations and discussions during the workshop. Moreover, those unable to attend could still participate by submitting predictions in written form during the workshop. This followed the spirit that everybody interested in making a prediction had the right to be heard. To arrive at a concise
Heavy Ion Collisions at the LHC - Last Call for Predictions
International Nuclear Information System (INIS)
In August 2006, the CERN Theory Unit announced to restructure its visitor program and to create a 'CERN Theory Institute', where 1-3 month long specific programs can take place. The first such Institute was held from 14 May to 10 June 2007, focusing on 'Heavy Ion Collisions at the LHC - Last Call for Predictions'. It brought together close to 100 scientists working on the theory of ultra-relativistic heavy ion collisions. The aim of this workshop was to review and document the status of expectations and predictions for the heavy ion program at the Large Hadron Collider LHC before its start. LHC will explore heavy ion collisions at ∼ 30 times higher center of mass energy than explored previously at the Relativistic Heavy Ion Collider RHIC. So, on the one hand, the charge of this workshop provided a natural forum for the exchange of the most recent ideas, and allowed to monitor how the understanding of heavy ion collisions has evolved in recent years with the data from RHIC, and with the preparation of the LHC experimental program. On the other hand, the workshop aimed at a documentation which helps to distinguish pre- from post-dictions. An analogous documentation of the 'Last Call for Predictions' (1) was prepared prior to the start of the heavy-ion program at the Relativistic Heavy Ion Collider RHIC, and it proved useful in the subsequent discussion and interpretation of RHIC data. The present write-up is the documentation of predictions for the LHC heavy ion program, received or presented during the CERN TH Institute. The set-up of the CERN TH Institute allowed us to aim for the wide-most coverage of predictions. There were more than 100 presentations and discussions during the workshop. Moreover, those unable to attend could still participate by submitting predictions in written form during the workshop. This followed the spirit that everybody interested in making a prediction had the right to be heard. To arrive at a concise document, we required that each
Electrons with continuous energy distribution from energetic heavy ion collisions
International Nuclear Information System (INIS)
The properties and origin of continuous electron spectrum emitted in high energy heavy ion collisions are reviewed. The basic processes causing the characteristic regions of the continuous spectrum are described. The contribution of electrons ejected from the target and from the projectile are investigated in detail in the cases of light and heavy projectiles. The recently recognized mechanisms, electron-capture-to-continuum (ECC) and electron-loss-to-continuum (ELC), leading to a cusp in forward direction, and their theoretical interpretations are discussed. The importance of data from ion-atom collisions in the field of atomic physics and in applications are briefly summarized. (D.Gy)
Coupling constant corrections in holographic heavy ion collisions
Grozdanov, Sašo
2016-01-01
We initiate a holographic study of coupling-dependent heavy ion collisions by analysing for the first time the effects of leading-order, inverse coupling constant corrections. In the dual description, this amounts to colliding gravitational shock waves in a theory with curvature-squared terms. We find that at intermediate coupling, nuclei experience less stopping and have more energy deposited near the lightcone. When the decreased coupling results in an 80% larger shear viscosity, the time at which hydrodynamics becomes a good description of the plasma created from high energy collisions increases by 25%. The hydrodynamic phase of the evolution starts with a wider rapidity profile and smaller entropy.
Towards Reconstructing the Final Stage of Heavy Ion Collisions
Wiedemann, Urs Achim
1997-01-01
A Fourier inversion problem lies at the heart of determining spatio-temporal characteristica of the final stage of a heavy ion collision: From the measured two-particle momentum correlations C(p_1,p_2) of identical particles, pions say, a Hanbury-Brown /Twiss (HBT) interferometric analysis aims at extracting as much information as possible about the Wigner phase space density S(x,p) of pion emitting sources in the collision region. Here, we discuss how this analysis allows to separate the effects of temperature and transverse flow which cannot be disentangled completely on the basis of single-particle spectra.
Beyond the thermal model in relativistic heavy-ion collisions
Wolschin, Georg
2016-08-01
Deviations from thermal distribution functions of produced particles in relativistic heavy-ion collisions are discussed as indicators for nonequilibrium processes. The focus is on rapidity distributions of produced charged hadrons as functions of collision energy and centrality, which are used to infer the fraction of particles produced from a central fireball as compared with that from the fragmentation sources that are out of equilibrium with the rest of the system. Overall thermal equilibrium would only be reached for large times t →∞ .
Beyond the thermal model in relativistic heavy-ion collisions
Wolschin, Georg
2016-01-01
Deviations from thermal distribution functions of produced particles in relativistic heavy-ion collisions are discussed as indicators for nonequilibrium processes. The focus is on rapidity distributions of produced charged hadrons as functions of collision energy and centrality which are used to infer the fraction of produced particles from a central fireball as compared to the one from the fragmentation sources that are out of equilibrium with the rest of the system. Overall thermal equilibrium would only be reached for large times t -> infinity.
Gauge/String Duality, Hot QCD and Heavy Ion Collisions
Casalderrey-Solana, Jorge; Mateos, David; Rajagopal, Krishna; Wiedemann, Urs Achim
2011-01-01
Over the last decade, both experimental and theoretical advances have brought the need for strong coupling techniques in the analysis of deconfined QCD matter and heavy ion collisions to the forefront. As a consequence, a fruitful interplay has developed between analyses of strongly-coupled non-abelian plasmas via the gauge/string duality (also referred to as the AdS/CFT correspondence) and the phenomenology of heavy ion collisions. We review some of the main insights gained from this interplay to date. To establish a common language, we start with an introduction to heavy ion phenomenology and finite-temperature QCD, and a corresponding introduction to important concepts and techniques in the gauge/string duality. These introductory sections are written for nonspecialists, with the goal of bringing readers ranging from beginning graduate students to experienced practitioners of either QCD or gauge/string duality to the point that they understand enough about both fields that they can then appreciate their in...
On local and global equilibrium in heavy ion collisions
Sollfrank, J
1999-01-01
The thermal model is commonly used in two different ways for the description of hadron production in ultra-relativistic heavy ion collision. One is the application of the thermal model to 4pi integrated data and the other is the thermal description of central dN/dy ratios. While the first method implicitly assumes global equilibrium the other scenario assumes Bjorken scaling within the investigated rapidity range. Both assumptions are only approximations for real physical collision systems. We study the impact of both approximations for the extraction of thermal parameters on the exemplary case of S+S collisions at SPS energies. The particle distributions are modeled by a hydrodynamical description of the relevant collision system.
Jets and Vector Bosons in Heavy Ion Collisions
Directory of Open Access Journals (Sweden)
de la Cruz Begoña
2013-11-01
Full Text Available This paper reviews experimental results on jets and electroweak boson (photon,Wand Z production in heavy-ion collisions, from the CMS and ATLAS detectors, using data collected during 2011 PbPb run and pp data collected at an equivalent energy. By comparing the two collision systems, the energy loss of the partons propagating through the medium produced in PbPb collisions can be studied. Its characterization is done using dijet events and isolated photon-jet pairs. Since the electroweak gauge bosons do not participate in the strong interaction, and are thus unmodified by the nuclear medium, they serve as clean probes of the initial state in the collision.
Approach to equilibrium in high energy heavy ion collisions
International Nuclear Information System (INIS)
This thesis deals with the theory of the early stages of a heavy ion collision. Just after such a collision, the matter produced - called the Quark-Gluon-Plasma (QGP) - has been shown to be far out of thermal equilibrium. One would like to know whether the QGP thermalizes, and what is the typical time scale for this. Proving that the QGP thermalizes would also justify from first principles the hydrodynamical treatment of the subsequent evolution of a heavy ion collision. After having recalled some essential theoretical concepts, the manuscript addresses these questions in two different theories. In a first part, we study a scalar field theory. Starting from an out of equilibrium initial condition, one studies the approach to equilibrium in a fixed volume or in a one-dimensional expanding system. In both cases, clear signs of thermalization are obtained: an equation of state is formed, the pressure tensor becomes isotropic and the occupation number approaches a classical thermal distribution. These results are obtained thanks to the classical statistical approximation (CSA), that includes contributions beyond the Leading Order perturbative calculation. In a second part, the Color Glass Condensate - a quantum chromodynamics (QCD) effective theory well suited to describe the early life of the QGP - is used to treat more realistically the approach to thermalization in heavy ion collisions. After having derived some analytical prerequisites for the application of the CSA, the numerical simulations performed with the Yang-Mills equations show evidences of an early onset of hydrodynamical behavior of the QGP: the system becomes isotropic on short time scales, while the shear viscosity over entropy ratio is very small, which is characteristic of a quasi perfect fluid. (author)
Statistical multifragmentation features of midvelocity source in semiperipheral heavy-ion collisions
Casini, G; Maurenzig, P R; Olmi, A; Botvina, A S
2009-01-01
Some characteristics of midvelocity emissions in semiperipheral heavy-ion collisions at Fermi energies are discussed in the framework of a multifragmenting scenario. We report on binary dissipative collisions of 93Nb + 93Nb at 38AMeV in which we measured an abundant emission of particles and fragments not originated from the usual evaporative decay of hot primary fragments. We checked the compatibility of these emissions with the multifragmentation of a source which forms in the overlap region. One can fairly well reproduce the data assuming a hot and dilute source, possibly more n-rich than the initial nuclei; the results appear to be insensitive to the source size.
Can quark effects be observed in intermediate heavy ion collisions?
da Silva, D. T.; Hadjimichef, D.
2003-01-01
In recent years a tentative description of the short-range part of hadron interactions with constituent quark interchange has been developed providing an alternative approach to meson physics. Quark interchange plays a role, for example, in the nucleon-nucleon ($NN$) phase-shifts and cross-section. In heavy ion collision simulations at intermediate energies one of the main features is the $NN$ cross-section in the collisional term, where in most cases it is an input adjusted to the free space...
Observing -violation in relativistic heavy-ion collisions
Indian Academy of Sciences (India)
Rajarshi Ray
2003-05-01
Under certain situations, partons formed in heavy-ion collision experiments may expand out forming a shell-like structure. The partons in the outer shell subsequently hadronize, leaving a bubble of pure deconﬁned vacuum for a ﬁrst-order quark–hadron phase transition. The bubble collapses and may eventually decay into particles which may thermalize to temperatures exceeding the electroweak transition temperature (∼ 100 GeV) at LHC. This will lead to the possibility of unsuppressed electroweak baryon number violating processes.
Is the Chiral Vortical Effect Vanishing in Heavy Ion Collisions?
Landsteiner, Karl; Pena-Benitez, Francisco
2013-01-01
We study the frequency dependence of all the chiral vortical and magnetic conductivities for a relativistic chiral gas of free fermions and for a strongly coupled CFT with holographic dual in four dimensions. Both systems present gauge and gravitational anomalies and we compute their contribution to the conductivities. The chiral vortical conductivities and the chiral magnetic conductivity in the energy current show an unexpected frequency dependence in the form of a delta centered at zero frequency. We argue that this makes the CVE practically unobservable in heavy ion collisions. In the appendix we discuss why the CME seems to vanish in the consistent current for a particular implementation of the axial chemical potential.
Dynamical description of heavy-ion collisions at Fermi energies
Directory of Open Access Journals (Sweden)
Napolitani P.
2016-01-01
Full Text Available Descriptions of heavy-ion collisions at Fermi energies require to take into account in-medium dissipation and phase-space fluctuations. The interplay of these correlations with the one-body collective behaviour determines the properties (kinematics and fragment production and the variety of mechanisms (from fusion to neck formation and multifragmentation of the exit channel. Starting from fundamental concepts tested on nuclear matter, we build up a microscopic description which addresses finite systems and applies to experimental observables.
Mass and charge distribution in heavy-ion collisions
International Nuclear Information System (INIS)
A statistical model based on the independent particle picture is used to calculate mass and charge distributions in deep inelastic heavy-ion collisions. Different assumptions on volume and charge equilibrations are compared with measured variances of charge distributions. One combination of assumptions is clearly favoured by experiment, and gives a reasonable description of the variance versus energy loss curves up to energy losses of about 200 MeV in the heavy systems Kr+Ho and Xe+Bi, and up to about 60 MeV for the light system Ar+Ca
Jet structure modifications in heavy-ion collisions with JEWEL
Elayavalli, Raghav Kunnawalkam
2016-01-01
Key features of jet-medium interactions in heavy-ion collisions are modifications to the jet structure. Recent results from experiments at the LHC and RHIC have motivated several theoretical calculations and monte carlo models towards predicting these observables simultaneously. In this report, the recoil picture in \\textsc{Jewel} is summarized and two independent procedures through which background subtraction can be performed in \\textsc{Jewel} are introduced. Information of the medium recoil in \\textsc{Jewel} significantly improves its description of several jet shape measurements.
Thermalization and isotropization in heavy-ion collisions
Indian Academy of Sciences (India)
Michael Strickland
2015-05-01
Our current understanding of the processes driving the thermalization and isotropization of the quark gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions (URHICs) is reviewed. Initially, the phenomenological evidence in favour of the creation of a thermal but momentum–space anisotropic QGP in URHICs is discussed. Further, the degree of isotropization using viscous (dissipative) hydrodynamics, weak-coupling approaches to QGP dynamics, and strong-coupling approaches to QGP dynamics are discussed. Finally, recent progress in the area of real-time non-Abelian gauge field simulations and non-Abelian Boltzmann–Vlasov-based hard-loop simulations are reported.
Angular correlations and fragmentation in intermediate energy heavy ion collisions
International Nuclear Information System (INIS)
Intermediate energy heavy-ion collisions have been studied from 35 A MeV up to 94 A MeV at various accelerators. Angular correlations between light particles and detection of projectile- and target-fragments have been used to investigate the reaction mechanisms in this transition region between low- and high energy. An excess of correlations is observed in the particle-particle elastic scattering plane. This excess increases with particle mass and can be understood in terms of momentum conservation. The fragmentation measurements gives an indication that both energy and momentum transfer to the spectator volumes does occur. (author)
Viscous potential flow analysis of peripheral heavy ion collisions
Wang, D J; Csernai, L P
2013-01-01
The conditions for the development of a Kelvin-Helmholtz Instability (KHI) for the Quark-gluon Plasma (QGP) flow in a peripheral heavy-ion collision is investigated. The projectile and target side particles are separated by an energetically motivated hypothetical surface, characterized with a phenomenological surface tension. In such a view, a classical potential flow approximation is considered and the onset of the KHI is studied. The growth rate of the instability is computed as function of phenomenological parameters characteristic for the QGP fluid: viscosity, surface tension and flow layer thickness.
Hydrodynamic analysis of heavy ion collisions at RHIC
Hirano, Tetsufumi
2008-01-01
Current status of dynamical modeling of relativistic heavy ion collisions and hydrodynamic description of the quark gluon plasma is reported. We find the hadronic rescattering effect plays an important role in interpretation of mass splitting pattern in the differential elliptic flow data observed at RHIC. To demonstrate this, we predict the elliptic flow parameter for phi mesons to directly observe the flow just after hadronisation. We also discuss recent applications of outputs from hydrodynamic calculations to J/psi suppression, thermal photon radiation and heavy quark diffusion.
Isotropization and hydrodynamization in weakly coupled heavy-ion collisions
Kurkela, Aleksi
2015-01-01
We numerically solve 2+1D effective kinetic theory of weak coupling QCD under longitudinal expansion relevant for early stages of heavy-ion collisions. We find agreement with viscous hydrodynamics and classical Yang-Mills simulations in the regimes where they are applicable. By choosing initial conditions that are motivated by color-glass-condensate framework we find that for Q=2GeV and $\\alpha_s$=0.3 the system is approximately described by viscous hydrodynamics well before $\\tau \\lesssim 1.0$ fm/c.
Correlation search for coherent pion emission in heavy ion collisions
Akkelin, S. V.; Lednicky, R.; Sinyukov, Yu. M.
2001-01-01
The methods allowing to extract the coherent component of pion emission conditioned by the formation of a quasi-classical pion source in heavy ion collisions are suggested. They exploit a nontrivial modification of the quantum statistical and final state interaction effects on the correlation functions of like and unlike pions in the presence of the coherent radiation. The extraction of the coherent pion spectrum from pi+pi-, pi+pi+ and pi-pi- correlation functions and single--pion spectra is...
Two models with rescattering for high energy heavy ion collisions
Bøggild, H.; Hansen, Ole; Humanic, T. J.
2006-12-01
The effects of hadronic rescattering in high energy relativistic Au+Au collisions are studied using two very different models to describe the early stages of the collision. One model is based on a hadronic thermal picture and the other on a superposition of parton-parton collisions. Operationally, the output hadrons from each of these models are used as input to a hadronic rescattering calculation. The results of the rescattering calculations from each model are then compared with rapidity and transverse momentum distributions from the BNL Relativistic Heavy Ion Collider BRAHMS experiment. In spite of the different points of view of the two models of the initial stage, after rescattering, the observed differences between the models are mostly “washed out” and both models give observables that agree roughly with each other and with experimental data.
Pseudorapidity correlations in heavy ion collisions from viscous fluid dynamics
Monnai, Akihiko
2015-01-01
We demonstrate by explicit calculations in 3+1 dimensional viscous relativistic fluid dynamics how two-particle pseudorapidity correlation functions in heavy ion collisions at the LHC and RHIC depend on the number of particle producing sources and the transport properties of the produced medium. In particular, we present results for the Legendre coefficients of the two-particle pseudorapidity correlation function in Pb+Pb collisions at 2760 GeV and Au+Au collisions at 200 GeV from viscous hydrodynamics with three dimensionally fluctuating initial conditions. Our results suggest that these coefficients provide important constraints on initial state fluctuations and the transport properties of the quark gluon plasma.
Pion and photon production in heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Gabor,D.
2008-03-16
Measurement of neutral pions and direct photons are closely connected experimentally, on the other hand they probe quite different aspects of relativistic heavy ion collisions. In this short review of the {pi}{sup 0} results from the PHENIX experiment at RHIC our focus is on the {phi}-integrated nuclear modification factor, its energy and system size dependence, and the impact of these results on parton energy loss models. We also discuss the current status of high p{sub T} and thermal direct photon measurements both in p+p and Au+Au collisions. Recognizing the advantages of measuring not only the 'signal', but also all the 'references' needed for proper interpretation in the same experiments (with same or similar systematics) we argue that RHIC should regularly include d+A and even d+d collisions into its system size and energy scan.
Production of spectator hypermatter in relativistic heavy-ion collisions
Botvina, A S; Steinheimer, J; Bleicher, M; Mishustin, I N
2011-01-01
We study the formation of large hyper-fragments in relativistic heavy-ion collisions within two transport models, DCM and UrQMD. Our goal is to explore a new mechanism for the formation of strange nuclear systems via capture of hyperons by relatively cold spectator matter produced in semi-peripheral collisions. We investigate basic characteristics of the produced hyper-spectators and evaluate the production probabilities of multi-strange systems. Advantages of the proposed mechanisms over an alternative coalescence mechanism are analysed. We also discuss how such systems can be detected taking into account the background of free hyperons. This investigation is important for the development of new experimental methods for producing hyper-nuclei in peripheral relativistic nucleus-nucleus collisions, which are now underway at GSI and are planned for the future FAIR and NICA facilities.
Longitudinal fluid dynamics for ultrarelativistic heavy-ion collisions
Satarov, L. M.; Mishustin, I. N.; Merdeev, A. V.; Stöcker, H.
2007-02-01
We developed a 1+1 dimensional hydrodynamical model for central heavy-ion collisions at ultrarelativistic energies. Deviations from Bjorken's scaling are taken into account by implementing finite-size profiles for the initial energy density. The calculated rapidity distributions of pions, kaons, and antiprotons in central Au+Au collisions at sNN=200 GeV are compared with experimental data of the BRAHMS Collaboration. The sensitivity of the results to the choice of the equation of state, the parameters of the initial state, and the freeze-out conditions were investigated. Experimental constraints on the total energy of produced particles were used to reduce the number of model parameters. The best fits of experimental data were obtained for soft equations of state and Gaussian-like initial profiles of the energy density. It was found that initial energy densities required for fitting the experimental data decrease with the increasing critical temperature of the phase transition.
Heavy ion collisions: Correlations and Fluctuations in particle production
Voloshin, S A
2005-01-01
Correlations and fluctuations (the latter are directly related to the 2-particle correlations) is one of the important directions in analysis of heavy ion collisions. At the current stage of RHIC exploration, when the details matter, basically any physics question is addressed with help of correlation techniques. In this talk I start with a general introduction to the correlation and fluctuation formalism and discuss weak and strong sides of different type of observables. In more detail, I discuss the two-particle $p_t$ correlations/$\\mpt$ fluctuations. In spite of not observing any dramatic changes in the event-by-event fluctuations with energy, which would indicate a possible phase transition, such correlations measurements remain an interesting and important subject, bringing valuable information. Lastly, I show how radial flow can generate characteristic azimuthal, transverse momentum and rapidity correlations, which could qualitatively explain many of recently observed phenomena in nuclear collisions.
Causal Viscous Hydrodynamics for Relativistic Heavy Ion Collisions
Song, Huichao
2009-01-01
The viscosity of the QGP is a presently hotly debated subject. Since its computation from first principles is difficult, it is desirable to try to extract it from experimental data. Viscous hydrodynamics provides a tool that can attack this problem and which may work in regions where ideal hydrodynamics begins to fail. This thesis focuses on viscous hydrodynamics for relativistic heavy ion collisions. We first review the 2nd order viscous equations obtained from different approaches, and then report on the work of the Ohio State University group on setting up the equations for causal viscous hydrodynamics in 2+1 dimensions and solving them numerically for central and noncentral Cu+Cu and Au+Au collisions at RHIC energies and above. We discuss shear and bulk viscous effects on the hydrodynamic evolution of entropy density, temperature, collective flow, and flow anisotropies, and on the hadron multiplicity, single particle spectra and elliptic flow. Viscous entropy production and its influence on the centrality...
Puzzling positron peaks in heavy-ion collisions
International Nuclear Information System (INIS)
Characteristic features of positron creation in collisions of very heavy ions are depicted. First continuum solutions of the two-centre Dirac equation are presented. Calculated e+-production probabilities are compared with experimental data. The observation of puzzling peak structures in positron spectra is illuminated. Their relationship with the spontaneous positron emission in overcritical fields and, especially, with the hypothesis of a ''new particle creation'' is investigated. The ability of δ-electrons and positrons to carry precise informations on the time-scale of nuclear reactions in deep-inelastic and intermediate-energy collisions is demonstrated. As an outlook we discuss positron production in crossed beams of bare uranium nuclei. (orig.)
Peculiarities of quasifission reactions in heavy ion collisions
Nasirov, Avazbek; Oh, Yongseok
2015-01-01
The probability of the formation and decay of a dinuclear system is investigated for a wide range of relative angular momentum values. The mass and angular distributions of the quasifission fragments are studied for understanding the reaction mechanisms of the heavy ion collision of $^{78}$Kr(10 $A$ MeV) + $^{40}$Ca within dinuclear system model. The quasifission products contribute to the mass-symmetric region of the mass distribution in collisions with the large orbital angular momentum. The analysis of the mass and angular distributions of the quasifission fragments shows the possibility of the $180^{\\circ}$ rotation of the system so that projectile-like products can be observed in the forward hemisphere with large cross sections, which can explain the phenomenon observed recently in the ISODEC experiment.
Anomalous transport model study of chiral magnetic effects in heavy ion collisions
Sun, Yifeng; Li, Feng
2016-01-01
Using an anomalous transport model for massless quarks, we study the effect of magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in non-central heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision, which subsequently leads to a splitting between the elliptic flows of quarks and antiquarks as expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the Relativistic Heavy Ion Collider (RHIC).
Dumitru, Adrian; Nara, Yasushi
2012-03-01
Multiplicity fluctuations at midrapidity in pp collisions at high energies are described by a negative binomial distribution and exhibit approximate Koba-Nielsen-Olesen (KNO) scaling. We find that these KNO fluctuations are important also for reproducing the multiplicity distribution in d+Au collisions observed at the Relativistic Heavy-Ion Collider (RHIC), adding to the Glauber fluctuations of the number of binary collisions or participants. We predict that the multiplicity distribution in p+Pb collisions at the Large Hadron Collider (LHC) also deviates little from the KNO scaling function. Finally, we analyze various moments of the eccentricity of the collision zone in A+A collisions at RHIC and LHC and find that particle production fluctuations increase fluctuation dominated moments such as the triangularity ɛ3 substantially.
Search for Nuclei in Heavy Ion Collisions at Ultrarelativistic Energies
2002-01-01
We would like to know if nuclei are still present after a collision of two heavy ions at ultrarelativistic energies. If one can detect some of them at large angle ($>$10-15|0) they very likely come from a multifragmentation of the excited target spectators. Such a multifragmentation in several nuclei has been in proton induced reactions at Fermilab and it was interpreted as a gas-liquid phase transition in nuclei matter near the critical point. With heavy ions the energy deposited in the target spectators will be much higher than in the case of protons and a different mechanism should be involved if nuclei are still observed. \\\\ \\\\ We propose to detect nuclei using 1-2 silicon telescopes and a 1-2mg/cm|2 Au target bombarded by an |1|6O or |3|2S beam at 226 GeV/u. The set-up will be installed in a small cube located just before the NA38 experiment and should not perturb it.\\\\ \\\\ Data from |1|6O incident on Au have been taken last year. The experiment is presently taking data with |3|2S ions.
Bremsstrahlung from Electrons and Positrons in Peripheral Relativistic Heavy Ion Collisions
Hencken, Kai; Trautmann, Dirk; Baur, Gerhard
1999-01-01
We study the spectrum of the bremsstrahlung photons coming from the electrons and positrons, which are produced in the strong electromagnetic fields present in peripheral relativistic heavy ion collisions. We compare different approaches, making use of the exact pair production cross section in heavy ion collisions as well as the double equivalent photon approximation.
Jet Physics in Heavy Ion Collisions with Compact Muon Solenoid detector at the LHC
Lokhtin, I P
2006-01-01
The status of CMS jet simulations and physics analysis in heavy ion collisions is presented. Jet reconstruction and high transverse momentum particle tracking in the high multiplicity environment of heavy ion collisions at the LHC using the CMS calorimetry and tracking system are described. The Monte Carlo tools used to simulate jet quenching are discussed.
Science and art in heavy-ion collisions
International Nuclear Information System (INIS)
One of the more intriguing phenomena discovered in heavy-ion physics is the seeming appearance of high energy structure in the excitation spectra of inelastically scattered heavy ions. For reasons illustrated, these may well be a phenomena unique to heavy ions and their explanation perhaps unique to TDHF
Search for QCD Hawking Radiation in Heavy Ion Collisions
Stiles, Laura; Murray, Michael
2008-04-01
A wide variety of measurements at RHIC, for example v2 and energy loss, suggest that the partonic matter created in heavy collisions thermalizes early. One possible mechanism for this is the creation of the QCD analogue to gravitational black holes [1]. Such objects have no memory of their creation and radiate with a characteristic temperature, T, that can depend only on their energy, charge, and angular momentum. This hypothesis is consistent with the growth of multiplicity with s in e+e- collisions and thermal temperature observed at LEP. For central heavy ion collisions the angular momentum of the system is approximately zero and the model predicts a universal dependence of the chemical freezeout temperature on the ratios of charge to transverse energy. To test this prediction against BRAHMS data, We have fitted data on π, K, p and p from central Au + Au collisions at several rapidities and energies, using the THERMUS code. The experimental dependence of the temperature on the ratio of charge to transverse energy will be compared to the Hawking radiation predictions. By comparing data sets at different energy, centrality and rapidity we can select systems with the same ratio of baryon number to energy but different rapidities. This may allow us to test for any effect of angular momentum on temperature. [1] P. Castorina, D. Kharzeev and H. Satz, Eur. Phys. J. C 52, 187 (2007)
The Freezeout Parameters in Heavy-Ion Collisions
Tawfik, A
2005-01-01
It is shown that the freezeout parameters estimated in heavy-ion collisions all have the common property that the entropy density $s$ normalized to $T^3$ is constant. The value of $s/T^3$ has been taken from lattice QCD simulations at zero baryo-chemical potential $\\mu_B$ and assumed to remain constant at finite $\\mu_B$ in a hadron resonance gas model. This implies that the hadronic matter in rest frame of produced system can be determined by constant degrees of freedom. The entropy content is reflected in the multiplicity of produced particles in final state. We made predictions for freezeout parameters at very low temperatures. Furthermore, we found that the strangeness degrees of freedom are very essential at low incident energies.
Fluctuations of Particle Yield Ratios in Heavy-Ion Collisions
Tawfik, A
2008-01-01
We study the dynamical fluctuations of various particle yield ratios at different incident energies. Assuming that the particle production yields in the hydronic final state are due to equilibrium chemical processes ($\\gamma=1$), the experimental results available so far are compared with the hadron resonance gas model (HRG) taking into account the limited momentum acceptance in heavy-ion collisions experiments. Degenerated light and conserved strange quarks are presumed at all incident energies. At the SPS energies, the HRG with $\\gamma=1$ provides a good description for the measured dynamical fluctuations in $(K^++K^-)/(\\pi^++\\pi^-)$. To reproduce the RHIC results, $\\gamma$ should be larger than one. We also studied the dynamical fluctuations of $(p+\\bar{p})/(\\pi^++\\pi^-)$. It is obvious that the energy-dependence of these dynamical fluctuations is non-monotonic.
Fractal clusters and intermittency in relativistic heavy ion collisions
Antoniou, Nikos G; Diakonos, F K
2000-01-01
We investigate the formation of particle clusters (pions) associated with the chiral QCD phase transition in thermodynamic equilibrium. The geometry of these clusters at the critical point (T=T/sub c/) turns out to be fractal reflecting the self similar structure of the density fluctuations of the produced pions. The fractal dimension of the "critical" clusters is related to the critical exponents characterizing the phase transition. We examine the possibility to observe such pion clusters in relativistic heavy ion collisions. A Monte Carlo simulation of the critical system in 3D is performed leading to a typical set of "critical" events. Factorial moment analysis of the rapidity and transverse momentum distribution for these events shows a characteristic intermittency pattern. Mini-jet like structures arise in a azimuth angle rapidity lego plot. These features allow for a unique identification of the class of "critical events" in an event by event analysis in current and future experiments with relativistic ...
Antihyperon-Production in Relativistic Heavy Ion Collision
Greiner, C; Greiner, Carsten; Leupold, Stefan
2001-01-01
Recently it has been shown that the observed antiproton yield in heavy-ion collisions at CERN-SpS energies can be understood by multi-pionic interactions which enforce local chemical equilibrium of the antiprotons with the nucleons and pions. Here we show that antihyperons are driven towards local chemical equilibrium with pions, nucleons and kaons on a timescale of less than 3 fm/c when applying a similar argument for the antihyperons by considering the inverse channel of annihilation reactions anti-Y + p to pions + kaons. These multi-mesonic reactions easily explain the antihyperon yields at CERN-SpS energies as advertised in pure thermal, hadronic models without the need of a quark gluon plasma phase. In addition, the argument also applies for AGS energies.
Error Estimation for Moments Analysis in Heavy Ion Collision Experiment
Luo, Xiaofeng
2011-01-01
Higher moments of conserved quantities are predicted to be sensitive to the correlation length and connected to the thermodynamic susceptibility. Thus, higher moments of net-baryon, net-charge and net-strangeness have been extensively studied theoretically and experimentally to explore phase structure and bulk properties of QCD matters created in heavy ion collision experiment. As the higher moments analysis is statistics hungry study, the error estimation is crucial to extract physics information from the limited experimental data. In this paper, we will derive the limit distributions and error formula based on Delta theorem in statistics for various order moments used in the experimental data analysis. The Monte Carlo simulation is also applied to test the error formula.
Heavy Ions Collision evolution modeling with ECHO-QGP
Rolando, Valentina; Beraudo, Andrea; Del Zanna, Luca; Becattini, Francesco; Chandra, Vinod; De Pace, Arturo; Nardi, Marzia
2014-01-01
We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in $(3+1)-$D, with dissipative terms included within the framework of Israel-Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper-Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel-Stewart case, up to very large times and without any ad hoc tuning of the algorithm.
Hidden beauty and charm of relativistic heavy ion collisions
International Nuclear Information System (INIS)
The goal of the SPS, RHIC, and LHC heavy-ion programs is to validate the existence and study the properties of the quark-gluon plasma (QGP), a phase of strongly - interacting matter at high energy density where quarks and gluons are no longer bound within hadrons. The quarkonia states (J/ψ and γ) have been among the most popular tools since their suppression was proposed as a signal of QGP formation. This is thought to be a direct effect of deconfinement, when the binding potential between the constituents of a quarkonium state, a heavy quark and its antiquark, is screened by the colour charges of the surrounding light quarks and gluons. This feebly bound quarkonia state then can be broken up by the gluon collisions
Medium effects on charged pion ratio in heavy ion collisions
International Nuclear Information System (INIS)
We have recently studied in the delta-resonance–nucleon-hole model the dependence of the pion spectral function in hot dense asymmetric nuclear matter on the charge of the pion due to the pion p-wave interaction in nuclear medium. In a thermal model, this isospin-dependent effect enhances the ratio of negatively charged to positively charged pions in neutron-rich nuclear matter, and the effect is comparable to that due to the uncertainties in the theoretically predicted stiffness of nuclear symmetry energy at high densities. This effect is, however, reversed if we also take into account the s-wave interaction of the pion in nuclear medium as given by chiral perturbation theory, resulting instead in a slightly reduced ratio of negatively charged to positively charged pions. Relevance of our results to the determination of the nuclear symmetry energy from the ratio of negatively to positively charged pions produced in heavy ion collisions is discussed. (author)
Effect of correlation on cumulants in heavy-ion collisions
Mishra, D K; Netrakanti, P K
2015-01-01
We study the effects of correlation on cumulants and their ratios of net-proton multiplicity distribution which have been measured for central (0-5\\%) Au+Au collisions at Relativistic Heavy Ion Collider (RHIC). This effect has been studied assuming individual proton and anti-proton distributions as Poisson or Negative Binomial Distribution (NBD). In-spite of significantly correlated production due to baryon number, electric charge conservation and kinematical correlations of protons and anti-protons, the measured cumulants of net-proton distribution follow the independent production model. In the present work we demonstrate how the introduction of correlations will affect the cumulants and their ratios for the difference distributions. We have also demonstrated this study using the proton and anti-proton distributions obtained from HIJING event generator.
Fluctuating Glasma Initial Conditions and Flow in Heavy Ion Collisions
Schenke, Björn; Tribedy, Prithwish; Venugopalan, Raju
2012-06-01
We compute initial conditions in heavy ion collisions within the color glass condensate framework by combining the impact parameter dependent saturation model with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this impact parameter dependent Glasma description includes quantum fluctuations of color charges on the length scale determined by the inverse nuclear saturation scale Qs. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity ɛ3/ɛ2 is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and v2,3,4(pT) of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution.
Effect of correlations on cumulants in heavy-ion collisions
Mishra, D. K.; Garg, P.; Netrakanti, P. K.
2016-02-01
We study the effects of correlations on cumulants and their ratios of net-proton multiplicity distributions which have been measured for central (0%-5%) Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). This effect has been studied by assuming individual proton and antiproton distributions as a Poisson or negative binomial distribution (NBD). In spite of significantly correlated production due to baryon number, electric charge conservation, and kinematical correlations of protons and antiprotons, the measured cumulants of the net-proton distribution follow the independent-production model. In the present work we demonstrate how the introduction of the correlations will affect the cumulants and their ratios for the difference distributions. We have also demonstrated this study using the proton and antiproton distributions obtained from the hijing event generator.
Modelling early stages of relativistic heavy-ion collisions
Directory of Open Access Journals (Sweden)
Ruggieri M.
2016-01-01
Full Text Available In this study we model early time dynamics of relativistic heavy ion collisions by an initial color-electric field which then decays to a plasma by the Schwinger mechanism. The dynamics of the many particles system produced by the decay is described by relativistic kinetic theory, taking into account the backreaction on the color field by solving self-consistently the kinetic and the field equations. Our main results concern isotropization and thermalization for a 1+1D expanding geometry. In case of small η/s (η/s ≲ 0.3 we find τisotropization ≈ 0.8 fm/c and τthermalization ≈ 1 fm/c in agreement with the common lore of hydrodynamics.
Fluctuating Glasma initial conditions and flow in heavy ion collisions
Schenke, Bjoern; Venugopalan, Raju
2012-01-01
We compute initial conditions in heavy-ion collisions within the Color Glass Condensate (CGC) framework by combining the impact parameter dependent saturation model (IP-Sat) with the classical Yang-Mills description of initial Glasma fields. In addition to fluctuations of nucleon positions, this IP-Glasma description includes quantum fluctuations of color charges on the length-scale determined by the inverse nuclear saturation scale Q_s. The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity is close to that in a model tuned to reproduce experimental flow data. We compare transverse momentum spectra and v_(2,3,4)(p_T) of pions from different models of initial conditions using relativistic viscous hydrodynamic evolution.
Equilibration of matter in relativistic heavy-ion collisions
International Nuclear Information System (INIS)
The chemical and thermal equilibration in the central zone of heavy-ion collisions at energies from AGS to SPS is studied within the microscopic transport model. Yields and energy spectra obtained for the central cell in the reaction are compared to the predictions of the thermal statistical model. It is found that kinetic, thermal, and chemical equilibration of the expanding hadronic matter are nearly approached for the period of 10-18 fm/c. Within this time the matter in the cell expands almost isentropically. For the bombarding energies around 40 AGeV the system crosses the critical point in the T - μB plane predicted by lattice QCD calculations. The net strangeness in the central cell is negative (though small). The characteristic kink in the T - μB diagrams corresponding to beginning of the equilibrated phase is observed for all energies. The origin of this phenomenon deserves further investigation. (author)
Production of photons in relativistic heavy-ion collisions
Paquet, Jean-François; Shen, Chun; Denicol, Gabriel S.; Luzum, Matthew; Schenke, Björn; Jeon, Sangyong; Gale, Charles
2016-04-01
In this work it is shown that the use of a hydrodynamical model of heavy-ion collisions which incorporates recent developments, together with updated photon emission rates, greatly improves agreement with both ALICE and PHENIX measurements of direct photons, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy. The event-by-event hydrodynamical model uses the impact parameter dependent Glasma model (IP-Glasma) initial states and includes, for the first time, both shear and bulk viscosities, along with second-order couplings between the two viscosities. The effect of both shear and bulk viscosities on the photon rates is studied, and those transport coefficients are shown to have measurable consequences on the photon momentum anisotropy.
The production of photons in relativistic heavy-ion collisions
Paquet, Jean-François; Denicol, Gabriel S; Luzum, Matthew; Schenke, Björn; Jeon, Sangyong; Gale, Charles
2015-01-01
In this work it is shown that the use of a hydrodynamical model of heavy ion collisions which incorporates recent developments, together with updated photon emission rates greatly improves agreement with both ALICE and PHENIX measurements of direct photons, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy. The event-by-event hydrodynamical model uses IP-Glasma initial states and includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. The effect of both shear and bulk viscosities on the photon rates is studied, and those transport coefficients are shown to have measurable consequences on the photon momentum anisotropy.
Heavy ion collision evolution modeling with ECHO-QGP
Rolando, V.; Inghirami, G.; Beraudo, A.; Del Zanna, L.; Becattini, F.; Chandra, V.; De Pace, A.; Nardi, M.
2014-11-01
We present a numerical code modeling the evolution of the medium formed in relativistic heavy ion collisions, ECHO-QGP. The code solves relativistic hydrodynamics in (3 + 1)D, with dissipative terms included within the framework of Israel-Stewart theory; it can work both in Minkowskian and in Bjorken coordinates. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation are based on the Cooper-Frye prescription. The code is validated against several test problems and shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach and the high-order methods employed. In particular it beautifully agrees with the semi-analytic solution known as Gubser flow, both in the ideal and in the viscous Israel-Stewart case, up to very large times and without any ad hoc tuning of the algorithm.
A Simple Model of Wings in Heavy-Ion Collisions
Parikh, Aditya
2015-01-01
We create a simple model of heavy ion collisions independent of any generators as a way of investigating a possible source of the wings seen in data. As a first test, we reproduce a standard correlations plot to verify the integrity of the model. We then proceed to test whether an η dependent v2 could be a source of the wings and take projections along multiple Δφ intervals and compare with data. Other variations of the model are tested by having dN/dφ and v2 depend on η as well as including pions and protons into the model to make it more realistic. Comparisons with data seem to indicate that an η dependent v2 is not the main source of the wings.
Lambda-Lambda interaction from relativistic heavy-ion collisions
Morita, Kenji; Ohnishi, Akira
2014-01-01
We investigate the two-particle intensity correlation function of $\\Lambda$ in relativistic heavy-ion collisions. We find that the behavior of the $\\Lambda\\Lambda$ correlation function at small relative momenta is fairly sensitive to the interaction potential and collective flows. By comparing the results of different source functions and potentials, we explore the effect of intrinsic collective motions on the correlation function. We find that the recent STAR data gives a strong constraint on the scattering length and effective range of $\\Lambda\\Lambda$ interaction as, $-1.8~\\mathrm{fm}^{-1} < 1/a_0 < -0.8~\\mathrm{fm}^{-1}$ and $3.5~\\mathrm{fm} < r_\\mathrm{eff} < 7~\\mathrm{fm}$, respectively. Implication for the signal of existence of $H$-dibaryon is discussed. Comparison with the scattering parameters obtained from the double $\\Lambda$ hypernucleus may reveal in-medium effects in the $\\Lambda\\Lambda$ interaction.
Theory of multiphonon excitation in heavy-ion collisions
Bertulani, C A; Hussein, M S
1995-01-01
We study the effects of channel coupling in the excitation dynamics of giant resonances in relativistic heavy ions collisions. For this purpose, we use a semiclassical approximation to the Coupled-Channels problem and separate the Coulomb and the nuclear parts of the coupling into their main multipole components. In order to assess the importance of multi-step processes, we neglect the resonance widths and solve the set of coupled equations exactly. Finite widths are then considered. In this case, we handle the coupling of the ground state with the dominant Giant Dipole Resonance exactly and study the excitation of the remaining resonances within the Coupled-Channels Born Approximation. A comparison with recent experimental data is made.
A Cone Jet-Finding Algorithm for Heavy-Ion Collisions at LHC Energies
Blyth, S.-L.; Horner, M. J.; Awes, T.; Cormier, T; Gray, H; J.L. Klay; Klein, S. R.; van Leeuwen, M.; Morsch, A.(European Organization for Nuclear Research (CERN), Geneva, Switzerland); G. Odyniec; Pavlinov, A.
2008-01-01
Standard jet finding techniques used in elementary particle collisions have not been successful in the high track density of heavy-ion collisions. This paper describes a modified cone-type jet finding algorithm developed for the complex environment of heavy-ion collisions. The primary modification to the algorithm is the evaluation and subtraction of the large background energy, arising from uncorrelated soft hadrons, in each collision. A detailed analysis of the background energy and its eve...
Freeze-out dynamics in heavy-ion collisions: Recent advances
Indian Academy of Sciences (India)
Francesco Becattini
2015-05-01
We briefly review recent advances in the subject of hadron production in relativistic heavy-ion collisions. We focus on the issues of chemical freeze-out, chemical equilibration and the role of post-hadronization inelastic collisions. From the observations collected in elementary and heavy-ion collisions, a picture emerges in which hadrons are born in chemical equilibrium at hadronization, thereafter undergoing inelastic and elastic collisions whose impact on the primordial distribution depends on the system size.
Quantifying the sQGP - Heavy Ion Collisions at RHIC
Energy Technology Data Exchange (ETDEWEB)
Seto, Richard [Univ. of California, Riverside, CA (United States)
2014-12-01
This is the closeout for DE-FG02-86ER40271 entitled Quantifying the sQGP - Heavy Ion Collisions at the RHIC. Two major things were accomplished. The first, is the physics planning, design, approval, construction, and commissioning of the MPC-EX. The MPC-EX is an electromagnetic calorimeter covering a rapidity of 3<|eta|<4, which was added to the PHENIX detector. Its primary aim is to measure low-x gluons, in order to understand the suppression seen in a variety of signatures, such as the J/Psi. A candidate to explain this phenomena is the Color Glass Condensate (CGC) A second task was to look at collisions of asymmetric species, in particularly Cu+Au. The signature was the suppression of J/Psi mesons at forward and backward rapidity, where a stronger suppression was seen in the copper going direction. While the blue of the suppression is due to hot nuclear matter effects (e.g. screening) the increase in suppression on the Au side was consistent with cold nuclear matter effects seen in d+Au collisions. A major candidate for the explanation of this phenomena is the aforementioned CGC. Finally the work on sPHENIX, particularly an extension to the forward region, called fsPHENIX is described.
Indian Academy of Sciences (India)
Subrata Pal
2015-05-01
We review the transport models that are widely used to study the properties of the quark-gluon plasma formed in relativistic heavy-ion collisions at RHIC and LHC. We show that transport model analysis of two important and complementary observables, the anisotropic flow of bulk hadrons and suppression of hadron yields at high transverse momentum, provide exciting new information on the properties of the plasma formed.
Effects of Longitudinal Fluctuations in Heavy-Ion Collisions
Raniwala, Rashmi; Loizides, Constantin
2016-01-01
In collisions of identical nuclei at a given impact parameter, the number of nucleons participating in the overlap region of each nucleus can be unequal due to nuclear density fluctuations. The asymmetry due to the unequal number of participating nucleons, which may be experimentally accessible by measuring either the energy in ZDC or the number of spectator nucleons, causes a shift of the center of mass rapidity of the participant zone. In a Monte Carlo Glauber model the average rapidity-shift is found to be almost linearly related to the asymmetry. Using Monte Carlo data for Pb-Pb collisions at 2.76 TeV generated with the HIJING model, we demonstrate that the rapidity distribution of produced particles is affected by the asymmetry, and that the effect can be quantitatively related to the average rapidity-shift via a third-order polynomial with a dominantly linear term. Experimental estimates of the spectator asymmetry may be used to further constrain the initial conditions in ultra-relativistic heavy ion co...
Atomic excitations in heavy ion collisions with nuclear contact
International Nuclear Information System (INIS)
The dynamical semiclassical theory of atomic excitations, especially of positron creation, in heavy ion scattering is presented and extended to collisions with nuclear contact. The characteristic dependence of inner shell vacancy formation on nuclear reaction times as well as the emergence of interference patterns in the energy spectra of emitted delta-electrons and positrons in delayed collisions is discussed in terms of a simplified, schematic model for the nuclear reaction dynamics. In addition, the spontaneous decay mechanism in giant nuclear systems with Z> or approx.173 leads, for sufficiently long reaction times, to a characteristic line in the positron spectra at the position of the 1ssigma-resonance. The position and width of the positron line is calculated in dependence on the nuclear configuration taking into account the influence of the electron-electron interaction. Furthermore, a quantum mechanical extension of our semiclassical treatment of the atomic scattering process and its effect on atomic positron spectra are discussed. In addition, the influence of E0-transitions in the giant nuclear system on positron emission is treated qualitatively in a semiclassical approximation, indicating that nuclear collective modes can be revealed by the measurement of Stokes and anti-Stokes lines in the positron spectra. (orig./HSI)
$K^{*}$ vector meson resonances dynamics in heavy-ion collisions
Ilner, Andrej; Markert, Christina; Bratkovskaya, Elena
2016-01-01
We study the strange vector meson ($K^*, \\bar K^*$) dynamics in relativistic heavy-ion collisions based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which incorporates partonic and hadronic degrees-of-freedom, a phase transition from hadronic to partonic matter - Quark-Gluon-Plasma (QGP) - and a dynamical hadronization of quarks and antiquarks as well as final hadronic interactions. We investigate the role of in-medium effects on the $K^*, \\bar K^*$ meson dynamics by employing Breit-Wigner spectral functions for the $K^*$'s with self-energies obtained from a self-consistent coupled-channel G-matrix approach. Furthermore, we confront the PHSD calculations with experimental data for p+p, Cu+Cu and Au+Au collisions at energies up to $\\sqrt{{s}_{NN}} = 200$~GeV. Our analysis shows that at relativistic energies most of the final $K^*$s (observed experimentally) are produced during the late hadronic phase, dominantly by the $K+ \\pi \\to K^*$ channel, such that the fraction of the $K^*$s...
Photon and dilepton production in high-energy heavy-ion collisions
Indian Academy of Sciences (India)
Takao Sakaguchi
2015-05-01
The recent results on direct photons and dileptons in high-energy heavy-ion collisions, obtained particularly at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) are reviewed. The results are new not only in terms of the probes, but also in terms of the precision. We shall discuss the physics learned from the results.
An integrated Boltzmann+hydrodynamics approach to heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Petersen, Hannah
2009-04-22
In this thesis the first fully integrated Boltzmann+hydrodynamics approach to relativistic heavy ion reactions has been developed. After a short introduction that motivates the study of heavy ion reactions as the tool to get insights about the QCD phase diagram, the most important theoretical approaches to describe the system are reviewed. The hadron-string transport approach that this work is based on is the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) approach. Predictions for the charged particle multiplicities at LHC energies are made. The next step is the development of a new framework to calculate the baryon number density in a transport approach. Time evolutions of the net baryon number and the quark density have been calculated at AGS, SPS and RHIC energies. Studies of phase diagram trajectories using hydrodynamics are performed. The hybrid approach that has been developed as the main part of this thesis is based on the UrQMD transport approach with an intermediate hydrodynamical evolution for the hot and dense stage of the collision. The full (3+1) dimensional ideal relativistic one fluid dynamics evolution is solved using the SHASTA algorithm. Three different equations of state have been used, namely a hadron gas equation of state without a QGP phase transition, a chiral EoS and a bag model EoS including a strong first order phase transition. For the freeze-out transition from hydrodynamics to the cascade calculation two different set-ups are employed. The parameter dependences of the model are investigated and the time evolution of different quantities is explored. The hybrid model calculation is able to reproduce the experimentally measured integrated as well as transverse momentum dependent v{sub 2} values for charged particles. The multiplicity and mean transverse mass excitation function is calculated for pions, protons and kaons in the energy range from E{sub lab}=2-160 A GeV. The HBT correlation of the negatively charged pion source
Extracting the symmetry energy information with heavy ion collisions
International Nuclear Information System (INIS)
Nuclear symmetry energy plays an important role in the properties of nuclei and neutron stars. Since theoretical predictions of the density dependence of symmetry energy S(ρ) from microscopic nucleon-nucleon interactions show large uncertainties, especially in the region of suprasaturation density, constraining the density dependence of symmetry energy has become one of the main goals in nuclear physics and has stimulated many theoretical and experimental studies. In this paper, we have reviewed the ImQMD05 code and its description on charge distribution, collective flow and nuclear-nuclear stopping. By comparing ImQMD05 prediction with data, the isoscalar part of nucleonic mean field, the energy and density dependence of in-medium NN cross sectoin in the ImQMD05 were determined. In order to extracting the symmetry energy information by comparing the ImQMD05 calculations with the data for 112,124Sn +112,124 Sn at Ebeam=50 MeV/u, the influence of symmetry potential and in-medium NN cross section on the isospin sensitive observables of intermediate-energy heavy-ion collisions was investigated. Focusing on the region above the Fermi energy, our results show that the symmetry potential plays a more important role in the experimental observables, such as double neutron to proton ratio and the isospin transport ratio Ri, than that the in-medium nucleon-nucleon cross section does. Since the copious production of intermediate mass fragments is a distinguishing feature of intermediate-energy heavy-ion collisions, we also examined the influence of cluster emission on the isospin transport ratio using different isospin tracers. The values of the isospin transport ratios with the tracer defined by the isospin asymmetry of the heaviest fragments with Z≥20 in the projectile region is greater than those obtained from projectile residues (emitting source). This phenomenon can be tested experimentally. By comparing the ImQMD05 predictions with the data for three observables, the
Electromagnetic fields and anomalous transports in heavy-ion collisions --- A pedagogical review
Huang, Xu-Guang
2015-01-01
The hot and dense matter generated in heavy-ion collisions may contain domains in which the P and CP symmetries of QCD are violated. Moreover, heavy-ion collisions can generate extremely strong magnetic fields as well as electric fields. The interplay among the electromagnetic field, triangle anomaly, and the P and CP violation of QCD leads to a number of macroscopic quantum phenomena known as the anomalous transports. The purpose of the article is to give a pedagogical review of various properties of the electromagnetic fields, the anomalous transports phenomena, and their experimental signatures in heavy-ion collisions.
Bottomonium production with statistical hadronization in heavy-ion collisions at collider energies
Byungsik, Hong
2004-01-01
We present the bottomonium production estimated by using the hybrid model that combines direct bb pair creation in hard scattering and a statistical hadronization of the deconfined quark-gluon plasma. Complete color screening and full equilibration of the deconfined quark matter is assumed in the quark-gluon plasma phase. An enhanced production of the Upsilon (1S) state is predicted at collider energies. However, a significant, difference between the RHIC (Relativistic Heavy Ion Collider) and the LHC (Large Hadron Collider) is expected in the centrality dependence of the Upsilon (1S) production. Normalizing the Upsilon (1S) production by the average number of binary collisions, we expect about a factor of five decrease from half-overlap to central collisions at the RHIC, but almost no change at the LHC. Plans for measuring the bottomonium production cross-sections in future collider experiments are summarized. (28 refs).
Formation of hypernuclei in heavy-ion collisions around the threshold energies
Botvina, A S; Steinheimer, J; Bleicher, M; Pochodzalla, J
2016-01-01
In relativistic ion collisions there are excellent opportunities to produce and investigate hyper-nuclei. We have systematically studied the formation of hypernuclear spectator residues in peripheral heavy-ion collisions with the transport DCM and UrQMD models. The hyperon capture was calculated within the potential and coalescence approaches. We demonstrate that even at the beam energies around and lower than the threshold for producing Lambda hyperons in binary nucleon-nucleon interactions a considerable amount of hypernuclei, including multi-strange ones, can be produced. This is important for preparation of new experiments on hypernuclei in the wide energy range. The uncertainties of the predictions are investigated within the models, and the comparison with the strangeness production measured in experiments is also performed.
The study of hadron dynamics in relativistic heavy ion collisions
International Nuclear Information System (INIS)
In this thesis, pion emission patterns were studied in two reaction systems Ar + Ca and Au + Au at 1 GeV/u, with the aim to improve the understanding of the pion production in relativistic heavy ion collisions. The study of the high energy tail of the π0-momentum spectrum was regarded as promising because of its sensitivity to compression since it did not appear in small reaction systems. Experiments were performed with TAPS together with the Forward Wall of the FoPi-collaboration at GSI. The combined measurement of charged particle multiplicities in the Forward Wall and the particles entering TAPS enabled an exclusive study of the pion production. TAPS was tested in separate experiments and its capabilities were demonstrated by measuring different reaction products, like photons, charged particles and neutrons. The data analysis involved new methods to treat the background contamination below the invariant mass peak of the π0-meson due to the geometry of the detector and to perform particle identification in a high particle multiplicity environment. (orig.)
Thermal Electromagnetic Radiation in Heavy-Ion Collisions
Rapp, R
2016-01-01
We review the potential of precise measurements of electromagnetic probes in relativistic heavy-ion collisions for the theoretical understanding of strongly interacting matter. The penetrating nature of photons and dileptons implies that they can carry undistorted information about the hot and dense regions of the fireballs formed in these reactions and thus provide a unique opportunity to measure the electromagnetic spectral function of QCD matter as a function of both invariant mass and momentum. In particular we report on recent progress on how the medium modifications of the (dominant) isovector part of the vector current correlator ($\\rho$ channel) can shed light on the mechanism of chiral symmetry restoration in the hot and/or dense environment. In addition, thermal dilepton radiation enables novel access to (a) the fireball lifetime through the dilepton yield in the low invariant-mass window $0.3 \\; \\mathrm{GeV} \\leq M \\leq 0.7 \\; \\mathrm{GeV}$, and (b) the early temperatures of the fireball through th...
Thermal electromagnetic radiation in heavy-ion collisions
Rapp, R.; van Hees, H.
2016-08-01
We review the potential of precise measurements of electromagnetic probes in relativistic heavy-ion collisions for the theoretical understanding of strongly interacting matter. The penetrating nature of photons and dileptons implies that they can carry undistorted information about the hot and dense regions of the fireballs formed in these reactions and thus provide a unique opportunity to measure the electromagnetic spectral function of QCD matter as a function of both invariant mass and momentum. In particular we report on recent progress on how the medium modifications of the (dominant) isovector part of the vector current correlator ( ρ channel) can shed light on the mechanism of chiral symmetry restoration in the hot and/or dense environment. In addition, thermal dilepton radiation enables novel access to a) the fireball lifetime through the dilepton yield in the low invariant-mass window 0.3 GeV ≤ M ≤ 0.7 GeV, and b) the early temperatures of the fireball through the slope of the invariant-mass spectrum in the intermediate-mass region (1.5 GeV < M < 2.5 GeV). The investigation of the pertinent excitation function suggests that the beam energies provided by the NICA and FAIR projects are in a promising range for a potential discovery of the onset of a first-order phase transition, as signaled by a non-monotonous behavior of both low-mass yields and temperature slopes.
Effect of entrance channel on dynamics of heavy ions collision
Naderi, D.
2016-01-01
A combined dynamical model using concept of dinuclear systems (DNS) and one-dimensional (1D) Langevin equations was applied to investigate the effect of entrance channel on dynamics of heavy ions collision. The 30Si+170Er, 16O+184W and 19F+181Ta reactions which formed the compound nucleus 200Pb have been considered to study this effect. We studied these reactions dynamically and calculated the ratio of evaporation residue cross-section to fusion cross-section (σER/σFus) as a tool for investigation of entrance channel effect. Results of combined model are compared with available experimental data and results of 1D Langevin equations. Obtained results based on combined model are in better agreement with experimental data in comparison with results of Langevin equations. We concluded for 30Si+170Er and 19F+181Ta reactions the results of combined model that support the quasi-fission process are different relative to Langevin dynamical approach, whereas for 16O+184W system the two models give similar results.
Two-pion correlations in heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Zajc, W.A.
1982-08-01
An application of intensity interferometry to relativistic heavy ion collisions is reported. Specifically, the correlation between two like-charged pions is used to study the reactions Ar+KCl..-->..2..pi../sup +-/+X and Ne+NaF..-->..2..pi../sup -/+X. Source sizes are obtained that are consistent with a simple geometric interpretation. Lifetimes are less well determined but are indicative of a faster pion production process than predicted by Monte Carlo cascade calculations. There appears to be a substantial coherent component of the pion source, although measurement is complicated by the presence of final state interactions. Additionally, the generation of spectra of uncorrelated events is discussed. In particular, the influence of the correlation function on the background spectrum is analyzed, and a prescription for removal of this influence is given. A formulation to describe the statistical errors in the background is also presented. Finally, drawing from the available literature, a self-contained introduction to Bose-Einstein correlations and the Hanbury-Brown - Twiss effect is provided, with an emphasis on points of contact between classical and quantum mechanical descriptions.
On the Spiral Structures in Heavy-Ion Collisions
Rustamov, A
2016-01-01
It is well established that many galaxies, like our Milky Way, exhibit spiral patterns. The entire galactic disc rotates about the galactic centre with different speed; higher closer to the centre, lower at greater distances - that is, galactic discs do not rotate like a solid compact disc. The spiral arms are the part of the galactic disc where many young stars are being born. Since young stars are also brightest, we can see the spiral structure of other galaxies from afar. Typically spiral galaxies are copiously observed at redshifts z ~ 1. The recently observed grand-design galaxy Q2343-BX442 at z=2.18, however, implies uncertain origin of its spiral structure. Indeed such "old" galaxies usually look rather clumpy because of their dynamically hot discs. In this report, based on self-similarity, we argue that spiral structures may also appear in heavy-ion collisions as messengers of phase transitions. Thus spiral structures in galactic patters may be traced back to a few microseconds after the Big Bang.
Two-pion correlations in heavy ion collisions
International Nuclear Information System (INIS)
An application of intensity interferometry to relativistic heavy ion collisions is reported. Specifically, the correlation between two like-charged pions is used to study the reactions Ar+KCl→2π/sup +-/+X and Ne+NaF→2π-+X. Source sizes are obtained that are consistent with a simple geometric interpretation. Lifetimes are less well determined but are indicative of a faster pion production process than predicted by Monte Carlo cascade calculations. There appears to be a substantial coherent component of the pion source, although measurement is complicated by the presence of final state interactions. Additionally, the generation of spectra of uncorrelated events is discussed. In particular, the influence of the correlation function on the background spectrum is analyzed, and a prescription for removal of this influence is given. A formulation to describe the statistical errors in the background is also presented. Finally, drawing from the available literature, a self-contained introduction to Bose-Einstein correlations and the Hanbury-Brown - Twiss effect is provided, with an emphasis on points of contact between classical and quantum mechanical descriptions
A semi-holographic model for heavy-ion collisions
Iancu, Edmond
2014-01-01
We develop a semi-holographic model for the out-of-equilibrium dynamics during the partonic stages of an ultrarelativistic heavy-ion collision. The model combines a weakly-coupled hard sector, involving gluon modes with energy and momenta of the order of the saturation momentum and relatively large occupation numbers, with a strongly-coupled soft sector, which physically represents the soft gluons radiated by the hard partons. The hard sector is described by perturbative QCD, more precisely, by its semi-classical approximation (the classical Yang-Mills equations) which becomes appropriate when the occupation numbers are large. The soft sector is described by a marginally deformed conformal field theory, which in turn admits a holographic description in terms of classical Einstein's equations in $AdS_5$ with a minimally coupled massless `dilaton'. The model involve two free parameters which characterize the gauge-invariant couplings between the hard and soft sectors. Via these couplings, the hard modes provide...
INFN what next ultra-relativistic heavy-ion collisions
Dainese, A.; Usai, G.; Antonioli, P.; Arnaldi, R.; Beraudo, A.; Bruna, E.; Bruno, G.E.; Bufalino, S.; Di Nezza, P.; Lombardo, M.P.; Nania, R.; Noferini, F.; Oppedisano, C.; Piano, S.; Prino, F.; Rossi, A.; Agnello, M.; Alberico, W.M.; Alessandro, B.; Alici, A.; Andronico, G.; Antinori, F.; Arcelli, S.; Badala, A.; Barbano, A.M.; Barbera, R.; Barile, F.; Basile, M.; Becattini, F.; Bedda, C.; Bellini, F.; Beole, S.; Bianchi, L.; Bianchin, C.; Bonati, C.; Bossu, F.; Botta, E.; Caffarri, D.; Camerini, P.; Carnesecchi, F.; Casula, E.; Cerello, P.; Cicalo, C.; Cifarelli, M.L.; Cindolo, F.; Colamaria, F.; Colella, D.; Colocci, M.; Corrales Morales, Y.; Cortese, P.; De Caro, A.; De Cataldo, G.; De Falco, A.; De Gruttola, D.; D'Elia, M.; De Marco, N.; De Pasquale, S.; Di Bari, D.; Elia, D.; Fantoni, A.; Feliciello, A.; Ferretti, A.; Festanti, A.; Fionda, F.; Fiorenza, G.; Fragiacomo, E.; Fronze, G.G.; Girard, M. Fusco; Gagliardi, M.; Gallio, M.; Garg, K.; Giubellino, P.; Greco, V.; Grossi, E.; Guerzoni, B.; Hatzifotiadou, D.; Incani, E.; Innocenti, G.M.; Jacazio, N.; Das, S. Kumar; La Rocca, P.; Lea, R.; Leardini, L.; Leoncino, M.; Lunardon, M.; Luparello, G.; Mantovani Sarti, V.; Manzari, V.; Marchisone, M.; Margagliotti, G.V.; Masera, M.; Masoni, A.; Mastroserio, A.; Mazzilli, M.; Mazzoni, M.A.; Meninno, E.; Mesiti, M.; Milano, L.; Moretto, S.; Muccifora, V.; Nappi, E.; Nardi, M.; Nicassio, M.; Pagano, P.; Pappalardo, G.S.; Pastore, C.; Paul, B.; Petta, C.; Pinazza, O.; Plumari, S.; Preghenella, R.; Puccio, M.; Puddu, G.; Ramello, L.; Ratti, C.; Ravasenga, I.; Riggi, F.; Ronchetti, F.; Rucci, A.; Ruggieri, M.; Rui, R.; Sakai, S.; Scapparone, E.; Scardina, F.; Scarlassara, F.; Scioli, G.; Siddhanta, S.; Sitta, M.; Soramel, F.; Suljic, M.; Terrevoli, C.; Trogolo, S.; Trombetta, G.; Turrisi, R.; Vercellin, E.; Vino, G.; Virgili, T.; Volpe, G.; Williams, M.C.S.; Zampolli, C.
2016-01-01
This document was prepared by the community that is active in Italy, within INFN (Istituto Nazionale di Fisica Nucleare), in the field of ultra-relativistic heavy-ion collisions. The experimental study of the phase diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP) deconfined state will proceed, in the next 10-15 years, along two directions: the high-energy regime at RHIC and at the LHC, and the low-energy regime at FAIR, NICA, SPS and RHIC. The Italian community is strongly involved in the present and future programme of the ALICE experiment, the upgrade of which will open, in the 2020s, a new phase of high-precision characterisation of the QGP properties at the LHC. As a complement of this main activity, there is a growing interest in a possible future experiment at the SPS, which would target the search for the onset of deconfinement using dimuon measurements. On a longer timescale, the community looks with interest at the ongoing studies and discussions on a possible fixed-target p...
Towards relativistic heavy ion collisions by small steps towards the stars
International Nuclear Information System (INIS)
A review lecture is given on current attempts to search for the exotic processes occurring in relativistic heavy ion collisions. From peripheral collisions the discussion proceeds to central collisions and lastly the search for the exotic, in which the tools developed for the study of peripheral and central collisions are used. 200 references
Towards relativistic heavy ion collisions by small steps towards the stars. [Review
Energy Technology Data Exchange (ETDEWEB)
Scott, D.K.
1979-03-01
A review lecture is given on current attempts to search for the exotic processes occurring in relativistic heavy ion collisions. From peripheral collisions the discussion proceeds to central collisions and lastly the search for the exotic, in which the tools developed for the study of peripheral and central collisions are used. 200 references. (JFP)
Shi, Shusu
2016-01-01
Strange hadrons, especially multi-strange hadrons are good probes for the early partonic stage of heavy ion collisions due to their small hadronic cross sections. In this paper, I give a brief review on the elliptic flow measurements of strange and multi-strange hadrons in relativistic heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC).
On the quantum mechanics of deep inelastic collisions between heavy ions
International Nuclear Information System (INIS)
An overview of the quantum-mechanical foundations of the dynamical behaviour of deep inelastic collisions between heavy ions is given. The use of time dependent Hartree-Fock method is stressed. (L.C.)
Two views on the Bjorken scenario for ultra-relativistic heavy-ion collisions
Maire, Antonin
2011-01-01
The sketch describes the Bjorken scenario foreseen for the collision of ultra-relativistic heavy-ions, leading to the creation of strongly-interacting hot and dense deconfined matter, the so-called Quark-Gluon Plasma (QGP).
Review of anisotropic flow correlations in ultrarelativistic heavy-ion collisions
Zhou, You
2016-01-01
Anisotropic flow phenomena is a key probe of the existence of Quark-Gluon Plasma. Several new observable associated with correlations between anisotropic flow harmonics are developed, which are expected to be sensitive to the initial fluctuations and transport properties of the created matter in heavy ion collisions. I review recent developments of correlations of anisotropic flow harmonics. The experimental measurements, together with the comparisons to theoretical model calculations, open up new opportunities of exploring novel QCD dynamics in heavy-ion collisions.
Azimuthal correlations between directed and elliptic flow in heavy ion collisions
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A method for investigating the azimuthal correlations between directed and elliptic flow in heavy ion collisions is described.The transverse anisotropy of particle emission at AGS energies is investigated within the RQMD model.It is found that the azimuthal correlations between directed and elliptic flow are sensitive to the incident energy and impact parameter.The fluctuations in the initial stage and dynamical evolution of heavy ion collisions are not negligible.
From many body wee partons dynamics to perfect fluid: a standard model for heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Venugopalan, R.
2010-07-22
We discuss a standard model of heavy ion collisions that has emerged both from experimental results of the RHIC program and associated theoretical developments. We comment briefly on the impact of early results of the LHC program on this picture. We consider how this standard model of heavy ion collisions could be solidified or falsified in future experiments at RHIC, the LHC and a future Electro-Ion Collider.
Open heavy-flavor production and suppression in heavy-ion collisions
Nahrgang, Marlene
2015-01-01
Heavy-flavor observables are valuable probes of the quark-gluon plasma, which is expected to be produced in ultrarelativistic heavy-ion collisions. These experiments offer the unique opportunity to study strongly interacting matter at high temperatures and densities in the laboratory. In this overview talk I will summarize the current theoretical status of heavy-flavor production and suppression in heavy-ion collisions and discuss open challenges.
An inversion-asymmetric source function for HBT analysis in relativistic heavy ion collisions
Lianshou, Liu; Shusu, Shi; Jiaxin, Du
2006-01-01
The inversion-asymmetry of the emission source in relativistic heavy ion collision under the Bertsch-Pratt convention is discussed and explicitly exhibited by a Monte Carlo model. The Gaussian source function popularly used in the HBT analysis of relativistic heavy ion collisions is invalid in this case. An inversion-asymmetric source function is suggested. A method for extracting the inversion-asymmetry degree of the source together with the source size from experimental data is proposed.
Systematics of Charged Particle Production in Heavy-Ion Collisions with the PHOBOS Detector at Rhic
Steinberg, Peter A.; Back, B. B.; Baker, M. D.; Barton, D. S.; Betts, R. R.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Corbo, J.; Decowski, M. P.; Garcia, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Henderson, C.; Hicks, D.; Hofman, D.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Michałowski, J.; Mignerey, A.; Mülmenstädt, J.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Rafelski, M.; Rbeiz, M.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tang, J.-L.; Teng, R.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wadsworth, B.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.
2002-03-01
The multiplicity of charged particles produced in Au+Au collisions as a function of energy, centrality, rapidity and azimuthal angle has been measured with the PHOBOS detector at RHIC. These results contribute to our understanding of the initial state of heavy ion collisions and provide a means to compare basic features of particle production in nuclear collisions with more elementary systems.
Effect of final state interactions on subthreshold K- production in heavy-ion collisions
International Nuclear Information System (INIS)
Recently, experiments were carried out at Bevalac to detect K- in heavy-ion (Si-Si) collisions at an incident energy of 2.1 GeV/nucleon. The threshold for K- production in the nucleon-nucleon collision is approx. 2.5 GeV. The observation of K- at subthreshold energies in heavy-ion collisions implies that more than one projectile nucleon must be involved in converting their kinetic energies into the mass of K-. This experiment provides therefore the possibility of studying nuclear collective effects, such as Fermi motions, coherent production, and multiple collisions. Preliminary data can be largely explained by conventional rescattering theory
Cern academic training programme 2011: Selected Topics in the Physics of Heavy Ion Collisions
PH Department
2011-01-01
LECTURE SERIES 14, 15 & 16 March 2011 Selected Topics in the Physics of Heavy Ion Collisions 11:00-12:00 - Bldg. 222-R-001 - Filtration Plant In these lectures, I discuss some classes of measurements accessible in heavy ion collisions at the LHC. How can these observables be measured, to what extent can they be calculated, and what do they tell us about the dense mesoscopic system created during the collision? In the first lecture, I shall focus in particular on measurements that constrain the spatio-temporal picture of the collisions and that measure centrality, orientations and extensions. In the subsequent lectures, I then discuss on how classes of measurements allow one to characterize collective phenomena, and to what extent these measurements can constrain the properties of matter produced in heavy ion collisions. Organiser: Maureen Prola-Tessaur/PH-EDU
Longitudinal Decorrelation of Anisotropic Flows in Heavy-ion Collisions at the LHC
Pang, Long-Gang; Roy, Victor; Wang, Xin-Nian; Ma, Guo-Liang
2014-01-01
Fluctuations in the initial transverse energy-density distribution lead to anisotropic flows as observed in central high-energy heavy-ion collisions. Studies of longitudinal fluctuations of the anisotropic flows can shed further lights on the initial conditions and dynamical evolution of the hot quark-gluon matter in these collisions. Correlations between anisotropic flows with varying pseudo-rapidity gaps in Pb+Pb collisions at the LHC are investigated using both an event-by-event (3+1)-D ideal hydrodynamical model with fluctuating initial conditions and the AMPT Monte Carlo model for high-energy heavy-ion collisions. Anisotropic flows at different pseudo-rapidities are found to become significantly decorrelated with increasing pseudo-rapidity gaps due to longitudinal fluctuations in the initial states of heavy-ion collisions. The longitudinal correlation of the elliptic flow shows a strong centrality dependence while the correlation of the triangular flow is independent of the centrality. Longitudinal fluct...
Funny hills in pion spectra from heavy-ion collisions
International Nuclear Information System (INIS)
A discussion of some of the systematic features of the pion spectra in heavy-ions reactions is given. A discussion of the hills and valleys in heavy ion pion spectra that show up at the lower pion energies is given. The following topics are discussed: (1) three kinds of funny hills; (2) π-/+ ratios near center of mass; (3) new Monte Carlo studies of charged pion spectra; and (4) pion orbiting about fireballs and Bose-Einstein behavior as explanation for the mid-rapidity P/sub perpendicular to/ approx. = 0.4 to 0.5 m/sub π/c hill
Radion and Higgs Signals in Peripheral Heavy Ion Collisions at the LHC
Lietti, S. M.; Roldao, C. G.
2002-01-01
We investigate the sensitivity of the heavy ion mode of the LHC to Higgs boson and Radion production via photon-photon fusion through the analysis of the processes photon to photon photon, photon photon to b anti-b, and photon photon to g g in peripheral heavy ion collisions. We suggest cuts to improve the Higgs and Radion signal over standard model background ratio and determine the capability of LHC to detect these particles production.
Searching for Anomalous Higgs Couplings in Peripheral Heavy Ion Collisions at the LHC
Lietti, S. M.; A.A. Natale; Roldao, C. G.; Rosenfeld, R
2000-01-01
We investigate the sensitivity of the heavy ion mode of the LHC to anomalous Higgs boson couplings to photons, H-photon-photon, through the analysis of the processes photon photon to b anti-b and photon photon to photon photon in peripheral heavy ion collisions. We suggest cuts to improve the signal over background ratio and determine the capability of LHC to impose bounds on anomalous couplings by searching for a Higgs boson signal in these modes.
Highlights from Heavy Ion Collisions at RHIC and the Acoustics of the Little Bangs
Sorensen, Paul
2012-01-01
At the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, heavy nuclei are collided at high energies to create matter that is hot enough and dense enough to dissolve hadrons into a quark-gluon-plasma (QGP). In this lecture, dedicated to the memory of Aditya Sambamurti, I present an introduction to heavy-ion collisions and highlights from the first decade of RHIC results.
Theory of heavy ion collision physics in hadron therapy
2013-01-01
Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features detailed reviews written by leading international researchers. This volume focuses on the theory of heavy ion physics in medicine.
Collective ﬂow in relativistic heavy-ion collisions
Indian Academy of Sciences (India)
R S Bhalerao
2003-11-01
A brief introduction is given to the ﬁeld of collective ﬂow, currently being investigated experimentally at the Relativistic Heavy-Ion Collider, Brookhaven National Laboratory. It is followed by an outline of the work that I have been doing in this ﬁeld, in collaboration with Nicolas Borghini and Jean-Yves Ollitrault.
Intranuclear cascade description of relativistic heavy-ion collisions
International Nuclear Information System (INIS)
A microscopic theory of heavy ion reactions based on the intranuclear cascade model is briefly discussed in an attempt to study the compression of nuclear matter. Double differential cross sections of 20Ne + 238U are shown as functions of impact parameter and bombarding energy for energies between 100 and 900 MeV/nucleon
Problems of quantum electrodynamics in heavy-ion collisions
International Nuclear Information System (INIS)
The use of heavy ion reactions in studying basic problems of very strongly bound particles is discussed. Specifically, the fusion of two heavy nuclei, e.g., u + u, to form a superheavy quasimolecule is considered theoretically, with suggestions given for possible experiments. (12 figures)
Deuteron Photodissociation in Ultraperipheral Relativistic Heavy-Ion on Deuteron Collisions
Klein, Spencer; Vogt, Ramona
2003-01-01
In ultraperipheral relativistic deuteron on heavy-ion collisions, a photon emitted from the heavy nucleus may dissociate the deuterium ion. We find deuterium breakup cross sections of 1.38 barns for deuterium-gold collisions at a center of mass energy of 200 GeV per nucleon, as studied at the Relativistic Heavy Ion Collider, and 2.49 barns for deuterium-lead collisions at a center of mass energy of 6.2 TeV, as proposed for the Large Hadron Collider. This cross section includes an energy-indep...
Hard Photons Beyond Proton-Neutron Bremsstrahlung in Heavy-Ion Collisions
Gudima, K.; Ploszajczak, M.
1999-01-01
We report on the study of extremely high energy photons, pions and etas, produced in intermediate energy heavy-ion collisions. Possibility of imaging the final-state phase space in these collisions by the Bose-Einstein correlations for photons is critically examined.
Heavy ion collisions and the site-bond percolation
Energy Technology Data Exchange (ETDEWEB)
Desbois, J.
1987-05-01
Site-bond percolation on a lattice is used for the investigation of heavy ions reactions. A model characterized by two parameters, p and q, is worked out and a critical zone in the p, q plane is shown up. Analytical expressions for various quantities concerning percolation and evaporation are established. Calculations of energy spectra, linear momentum transfer, fragment multiplicities and mass yields at various bombarding energies are compared with experimental data. Different possibilities for the attainment of the multifragmentation regime are discussed.
Hadronization and strangeness production in heavy-ion collisions
Biro, T S; Zimányi, J; Traxler, C T
1999-01-01
The hadronization process of a quark matter possibly formed in relativistic heavy ion experiments at CERN SPS and RHIC is addressed in the framework of a non-equilibrium approach using hadron formation rates for effectively massive quarks and gluons. After a brief review of the relevant thermodynamical concepts consequences of string formation on the hadron composition are investigated in the transchemical quark fusion model and in a molecular dynamical simulation of the semiclassical chromodielectric model. (75 refs).
Spectator and participant decay in heavy ion collisions
Gaitanos, T.; Wolter, H. H.; Fuchs, C.
1999-01-01
We analyze the thermodynamical state of nuclear matter in transport calculations of heavy--ion reactions. In particular we determine temperatures and radial flow parameters from an analysis of fragment energy spectra and compare to local microscopic temperatures obtained from an analysis of local momentum space distributions. The analysis shows that the spectator reaches an equilibrated freeze-out configuration which undergoes simultaneous fragmentation. The fragments from the participant reg...
Collision-geometry fluctuations and triangular flow in heavy-ion collisions
Alver, B.; Roland, G.
2010-05-01
We introduce the concepts of participant triangularity and triangular flow in heavy-ion collisions, analogous to the definitions of participant eccentricity and elliptic flow. The participant triangularity characterizes the triangular anisotropy of the initial nuclear overlap geometry and arises from event-by-event fluctuations in the participant-nucleon collision points. In studies using a multiphase transport model (AMPT), a triangular flow signal is observed that is proportional to the participant triangularity and corresponds to a large third Fourier coefficient in two-particle azimuthal correlation functions. Using two-particle azimuthal correlations at large pseudorapidity separations measured by the PHOBOS and STAR experiments, we show that this Fourier component is also present in data. Ratios of the second and third Fourier coefficients in data exhibit similar trends as a function of centrality and transverse momentum as in AMPT calculations. These findings suggest a significant contribution of triangular flow to the ridge and broad away-side features observed in data. Triangular flow provides a new handle on the initial collision geometry and collective expansion dynamics in heavy-ion collisions.
Studying Heavy Ion Collisions Using Methods From Cosmic Microwave Background (CMB Analysis
Directory of Open Access Journals (Sweden)
Gaardhøje J. J.
2014-04-01
Full Text Available We present and discuss a framework for studying the morphology of high-multiplicity events from relativistic heavy ion collisions using methods commonly employed in the analysis of the photons from the Cosmic Microwave Background (CMB. The analysis is based on the decomposition of the distribution of the number density of (charged particles expressed in polar and azimuthal coordinates into a sum of spherical harmonic functions. We present an application of the method exploting relevant symmetries to the study of azimuthal correlations arizing from collective flow among charged particles produced in relativistic heavy ion collisions. We discuss perspectives for event-by- event analyses, which with increasing collision energy will eventually open entirely new dimensions in the study of ultrarelaticistic heavy ion reactions.
Modeling production of some high-mass secondaries in heavy-ion collisions
International Nuclear Information System (INIS)
In the light of a newly proposed phenomenological model offered by the combinational approach, we attempt to interpret with a modest degree of success the measured data on production of the pT-spectra of the lambda (Λ) baryons and phi (Φ) mesons in some heavy-ion collisions. The choices of the specific varieties for the present study are influenced by the two factors: (i) availability of data in ΝΝ(ΡΡ/ΡΡ¯) reactions at some high energies and also in a few heavy-ion collisions at several energies; and (ii) the status and importance of the specific particle(s) from various physical considerations. (author)
Measurement Of The Heavy-Ion Collision Event Characteristics With The Atlas Experiment At The Lhc
Directory of Open Access Journals (Sweden)
Iwona Grabowska-Bołd
2015-01-01
Full Text Available Heavy-ion collisions at extreme energies can reproduce conditionspresent in the early Universe. The new state of very dense and hotmatter of deconfined quarks and gluons, called the Quark GluonPlasma~(QGP, is observed. This state is characterised by very lowviscosity resembling the properties of a perfect fluid. In suchmedium, the density fluctuations can be easily spread. In experimentalpractice, the size of these fluctuations is estimated by measuring theangular correlation of produced particles. The aim of this paper isto present measurements of the azimuthal anisotropy of chargedparticles produced in heavy-ion collisions using the ATLAS detector atthe LHC. Two measurement techniques are presented and compared.
Microscopic Calculation of Pre-Compound Excitation Energies for Heavy-Ion Collisions
Umar, A S; Maruhn, J A; Reinhard, P -G
2009-01-01
We introduce a microscopic approach for calculating the excitation energies of systems formed during heavy-ion collisions. The method is based on time-dependent Hartree-Fock (TDHF) theory and allows the study of the excitation energy as a function of time or ion-ion separation distance. We discuss how this excitation energy is related to the estimate of the excitation energy using the reaction $Q$-value, as well as its implications for dinuclear pre-compound systems formed during heavy-ion collisions.
Importance of the Bulk Viscosity of QCD in Ultrarelativistic Heavy-Ion Collisions.
Ryu, S; Paquet, J-F; Shen, C; Denicol, G S; Schenke, B; Jeon, S; Gale, C
2015-09-25
We investigate the consequences of a nonzero bulk viscosity coefficient on the transverse momentum spectra, azimuthal momentum anisotropy, and multiplicity of charged hadrons produced in heavy ion collisions at LHC energies. The agreement between a realistic 3D hybrid simulation and the experimentally measured data considerably improves with the addition of a bulk viscosity coefficient for strongly interacting matter. This paves the way for an eventual quantitative determination of several QCD transport coefficients from the experimental heavy ion and hadron-nucleus collision programs. PMID:26451547
Steckmeyer, J C; Grotowski, K; Pawowski, P; Aiello, S; Anzalone, A; Bini, M; Borderie, B; Bougault, R; Cardella, G; Casini, G; Cavallaro, S; Charvet, J L; Dayras, R; De Filippo, E; Durand, D; Femin, S; Frankland, J D; Galíchet, E; Geraci, M; Giustolisi, F; Guazzoni, P; Iacono-Manno, M; Lanzalone, G; Lanzan, G; Le Neindre, N; Lo Nigro, S; Lo Piano, F; Olmi, A; Pagano, A; Papa, M; Pârlog, M; Pasquali, G; Piantelli, S; Pirrone, S; Politi, G; Porto, F; Rivet, M F; Rizzo, F; Rosato, E; Roy, R; Sambataro, S; Sperduto, M L; Stefanini, A A; Sutera, C; Tamain, B; Vient, E; Volant, C; Wieleczko, J P; Zetta, L
2005-01-01
A simple procedure for evaluating the excitation energy and the spin transfer in heavy-ion dissipative collisions is proposed. It is based on a prediction of the GEMINI evaporation code : for a nucleus with a given excitation energy, the average number of emitted protons decreases with increasing spin, whereas the average number of alpha particles increases. Using that procedure for the reaction 107Ag+58Ni at 52 MeV/nucleon, the excitation energy and spin of quasi-projectiles have been evaluated. The results obtained in this way have been compared with the predictions of a model describing the primary dynamic stage of heavy-ion collisions.
Jet reconstruction and calibration in heavy-ion collisions with the ATLAS detector
Kosek, Tomas; The ATLAS collaboration
2014-01-01
Jets produced in heavy-ion collisions are one of the important hard probes that provide information about the hot and dense medium created in heavy ion collisions. The performance of the jet reconstruction is of great importance since it provides basis for each jet measurement. Due to the large underlying background and its fluctuations, the precise jet reconstruction is nontrivial and challenging. Beside the basic jet performance we concentrate namely on the methods used for the calibration of jet energy. The so-called numerical inversion used to calibrate jets in the ATLAS experiment is introduced and discussed.
Elliptic Flow and Jet Quenching of a Parton System after Relativistic Heavy Ion Collision
Shin, Ghi R
2007-01-01
We obtain the initial phase space distribution after relativistic heavy ion collision by the CGC shattering method incorporating the uncertainty principle and solve the semi-classical Boltzmann equation which includes the gluon radiation processes. We present as a function of time the attenuation rate of high $p_T$ partons, which have transverse momenta over 6 $GeV/c$, in the medium which is formed after relativistic heavy ion collision. We calculate the elliptic flow as a function of an impact parameter, time and transverse momentum and also present the polar anisotropy, which gives the initial condition for color filamentation.
Hu, Ying; Zhang, Wei-Ning; Ren, Yan-Yu(Department of Physics, Harbin Institute of Technology, Harbin, Heilongjiang 150006, China)
2014-01-01
We investigate the fluctuations of pion elliptic flow, triangular flow, and Hanbury-Brown-Twiss (HBT) correlation functions for the hydrodynamic sources with fluctuating initial conditions in the heavy ion collisions of the Au-Au at $\\sqrt{s_{NN}}=200$ GeV and the Pb-Pb at $\\sqrt{s_{NN}} =2.76$ TeV. A method based on event-subcollection analysis is used to detect these fluctuations in ultrarelativistic heavy ion collisions. We introduce a granularity length to describe the granular inhomogene...
Universal behavior of charged particle production in heavy ion collisions at RHIC energies
Steinberg, Peter A.; Back, B. B.; Baker, M. D.; Barton, D. S.; Betts, R. R.; Ballintijn, M.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Michałowski, J.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tang, J.-L.; Teng, R.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wadsworth, B.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.; Phobos Collaboration
2003-04-01
The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at √ SNN = 19.6, 130 and 200 GeV. Two kinds of universal behavior are observed in charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/ overlinepp and e +e - data. / in nuclear collisions at high energy scales with √ s in a similar way as Nch in e +e - collisions and has a very weak centrality dependence. This feature may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions.
Universal behavior of charged particle production in heavy ion collisions at RHIC energies
International Nuclear Information System (INIS)
The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at √SNN = 19.6, 130 and 200 GeV. Two kinds of universal behavior are observed in charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/p-barp and e+e- data. ch>/part/2> in nuclear collisions at high energy scales with √s in a similar way as Nch in e+e- collisions and has a very weak centrality dependence. This feature may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions
Charmonium dissociation by mesons in heavy-ion collisions
Lykasov, Gennady I.; Cassing, Wolfgang
2006-01-01
The charmonium dissociation by mesons in relativistic heavy-ion reactions is analyzed within the Regge approach. It is shown that the inclusion of the initial and final state interactions in the dissociation of J/Psi to bar{D}* D* close to threshold increases the cross section significantly and can not be neglected in comparison to the total dissociation rate. This is due to resonant bar{D}*-D* interactions in sqrt{s} close to the masses of the Psi(4.04) and Psi(4.16) mesons. We also investig...
Heavy ion collisions and the site-bond percolation
International Nuclear Information System (INIS)
Site-bond percolation on a lattice is used for the investigation of heavy ions reactions. A model characterized by two parameters, p and q, is worked out and a critical zone in the p, q plane is shown up. Analytical expressions for various quantities concerning percolation and evaporation are established. Calculations of energy spectra, linear momentum transfer, fragment multiplicities and mass yields at various bombarding energies are compared with experimental data. Different possibilities for the attainment of the multifragmentation regime are discussed. (orig.)
Charged particle multiplicity in relativistic heavy-ion collisions
International Nuclear Information System (INIS)
What follows is a brief overview of the E814 silicon multiplicity detector and some of the data taken with it during a June 89 heavy ion physics run at the BNL AGS. The beam was 14.6 GeV/c/u 28Si on targets of Pb, Cu, and Al. For the data presented below all of the target thicknesses were 1.2% of a Si interaction length. All of the data shown below are still in analysis and none are final
High energy heavy ion collisions from the view point of the 'strong field physics'
International Nuclear Information System (INIS)
In the high energy heavy ion collisions at the facilities like RHIC and LHC, two strongest fields in the present universe are generated. First of all, a very strong electromagnetic field is generated, though its duration is very short due to the very high speed collisions of nuclei and the large electric charges. On the other hand, the nuclei are described as the high density saturation gluon state just before the moment of the collision and the high density gluon is released by the collision. A very strong color electromagnetic field is generated. The color glass condensate (CGC) is a reasonable picture. In this text, dynamics of the GLASMA (Glass + plasma), the new physics brought about by those 'strong fields', are introduced and are explained how the yet unsolved problems of the heavy ion collisions are going to be investigated on the new view point. The mechanism of the apparitions of the strong electromagnetic field and the strong color electromagnetic field are explained at first. The heavy ion collisions can be described as the process CGC to develop into QGP. As the phenomena under the strong electromagnetic field and the heavy ion collisions, their synchrotron radiations, the photon birefringence, the photon decay, the splitting of photons and the chiral phase transitions under high field are picked up. Concerning the strong color electromagnetic field dynamics and the heavy ion collisions, the plasma flux tube dynamics, the color magnetic flux tube, the color electric flux tube and the coexisting case of the color electric field and magnetic field are presented. (S. Funahashi)
Time evolution of the central region in ultrarelativistic heavy-ion collisions
International Nuclear Information System (INIS)
We investigate time development of the central region in ultrarelativistic nucleus-nucleus collisions by using the event generator URASiMA in order to study the space-time structure in high energy heavy-ion collisions. We focus on time dependence of particle-number densities and temperature of the central region in highly relativistic head-on nucleus-nucleus collisions. (author)
Open heavy flavor and other hard probes in ultra-relativistic heavy-ion collisions
International Nuclear Information System (INIS)
In this thesis hard probes are studied in the partonic transport model BAMPS (Boltzmann Approach to MultiParton Scatterings). Employing Monte Carlo techniques, this model describes the 3+1 dimensional evolution of the quark gluon plasma phase in ultra-relativistic heavy-ion collisions by propagating all particles in space and time and carrying out their collisions according to the Boltzmann equation. Since hard probes are produced in hard processes with a large momentum transfer, the value of the running coupling is small and their interactions should be describable within perturbative QCD (pQCD). This work focuses on open heavy flavor, but also addresses the suppression of light parton jets, in particular to highlight differences due to the mass. For light partons, radiative processes are the dominant contribution to their energy loss. For heavy quarks, we show that also binary interactions with a running coupling and an improved Debye screening matched to hard-thermal-loop calculations play an important role. Furthermore, the impact of the mass in radiative interactions, prominently named the dead cone effect, and the interplay with the Landau-Pomeranchuk-Migdal (LPM) effect are studied in great detail. Since the transport model BAMPS has access to all medium properties and the space time information of heavy quarks, it is the ideal tool to study the dissociation and regeneration of J/ψ mesons, which is also investigated in this thesis.
Track reconstruction in heavy ion collisions with the CMS silicon tracker
Roland, C
2006-01-01
The Large Hadron Collider at CERN will collide protons at \\sqrtS = 14TeV and lead ions at \\sqrt$\\S_{NN}$. The study of heavy ion collisions is an integral part of the physics program of the Compact Muon Solenoid (CMS). Central heavy ion events at LHC energies are expected to produce a multiplicity of up to 3500 charged particles per unit of rapidity. The CMS detector features a large acceptance and high resolution silicon tracker consisting of pixel and strip detector layers. We describe the algorithms used for pattern recognition in the very high track density environment of heavy ion collisions. Detailed studies using the full detector simulation and reconstruction are presented and achieved reconstruction efficiencies, fake rates and resolutions are discussed.
International Nuclear Information System (INIS)
The following topics were dealt with: Experimental results on ultrarelativistic heavy ion collisions, QCD thermodynamics, equilibration in relativistic heavy ion collisions, lattice QCD, space- time evolution and Hanbury-Brown-Twiss correlations, vector meson production, high-pT and small-x physics. (HSI)
International Nuclear Information System (INIS)
The collective processes in collision of heavy-ions with atomic nuclei are discussed. Measured data on the S+Ti collision at Esub(LAB)=105, 130 and 144 MeV have been analysed in terms of a ''fission-like'' processes which seem to be a special case of deep inelastic collisions whose total available kinetic energy is completely dissipated. Applying transport theory it was possible to introduce a ''clock'' for measuring the time scale of nuclear processes in collision of heavy-ions by measuring the FWHM of mass distribution of emitted reaction products. Experimental data on continuum gamma spectra from Cu+Au collision at Esub(LAB)=400 MeV are presented and the angular momentum dissipation in this reaction is discussed. (author)
Multi Module Modeling of Ultra-Relativistic Heavy Ion Collisions.
Energy Technology Data Exchange (ETDEWEB)
Magas, V. K.; Csernai, L. P. (László P.); Keranen, A.; Manninen, J.; Strottman, D. D. (Daniel D.)
2002-01-01
Multi Module Model is required for the realistic and detailed description of an ultrarelativistic heavy ion reaction. We are working in the framework of such a model: initial stages are described by Effective String Rope Model with expanding final streaks; hydrodynamical approach is used for the intermediate stages. This paper is mainly devoted to Third Module - the one dealing with Freeze Out (FO). Two possibilities are discussed in details: (A) freeze out at the constant time hypersurface, where the statistical production model is used to describe post FO particle species; and (B) simultaneous hadronization and freeze out from supercooled QGP. For the last case the ALCOR-like algorithm for calculation of the post FO particle species is presented, due to the fact that these do not have time to reach chemical equilibrium.
(Anti-)strangeness production in heavy-ion collisions
Moreau, Pierre; Ko, Che-Ming; Cassing, Wolfgang; Bratkovskaya, Elena
2015-01-01
The production and dynamics of strange and antistrange hadrons in heavy-ion reactions from $\\sqrt{s_{NN}} \\approx$ 3 GeV to 200 GeV is analyzed within the Parton-Hadron-String-Dynamics (PHSD) transport model. The PHSD results for strange baryon and antibaryon production are roughly consistent with the experimental data starting from upper SPS energies. Nevertheless, hadronic final state flavor-exchange reactions are important for the actual abundances, in particular at large rapidities where hadronic dynamics, parton fragmentation and string decay dominate. A striking disagreement between the PHSD results and the available data persists, however, for bombarding energies below $\\sqrt{s_{NN}} \\approx$ 8 GeV where the strangeness production is significantly underestimated as in earlier HSD studies. This finding implies that the strangeness enhancement seen experimentally at FAIR/NICA energies cannot be attributed to a deconfinement phase transition or crossover but probably involves the approximate restoration o...
Collision geometry fluctuations and triangular flow in heavy-ion collisions
Alver, B
2010-01-01
We introduce the concepts of participant triangularity and triangular flow in heavy-ion collisions, analogous to the definitions of participant eccentricity and elliptic flow. The participant triangularity characterizes the triangular anisotropy of the initial nuclear overlap geometry and arises from event-by-event fluctuations in the participant-nucleon collision points. In studies using a multi-phase transport model (AMPT), a triangular flow signal is observed that is proportional to the participant triangularity and corresponds to a large third Fourier coefficient in two-particle azimuthal correlation functions. Using two-particle azimuthal correlations at large pseudorapidity separations measured by the PHOBOS and STAR experiments, we show that this Fourier component is also present in data. Ratios of the second and third Fourier coefficients in data exhibit similar trends as a function of centrality and transverse momentum as in AMPT calculations. These findings suggest a significant contribution of tria...
Models for exclusive vector meson production in heavy-ion collisions
Lappi, T.; Mäntysaari, H.
2013-01-01
We discuss coherent and incoherent photoproduction of $J/\\Psi$ vector mesons in high energy heavy ion collisions. In a dipole picture for the photon both can be naturally related to the dipole cross section that is also probed in inclusive DIS. We compare results of a particular calculation to ALICE data.
Delta Resonance production and propagation in intermediate-energy heavy-ion collisions
Holzmann, R
1996-01-01
The role of the Delta resonance in subthreshold pion production is discussed and illustrated with pi(0) data measured in heavy-ion collisions at 95 MeV/u with the photon spectrometer TAPS at GANIL. Particular emphasis is put on the Delta capture reaction and a cross section for this process is obtai
Event-by-event cluster analysis of final states from heavy ion collisions
Fialkowski, K.; Wit, R.
1999-01-01
We present an event-by-event analysis of the cluster structure of final multihadron states resulting from heavy ion collisions. A comparison of experimental data with the states obtained from Monte Carlo generators is shown. The analysis of the first available experimental events suggests that the method is suitable for selecting some different types of events.
Hot nuclei and search for multifragmentation in medium-energy heavy-ion collisions
International Nuclear Information System (INIS)
Some recent determinations of the excitation energies and temperatures of composite systems formed in intermediate-energy heavy-ion collisions are described and the issue of a limiting temperature is discussed. Several examples of experimental investigations of an eventual occurrence of a multifragmentation process are also described
On chemical equilibrium in high-energy heavy-ion collisions
Kaneta, M
2001-01-01
The thermal fitting parameters depend on the phase space coverage. It is questionable to interpret the fitting results extracted from the experimental measured particle yields within finite phase space. We test this idea with the transport models RQMD and NEXUS for heavy-ion collisions at both SPS and RHIC energies. (11 refs).
Fermionic Molecular Dynamics Multifragmentation in heavy-ion collisions and in excited nuclei
Feldmeier, H
1997-01-01
Within Fermionic Molecular Dynamics we investigate fragmentation of a compound system which was created in a heavy-ion collision at a beam energy in the Fermi energy domain and the decay of excited iron nuclei. We show that in FMD many-body correlations play an important role in the formation of fragments.
Hydrodynamics with spontaneous symmetry breaking application to relativistic heavy ion collisions
Lallouet, Y; Pujol, C
2003-01-01
In this paper we apply hydrodynamics for systems with continuous broken symmetries to heavy ion collisions in the framework of (1+1) dimensional Bjorken model. The temperature profile with respect to proper time determined in that context is compared with the one obtained when M\\"{u}ller-Israel-Stewart second order theory of dissipation is included on top of standard hydrodynamics.
ATLAS One of the first Heavy ions collisions with stable beams- Event Display - November 2015
ATLAS Collaboration
2015-01-01
One of the first heavy ions collisions with stable beams recorded by ATLAS in November 2015. Tracks reconstructed from hits in the inner tracking detector are shown as orange arcs curving in the solenoidal magnetic field. The green and yellow bars indicate energy deposits in the Liquid Argon and Scintillating Tile calorimeters respectively. The beam pipe and the inner detectors are also shown.
Photon-jet correlation in heavy ion collisions at the LHC
Kodolova, Olga; Nikitenko, A N
2002-01-01
Transverse momentum imbalance between a jet produced with a hard photon is considered as a signal of medium-induced partonic energy loss in ultrarelativistic heavy ion collisions. We analyze photon-jet correlation in the context of a real experimental situation at the LHC, the problem of neutral pion background being discussed.
An Analytic Solution of Hydrodynamic Equations with Source Terms in Heavy Ion Collisions
Zhuang, Pengfei; Yang, Zhenwei
2000-01-01
The energy and baryon densities in heavy ion collisions are estimated by analytically solving a 1+1 dimensional hydrodynamical model with source terms. Particularly, a competition between the energy and baryon sources and the expansion of the system is discussed in detail.
Production of Dileptons in Heavy Ion Collisions at SPS-Energies
Koch, V.
1999-01-01
In this contribution we will discuss the production of low mass dileptons in SPS-energy heavy ion collisions. We briefly review the current theoretical situation before we turn to the analysis of the recent data for Pb+Au. We also will discuss the role of baryons as a source for dileptons.
Remark on statistical model fits to particle ratios in relativistic heavy ion collisions
Becattini, F.
2007-01-01
In order to determine the chemical freeze-out parameters of the hadron-emitting source in relativistic heavy ion collisions some studies in literature perform fits by using as data input a subsample of ratios calculated out of experimentally measured hadron yields instead of yields themselves. We show that this is a statistically incorrect method fit, implying a bias in the extracted parameters.
How big is the source that produces quark gluon plasma in heavy ion collisions?
Jain, Ambar; Ravishankar, V.
2003-01-01
We study, for the first time, the spatial extension of the "source" that produces quark gluon plasma (QGP) in ultra relativistic heavy ion collisions. The longitudinal dimension is studied as a function of time as the system evolves. The source size is found to exhibit a novel non-classical feature.
Hadronic matter compressibility from event-by-event analysis of heavy-ion collisions
Mrowczynski, Stanislaw
1997-01-01
We propose a method to measure the hadronic matter compressibility by means of the event-by-event analysis of heavy-ion collisions at high energies. The method, which utilizes the thermodynamical relation between the compressibility and the particle number fluctuations, requires a simultaneous measurement of the particle source size, temperature and particle multiplicity.
Fragment Isospin as a Probe of Heavy-Ion Collisions
Xu, H; Davin, B; Beaulieu, L; Larochelle, Y; Lefort, T; Yañez, R; De Souza, R T; Liu, T X; Liu, X D; Lynch, W G; Shomin, R; Tan, W P; Tsang, M B; Molen, A V; Wagner, A; Xi Hong Fei; Gelbke, C K; Charity, R J; Sobotka, L G; Botvina, A S
2002-01-01
Isotope ratios of fragments produced at mid-rapidity in peripheral and central collisions of 114Cd ions with 92Mo and 98Mo target nuclei at E/A = 50 MeV are compared. Neutron-rich isotopes are preferentially produced in central collisions as compared to peripheral collisions. The influence of the size (A), density, N/Z, E*/A, and Eflow/A of the emitting source on the measured isotope ratios was explored by comparison with a statistical model (SMM). The mid-rapidity region associated with peripheral collisions does not appear to be neutron-enriched relative to central collisions.
The production of Higgs bosons in high-energetic heavy-ion collisions
International Nuclear Information System (INIS)
The aim of this diploma thesis was to produce the Higgs boson in high-energetic, peripheral heavy-ion collisions by purely electromagnetic processes. In order to take only peripheral collisions into consideration and to avoid the strong hadronic background of central collisions the equivalent-photon method for the case of the Higgs boson was extended concerning an impact-parameter study. By this it was possible to exclude the contribution of central collisions by cut in the impact parameter at b=2R, in order to determine thus the production rate for purely peripheral collisions. (orig./HSI)
Hunting down the quark-gluon plasma in relativistic heavy-ion collisions
Heinz, Ulrich
1999-01-01
The present status of the heavy-ion program to search for quark-gluon plasma is reviewed. The goal of this program is to recreate the Big Bang in the laboratory, by generating small chunks of exploding quark-gluon plasma (``The Little Bang''). I argue that the analogues of the three pillars of Big Bang Theory (Hubble flow, microwave background radiation, and primordial nucleosynthesis) have now been firmly established in heavy-ion collisions at SPS energies: there is convincing evidence for s...
Charge separation with fluctuating domains in relativistic heavy-ion collisions
Shou, Qi-Ye; Ma, Guo-Liang; Ma, Yu-Gang
2014-01-01
Charge separation induced by the chiral magnetic effect suggested that some ${\\cal P}$- or ${\\cal CP}$-odd metastable domains could be produced in a QCD vacuum in the early stage of relativistic heavy-ion collisions. Based on a multi-phase transport model, our results suggest that a domain-based scenario with final state interactions can describe the solenoidal tracker at RHIC detector (STAR) measurements of both same- and opposite-charge azimuthal angle correlations, $$, in Au+Au collisions ...
Semiclassical approach to sequential fission in peripheral heavy-ion collisions
Directory of Open Access Journals (Sweden)
Strazzeri Andrea
2016-01-01
Full Text Available A closed-form theoretical approach describing in a single picture both the evaporation component and the fast nonequilibrium component of the sequential fission of projectilelike fragments in a semiperipheral heavy-ion collision is derived and then applied to the dynamical fission observed in the 124Sn+64Ni semiperipheral collision at 35A MeV. Information on opposite polarization effects of the fissioning projectilelike fragments and on their “formation-to-fast fission lifetimes” are obtained.
Anisotropy of low energy direct photons in relativistic heavy ion collisions
Koide, T.; Kodama, T.
2016-09-01
Using the Wigner function approach for electromagnetic radiation fields, we investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions. The angular distribution reveals information of the initial geometric configurations, which is reflected in the anisotropic parameter v 2, with an increasing v 2 as energy decreases. This behavior is qualitatively different to the v 2 from the hadrons produced in the collisions.
Event-by-event generation of vorticity in heavy-ion collisions
Deng, Wei-Tian
2016-01-01
In a noncentral heavy-ion collision, the two colliding nuclei have finite angular momentum in the direction perpendicular to the reaction plane. After the collision, a fraction of the total angular momentum is retained in the produced hot quark-gluon matter and is manifested in the form of fluid shear. Such fluid shear creates finite flow vorticity. We study some features of such generated vorticity, including its strength, beam energy dependence, centrality dependence, and spatial distribution.
Cluster approach to intranuclear cascade for relativistic heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Kodama, T.; Duarte, S.B.; Chung, K.C.; Nazareth, R.A.M.S.
1982-08-23
A new approach to the intranuclear cascade model for relativistic heavy-ion reactions is presented. The effect of nucleon concentration on the collision process is explicitly included. It is found that the contributions from the nonbinary processes are far from being negligible. Such processes are shown to broaden the angular distribution of inclusive proton spectra for /sup 20/Ne+/sup 238/U head-on collisions.
Production of gluons in the classical field model for heavy ion collisions
Lappi, T
2003-01-01
The initial stages of relativistic heavy ion collisions are studied numerically in the framework of a 2+1 dimensional classical Yang-Mills theory. We calculate the energy and number densities and momentum spectra of the produced gluons. The model is also applied to non central collisions. The numerical results are discussed in the light of RHIC measurements of energy and multiplicity and other theoretical calculations. Some problems of the present approach are pointed out.
Anisotropicity of Low Energy Direct Photons in Relativistic Heavy Ion Collisions
Koide, T
2016-01-01
We investigate the behavior of low energy photons radiated by deceleration processes of two colliding nuclei in relativistic heavy ion collisions, where their angular distribution reveals information of the initial geometric configurations. Such a property is reflected in the anisotropic parameter v_{2}, showing an increasing v_{2} as energy decreases, which is qualitatively different behavior from v_{2} from hadrons produced in the collisions.
Linear and cubic response to the initial eccentricity in heavy-ion collisions
Noronha-Hostler, Jacquelyn; Gardim, Fernando G; Ollitrault, Jean-Yves
2016-01-01
We study the relation between elliptic flow, $v_2$ and the initial eccentricity, $\\varepsilon_2$, in heavy-ion collisions, using hydrodynamic simulations. Significant deviations from linear eccentricity scaling are seen in more peripheral collisions. We identify the mechanism responsible for these deviations as a cubic response, which we argue is a generic property of the hydrodynamic response to the initial density profile. The cubic response increases elliptic flow fluctuations, thereby improving agreement of initial condition models with experimental data.
The Transverse Structure of the Baryon Source in Relativistic Heavy Ion Collisions
Polleri, A.; Mattiello, R.; Mishustin, I. N.; Bondorf, J. P.
1999-01-01
A direct method to reconstruct the transverse structure of the baryon source formed in a relativistic heavy ion collision is presented. The procedure makes use of experimentally measured proton and deuteron spectra and assumes that deuterons are formed via two-nucleon coalescence. The transverse density shape and flow profile are reconstructed for Pb+Pb collisions at the CERN-SPS. The ambiguity with respect to the source temperature is demonstrated and possible ways to resolve it are discussed.
Anomalous transport model study of chiral magnetic effects in heavy ion collisions
Sun, Yifeng; Ko, Che Ming; Li, Feng
2016-10-01
Using an anomalous transport model for massless quarks and antiquarks, we study the effect of a magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in noncentral heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision. The electric quadrupole moment subsequently leads to a splitting between the elliptic flows of quarks and antiquarks. The slope of the charge asymmetry dependence of the elliptic flow difference between positively and negatively charged particles is positive, which is expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the BNL Relativistic Heavy Ion Collider, only if the Lorentz force acting on the charged particles is neglected and the quark-antiquark scattering is assumed to be dominated by the chirality changing channel.
Observation of the Mott effect in heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Gudima, K.; Ploszajczak, M.; Bozek, P.; Danielewicz, P.
1997-10-01
The possibility of the observation of the Mott momentum in the distribution of the deuterons produced in the process p + n - d + {gamma} in the first stage of the nuclear collision is presented. The correlation of the hard photon with the deuteron allows to select deuterons produced at the beginning of the collision. (authors).
Initial state fluctuations in collisions between light and heavy ions
Welsh, Kevin; Heinz, Ulrich W
2016-01-01
In high energy collisions involving small nuclei (p+p or x+Au collisions where x=p, d, or $^3$He) the fluctuating size, shape and internal gluonic structure of the nucleon is shown to have a strong effect on the initial size and shape of the fireball of new matter created in the collision. A systematic study of the eccentricity coefficients describing this initial fireball state for several semi-realistic models of nucleon substructure and for several practically relevant collision systems involving small nuclei is presented. The key importance of multiplicity fluctuations in such systems is pointed out. Our results show large differences from expectations based on conventional Glauber model simulations of the initial state created in such collisions.
Magnetic effects in heavy-ion collisions at intermediate energies
International Nuclear Information System (INIS)
The time evolution and space distribution of internal electromagnetic fields in heavy-ion reactions at beam energies between 200 and 2000 MeV/nucleon are studied within an isospin-dependent Boltzmann-Uhling-Uhlenbeck transport model (ibuu11). While the magnetic field can reach about 7x1016 G, which is significantly higher than the estimated surface magnetic field (∼1x1015 G) of magnetars, it has almost no effect on nucleon observables because the Lorentz force is normally much weaker than the nuclear force. Very interestingly, however, the magnetic field generated by the projectilelike (targetlike) spectator has a strong focusing and defocusing effect on positive and negative pions at forward (backward) rapidities. Consequently, the differential π-/π+ ratio as a function of rapidity is significantly altered by the magnetic field, whereas the total multiplicities of both positive and negative pions remain about the same. At beam energies above about 1 GeV/nucleon, while the integrated ratio of total π- to π+ multiplicities is not, the differential π-/π+ ratio is sensitive to the density dependence of nuclear symmetry energy Esym(ρ). Our findings suggest that magnetic effects should be carefully considered in future studies of using the differential π-/π+ ratio as a probe of the Esym(ρ) at suprasaturation densities.
Weil, J; Staudenmaier, J; Pang, L G; Oliinychenko, D; Mohs, J; Kretz, M; Kehrenberg, T; Goldschmidt, A; Bäuchle, B; Auvinen, J; Attems, M; Petersen, H
2016-01-01
The microscopic description of heavy-ion reactions at low beam energies is achieved within hadronic transport approaches. In this article a new approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced and applied to study the production of non-strange particles in heavy-ion reactions at $E_{\\rm kin}=0.4-2A$ GeV. First, the model is described including details about the collision criterion, the initial conditions and the resonance formation and decays. To validate the approach, equilibrium properties such as detailed balance are presented and the results are compared to experimental data for elementary cross sections. Finally results for pion and proton production in C+C and Au+Au collisions is confronted with HADES and FOPI data. Predictions for particle production in $\\pi+A$ collisions are made.
Origins of the di-jet asymmetry in heavy ion collisions
Milhano, José Guilherme
2015-01-01
The di-jet asymmetry --- the measure of the momentum imbalance in a di-jet system --- is a key jet quenching observable. Using the event generator \\jewel we show that the di-jet asymmetry is dominated by fluctuations both in proton-proton and in heavy ion collisions. We discuss how in proton-proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy ion collisions two additional sources contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable.
Triggering on Hard Probes in Heavy-Ion Collisions with the CMS Experiment at the LHC
Roland, Christof
2009-01-01
Studies of heavy-ion collisions at the LHC will benefit from an array of qualitatively new probes not readily available at lower collision energies. These include fully formed jets at $E_T > 50$~GeV, Z$^0$'s and abundantly produced heavy flavors. For Pb+Pb running at LHC design luminosity, the collision rate in the CMS interaction region will exceed the available bandwidth to store data by several orders of magnitude. Therefore an efficient trigger strategy is needed to select the few percent of the incoming events containing the most interesting signatures. In this report, we will present the heavy-ion trigger strategy developped for the unique two-layer trigger system of the CMS experiment consisting of a ``Level-1'' trigger based on custom electronics and a High Level Trigger (HLT) implemented using a large cluster of commodity computers.
Two components in charged particle production in heavy-ion collisions
Bylinkin, A. A.; Chernyavskaya, N. S.; Rostovtsev, A. A.
2016-02-01
Transverse momentum spectra of charged particle production in heavy-ion collisions are considered in terms of a recently introduced Two Component parameterization combining exponential ("soft") and power-law ("hard") functional forms. The charged hadron densities calculated separately for them are plotted versus number of participating nucleons, Npart. The obtained dependences are discussed and the possible link between the two component parameterization introduced by the authors and the two component model historically used for the case of heavy-ion collisions is established. Next, the variations of the parameters of the introduced approach with the center of mass energy and centrality are studied using the available data from RHIC and LHC experiments. The spectra shapes are found to show universal dependences on Npart for all investigated collision energies.
Heavy Quarkonium Dissociation Cross Sections in Relativistic Heavy-Ion Collisions
Energy Technology Data Exchange (ETDEWEB)
C.-Y. Wong; Eric Swanson; Ted Barnes
2001-12-01
Many of the hadron-hadron cross sections required for the study of the dynamics of matter produced in relativistic heavy-ion collisions can be calculated using the quark-interchange model. Here we evaluate the low-energy dissociation cross sections of J/{psi}, {psi}', {chi}, {Upsilon}, and {Upsilon}' in collision with {pi}, {rho}, and K, which are important for the interpretation of heavy-quarkonium suppression as a signature for the quark gluon plasma. These comover dissociation processes also contribute to heavy-quarkonium suppression, and must be understood and incorporated in simulations of heavy-ion collisions before QGP formation can be established through this signature.
Freeze-Out Parameters in Heavy-Ion Collisions at AGS, SPS, RHIC, and LHC Energies
International Nuclear Information System (INIS)
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
Reaction-diffusion equation for quark-hadron transition in heavy-ion collisions
Bagchi, Partha; Sengupta, Srikumar; Srivastava, Ajit M
2015-01-01
Reaction-diffusion equations with suitable boundary conditions have special propagating solutions which very closely resemble the moving interfaces in a first order transition. We show that the dynamics of chiral order parameter for chiral symmetry breaking transition in heavy-ion collisions, with dissipative dynamics, is governed by one such equation, specifically, the Newell-Whitehead equation. Further, required boundary conditions are automatically satisfied due to the geometry of the collision. The chiral transition is, therefore, completed by a propagating interface, exactly as for a first order transition, even though the transition actually is a crossover for relativistic heavy-ion collisions. Same thing also happens when we consider the initial confinement-deconfinement transition with Polyakov loop order parameter. The resulting equation, again with dissipative dynamics, can then be identified with the reaction-diffusion equation known as the Fitzhugh-Nagumo equation which is used in population genet...
Origins of the di-jet asymmetry in heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Milhano, Jose Guilherme; Zapp, Korinna Christine [Universidade de Lisboa, CENTRA, Instituto Superior Tecnico, Lisbon (Portugal); CERN, Physics Department, Theory Unit, Geneva 23 (Switzerland)
2016-05-15
The di-jet asymmetry - the measure of the momentum imbalance in a di-jet system - is a key jet quenching observable. Using the event generator Jewel we show that the di-jet asymmetry is dominated by fluctuations both in proton-proton and in heavy-ion collisions. We discuss how in proton-proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy-ion collisions two additional sources can contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable. (orig.)
Jet results in heavy ion collisions with the ATLAS experiment at the LHC
Perepelitsa, Dennis; The ATLAS collaboration
2015-01-01
In relativistic collisions of heavy ions, a hot medium with a high density of unscreened color charges is produced, and jets propagating through this medium are known to suffer energy loss. This results in several distinct effects seen in central heavy ion collisions: the yield of inclusive jets measured via the nuclear modification factor is observed to be strongly suppressed; the yield of events with highly asymmetric dijet pairs is observed to be increased; the jet fragmentation is modified. In proton-lead collisions, the production of hard processes is expected to be modified via a modification of nuclear parton distribution functions. While the theory predicts rather small effects to be observed, the data show interesting unexpected features: the nuclear modification factor exhibits a strong centrality dependence; charged particle spectra show an enhancement at large transverse momenta with respect to the proton-proton reference. In this talk, we will summarize the most recent results by ATLAS involving ...
Origins of the di-jet asymmetry in heavy-ion collisions
Milhano, José Guilherme; Zapp, Korinna Christine
2016-05-01
The di-jet asymmetry—the measure of the momentum imbalance in a di-jet system—is a key jet quenching observable. Using the event generator Jewel we show that the di-jet asymmetry is dominated by fluctuations both in proton-proton and in heavy-ion collisions. We discuss how in proton-proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy-ion collisions two additional sources can contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable.
Directory of Open Access Journals (Sweden)
Raghunath Sahoo
2015-01-01
Full Text Available We review the charged particle and photon multiplicities and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons, and the transverse energy measurement.
International Nuclear Information System (INIS)
We review the charged particle and photon multiplicities and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons, and the transverse energy measurement
Collective effects in light-heavy ion collisions
Schenke, Bjoern
2014-01-01
We present results for the azimuthal anisotropy of charged hadron distributions in A+A, p+A, d+A, and He3+A collisions within the IP-Glasma+MUSIC model. Obtained anisotropies are due to the fluid dynamic response of the system to the fluctuating initial geometry of the interaction region. While the elliptic and triangular anisotropies in peripheral Pb+Pb collisions at root-s=2.76 TeV are well described by the model, the same quantities in root-s=5.02 TeV p+Pb collisions underestimate the experimental data. This disagreement can be due to neglected initial state correlations or the lack of a detailed description of the fluctuating spatial structure of the proton, or both. We further present predictions for azimuthal anisotropies in p+Au, d+Au, and He3+Au collisions at root-s=200 GeV. For d+Au and 3He+Au collisions we expect the detailed substructure of the nucleon to become less important.
Collective effects in light-heavy ion collisions
Schenke, Björn; Venugopalan, Raju
2014-11-01
We present results for the azimuthal anisotropy of charged hadron distributions in A+A, p+A, d+A, and 3He+A collisions within the IP-Glasma+MUSIC model. Obtained anisotropies are due to the fluid dynamic response of the system to the fluctuating initial geometry of the interaction region. While the elliptic and triangular anisotropies in peripheral Pb+Pb collisions at √{ s} = 2.76 TeV are well described by the model, the same quantities in √{ s} = 5.02 TeV p+Pb collisions underestimate the experimental data. This disagreement can be due to neglected initial state correlations or the lack of a detailed description of the fluctuating spatial structure of the proton, or both. We further present predictions for azimuthal anisotropies in p+Au, d+Au, and 3He+Au collisions at √{ s} = 200 GeV. For d+Au and 3He+Au collisions we expect the detailed substructure of the nucleon to become less important.
Collective effects in light–heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Schenke, Björn; Venugopalan, Raju
2014-11-15
We present results for the azimuthal anisotropy of charged hadron distributions in A+A, p+A, d+A, and {sup 3}He+A collisions within the IP-Glasma+MUSIC model. Obtained anisotropies are due to the fluid dynamic response of the system to the fluctuating initial geometry of the interaction region. While the elliptic and triangular anisotropies in peripheral Pb+Pb collisions at √(s)=2.76 TeV are well described by the model, the same quantities in √(s)=5.02 TeV p+Pb collisions underestimate the experimental data. This disagreement can be due to neglected initial state correlations or the lack of a detailed description of the fluctuating spatial structure of the proton, or both. We further present predictions for azimuthal anisotropies in p+Au, d+Au, and {sup 3}He+Au collisions at √(s)=200 GeV. For d+Au and {sup 3}He+Au collisions we expect the detailed substructure of the nucleon to become less important.
z-scaling in heavy ion collisions at the RHIC
Tokarev, M. V.
2007-09-01
Experimental data on transverse particle spectra obtained by the STAR, PHENIX, PHOBOS, and BRAHMS collaborations at the RHIC are analyzed in the framework of the generalized concept of z-scaling. It was developed for analysis of inclusive particle production in proton-(anti)proton collisions at high p T and high multiplicities. The general scheme of the approach based on the physical principles of self-similarity, locality, and fractality is reviewed. Independence of the scaling function ψ( z) from energy, multiplicity, and atomic weight for h ±, π ±,0, K {/S 0}, and Λ hadrons produced in Au-Au and Cu-Cu collisions at √ s = 130 and 200 GeV is discussed. Based on z-scaling, the multiplicity dependence of pion transverse spectra up to p T = 25 GeV/ c in Au-Au collisions at √ s = 200 GeV for experiments at the RHIC is predicted.
Violent heavy ion collisions around the Fermi energy
International Nuclear Information System (INIS)
Experimental results on central collisions will be presented and it will be shown that a fusion process still occurs; deexcitation of the hot fused systems formed will be discussed. Then, from the qualitative evolution of central collision products from different reactions studied in the E/A range 20-84 MeV, the vanishing of fusion processes will be inferred; it will be discussed in terms of critical energy deposit and maximum excitation energy per nucleon that nuclei can carry. Finally results concerning the large production of light fragments (3 < approximately Z < approximately 12) experimentally observed in the Fermi energy domain will be presented and discussed in terms of a multifragmentation of the whole nuclear system or of part of it for intermediate impact parameter collisions (109 refs, 49 fig)
Introduction to high-energy heavy-ion collisions
Wong, Cheuk-Yin
1994-01-01
Written primarily for researchers and graduate students who are new in this emerging field, this book develops the necessary tools so that readers can follow the latest advances in this subject. Readers are first guided to examine the basic informations on nucleon-nucleon collisions and the use of the nucleus as an arena to study the interaction of one nucleon with another. A good survey of the relation between nucleon-nucleon and nucleus-nucleus collisions provides the proper comparison to study phenomena involving the more exotic quark-gluon plasma. Properties of the quark-gluon plasma and s
Denicol, Gabriel S; Jeon, Sangyong
2015-01-01
If the bulk viscosity of QCD matter is large, the effective pressure of the hot and dense matter created in ultrarelativistic heavy ion collisions can become negative, leading to instabilities in the evolution of the plasma. In the context of heavy ion collisions, this effect is sometimes referred to as cavitation. In this contribution we discuss the onset of cavitation in event-by-event hydrodynamic simulations of ultrarelativistic heavy ion collisions at LHC energies. We estimate how large the bulk viscosity of the QGP has to be in the QCD (pseudo) phase transition region in order for the effective pressure of the system to actually become negative.
International Nuclear Information System (INIS)
The study of reaction products, fragments and light charged particles, emitted during heavy-ion collisions at intermediate energies has shown the dominant binary dissipative character of the reaction, which is persisting for almost all impact parameters. However, in comparison with this purely binary process, an excess of nuclear matter is observed in-between the quasi-projectile and the quasi-target. To understand the mechanisms producing such an excess, this work studies more precisely the breakup in two fragments of the quasi-projectile formed in Xe+Sn, from 25 to 50 MeV/u, and Gd+C and Gd+U at 36 MeV/u. The data were obtained during the first INDRA experiment at GANIL. The angular distributions of the two fragments show the competition between statistical fission and non-equilibrated breakup of the quasi-projectile. In the second case, the two fragments are aligned along the separation axis of the two primary partners. The comparison of the fission directions and probabilities with statistical models allows us to measure the fission time, as well as the angular momentum, temperature and size of the fissioning residue. The relative velocities are compatible with Coulomb and thermal effects in the case of statistical fission and are found much higher for the breakup of a non-equilibrated quasi-projectile, which indicates that the projectile was deformed during interaction with the target. Such deformations should be compared with dynamical calculations in order to constrain the viscosity of nuclear matter and the parameters of the nucleon-nucleon interaction, (author)
Large mass diphotons and dileptons from relativistic heavy ion collisions
International Nuclear Information System (INIS)
In this work it has been suggested that an experimental detection of the large mass diphotons could provide a valuable confirmation of the results obtained from the measurement of dileptons. A comparison of the measurements of dileptons and diphotons may also provide additional information about the dynamics of evolution of the collision
J/psi elliptic flow in relativistic heavy ion collisions
Yunpeng LIU; Xu, Nu; Zhuang, Pengfei
2009-01-01
The J/psi elliptic flow in high energy nuclear collisions is calculated in a transport model. While the flow is very small at SPS and RHIC energies, it is strongly enhanced at LHC energy due to the dominance of the regeneration mechanism.
Dileptons in high-energy heavy-ion collisions
Indian Academy of Sciences (India)
Ralf Rapp
2003-04-01
The current status of our understanding of dilepton production in ultra-relativistic heavyion collisions is discussed with special emphasis on signals from the (approach towards) chirally restored and deconﬁned phases. In particular, recent results of the CERN-SPS low-energy runs are compared to model predictions and interpreted. Prospects for RHIC experiments are given.
Exploring the QCD phase diagram through relativistic heavy ion collisions
Mohanty, Bedangadas
2013-01-01
We present a review of the studies related to establishing the QCD phase diagram through high energy nucleus-nucleus collisions. We particularly focus on the experimental results related to the formation of a quark-gluon phase, crossover transition and search for a critical point in the QCD phase diagram.
International Nuclear Information System (INIS)
We systematically investigate the pion transverse momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss (HBT) interferometry in the granular source model for the heavy ion collisions of Au-Au at √(sNN)=200 GeV and Pb-Pb at √(sNN)=2.76 TeV with different centralities. The granular source model can well reproduce the experimental results of the heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). We examine the parameters involved in the granular source model. The experimental data of the momentum spectrum, elliptic flow, and HBT radii for the two collision energies and different centralities impose very strict constraints on the model parameters. They exhibit certain regularities for collision centrality and energy. The space-time structure and expansion velocities of the granular sources for the heavy ion collisions at the RHIC and LHC energies with different centralities are investigated
An experimental review on heavy flavor $v_{2}$ in heavy-ion collision
Nasim, Md; Huang, Huan Zhong
2016-01-01
For over a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) has been to study the properties of QCD matter under extreme conditions -high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb and U+U collisions at energies ranging from $\\sqrt{s_{NN}}$ = 7.7 GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nuclei-nuclei collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy flavor hadrons and...
Reaction-diffusion equation for quark-hadron transition in heavy-ion collisions
Bagchi, Partha; Das, Arpan; Sengupta, Srikumar; Srivastava, Ajit M.
2015-09-01
Reaction-diffusion equations with suitable boundary conditions have special propagating solutions which very closely resemble the moving interfaces in a first-order transition. We show that the dynamics of the chiral order parameter for the chiral symmetry breaking transition in heavy-ion collisions, with dissipative dynamics, is governed by one such equation; specifically, the Newell-Whitehead equation. Furthermore, required boundary conditions are automatically satisfied due to the geometry of the collision. The chiral transition is, therefore, completed by a propagating interface, exactly as for a first-order transition, even though the transition actually is a crossover for relativistic heavy-ion collisions. The same thing also happens when we consider the initial confinement-deconfinement transition with the Polyakov loop order parameter. The resulting equation, again with dissipative dynamics, can then be identified with the reaction-diffusion equation known as the FitzHugh-Nagumo equation which is used in population genetics. Observational constraints imply that the entire phase conversion cannot be achieved by such slow moving fronts, and some alternate faster dynamics needs also to be invoked; for example, involving fluctuations. We discuss the implications of these results for heavy-ion collisions. We also discuss possible extensions for the case of the early universe.
An Experimental Review on Heavy-Flavor v2 in Heavy-Ion Collision
Directory of Open Access Journals (Sweden)
Md. Nasim
2016-01-01
Full Text Available For over a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC and the Large Hadron Collider (LHC has been to study the properties of QCD matter under extreme conditions—high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb, and U+U collisions at energies ranging from sNN=7.7 GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy-flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nucleus-nucleus collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy-flavor hadrons and to outline the scientific opportunities in this sector due to future detector upgrade. We will mainly discuss the elliptic flow of open charmed meson (D-meson, J/ψ, and leptons from heavy-flavor decay at RHIC and LHC energy.
Pre-equilibrium effects and neck emission in 10-40 A MeV Heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Stefanini, A.A.; Bini, M.; Casini, G.; Maurenzig, P.R.; Olmi, A.; Pasquali, G.; Piantelli, S.; Poggi, G.; Taccetti, N. [Inst. Naz. di Fis. Nuc. and Univ. di Firenze, I-50125, Florence (Italy)
2001-09-01
Full text: The heavy ion collisions at energy between 10 and 100 A MeV are supposed to show characteristics intermediate between those of the low and high regimes. Recent measurements have shown that in heavy ion collisions at Fermi energies pre-equilibrium effects in the sharing of the excitation energy and angular momentum between the two colliding partners are present. Moreover, for less central collisions an intense emission of light charged particles (LCP) and especially of intermediate mass fragments (IMF) is found, not consistent with the statistical emission from the hot, fully accelerated major fragments. Our experiment has been optimized for extending previous results to more peripheral reactions. The collisions {sup 116} Sn + {sup 93} Nb and {sup 93}Nb + {sup ll6} Sn at 29.5 A MeV were studied at LNS, Catania, with an apparatus consisting of 24 parallel-plate detectors for heavy fragments (A {>=} 20), 96 {delta} E-E silicon telescopes and 160 scintillator phoswichs for LCP and IMF up to Z {approx_equal} 20. Binary events with only two heavy fragments were analysed with kinematic method, using the Total Kinetic Energy Loss (TKEL) to sort the data. Events up to grazing collisions could be measured thanks to the very low thresholds ({approx} 0.1 A MeV) for the target-like fragments. The experimental differences between the number of the PLF emitted nucleons in direct and reverse reactions point to pre-equilibrium effects. The deduced multiplicities of p, He and IMF vs. TKEL show that in most peripheral collisions selected in our experiment the multiplicity of mid-velocity IMF's, although small ({approx_equal} 5 x 10-2), greatly overcomes the statistical emission (by more than a factor of 20). (Author)
Study on the method of mini-jet identification in relativistic heavy ion collisions
De-sheng, Li; Gang, Chen
2011-01-01
In this thesis a set of methods identifying minijet from final state particles in the relativistic heavy ion collision events is established and the parameter dependence has been investigated in Au+Au collisions at $\\sqrt s= 200$GeV using a multiphase transport model (AMPT). It is found that the number of minijets reduces with the increasing of collision parameter and raises with the increasing of c.m energy. Furthermore, we analyze the rapidity and momentum distribution inside minijets identified using this method.
International Nuclear Information System (INIS)
The lectures presented at the Summer School on Nuclear Physics and High-energy Physics (1988) concern quark-gluon plasma researches in heavy ion collisions. The subjects presented are: high density matter equation and phase transition, dynamics of high energy nuclei-nuclei collisions and the definition of the parameters characterizing the interaction, possible signatures of the quark-gluon plasma, background noise estimation by collision dynamic model in the absence of a plasma, experimental results at high and low energy, the contribution of cosmic rays to the research of the quark-gluon plasma, discriminating analysis
Parton-hadron dynamics in heavy-ion collisions
Bratkovskaya, E L; Cassing, W; Konchakovski, V P; Linnyk, O; Marty, R; Berrehrah, H
2013-01-01
The dynamics of partons and hadrons in relativistic nucleus-nucleus collisions is analyzed within the novel Parton-Hadron-String Dynamics (PHSD) transport approach, which is based on a dynamical quasiparticle model for the partonic phase (DQPM) including a dynamical hadronization scheme. The PHSD approach is applied to nucleus-nucleus collisions from low SPS to LHC energies. The traces of partonic interactions are found in particular in the elliptic flow of hadrons and in their transverse mass spectra. We investigate also the equilibrium properties of strongly-interacting infinite parton-hadron matter characterized by transport coefficients such as shear and bulk viscosities and the electric conductivity in comparison to lattice QCD results.
Transport theory of dissipative heavy-ion collisions
International Nuclear Information System (INIS)
The lectures present the formulation of a transport theory, the derivation of a practicable transport equation (Fokker-Planck equation) and the evaluation of transport coefficients for dissipative (or deeply inelastic) heavyion collisions. The applicability of the theoretical concept is tested with remarkable success in the analyses of various experimental informations (mass transfer, angular-momentum dissipation and energy loss). Some critical remarks on the present situation of transport theories are added. Future developments are outlined. (orig.)
Two-Pion Interferometry for the Granular Source in Heavy Ion Collisions at LHC Energies
Institute of Scientific and Technical Information of China (English)
尹洪杰; 安飞; 张卫宁
2012-01-01
The space-time characters of the pion-emitting sources produced in the heavy ion collisions at the Large Hadron Collider (LHC) energies are investigated in a granular source model of quark-gluon plasma droplets. The results of two-pion interferometry indicate that the longi- tudinal interferometry radius is sensitive to the initial breakup time of the system. For a larger breakup time the values of the longitudinal interferometry radius for the LHC source are larger than that of the source produced in the collisions at the Relativistic Heavy Ion Collider's (RHIC) top energy. However, the values of the longitudinal radius are smaller if the source fragments at a smaller breakup time with a higher initial temperature of the droplets. The values of the transverse interferometry radius in the "side" direction for the LHC sources are larger than those for the RHIC source. The imaging analyses for the characteristic quantities of the granular sources are consistent with the interferometry radii.
Rencontres de Moriond QCD 2012: Probing the nature of heavy-ion collisions
Katarina Anthony
2012-01-01
Wednesday began with presentations by experiments worldwide on their investigations into the intriguing nature of the Quark Gluon Plasma (QGP). The ALICE Collaboration examined further preliminary results from the LHC’s 2010 Pb-Pb run, observing that particles containing strange quarks were more abundant than they are in proton-proton collisions – indicating the presence of QGP. They also presented results from the so-called “soft probes” that allow scientists to look at the collective behaviour of the QGP medium. The ATLAS and CMS Collaborations provided a very different approach to the study heavy ion physics: examining particle energy loss in the QGP by looking at the momentum of particle jets leaving the medium. ATLAS reported their results on a variety of studies using jets, charged hadrons and weak bosons produced in heavy-ion collisions during the 2010 run. Presenting their results from the 2011 run, the CMS Collaboration found that there is energy...
Two-particle interferometry for non-central heavy-ion collisions
Wiedemann, Urs Achim
1998-01-01
In non-central heavy ion collisions, identical two particle Hanbury-Brown/Twiss (HBT) correlations C(K,q) depend on the azimuthal direction of the pair momentum K. We investigate the consequences for a harmonic analysis of the corresponding HBT radius parameters. Our discussion includes both, a model- independent analysis of these parameters in the Gaussian approximation, and the study of a class of hydrodynamical models which mimic essential geometrical and dynamical properties of peripheral heavy ion collisions. Also, we discuss the additional geometrical and dynamical information contained in the harmonic coefficients of these HBT radius parameters. The leading contribution of their first and second harmonics are found to satisfy simple constraints. This allows for a minimal, azimuthally sensitive parametrization of all first and second harmonic coefficients in terms of only two additional fit parameters. We determine to what extent these parameters can be extracted from experimental data despite finite mu...
Institute of Scientific and Technical Information of China (English)
KE Hong-Wei; XU Ming-Mei; LIU Lian-Shou
2009-01-01
By studying the critical phenomena in continuum-percolation of discs, we find a new approach to locate the critical point, i.e.using the inflection point of P_∞ as an evaluation of the percolation threshold.The susceptibility, defined as the derivative of P_∞, possesses a finite-size scaling property, where the scaling exponent is the reciprocal of ν, the critical exponent of the correlation length.A possible application of this approach to the study of the critical phenomena in relativistic heavy ion collisions is discussed.The critical point for deconfinement can be extracted by the inflection point of P_(QGP)-the probability for the event with QGP formation.The finite-size scaling of its derivative can give the critical exponent ν, which is a rare case that can provide an experimental measure of a critical exponent in heavy ion collisions.
Free energy droplet formation in ultra-relativistic heavy-ion collision
International Nuclear Information System (INIS)
In ultra-relativistic heavy-ion collisions, quantum chromodynamics (QCD) predicts the phase transition from hadronic phase to the quark-gluon plasma phase. The lattice QCD calculations suggest the phase transition is of first order at a critical temperature around T ≈ 170 MeV. Such phase transition form a new state of matter, called the quark-gluon plasma (QGP). The fact is that the order of phase transitions are still unknown. In ultra-relativistic heavy-ion collisions, free energy droplet formation provide a unique opportunity as one of the promising experimental signature of the quark-gluon plasma. Thus, if transition is a first order then it may proceed with a supercooling quark gluon plasma followed by a nucleation and growth of droplet with the release of latent heat as the transition progress
Ray, Robert L
2016-01-01
Two-particle correlation measurements and analysis are an important component of the relativistic heavy-ion physics program. In particular, particle pair-number correlations on two-dimensional transverse momentum ($p_t$) allow unique access to soft, semi-hard and hard-scattering processes in these collisions. Precise measurements of this type of correlation are essential for understanding the dynamics in heavy-ion collisions. However, transverse momentum correlation measurements are especially vulnerable to statistical and systematic biases. In this paper the origins of these large bias effects are explained and mathematical correlation forms are derived from mean-$p_t$ fluctuation quantities in the literature in an effort to minimize bias. Monte Carlo simulations are then used to test the degree to which each correlation definition leads to unbiased results in realistic applications. Several correlation forms are shown to be unacceptable for data analysis applications while several others are shown to reprod...
Probing the nuclear equation-of-state and the symmetry energy with heavy-ion collisions
International Nuclear Information System (INIS)
The present status of studies aimed at constraining the nuclear equation of state with heavy-ion collision dynamics is presented. Multifragmentation phenomena, including their isotopic distributions, charge correlations and emission time-scales, may revel the existence of liquid-gas transitions in the phase diagram. Exploring the isotopic degree of freedom in nuclear dynamics is then required in order to constrain the equation of state of asymmetric nuclear matter which presently represents a major priority due to its relevance to both nuclear physics and astrophysics. Some observables that have successfully constrained the density dependence of the symmetry energy are presented, such as neutron-proton yield ratios and isospin diffusion and drift phenomena. The reported results and status of the art is discussed by also considering some of the present problems and some future perspectives for the heavy-ion collision community. (authors)
Novel quantum phenomena induced by strong magnetic fields in heavy-ion collisions
Hattori, Koichi
2016-01-01
The relativistic heavy-ion collisions create both hot quark-gluon matter and strong magnetic fields, and provide an arena to study the interplay between quantum chromodynamics (QCD) and quantum electrodynamics (QED). In recent years, it has been shown that such an interplay can generate a number of interesting quantum phenomena in hadronic and quark-gluon matter. In this short review, we first discuss some properties of the magnetic fields in heavy-ion collisions and then give an overview of the magnetic-field induced novel quantum effects. In particular, we focus on the magnetic effect on the heavy-flavor mesons, and the heavy quark transports, and also the phenomena closely related to chiral anomaly.
Diabaticity in heavy-ion collisions and its role in non-equilibrium neutron emission
International Nuclear Information System (INIS)
Slow collective nuclear motions such as heavy-ion collision slightly above the Coulomb barrier and induced nuclear fission imply collective velocities. In the vicinity of quasi-crossings of adiabatic levels the nuclear single-particle motion changes completely. A nucleon in the lower level before the crossing will find itself in the upper level if this has been unoccupied before and the nucleon will stay in the diabatic level. The diabatic potential now corresponds to the extra energy pumped into the system due to the diabatic production of particle-hole state. An interesting aspect of diabatic s.p. states is their connection with non-equilibrium neutron or proton emission in heavy-ion collisions. Several neutrons could be emitted of the s.p. states to the collective motion which produces highly excited s.p. states
Azimuthal asymmetry and correlations of hard photons in intermediate energy heavy ion collisions
International Nuclear Information System (INIS)
Hard photon emitted from energetic heavy ion collisions is of very interesting since it does not experience the late-stage nuclear interaction, therefore it is useful to explore the early-stage information of matter phase. In this work, we investigated the directed flow and elliptic flow for proton-neutron Bremsstrahlung hard photons in intermediate energy heavy-ion collisions. The positive directed flow and negative elliptic flow of directed photons are illustrated and they seem to be anti-correlated to the free proton's flow. Also we calculated the two-photon correlation functions from which the information of photon source was extracted, and while two-photon azimuthal correlations are presented as a good method to extract the elliptic flow parameter v2 of direct hard photons. (author)
Chatterjee, Arghya; Nayak, Tapan K; Sahoo, Nihar Ranjan
2016-01-01
Susceptibilities of conserved quantities, such as baryon number, strangeness and electric charge are sensitive to the onset of quantum chromodynamics (QCD) phase transition and are expected to provide information on the matter produced in heavy-ion collision experiments. A comprehensive study of the second-order diagonal susceptibilities and cross correlations has been made within a thermal model approach of the hadron resonance gas (HRG) model as well as with a hadronic transport model, UrQMD. We perform a detailed analysis of the effect of detector acceptances and choice of particle species in the experimental measurements of the susceptibilities for heavy-ion collisions corresponding to \\sNN = 4 GeV to 200 GeV. The transverse momentum cutoff dependence of suitably normalised susceptibilities are proposed as useful observables to probe the properties of the medium at freezeout.
Probing the nuclear equation-of-state and the symmetry energy with heavy-ion collisions
Directory of Open Access Journals (Sweden)
Verde Giuseppe
2014-03-01
Full Text Available The present status of studies aimed at constraining the nuclear equation of state with heavy-ion collision dynamics is presented. Multifragmentation phenomena, including their isotopic distributions, charge correlations and emission time-scales, may revel the existence of liquid-gas transitions in the phase diagram. Exploring the isotopic degree of freedom in nuclear dynamics is then required in order to constrain the equation of state of asymmetric nuclear matter which presently represents a major priority due to its relevance to both nuclear physics and astrophysics. Some observables that have successfully constrained the density dependence of the symmetry energy are presented, such as neutron-proton yield ratios and isospin diffusion and drift phenomena. The reported results and status of the art is discussed by also considering some of the present problems and some future perspectives for the heavy-ion collision community.
Hencken, Kai; Trautmann, Dirk; Baur, Gerhard
1998-01-01
We present a calculation of higher order effects for the impact parameter dependent probability for single and multiple electron-positron pairs in (peripheral) relativistic heavy ion collisions. Also total cross sections are given for SPS and RHIC energies. We make use of the expression derived recently by several groups where the summation of all higher orders can be done analytically in the high energy limit. An astonishing result is that the cross section, that is, integrating over all imp...
Lappi, T.; Mäntysaari, H.
2014-01-01
We compute cross sections for incoherent and coherent diffractive J/$\\Psi$ and $\\Psi(2S)$ production in ultraperipheral heavy ion collisions. The dipole models used in these calculations are obtained by fitting the HERA deep inelastic scattering data and compared with available electron-proton diffraction measurements. We obtain a reasonably good description of the available ALICE data. We find that the normalization of the ultraperipheral cross section has large model dependence, but the rap...
Heavy ion collisions at intermediate energies in a quark-gluon exchange framework
da Silva, D. T.; Hadjimichef, D.
2002-01-01
Heavy ion collisions at intermediate energies can be studied in the context of the Vlasov-Uehling-Uhlenbeck (VUU) model. One of the main features in this model is the nucleon-nucleon (NN) cross section in the collisional term. Quark interchange plays a role in the NN interaction and its effect can be observed in the cross section. We explore the possibility that quark interchange effects can appear in observables at energies lower than RHIC.
The QCD Pomeron in Ultraperipheral Heavy Ion Collisions: II. Heavy Quark Production
Goncalves, V. P.; Machado, M. V. T.
2003-01-01
The heavy quark production in ultraperipheral heavy ion collisions is investigated, in particular we focus on the results from the coherent interactions given by the two-photon process. One addresses the heavy quark total cross sections at photon level considering the saturation model and the BFKL dynamics in the color dipole picture. The corresponding cross sections at nuclear level are presented. It is verified that the QCD dynamics implies an enhancement of the cross section in comparison ...
Electromagnetic Heavy Lepton Pair Production in Relativistic Heavy-Ion Collisions
Sengul, M. Y.; Guclu, M. C.; Mercan, O.; Karakus, N. G.
2015-01-01
We calculate the cross sections of electromagnetic productions of muon and tauon pair productions from the ultra-relativistic heavy ion collisions. Since the Compton wavelengths of muon and tauon are comparable to the radius of the colliding ions, nuclear form factors play important roles for calculating the cross sections. Recent measurement [1] indicates that the neutrons are differently distributed from the protons therefore this affects the cross section of the heavy lepton pair productio...
Event-by-event analysis of heavy ion collisions and thermodynamical fluctuations
Shuryak, E. V.
1997-01-01
The event-by-event analysis of heavy ions collisions is becoming possible with advent of large acceptance detectors: it can provide dynamical information which cannot be obtained from inclusive spectra. We identify some observables which can be related to standard thermodynamical fluctuations and therefore may provide information about properties of hadronic matter at the freeze-out stage. Among those are fluctuations of ``apparent temperature'' (the $p_t$ slope), as well as the population of...
Auditore L.; Pagano A.; Russotto P.
2015-01-01
At Laboratori Nazionali del Sud (LNS) the CHIMERA 4π multidetector has been designed and setup to detect charged particles emitted in heavy ion collisions at intermediate energies. Properties and performances of CHIMERA have been widely demonstrated by published results obtained in the performed experiments. Moreover, in recent years, a new charged particle detector (ChPD) for correlation studies (FARCOS) has been designed, and recently a first prototype has been coupled to CHIMERA, in order ...
Stochastic approaches to dynamics of heavy ion collisions, the case of thermal fission
Energy Technology Data Exchange (ETDEWEB)
Boilley, D.; Abe, Y. [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Suraud, E. [Universite Paul Sabatier, 31 - Toulouse (France). Lab. de Physique Quantique; Ayik, S. [Tennessee Technological Univ., Cookeville, TN (United States)
1994-03-30
In order to study the influence of fluctuations on various phenomena linked to heavy ion collisions, a Langevin equation has been derived from a microscopic model. Parameters entering this equation are completely determined from microscopic quantities characterizing nuclear matter. This equation has been applied to various phenomena at intermediate energies. This paper focuses on large amplitude motions and especially thermal fission. Fission rate is calculated and compared to experimental results.
Multifragmentation in asymmetric heavy-ion collisions. An experimental trace search
International Nuclear Information System (INIS)
The author presents a review about experimental studies of multifragmentation in heavy ion collisions. After a description of the experimental methods for the study of such processes he describes the emission characteristics of medium heavy fragments like energy and angular distribution, production cross sections, and multiplicity. Then he considers statistical aspects of highly excited nuclei. Then the production of unstable fragments is discussed. Finally the author discusses the study of pp correlations looking for interference effects. (HSI)
Photon-Photon Luminosities in Relativistic Heavy Ion Collisions at LHC Energies
Hencken, Kai; Trautmann, Dirk; Baur, Gerhard
1995-01-01
Effective photon-photon luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding photon-photon luminosities at electron-positron and future Photon Linear Colliders (PLC). Higher order corrections as well as inelastic processes are discussed. It is concluded that feasible high luminosity Ca-Ca collisions at the Large Hadron Collider (LHC)...
Photon-Photon Luminosities in Relativistic Heavy Ion Collisions at LHC Energies
Hencken, Kai; Trautmann, Dirk; Baur, Gerhard
1994-01-01
Effective photon-photon luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding photon-photon luminosities at electron-positron and future Photon Linear Colliders (PLC). Higher order corrections as well as inelastic processes are discussed. It is concluded that feasible high luminosity Ca-Ca collisions at the Large Hadron Collider (LHC)...
Net baryon density in Au+Au collisions at the Relativistic Heavy Ion Collider
Bass, S A; Srivastava, D K; Bass, Steffen A.; Müller, Berndt; Srivastava, Dinesh K.
2003-01-01
We calculate the net baryon rapidity distribution in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) in the framework of the Parton Cascade Model (PCM). Parton rescattering and fragmentation leads to a substantial increase in the net baryon density at mid-rapidity over the density produced by initial primary parton-parton scatterings. The PCM is able to describe the measured net baryon density at RHIC.
Light-fronts approach to electron-positron pair production in ultrarelativistic heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Wells, J.C. [Oak Ridge National Lab., TN (United States). Center for Computational Sciences; Segev, B. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States). Inst. for Theoretical Atomic and Molecular Physics
1998-03-01
The authors solve, in an ultrarelativistic limit, the time-dependent Dirac equation describing electron-positron pair production in peripheral relativistic heavy ion collisions using light front variables and a light-fronts representation, obtaining nonperturbative results for the free pair-creation amplitudes in the collider frame. Their result reproduces the result of second-order perturbation theory in the small charge limit while nonperturbative effects arise for realistic charges of the ions.
Formulation of relativistic dissipative fluid dynamics and its applications in heavy-ion collisions
Jaiswal, Amaresh
2014-01-01
Relativistic fluid dynamics finds application in astrophysics, cosmology and the physics of high-energy heavy-ion collisions. In this thesis, we present our work on the formulation of relativistic dissipative fluid dynamics within the framework of relativistic kinetic theory. We employ the second law of thermodynamics as well as the relativistic Boltzmann equation to obtain the dissipative evolution equations. We present a new derivation of the dissipative hydrodynamic equations using the sec...
Heavy-Ion Collisions and Black Holes in Anti-de-Sitter Space
Ellis, John
1999-01-01
Recent developments linking non-perturbative quantum gauge theories in Minkowski space to classical gravity theories in anti-de-Sitter space are reviewed at a simple level. It is suggested how these spectacular advances may be extended to discuss the quark-gluon phase transition in terms of black holes in anti-de-Sitter space, with possible relevance to heavy-ion collisions.
On the accuracy of using Fokker Planck equation in heavy ion collision
Dutta, Nirupam
2015-01-01
Application of Fokker-Planck equation to heavy quark transport in the evolving medium created in heavy ion collision is critically scrutinised. We realise that the approach introduces a moderate uncertainty in drag and diffusion coefficients culminating in huge ambiguity in the theoretical prediction of nuclear modification factor $R_{AA}$. Quantitative estimation of the error is presented by considering recent developments in this field.
Various Models for Pion Probability Distributions from Heavy-Ion Collisions
Mekjian, A. Z.; Schlei, B. R.; Strottman, D.
1998-01-01
Various models for pion multiplicity distributions produced in relativistic heavy ion collisions are discussed. The models include a relativistic hydrodynamic model, a thermodynamic description, an emitting source pion laser model, and a description which generates a negative binomial description. The approach developed can be used to discuss other cases which will be mentioned. The pion probability distributions for these various cases are compared. Comparison of the pion laser model and Bos...
Size of the thermal source in relativistic heavy-ion collisions
Bozek, Piotr
2005-01-01
The dependence of the size of the thermal source on the centrality in ultrarelativistic heavy-ion collisions is studied. The interaction region consists of a well defined thermalized core, and of an outer mantle where the production scales with the number of participants. The thermal source builds up in the region with the largest density of participants in the transverse plane. Particle production in the thermalized core is enhanced in comparison to the wounded nucleon model. The change of t...
Baryon production and net-proton distributions in relativistic heavy ion collisions
Yang, C. B.; X Wang
2011-01-01
The higher order moments of the net-baryon distributions in relativistic heavy ion collisions are useful probes for the QCD critical point and fluctuations. We study the net-proton distributions and their moments in a simple model which considers the baryon stopping and pair production effects in the processes. It is shown that a single emission source model can explain the experimental data well. Centrality and energy dependence of the distributions and higher moments is discussed.
Source chaoticity in relativistic heavy ion collisions at SPS and RHIC
Morita, Kenji; Muroya, Shin; NAKAMURA, Hiroki
2006-01-01
We investigate degree of coherence of pion sources produced in relativistic heavy ion collisions using multi-particle interferometry. In order to obtain ``true'' chaoticity, lambda^true from two-pion correlation functions measured in experiments, we make a correction for long-lived resonance decay contributions. Using this lambda^true and the weight factor which are obtained from parameter fitted to two- and three-pion correlation function, we calculate a chaotic fraction epsilon and the numb...
Ayala, Alejandro; Sanchez, Angel
2001-01-01
We examine the effects that a confining boundary together with hydrodynamical expansion play on two-pion distributions in relativistic heavy-ion collisions. We show that the effects arise from the introduction of further correlations due both to collective motion and the system's finite size. As is well known, the former leads to a reduction in the apparent source radius with increasing average pair momentum K. However, for small K, the presence of the boundary leads to a decrease of the appa...
Graviton Production in Relativistic Heavy-Ion Collisions
Ahern, Sean C.; Norbury, John W.; Poyser, William J.
2000-01-01
We study the feasibility of producing the graviton of the novel Kaluza-Klein theory in which there are d large compact dimensions in addition to the 4 dimensions of Minkowski spacetime. We calculate the cross section for producing such a graviton in nucleus-nucleus collisions via t-channel photon-photon fusion using the semiclassical Weizsacker-Williams method and show that it can exceed the cross section for graviton production in electron-positron scattering by several orders of magnitude.
Intermediate Mass Fragments Emission in Peripheral Heavy-Ion Collisions
Bini, M.; Casini, G.; Maurenzig, P. R.; Olmi, A.; Pasquali, G.; Piantelli, S.; Poggi, G.; Stefanini, A. A.; Taccetti, N.
The collision 116Sn + 93Nb at 29.5 AMeV in direct and reverse kinematics has been studied at LNS in Catania. In particular the emission pattern in the νperp - νpar plane of Intermediate Mass Fragments with Z=3-7 (IMF's) shows that for peripheral reactions most of IMF's are emitted at velocities intermediate between those of the projectile- and target-like products. From coulomb trajectory calculations one can infere that these IMF's are produced mainly in the interaction zone, in a short time interval at the end of the target-projectile interaction.
Energy dependence of resonance production in relativistic heavy ion collisions
Shao, Feng-lan; Wang, Rui-qin; Zhang, Mao-sheng
2016-01-01
The production of hadronic resonances $K^{*}(892)$, $\\phi(1020)$, $\\Sigma^{*}(1385)$, and $\\Xi^{*}(1530)$ in central AA collisions at $\\sqrt{s_{NN}}=$ 17.3, 200, and 2760 GeV are systematically studied. The direct production of these resonances at system hadronization are described by the quark combination model and the effects of hadron multiple-scattering stage are dealt with by a ultra-relativistic quantum molecular dynamics model (UrQMD). We study the contribution of these two production sources to final observation and compare the final spectra with the available experimental data. The $p_T$ spectra of $K^{*}(892)$ calculated directly by quark combination model are explicitly higher than the data at low $p_T \\lesssim 1.5$ GeV and taking into account the modification of rescattering effects the resulting final spectra well agree with the data at all three collision energies. The rescattering effect on $\\phi(1020)$ production is weak and including it can slightly improve our description at low $p_T$ on the...
Entropy Production and Effective Viscosity in Heavy-Ion Collisions
Ivanov, Yu B
2016-01-01
Entropy production and an effective viscosity in central Au+Au collisions are estimated in a wide range of incident energies 3.3 GeV $\\le \\sqrt{s_{NN}}\\le$ 39 GeV. The simulations are performed within a three-fluid model employing three different equations of state with and without deconfinement transition, which are equally good in reproduction of the momentum-integrated elliptic flow of charged particles in the considered energy range. It is found that more that 80\\% entropy is prodused during a short early collision stage which lasts $\\sim$1 fm/c at highest considered energies $\\sqrt{s_{NN}}\\ge$ 20 GeV. The estimated values of the viscosity-to-entropy ratio ($\\eta/s$) are approximately the same in all considered scenarios. At final stages of the system expansion they range from $\\sim$0.05 at highest considered energies to $\\sim$0.5 lowest ones. It is found that the $\\eta/s$ ratio decreases with the temperature ($T$) rise approximately as $\\sim 1/T^4$ and exhibits a rather weak dependence on the net-baryon ...
Subthreshold Production of Neutral Pions in Heavy Ion Collisions
2002-01-01
The pion production below the threshold at 290 MeV/u (corresponding to the minimum beam velocity at which pions can be produced in nucleon-nucleon collisions) is sensitive to coherent effects in the momentum distribution of the nucleons in the internuclear collision region. Such collective or coherent effects would manifest themselves in an enhancement of the observed cross section with respect to a prediction on the basis of model momentum distributions, e.g. from the Fermi gas model. \\\\ \\\\ With neutral pions such experiments can be extended to rather low energies and rather small cross sections (in the sub-@mb range) due to the fact that the @p|0's leave the composite nuclear system undisturbed by the Coulomb forces and that their decay $\\gamma$ rays can be detected with high efficiency also at very low pion momentum. In our experiments using |1|2C~ions of 60, 74 and 84~MeV/u and |1|80 of 84~MeV/u we were able to clearly sep from background from different sources. The large efficiency of the annular lead gl...
Elliptic flow in heavy-ion collisions at NICA energies
B. Ivanov, Yu.; Soldatov, A. A.
2016-08-01
The transverse-momentum-integrated elliptic flow of charged particles at midrapidity, v2 (charged), and that of identified hadrons from Au+Au collisions are analyzed in the range of incident energies relevant to the Nuclotron-based Ion Collider Facility (NICA). Simulations are performed within a three-fluid model employing three different equations of state (EoSs): a purely hadronic EoS and two versions of the EoS involving the deconfinement transition-a first-order phase transition and a smooth crossover one. The present simulations demonstrate low sensitivity of v2 (charged) to the EoS. All considered scenarios equally well reproduce recent STAR data on v2 (charged) for mid-central Au+Au collisions and properly describe its change of sign at the incident energy decrease below √{s_{NN}} ≈ 3.5 GeV. The predicted integrated elliptic flow of various species exhibits a stronger dependence on the EoS. A noticeable sensitivity to the EoS is found for anti-protons and, to a lesser extent, for K- mesons. Presently there are no experimental data that could verify these predictions. Future experiments at NICA could corroborate these findings.
Directory of Open Access Journals (Sweden)
Auditore L.
2015-01-01
Full Text Available At Laboratori Nazionali del Sud (LNS the CHIMERA 4π multidetector has been designed and setup to detect charged particles emitted in heavy ion collisions at intermediate energies. Properties and performances of CHIMERA have been widely demonstrated by published results obtained in the performed experiments. Moreover, in recent years, a new charged particle detector (ChPD for correlation studies (FARCOS has been designed, and recently a first prototype has been coupled to CHIMERA, in order to test performances in view of correlation measurements in coincidence with 4π detectors. Simultaneous neutrons and charged particles detection in heavy ion collisions represents an important experimental progress for future experiments to be performed with both stable and exotic nuclei. In order to investigate about this possibility, simple Monte Carlo simulations have been performed. Preliminary simulations have been carried out by means of MCNPX transport code to evaluate the perturbation effects, including cross-talk and time response, induced in CHIMERA and/or FARCOS Si-CsI(Tl telescopes on (typical 20MeV neutron signals coming froma typical reaction in heavy ion collisions at the Fermi energy. Moreover, first data analysis results of the INKIISSY experiment indicates sizable probability to detect neutrons by properly shadowing CHIMERA Si-CsI(Tl telescopes. Analysis is still in progress.
Study of jet quenching in heavy ion collisions at LHC using ATLAS detector
Štefko, Pavol
2015-01-01
Quark-Gluon Plasma (QGP) is one of the most extreme states of matter which exists only in extraordinary conditions of heavy-ion collisions that can be achieved at particle accelerators. Interactions between the partons and the hot, dense QGP are expected to cause the loss of the jet energy, which is phenomenon called jet quenching. In this talk we provide an introduction to the problematics of ultra-relativistic heavy ion collisions and we show how the jet quenching can be used to analyze the properties of QGP. We also present some “work in progress” results of the jet analysis done on the data taken by the ATLAS detector during the 2011 heavy-ion run at the LHC. Jets are studied as a function of collision centrality and dijet energy imbalance. Dijets are observed to be increasingly asymmetric with increasing centrality. The study of charged particles indicates an increase of yields of low- p T tracks in events with strongly quenched jets
Basu, Sumit; Nayak, Tapan K.; Datta, Kaustuv
2016-06-01
Heavy-ion collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN probe matter at extreme conditions of temperature and energy density. Most of the global properties of the collisions can be extracted from the measurements of charged-particle multiplicity and pseudorapidity (η ) distributions. We have shown that the available experimental data on beam energy and centrality dependence of η distributions in heavy-ion (Au +Au or Pb +Pb ) collisions from √{sNN}=7.7 GeV to 2.76 TeV are reasonably well described by the AMPT model, which is used for further exploration. The nature of the η distributions has been described by a double Gaussian function using a set of fit parameters, which exhibit a regular pattern as a function of beam energy. By extrapolating the parameters to a higher energy of √{sNN}=5.02 TeV, we have obtained the charged-particle multiplicity densities, η distributions, and energy densities for various centralities. Incidentally, these results match well with some of the recently published data by the ALICE Collaboration.
Chemical Instability in Heavy Ion Collisions at Intermediate Energies
Institute of Scientific and Technical Information of China (English)
ZhangFengshou; LiWenfei
2003-01-01
With the establishment of secondary beam facilities at many laboratories around the world, one can investi-gate the properties of nuclei very far from the β stability line and isospin degrees of freedom in nuclear reactions at wide energy ranges. It is also possible to explore the chemical instability of hot and isospin-asymmetric nuclear matter. A better agreement with the experimental data has been found in our recent study by means of an isospin dependent quantum molecular dynamics (IQMD) mode. Recently experiments really reported the isospin dependence of multifragment production in reactions of 58Fe+58Fe and 58Ni+58Ni at higher incident energ.y; These phenomena may be related to the chemical instability in HIC induced by neutron-rich nuclei and therefore it is a challenge for theoretical and experimental nuclear physicists to investigate the chemical instability in heavv ion collisions.
The Skyrme Tensor Force in Heavy Ion Collisions
Stevenson, P D; Fracasso, S; Barton, M C; Umar, A S
2015-01-01
Background: [elided for arXiv character count] Purpose: With the advancement of computational power it is now possible to undertake TDHF calculations without any symmetry assumptions and incorporate the major strides made by the nuclear structure community in improving the energy density functionals used in these calculations. In particular, time-odd and tensor terms in these functionals are naturally present during the dynamical evolution, while being absent or minimally important for most static calculations. The parameters of these terms are determined by the requirement of Galilean invariance or local gauge invariance but their significance for the reaction dynamics have not been fully studied. This work addresses this question with emphasis on the tensor force. Method: The full version of the Skyrme force, including terms arising only from the Skyrme tensor force, is applied to the study of collisions within a completely symmetry-unrestricted TDHF implementation. Results: We examine the effect on fusion ...
Exotic charmed baryon production in ultrarelativistic heavy ion collisions
International Nuclear Information System (INIS)
The authors investigate multi-heavy baryon formation in Au + Au collision using an extended version of the combinatoric break up model for rehadronization. A penalty factor, p, is introduced to characterize the coalescence probability of a light quark with a heavy one. At LHC energy large production rate is found for certain multi-heavy baryons and mesons such as Ωccc, Ξcc, J/Ψ and suppression for Λc, D. They speculate also on the possible existence of a heavy bottom-charm six-quark baryon. A semiclassical and a gaussian estimate reveal that the octet-octet bbb-cc configuration can be energetically favored with respect to the singlet-singlet one
Calculation of supercritical Dirac resonances in heavy-ion collisions
Ackad, Edward
2008-01-01
This resonance is similar in character to other resonances in atomic physics. It is parameterized by its energy and its lifetime. A numerical discretization technique, the mapped Fourier grid method (MFG) is extended to the Dirac equation and is used to solve for the resonance parameters of a quasimolecular supercritical 1S$\\sigma$ state which arises, e.g., in a uranium-uranium collision. Direct methods using only the MFG method are shown to give reasonable estimates for the resonance parameters. Analytic continuation methods such as complex scaling (CS) of the coordinate or adding a complex absorbing potential (CAP) are then applied. They allow for more accurate determinations of the supercritical resonance parameters. The (extrapolated) augmented analytic continuation methods are used to investigate the effects of higher-order couplings, beyond the monopole approximation. For the nearly charge symmetric system of U$^{92+}$-Cf$^{98+}$, it is shown that the S-D quadrupole coupling is the next dominant interac...
Subleading harmonic flows in hydrodynamic simulations of heavy ion collisions
Mazeliauskas, Aleksas
2015-01-01
We perform a Principal Component Analysis (PCA) of $v_3(p_T)$ in event-by-event hydrodynamic simulations of Pb+Pb collisions at the LHC. The PCA procedure identifies two dominant contributions to the two particle correlation function, which together capture 99.9% of the squared variance. We find that the subleading flow (which is the largest source of flow factorization breaking in hydrodynamics) is predominantly a response to the radial excitations of a third-order eccentricity. We present a systematic study of the hydrodynamic response to these radial excitations in 2+1D viscous hydrodynamics. Finally, we construct a good geometrical predictor for the orientation angle and magnitude of the leading and subleading flows using two Fourier modes of the initial geometry.
Baryon femtoscopy in heavy-ion collisions at ALICE
Directory of Open Access Journals (Sweden)
Szymański Maciej Paweł
2014-04-01
Full Text Available In this report, femtoscopic measurements with pp, p¯p¯${\\rm{\\bar p\\bar p}}$, pp¯${\\rm{p\\bar p}}$, pΛ¯${\\rm{p}}\\bar \\Lambda $, p¯Λ${\\rm{\\bar p}}\\Lambda $ and ΛΛ¯$\\Lambda \\bar \\Lambda $ pairs in Pb–Pb collisions at √sNN = 2:76 TeV registered by ALICE at the LHC are presented. Emission source sizes extracted from the correlation analysis with (antiprotons grow with the event multiplicity, as expected. A method to extract the interaction potentials (e.g. for pΛ¯${\\rm{p}}\\bar \\Lambda $ and p¯Λ${\\rm{\\bar p}}\\Lambda $ pairs based on femtoscopy analysis is discussed. The importance of taking into account the so-called residual correlations induced by pairs contaminated by secondary particles is emphasized for all analyses mentioned above.
Bhattacharya, Trambak; Sahoo, Raghunath; Samantray, Prasant
2016-01-01
The evolution equation for inhomogeneous and anisotropic temperature fluctuations inside a medium is derived within the ambit of Boltzmann Transport Equation. Also, taking some existing realistic inputs we have analyzed the Fourier space variation of temperature fluctuation for the medium created after heavy-ion collisions. The effect of viscosity on the variation of fluctuations is investigated. Further, possible implications in hadronic and heavy-ion collisions are explored.
Jing Yang; Yan-Yu Ren; Wei-Ning Zhang
2015-01-01
We systematically investigate the pion transverse momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss (HBT) interferometry in the granular source model for the heavy ion collisions of Au-Au at sNN=200 GeV and Pb-Pb at sNN=2.76 TeV with different centralities. The granular source model can well reproduce the experimental results of the heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). We examine the parameters involved in the granul...
Transport phenomena in dissipative heavy-ion collisions
International Nuclear Information System (INIS)
The discovery of dissipative collisions between two atomic nuclei opened a new field of research in nuclear physics. Before that thermodynamic argumentation was infrequent and nonequilibrium statistical physics was absent in the scattering theory for atomic nuclei. The theory of nuclear physics was mainly written in terms of pure quantum states. The general acceptance of concepts like friction and diffusion took some time because the textbook arguments for a statistical treatment seem to be not applicable. Neither is the number of partaking constituents very large nor is the identification of the macroscopic variables evident, and the absence of a heat bath did not allow to use conventional nonequilibrium physics where the response of the subsystem to small deviations from equilibrium is studied. Nevertheless, the highly incomplete experimental measurements showed clearly a dissipative behaviour in observables like energy, scattering angle, mass and charge number. The collected data resemble the actions observed in Brownian movement but the fluctuations are much larger than expected from Einstein's relation between friction and diffusion. As the study of Brownian movement is the key to the understanding of all dissipative phenomena we use it to introduce the concepts which we then make use of in a specific dissipative model. We discuss the ''One-body Dissipation model'' in its richness of phenomena and compare its predictions to measured data. Special attention is paid to the nonequilibrium relation between friction (or mobility) and diffusion. (orig.)
The unreasonable effectiveness of hydrodynamics in heavy ion collisions
Noronha-Hostler, Jacquelyn; Gyulassy, Miklos
2015-01-01
Event-by-event hydrodynamic simulations of AA and pA collisions involve initial energy densities with large spatial gradients. This is associated with the presence of large Knudsen numbers ($K_n\\approx 1$) at early times, which may lead one to question the validity of the hydrodynamic approach in these rapidly evolving, largely inhomogeneous systems. A new procedure to smooth out the initial energy densities is employed to show that the initial spatial eccentricities, $\\varepsilon_n$, are remarkably robust with respect to variations in the underlying scale of initial energy density spatial gradients, $\\lambda$. For $\\sqrt{s_{NN}}=2.76$ TeV LHC initial conditions generated by the MCKLN code, $\\varepsilon_n$ (across centralities) remains nearly constant if the fluctuation scale varies by an order of magnitude, i.e., when $\\lambda$ varies from 0.1 to 1 fm. Given that the local Knudsen number $K_n\\approx \\frac{1}{\\lambda}$, the robustness of the initial eccentricities with respect to changes in the fluctuation sc...
Soft-Hard Event Engineering in Ultrarelativistic Heavy Ion Collisions
Noronha-Hostler, Jacquelyn; Noronha, Jorge; Gyulassy, Miklos
2016-01-01
Event-by-event hydrodynamic simulations are combined with a generic energy loss model to show that: (i) high $p_T >10$ GeV azimuthal asymmetry in mid-central collisions is well described by a linear response given as $v^{\\rm high}_{2}(p_T> 10 \\;{\\rm GeV})=\\chi^{\\rm high}_{2}(p_T) \\varepsilon_{2}$ where $\\varepsilon_{2}$ is the initial elliptic eccentricity that fluctuates from event to event and $\\chi^{high}_{2}(p_T)$ is approximately independent of the event by event fluctuations of bulk (low $p_T < 2\\; {\\rm GeV}$) elliptic flow, (ii) the high $p_T$ $\\pi^0$ nuclear modification observables $R_{AA}$, $v^{high}_2$, and $v^{high}_3$ are found to be compatible with available LHC data. Soft-Hard Event Engineering (SHEE) makes it possible to extract $\\chi^{\\rm high}_2(p_T)$ from sub-classes ${\\cal C}^s$ of data on $v^{\\rm high}_2(p_T; {\\cal C}^s)$ selected not only by bins of centrality but also by bins of bulk elliptic flow far from the average to test different models of energy loss.
Extracting $p\\Lambda$ scattering lengths from heavy ion collisions
Shapoval, V M; Lednicky, R; Sinyukov, Yu M
2015-01-01
The $p-\\Lambda \\oplus \\bar{p}-\\bar{\\Lambda}$ and $\\bar{p}-\\Lambda \\oplus p-\\bar{\\Lambda}$ correlation functions for 10% most central Au+Au collisions at top RHIC energy $\\sqrt{s_{NN}}=200$ GeV are modeled with Lednicky and Lyuboshitz analytical formula using the source radii extracted from the hydrokinetic model (HKM) simulations. For the baryon-antibaryon case the corresponding spin-averaged strong interaction scattering length is obtained by fitting the STAR correlation function. In contrast to the experimental results, where extracted $p\\bar{\\Lambda}$ source radius value was found $\\sim 2$ times smaller than the corresponding $p\\Lambda$ one, the calculations in HKM show both $p\\Lambda$ and $p\\bar{\\Lambda}$ effective source radii to be quite close, as expected from theoretical considerations. To obtain the satisfactory fit to the measured baryon-antibaryon correlation function at this large source radius value, the modified analytical approximation to the correlation function, effectively accounting for the...
Covariance Analysis of Symmetry Energy Observables from Heavy Ion Collision
Zhang, Yingxun; Li, Zhuxia
2015-01-01
Using covariance analysis, we quantify the correlations between the interaction parameters in a transport model and the observables commonly used to extract information of the Equation of State of Asymmetric Nuclear Matter in experiments. By simulating $^{124}$Sn+$^{124}$Sn, $^{124}$Sn+$^{112}$Sn and $^{112}$Sn+$^{112}$Sn reactions at beam energies of 50 and 120 MeV per nucleon, we have identified that the nucleon effective mass splitting are most strongly correlated to the neutrons and protons yield ratios with high kinetic energy from central collisions especially at high incident energy. The best observable to determine the slope of the symmetry energy, L, at saturation density is the isospin diffusion observable even though the correlation is not very strong ($\\sim$0.7). Similar magnitude of correlation but opposite in sign exists for isospin diffusion and nucleon isoscalar effective mass. At 120 MeV/u, the effective mass splitting and the isoscalar effective mass also have opposite correlation for the do...
Overview of quarkonium production in heavy-ion collisions at LHC
Hong, Byungsik
2016-07-01
Quarkonium has been regarded as one of the golden probes to identify the phase transition from confined hadronic matter to the deconfined quark-gluon plasma (QGP) in heavy-ion collisions. Recent data on the yields and momentum distributions of J/ψ and ϒ families in pp, pPb, and PbPb collisions at the Large Hadron Collider (LHC) are reviewed. The possible implications related to the propagation of quarkonia in the deconfined hot, dense matter and the modified parton distribution function (PDF) in cold nuclei are also discussed.
An Algorithm for Selecting QGP Candidate Events from Relativistic Heavy Ion Collision Data Sample
Lian Shou Liu; Yuan, H B; Lianshou, Liu; Qinghua, Chen; Yuan, Hu
1998-01-01
The formation of quark-gluon plasma (QGP) in relativistic heavy ion collision, is expected to be accompanied by a background of ordinary collision events without phase transition. In this short note an algorithm is proposed to select the QGP candidate events from the whole event sample. This algorithm is based on a simple geometrical consideration together with some ordinary QGP signal, e.g. the increasing of $K/\\pi$ ratio. The efficiency of this algorithm in raising the 'signal/noise ratio' of QGP events in the selected sub-sample is shown explicitly by using Monte-Carlo simulation.
Overview of quarkonium production in heavy-ion collisions at LHC
Directory of Open Access Journals (Sweden)
Hong Byungsik
2016-01-01
Full Text Available Quarkonium has been regarded as one of the golden probes to identify the phase transition from confined hadronic matter to the deconfined quark-gluon plasma (QGP in heavy-ion collisions. Recent data on the yields and momentum distributions of J/ψ and ϒ families in pp, pPb, and PbPb collisions at the Large Hadron Collider (LHC are reviewed. The possible implications related to the propagation of quarkonia in the deconfined hot, dense matter and the modified parton distribution function (PDF in cold nuclei are also discussed.
Density and expansion effects on pion spectra in relativistic heavy-ion collisions
Ayala, A P; Montaño-Zetina, L M; Ayala, Alejandro; Barreiro, Julio; Montano, Luis M.
1999-01-01
We compute the pion inclusive momentum distribution in heavy-ion collisions at AGS energies, assuming thermal equilibrium and accounting for density and expansion effects at the time of decoupling. We compare to data on mid rapidity charged pions produced in central Au + Au collisions and find a very good agreement. The shape of the distribution at low m_t-m is explained in part as an effect arising from the high mean pion density achieved in these reactions. The difference between the positive and negative pion distributions in the same region is attributed in part to the different average yields of each kind of charged pions.
Rapidity Profile of the Initial Energy Density in Heavy-Ion Collisions
Ozonder, Sener
2013-01-01
The rapidity dependence of the initial energy density in heavy-ion collisions is calculated from a three-dimensional McLerran-Venugopalan model (3dMVn) introduced by Lam and Mahlon. This model is infrared safe since global color neutrality is enforced. In this non-boost-invariant framework, the nuclei have non-zero thickness in the longitudinal direction. This results in Bjorken-x dependent unintegrated gluon distribution functions which lead to a rapidity-dependent initial energy density after the collision. The initial energy density and its rapidity dependence are important initial conditions for the quark gluon plasma and its hydrodynamic evolution.
Probing in-medium spin–orbit interaction with intermediate-energy heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Xu, Jun, E-mail: xujun@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Department of Physics and Astronomy, Texas A and M University-Commerce, Commerce, TX 75429-3011 (United States); Li, Bao-An, E-mail: Bao-An.Li@tamuc.edu [Department of Physics and Astronomy, Texas A and M University-Commerce, Commerce, TX 75429-3011 (United States); Department of Applied Physics, Xi' an Jiao Tong University, Xi' an 710049 (China)
2013-07-23
Incorporating for the first time both the spin and isospin degrees of freedom explicitly in transport model simulations of intermediate-energy heavy-ion collisions, we observe that a local spin polarization appears during collision process. Most interestingly, it is found that the nucleon spin up–down differential transverse flow is a sensitive probe of the spin–orbit interaction, providing a novel approach to probe both the density and isospin dependence of the in-medium spin–orbit coupling that is important for understanding the structure of rare isotopes and synthesis of superheavy elements.
Khandelwal, Govind S.; Khan, Ferdous
1989-01-01
An optical model description of energy and momentum transfer in relativistic heavy-ion collisions, based upon composite particle multiple scattering theory, is presented. Transverse and longitudinal momentum transfers to the projectile are shown to arise from the real and absorptive part of the optical potential, respectively. Comparisons of fragment momentum distribution observables with experiments are made and trends outlined based on our knowledge of the underlying nucleon-nucleon interaction. Corrections to the above calculations are discussed. Finally, use of the model as a tool for estimating collision impact parameters is indicated.
Anomalous transport effects and possible environmental symmetry violation in heavy-ion collisions
International Nuclear Information System (INIS)
The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible in such domains. We briefly review recent progress in both the theoretical understanding and experimental search of various anomalous transport effects (such as the chiral magnetic effect, chiral separation effect, chiral electric separation effect, chiral electric/magnetic waves, etc.) in the hot QCD fluid formed by such collisions. (author)
HBT Parameters and Space-Momentum Correlations in Relativistic Heavy-Ion Collisions
Institute of Scientific and Technical Information of China (English)
张景波; 霍雷; 张卫宁; 李新华; 许怒; 刘亦铭
2001-01-01
Using the relativistic quantum molecular dynamics approach, with a correlation after-burner, the physics of the transverse momentum dependence of the Hanbury-Brown and Twiss parameters is studied for Au t Au, Si + Si and p + p collisions at the centre-of-mass energy v s = 200 AGeV. The results indicate that the space-momentum correlations would affect such dependence in both heavy-ion and elementary collisions. The size parameters as a function of the transverse mass mt are sensitive to the degree of space-momentum correlations.
Analysis of calorimetry in ultra relativistic heavy ion collisions at 200 GeV per nucleon
International Nuclear Information System (INIS)
We draw up in this thesis the statement of the calorimetry analysis in ultra relativistic heavy ion collisions at 200 GeV/A. NA38 experiment studies the production of dimuons correlated with neutral transverse energy flow detected by an electromagnetic calorimeter. J/Ψ suppression in central collisions could be a signature of the quark-gluon plasma (Q.G.P.). Characteristics and limits of the apparatus are briefly described. On the other hand, calorimetry measurements and analysis methods are studied in details and future developments are proposed
Coherent photon-photon processes in disruptive and non-disruptive relativistic heavy-ion collisions
International Nuclear Information System (INIS)
Using an impact parameter formulation, differential probability distributions and cross sections for the production of lepton pairs via the photon-photon mechanism are calculated for relativistic heavy-ion collisions. The characteristic features of lepton pair production in disruptive as well as in non-disruptive A-A collisions are studied. Cross sections can be large, the very low k perpendicularto -values of the pairs will help to distinguish these pairs from the ones originating from other sources like Drell-Yan or thermal production. (orig.)
Anomalous transport effects and possible environmental symmetry 'violation' in heavy-ion collisions
Indian Academy of Sciences (India)
Jinfeng Liao
2015-05-01
The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible in such domains. We briefly review recent progress in both the theoretical understanding and experimental search of various anomalous transport effects (such as the chiral magnetic effect, chiral separation effect, chiral electric separation effect, chiral electric/magnetic waves, etc.) in the hot QCD fluid formed by such collisions.
Two-pion interferometry for the granular sources in ultrarelativistic heavy ion collisions
Zhang, Wei-Ning; Yin, Hong-Jie; Ren, Yan-Yu(Department of Physics, Harbin Institute of Technology, Harbin, Heilongjiang 150006, China)
2011-01-01
We investigate the two-pion interferometry in ultrarelativistic heavy ion collisions in the granular source model of quark-gluon plasma droplets. The pion transverse momentum spectra and HBT radii of the granular sources agree well with the experimental data of the $\\sqrt{s_{NN}}=200$ GeV Au-Au and $\\sqrt{s_{NN}}=2.76$ TeV Pb-Pb most central collisions. In the granular source model the larger initial system breakup time may lead to the larger HBT radii $R_{\\rm out}$, $R_{\\rm side}$, and $R_{\\...
The Shape and Flow of Heavy Ion Collisions (490th Brookhaven Lecture)
Energy Technology Data Exchange (ETDEWEB)
Schenke, Bjoern [BNL Physics Department
2014-12-18
The sun can’t do it, but colossal machines like the Relativistic Heavy Ion Collider (RHIC) at Brookhaven Lab and Large Hadron Collider (LHC) in Europe sure can. Quarks and gluons make up protons and neutrons found in the nucleus of every atom in the universe. At heavy ion colliders like RHIC and the LHC, scientists can create matter more than 100,000 times hotter than the center of the sun—so hot that protons and neutrons melt into a plasma of quarks and gluons. The particle collisions and emerging quark-gluon plasma hold keys to understanding how these fundamental particles interact with each other, which helps explain how everything is held together—from atomic nuclei to human beings to the biggest stars—how all matter has mass, and what the universe looked like microseconds after the Big Bang. Dr. Schenke discusses theory that details the shape and structure of heavy ion collisions. He will also explain how this theory and data from experiments at RHIC and the LHC are being used to determine properties of the quark-gluon plasma.
Schenke, Björn; Tribedy, Prithwish; Venugopalan, Raju
2012-09-01
The event-by-event multiplicity distribution, the energy densities and energy density weighted eccentricity moments ɛn (up to n=6) at early times in heavy-ion collisions at both the BNL Relativistic Heavy Ion Collider (RHIC) (s=200GeV) and the CERN Large Hardron Collider (LHC) (s=2.76TeV) are computed in the IP-Glasma model. This framework combines the impact parameter dependent saturation model (IP-Sat) for nucleon parton distributions (constrained by HERA deeply inelastic scattering data) with an event-by-event classical Yang-Mills description of early-time gluon fields in heavy-ion collisions. The model produces multiplicity distributions that are convolutions of negative binomial distributions without further assumptions or parameters. In the limit of large dense systems, the n-particle gluon distribution predicted by the Glasma-flux tube model is demonstrated to be nonperturbatively robust. In the general case, the effect of additional geometrical fluctuations is quantified. The eccentricity moments are compared to the MC-KLN model; a noteworthy feature is that fluctuation dominated odd moments are consistently larger than in the MC-KLN model.
A Review on ϕ Meson Production in Heavy-Ion Collision
Directory of Open Access Journals (Sweden)
Md. Nasim
2015-01-01
Full Text Available The main aim of the relativistic heavy-ion experiment is to create extremely hot and dense matter and study the QCD phase structure. With this motivation, experimental program started in the early 1990s at the Brookhaven Alternating Gradient Synchrotron (AGS and the CERN Super Proton Synchrotron (SPS followed by Relativistic Heavy Ion Collider (RHIC at Brookhaven and recently at Large Hadron Collider (LHC at CERN. These experiments allowed us to study the QCD matter from center-of-mass energies (sNN 4.75 GeV to 2.76 TeV. The ϕ meson, due to its unique properties, is considered as a good probe to study the QCD matter created in relativistic collisions. In this paper we present a review on the measurements of ϕ meson production in heavy-ion experiments. Mainly, we discuss the energy dependence of ϕ meson invariant yield and the production mechanism, strangeness enhancement, parton energy loss, and partonic collectivity in nucleus-nucleus collisions. Effect of later stage hadronic rescattering on elliptic flow (v2 of proton is also discussed relative to corresponding effect on ϕ meson v2.
Dynamics of light, intermediate, heavy and superheavy nuclear systems formed in heavy-ion collisions
Indian Academy of Sciences (India)
Manoj K Sharma; Gurvinder Kaur
2014-05-01
The dynamical description of light, intermediate, heavy and superheavy nuclei formed in heavy-ion collisions is worked out using the dynamical cluster decay model (DCM), with reference to various effects such as deformation and orientation, temperature, angular momentum etc. Based on the quantum mechanical fragmentation theory (QMFT), DCM has been applied to understand the decay mechanism of a large number of nuclei formed in low-energy heavy-ion reactions. Various features related to the dynamics of competing decay modes of nuclear systems are explored by addressing the experimental data of a number of reactions in light, intermediate, heavy and superheavy mass regions. The DCM, being a non-statistical description for the decay of a compound nucleus, treats light particles (LPs) or equivalently evaporation residues (ERs), intermediate mass fragments (IMFs) and fission fragments on equal footing and hence, provides an alternative to the available statistical model approaches to address fusion–fission and related phenomena.
Ayala, Alejandro; Dominguez, C A; Hernandez, L A
2016-01-01
We compute the production of thermal photons in relativistic heavy-ion collisions by gluon fusion in the presence of an intense magnetic field, and during the early stages of the reaction. This photon yield is an excess over calculations that do not consider magnetic field effects. We add this excess to recent hydrodynamic calculations that are close to describing the experimental transverse momentum distribution in RHIC and LHC. We then show that with reasonable values for the temperature, magnetic field strength, and strong coupling constant, our results provide a very good description of such excess. These results support the idea that the origin of at least some of the photon excess observed in heavy-ion experiments may arise from magnetic field induced processes.
Investigation of the intermediate LK molecular orbital radiation in heavy ion-atom collisions
International Nuclear Information System (INIS)
The continuum consisting of an intensive low-energy and a high-energy components in heavy-ion atom collision systems with atomic numbers Z1, Z2 > 28 is studied. The aim of the study is to prove that the C1 continuum cannot be caused by ridiative electron capture (REC) being molecular orbital (MO) radiation to the 2ptau level. It is shown that the comparison of the C1 yields obtained in Kr+Nb asymmetric collisions in gas and solid targets is associated with the formation of vacancies in the lower-Z collision partner and can be interpreted as quasimolecular radiation to the 2ptau orbital level. The strong suppression of the C2 component in the gas target experimets indicates that the MO radiation to the 1stau orbit is emitted preferentially in the two-collision process in symmetric and near-symmetric systems with Z1, Z2 <= 41
Fragmentation of molecules under charge-changing collisions of a few MeV heavy ions
International Nuclear Information System (INIS)
We investigated molecular fragmentation of CO and C2H2 molecules by impact of various fast heavy ions. Fragment ions produced in electron capture and loss collisions of projectile ions were measured in coincidence with final projectile charge states. Data acquisition using position sensitive detection system allows us to obtain 3D momentum imaging of fragment ions and kinetic energy release (KER) in various charge-changing collisions. It was found that the KER spectra show strong dependence on the type of charge-changing collisions. This may be caused by the difference of impact parameters associated with individual charge-changing collisions. Moreover we revealed the different fragmentation pathway between ion impacts and photoionization
Elliptic Flow, Initial Eccentricity and Elliptic Flow Fluctuations in Heavy Ion Collisions at RHIC
Nouicer, Rachid; Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Chai, Z.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Hauer, M.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holzman, B.; Iordanova, A.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Reed, C.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wysłouch, B.
2008-12-01
We present measurements of elliptic flow and event-by-event fluctuations established by the PHOBOS experiment. Elliptic flow scaled by participant eccentricity is found to be similar for both systems when collisions with the same number of participants or the same particle area density are compared. The agreement of elliptic flow between Au+Au and Cu+Cu collisions provides evidence that the matter is created in the initial stage of relativistic heavy ion collisions with transverse granularity similar to that of the participant nucleons. The event-by-event fluctuation results reveal that the initial collision geometry is translated into the final state azimuthal particle distribution, leading to an event-by-event proportionality between the observed elliptic flow and initial eccentricity.
Trace initial interaction from final state observable in relativistic heavy ion collisions
Wang, Meijuan; Wu, Yuanfang
2008-01-01
In order to trace the initial interaction in ultra-relativistic heavy ion collision in all azimuthal directions, two azimuthal multiplicity-correlation patterns -- neighboring and fixed-to-arbitrary angular-bin correlation patterns -- are suggested. From the simulation of Au + Au collisions at 200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting, we observe that the correlation patterns change gradually from out-of-plane preferential one to in-plane preferential one when the centrality of collision shifts from central to peripheral, meanwhile the anisotropic collective flow v_2 keeps positive in all cases. This regularity is found to be model and collision energy independent. The physics behind the two opposite trends of correlation patterns, in particular, the presence of out-of-plane correlation patterns at RHIC energy, are discussed.
New results on Coulomb effects in meson production in relativistic heavy ion collisions
Directory of Open Access Journals (Sweden)
Rybicki Andrzej
2014-01-01
Full Text Available We propose a new method of investigating the space-time evolution of meson production in heavy ion collisions, by making use of spectator-induced electromagnetic (“Coulomb” effects. The presence of two nuclear remnants (“spectator systems” in the non-central collision generates a strong Coulomb field, which modifies the trajectories of charged final state hadrons. This results in charge-dependent azimuthal anisotropies in final state meson emission. In our approach, this effect can be computed numerically by means of a high-statistics Monte Carlo simulation, using the distance between the meson formation zone and the spectator system as free parameter. Our simulation correctly describes the electromagnetic effect on azimuthal anisotropies observed for π+ and π−mesons in Au+Au collisions at lower RHIC energy, known from data recently reported by the STAR Collaboration. Similarly to our earlier studies of spectator-induced electromagnetic effects, also in the present study we find that these effects offer sensitivity to the position of the meson formation zone with respect to the spectator system. Therefore, we conclude that they can serve as a new tool to investigate the space-time evolution of meson production, and the dynamics of the heavy ion collision.
Antiproton-to-proton ratios for ALICE heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Tawfik, A., E-mail: atawfik@cern.ch [Egyptian Center for Theoretical Physics (ECTP), MTI University, Cairo (Egypt)
2011-06-01
Assuming that the final state of hadronization takes place along the freezeout line, which is defined by a constant entropy density, the antiproton-to-proton ratios produced in heavy-ion collisions are studied in framework of the hadron resonance gas (HRG) model. A phase transition from quark-gluon plasma to hadrons, a hadronization, has been conjectured in order to allow modifications in the phase-space volume and thus in the single-particle distribution function. Implementing both modifications in the grand-canonical partition function and taking into account the experimental acceptance in the heavy-ion collisions, the antiproton-to-proton ratios over center-of-mass energies {radical}(s) ranging from AGS to RHIC are very well reproduced by the HRG model. Comparing with the same particle ratios in pp collisions results in a gradually narrowing discrepancy with increasing {radical}(s). At LHC energy, the ALICE antiproton-to-proton ratios in the pp collisions turn to be very well described by the HRG model as well. It is likely that the ALICE AA-program will produce the same antiproton-to-proton ratios as the pp-one. Furthermore, the ratio gets very close to unity indicating that the matter-antimatter asymmetry nearly vanishes. The chemical potential calculated at this energy strengthens the assumption of almost fully matter-antimatter symmetry up to the LHC energy.
Antiproton-to-Proton Ratios for ALICE Heavy-Ion Collisions
Tawfik, A
2010-01-01
Assuming that the final state of hadronization takes place along the freezeout line, which is defined by a constant entropy density, the antiproton-to-proton ratios produced in heavy-ion collisions are studied in framework of the hadron resonance gas (HRG) model. A phase transition from quark--gluon plasma to hadrons, a hadronization, has been conjectured in order to allow modifications in the phase space volume and thus in single--particle distribution function. Implementing both modifications in the grand--canonical partition function and taking into account the experimental acceptance in heavy-ion collisions, the antiproton-to-proton ratios over center-of-mass energies $\\sqrt{s}$ ranging from AGS to RHIC are very well reproduced by the HRG model. Comparing with the same particle ratios in $pp$ collisions results in a gradually narrowing discrepancy with increasing $\\sqrt{s}$. At LHC energy, the ALICE antiproton-to-proton ratios in $pp$ collisions turn to be very well described by HRG model as well. It is l...
Study of heavy ions collision at SIS energies with the detector FOPI
International Nuclear Information System (INIS)
The present work has been carried out in the framework of experiments performed with the FOPI detector at the SIS/ESR accelerator facility of GSI-Darmstadt. It is devoted to the study of central and semi-central heavy ion collisions at beam energies ranging from 100 MeV to 2 GeV per nucleon. We present first generalities on relativistic heavy ion collisions then the FOPI detector with a special attention to the FOPI Inner Wall constructed by the Clermont-Ferrand group. The main results of the FOPI collaboration obtained with light and intermediate mass fragments and kaons are presented. A systematic study of the different forms of collection motion of nuclear matter, radial flow in very central reactions, sideward flow and squeeze-out in semi-central collisions, is performed. Further exciting possibilities concerning production and propagation of strangeness at SIS energies will be offered soon with the upgrade of the FOPI detector. The FOPI data have introduced constraints on parameters of theoretical models. Important progress concerning the knowledge of the properties of nuclear matter, the dynamics of the collisions and in-medium effects have been achieved. (author)
Probing Shadowed Nuclear Sea with Massive Gauge Bosons in the Future Heavy-Ion Collisions
Ru, Peng; Wang, Enke; Zhang, Wei-Ning
2015-01-01
The production of the massive bosons $Z^0$ and $W^{\\pm}$ could provide an excellent tool to study cold nuclear matter effects and the modifications of nuclear parton distribution functions (nPDFs) relative to parton distribution functions (PDFs) of a free proton in high energy nuclear reactions at the LHC as well as in heavy-ion collisions (HIC) with much higher center-of mass energies available in the future colliders. In this paper we calculate the rapidity and transverse momentum distributions of the vector boson and their nuclear modification factors in p+Pb collisions at $\\sqrt{s_{NN}}=63$TeV and in Pb+Pb collisions at $\\sqrt{s_{NN}}=39$TeV in the framework of perturbative QCD by utilizing three parametrization sets of nPDFs: EPS09, DSSZ and nCTEQ. It is found that in heavy-ion collisions at such high colliding energies, both the rapidity distribution and the transverse momentum spectrum of vector bosons are considerably suppressed in wide kinematic regions with respect to p+p reactions due to large nucl...
System Size and Energy Dependence of Dilepton Production in Heavy-Ion Collisions at SIS Energies
Bratkovskaya, E L; Thomere, M; Vogel, S; Bleicher, M
2013-01-01
We study the dilepton production in heavy-ion collisions at energies of 1-2 AGeV as well as in proton induced pp, pn, pd and p+A reactions from 1 GeV up to 3.5 GeV. For the analysis we employ three different transport models - the microscopic off-shell Hadron-String-Dynamics (HSD) transport approach, the Isospin Quantum Molecular Dynamics (IQMD) approach as well as the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) approach. We confirm the experimentally observed enhancement of the dilepton yield (normalized to the multiplicity of neutral pions $N_{\\pi^0}$) in heavy-ion collisions with respect to that measured in $NN = (pp+pn)/2$ collisions. We identify two contributions to this enhancement: a) the $pN$ bremsstrahlung which scales with the number of collisions and not with the number of participants, i.e. pions; b) the dilepton emission from intermediate $\\Delta$'s which are part of the reaction cycles $\\Delta \\to \\pi N ; \\pi N \\to \\Delta$ and $NN\\to N\\Delta; N\\Delta \\to NN$. With increasing system siz...
Final Report for Project ``Theory of ultra-relativistic heavy-ion collisions''
Energy Technology Data Exchange (ETDEWEB)
Ulrich W. Heinz
2012-11-09
In the course of this project the Ohio State University group led by the PI, Professor Ulrich Heinz, developed a comprehensive theoretical picture of the dynamical evolution of ultra-relativistic heavy-ion collisions and of the numerous experimental observables that can be used to diagnose the evolving and short-lived hot and dense fireball created in such collisions. Starting from a qualitative understanding of the main features based on earlier research during the last decade of the twentieth century on collisions at lower energies, the group exploited newly developed theoretical tools and the stream of new high-quality data from the Relativistic Heavy Ion Collider at Brookhaven National Laboratory (which started operations in the summer of the year 2000) to arrive at an increasingly quantitative description of the experimentally observed phenomena. Work done at Ohio State University (OSU) was instrumental in the discovery during the years 2001-2003 that quark-gluon plasma (QGP) created in nuclear collisions at RHIC behaves like an almost perfect liquid with minimal viscosity. The tool of relativistic fluid dynamics for viscous liquids developed at OSU in the years 2005-2007 opened the possibility to quantitatively determine the value of the QGP viscosity empirically from experimental measurements of the collective flow patterns established in the collisions. A first quantitative extraction of the QGP shear viscosity, with controlled theoretical uncertainty estimates, was achieved during the last year of this project in 2010. OSU has paved the way for a transition of the field of relativistic heavy-ion physics from a qualitative discovery stage to a new stage of quantitative precision in the description of quark-gluon plasma properties. To gain confidence in the precision of our theoretical understanding of quark-gluon plasma dynamics, one must test it on a large set of experimentally measured observables. This achievement report demonstrates that we have, at
MEGHNAD – A multi element detector array for heavy ion collision studies
Indian Academy of Sciences (India)
Satyajit Saha
2001-07-01
In the coming decade, the expanding ﬁeld of experimental nuclear physics in our country is going to see a quantum leap in research and developmental activities with new accelerator facilities like the variable energy cyclotron with ECR heavy ion source, the upcoming K-500 superconducting cyclotron, both at VECC, Calcutta, and the superconducting linac boosters at both the Pelletron Accelerator Facilities at TIFR, Mumbai and NSC, New Delhi. When heavy ion beam available from such machines fall on a target and undergo collision, very rich and often pristine ﬁelds of research open up. In order to carry on such activities, we have taken up a project to build a multi element gamma, heavy ion and neutron array of detectors (MEGHNAD) to detect and study the properties of a wide variety of particles like neutrons, protons, light mass clusters, massive ejected fragments, and gamma rays with good solid angle coverage and efﬁciency. Design of the detector array, performance of the prototype detector and brief outline of the research programme to be undertaken with the detector array will be discussed.
Ivanov, D. Yu.; Schiller, A.; Serbo, V. G.
1998-01-01
In recent works [Segev,Wells; Baltz, McLerran; Eichmann, Reinhardt, Schramm, Greiner] it was claimed that the Coulomb correction to the $e^+e^-$ production cross section in relativistic heavy-ion collisions is absent. We point out that this statement is in obvious contradiction to some well known results. We obtain large Coulomb corrections in the pair production cross section for the RHIC and LHC heavy-ion colliders.
Isospin Effect on Nuclear Stopping in Intermediate Energy Heavy Ion Collisions
Institute of Scientific and Technical Information of China (English)
2001-01-01
By using the isospin dependent quantum molecular dynamics model (IQMD), we study the dependence of nuclear stopping Qzz/A and R in intermediate energy heavy ion collisions on system size, initial N/Z, isospin symmetry potential and the medium correction of two-body cross sections. We find the effect of initial N/Z ratio, isospin symmetry potential on stopping is weak. The excitation function of Qzz/A and R depends on the form of medium correction of two-body cross sections and the equation of state of nuclear matter (EOS). Our results show the behavior of the excitation function of Qzz/A and
The Phases of QCD in Heavy Ion Collisions and Compact Stars
International Nuclear Information System (INIS)
I review arguments for the existence of a critical point E in the QCD phase diagram as a function of temperature T and baryon chemical potential μ. I describe how heavy ion collision experiments at the SPS and RHIC can discover the tell-tale signatures of such a critical point, thus mapping this region of the QCD phase diagram. I then review the phenomena expected in cold dense quark matter: color superconductivity and color-flavor locking. I close with a snapshot of ongoing explorations of the implications of recent developments in our understanding of cold dense quark matter for the physics of compact stars. (author)
How (non-)linear is the hydrodynamics of heavy ion collisions?
Energy Technology Data Exchange (ETDEWEB)
Floerchinger, Stefan; Wiedemann, Urs Achim [Physics Department, Theory Unit, CERN, CH-1211 Genève 23 (Switzerland); Beraudo, Andrea [Physics Department, Theory Unit, CERN, CH-1211 Genève 23 (Switzerland); Dep. de Fisica de Particulas, U. de Santiago de Compostela, E-15782 Santiago de Compostela, Galicia (Spain); Del Zanna, Luca [Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INFN - Sezione di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INAF - Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Inghirami, Gabriele [Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); INFN - Sezione di Firenze, Via G. Sansone 1, I-50019 Sesto F.no (Firenze) (Italy); Rolando, Valentina [INFN - Sezione di Ferrara, Via Saragat 1, I-44100 Ferrara (Italy); Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via Saragat 1, I-44100 Ferrara (Italy)
2014-07-30
We provide evidence from full numerical solutions that the hydrodynamical evolution of initial density fluctuations in heavy ion collisions can be understood order-by-order in a perturbative series in deviations from a smooth and azimuthally symmetric background solution. To leading linear order, modes with different azimuthal wave numbers do not mix. When quadratic and higher order corrections are numerically sizable, they can be understood as overtones with corresponding wave numbers in a perturbative series. Several findings reported in the recent literature result naturally from the general perturbative series formulated here.
Kinetic energy distributions of fragment ions in collisions of energetic heavy ions with C60
International Nuclear Information System (INIS)
Mass distributions of fragment ions of C60 produced in collisions with energetic heavy ions have been measured by means of time-of-flight (TOF) method. From the peak profile analysis, initial kinetic energy distributions (KED) of fragment ions were obtained. KED were investigated for three different projectiles. For all fragment ions except for C1+, KED peaked at a few eV kinetic energies. KED of C1+ was found to have a double-peak structure, indicating that the C1+ ions were produced through two different mechanisms. Also, it was found that the mean kinetic energies had strong correlation with electronic stopping cross-section. (author)
A universal description for the freezeout parameters in heavy-ion collisions
Tawfik, A
2006-01-01
It is shown that the freezeout parameters estimated in the heavy-ion collisions all are well described by a constant value of the entropy density $s$ divided by $T^3$. The value of $s/T^3$ has been taken from the lattice QCD simulations at zero baryo-chemical potential $\\mu_B$ and assumed to remain constant for finite $\\mu_B$. This implies that the hadronic matter in rest frame of produced system can be determined by constant degrees of freedom. Furthermore, this condition has been used to predict the freezeout parameters at low temperatures.
Ultra-relativistic heavy-ion collisions - a hot cocktail of hydrodynamics, resonances and jets
Directory of Open Access Journals (Sweden)
Zabrodin E.
2015-01-01
Full Text Available Ultra-relativistic heavy-ion collisions at energies of RHIC and LHC are considered. For comparison with data the HYDJET++ model, which contains the treatment of both soft and hard processes, is employed. The study focuses mainly on the interplay of ideal hydrodynamics, final state interactions and jets, and its influence on the development of harmonics of the anisotropic flow. It is shown that jets are responsible for violation of the number-of-constituent-quark (NCQ scaling at LHC energies. The interplay between elliptic and triangular flows and their contribution to higher flow harmonics and dihadron angular correlations, including ridge, is also discussed.
Two-stage model for fast particle emission in heavy-ion collisions
International Nuclear Information System (INIS)
Using Bertsch's trajectory model two physically distinct approaches is applied to describe fast particle emission in heavy-ion collisions. In the early stage particle emission in the spirit of the Fermi-jet mechanism is calculated. In the later stage, after neck formation, particles are assumed to be emitted from a rapidly expanding hot zone of appreciably large initial dimension, which is strongly anisotropic in momentum space. Absolute double-differential cross sections for preequilibrium neutron emission and obtain a remarkable agreement with experimental data without introducing free parameters are calculated
Creation of quark-gluon plasma in ultrarelativistic heavy-ion collisions
International Nuclear Information System (INIS)
We propose a unified space-time picture of baryon stopping and quark-gluon plasma creation in ultrarelativistic heavy-ion collisions. It is assumed that the highly Lorentz contracted nuclei are decelerated by the coherent color field which is formed between them after they pass through each other. This process continues until the field is neutralized by the Schwinger mechanism. Conservation of energy and momentum allow us to calculate the energy losses of the nuclear slabs and the initial energy density of the quark-gluon plasma. Significant deviations from the boost-invariant scenario have been found. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Santini, Elvira
2008-02-15
The vector meson spectral functions are calculated to the first order in the nuclear matter density assuming the dominant contribution comes from the couplings of the vector mesons to nucleons and nucleon resonances. An attempt is made to reproduce the HADES dilepton production data with the in-medium spectral functions of the vector mesons using the Relativistic Quantum Molecular Dynamics (RQMD) transport model developed earlier for modelling heavy-ion collisions. The results are sensitive to the in-medium broadening of nucleon resonances. A generally good agreement with the HADES data is achieved for selfconsistent treatment of the nucleon resonance broadening and the vector meson spectral functions. (orig.)
International Nuclear Information System (INIS)
The vector meson spectral functions are calculated to the first order in the nuclear matter density assuming the dominant contribution comes from the couplings of the vector mesons to nucleons and nucleon resonances. An attempt is made to reproduce the HADES dilepton production data with the in-medium spectral functions of the vector mesons using the Relativistic Quantum Molecular Dynamics (RQMD) transport model developed earlier for modelling heavy-ion collisions. The results are sensitive to the in-medium broadening of nucleon resonances. A generally good agreement with the HADES data is achieved for selfconsistent treatment of the nucleon resonance broadening and the vector meson spectral functions. (orig.)
Searching for axion-like particles with ultra-peripheral heavy-ion collisions
Knapen, Simon; Lou, Hou Keong; Melia, Tom
2016-01-01
We show that ultra-peripheral heavy-ion collisions at the LHC can be used to search for axion-like particles with mass below 100 GeV. The $Z^4$ enhanced photon-photon luminosity from the ions provides a large exclusive production rate, with a signature of a resonant pair of back-to-back photons and no other activity in the detector. In addition, we present both new and updated limits from recasting multi-photon searches at LEP II and the LHC, which are more stringent than those currently in the literature for the mass range 100 MeV to 100 GeV.
Initial state fluctuations and higher harmonic flow in heavy-ion collisions
Gale, Charles; Schenke, Bjoern; Tribedy, Prithwish; Venugopalan, Raju
2012-01-01
A framework combining Yang-Mills dynamics of the pre-equilibrium glasma with relativistic viscous hydrodynamic evolution of the quark-gluon plasma and hadron gas phases is presented. Event-by-event fluctuations of nucleon positions and color charges are taken into account, leading to negative binomial fluctuations of gluon multiplicities. Experimental anisotropic flow coefficients v2-v5 of charged hadron distributions in heavy-ion collisions at the Large Hadron Collider are well described. Furthermore, event-by-event distributions of v2, v3 and v4 measured by the ATLAS collaboration are reproduced.
Initial state fluctuations and higher harmonic flow in heavy-ion collisions
Gale, Charles; Jeon, Sangyong; Schenke, Björn; Tribedy, Prithwish; Venugopalan, Raju
2013-05-01
A framework combining Yang-Mills dynamics of the pre-equilibrium glasma with relativistic viscous hydrodynamic evolution of the quark-gluon plasma and hadron gas phases is presented. Event-by-event fluctuations of nucleon positions and color charges are taken into account, leading to negative binomial fluctuations of gluon multiplicities. Experimental anisotropic flow coefficients v2 - v5 of charged hadron distributions in heavy-ion collisions at the Large Hadron Collider are well described. Furthermore, event-by-event distributions of v2,v3andv4 measured by the ATLAS collaboration are reproduced.
Is the breakup time a free parameter when describing heavy ion collisions?
International Nuclear Information System (INIS)
Thermodinamic descriptions of heavy ion collisions generally include the so called breakup time (when to switch from continuum picture to a collisionless gas). While an appropriate choice of this time can help to reproduce the detected spectra, from the same reason this freedom may prevent us to reconstruct uniquely the compressed hot stages from the observables. This problem is absent if the calculated final spectra are insensitive on the breakup time at least in a domain. Here we show such an example in a model system. This example may give further arguments for the thermodynamic description. (author) 13 refs.; 4 figs
Re-hardening of hadron transverse mass spectra in relativistic heavy-ion collisions
Indian Academy of Sciences (India)
P K Sahu; N Otuka; M Isse; Y Nara; A Ohnishi
2006-05-01
We analyze the spectra of pions and protons in heavy-ion collisions at relativistic energies from 2 A GeV to 65+65 A GeV by using a jet-implemented hadron-string cascade model. In this energy region, hadron transverse mass spectra first show softening until SPS energies, and re-hardening may emerge at RHIC energies. Since hadronic matter is expected to show only softening at higher energy densities, this re-hardening of spectra can be interpreted as a good signature of the quark-gluon plasma formation.
Exotic hadrons and hadron-hadron interactions in heavy ion collisions
Ohnishi, A; Furumoto, T; Hyodo, T; Jido, D; Ko, C M; Morita, K; Lee, S H; Nielsen, M; Sekihara, T; Yasui, S; Yazaki, K
2013-01-01
We discuss the exotic hadron structure and hadron-hadron interactions in view of heavy ion collisions. First, we demonstrate that a hadronic molecule with a large spatial size would be produced more abundantly in the coalescence model compared with the statistical model result. Secondly, we constrain the Lambda-Lambda interaction by using the recently measured Lambda-Lambda correlation data. We find that the RHIC-STAR data favor the Lambda-Lambda scattering parameters in the range 1/a_0 = 3 fm.
Interferometry imaging for the evolving source in heavy ion collisions at HIRFL-CSR energy
Institute of Scientific and Technical Information of China (English)
YIN Hong-Jie; M. J. Efaaf; ZHANG Wei-Ning
2012-01-01
Imaging analysis of two-pion interferometry is performed for an evolving particle-emitting source in heavy ion collisions at HIRFL-CSR energy.The source evolution is described by the relativistic hydrodynamics in (2+1) dimensions. The model-independent characteristic quantities of the source are investigated and compared with the interferometry results obtained by the usual Gaussian formula fit.It is found that the firstorder source function moments can describe the source sizes.The ratio of the normalized standard deviation (O) to the first-order moment (R),(O)/(R),is sensitive to the shape of the source function.
Interferometry imaging for the evolving source in heavy ion collisions at HIRFL-CSR energy
International Nuclear Information System (INIS)
Imaging analysis of two-pion interferometry is performed for an evolving particle-emitting source in heavy ion collisions at HIRFL-CSR energy. The source evolution is described by the relativistic hydrodynamics in (2+1) dimensions. The model-independent characteristic quantities of the source are investigated and compared with the interferometry results obtained by the usual Gaussian formula fit. It is found that the first- order source function moments can describe the source sizes. The ratio of the normalized standard deviation a to the first-order moment R-tilde, σ-tilde/R-tilde, is sensitive to the shape of the source function. (authors)
Effect of quark gluon plasma on charm quark produced in relativistic heavy ion collision
International Nuclear Information System (INIS)
Charm quarks are produced mainly in the pre-equilibrium stage of heavy ion collision and serve as excellent probes entering the thermalized medium. They come out with altogether different momenta and energies and fragments into D-mesons and decay into non-photonic electrons which are observed experimentally. Here we present the effect of QGP on charm quark production using two different models: first one based on Wang-Huang-Sarcevic model of multiple scattering of partons and the second one is based on Parton Cascade Model with Boltzmann transport equation used for charm quark evolution in QGP
δ-electron spectroscopy and the atomic clock effect in heavy-ion collisions
International Nuclear Information System (INIS)
The properties of strongly bound electrons in superheavy quasimolecular systems with combined nuclear charge numbers Z = ZP + ZT ≥ 110 are investigated. The emission of δ-electrons may serve as an atomic clock for nuclear reactions which is associated with the large overlap of the electron probability density with the nuclear interior. Excitation and emission rates of inner-shell electrons in collisions of very heavy ions with beam energies at or above the nuclear Coulomb barrier depend explicitly on details of the nuclear dynamics. Theoretical and experimental results are reviewed. (orig.)
Lambda flow in heavy-ion collisions: the role of final-state interactions
Li, G. Q.; Ko, C. M.
1996-01-01
Lambda flow in Ni+Ni collisions at SIS energies is studied in the relativistic transport model (RVUU 1.0). It is found that for primordial lambdas the flow is considerably weaker than proton flow. The inclusion of final-state interactions, especially the propagation of lambdas in mean-field potential, brings the lambda flow close to that of protons. An accurate determination of lambda flow in heavy-ion experiments is shown to be very useful for studying lambda properties in dense matter.
Ultraviolet energy dependence of particle production sources in relativistic heavy-ion collisions
Wolschin, Georg
2015-01-01
The energy dependence of particle production sources in relativistic heavy-ion collisions is investigated from RHIC to LHC energies. Whereas charged-hadron production in the fragmentation sources follows a ln(s_NN/s_0) law, particle production in the mid-rapidity gluon-gluon source exhibits a much stronger dependence proportional to ln^3(s_NN/s_0), and becomes dominant between RHIC and LHC energies. The production of particles with pseudorapidities beyond the beam rapidity is also discussed.
Plumberg, Christopher
2015-01-01
Recent work has shown that a temperature dependence of the shear viscosity to entropy ratio, $\\eta/s$, influences the collective flow pattern in heavy-ion collisions in characteristic ways that can be measured by studying hadron transverse momentum spectra and their anisotropies. Here we point out that it also affects the pair momentum dependence of the Hanbury-Brown$-$Twiss (HBT) radii (the source size parameters extracted from two-particle intensity interferometry) and the variance of their event-by-event fluctuations. This observation establishes interferometric signatures as useful observables to complement the constraining power of single-particle spectra on the temperature dependence of $\\eta/s$.
Li, Qingfeng; Bleicher, Marcus; Stoecker, Horst
2006-01-01
The pion source as seen through HBT correlations at RHIC energies is investigated within the UrQMD approach. We find that the calculated transverse momentum, centrality, and system size dependence of the Pratt-HBT radii $R_L$ and $R_S$ are reasonably well in line with experimental data. The predicted $R_O$ values in central heavy ion collisions are larger as compared to experimental data. The corresponding quantity $\\sqrt{R_O^{2}-R_S^{2}}$ of the pion emission source is somewhat larger than e...
Hanbury-Brown/Twiss Interferometry for Relativistic Heavy-Ion Collisions: Theoretical Aspects
Heinz, Ulrich
1996-01-01
I discuss two-particle intensity interferometry as a method to extract from measured 1- and 2-particle momentum spectra information on the space-time geometry and dynamics of the particle emitting source. Particular attention is given to the rapid expansion and short lifetime of the sources created in relativistic heavy-ion collisions. Model-independent expressions for the HBT size parameters in terms of the space-time variances of the source are derived, and a new parametrization of the corr...
Strangeness production in heavy ion collisions at SPS and RHIC within two-source statistical model
Lu, Zhong-Dao; Faessler, Amand; Fuchs, C.; Zabrodin, E.
2002-01-01
The experimental data on hadron yields and ratios in central Pb+Pb and Au+Au collisions at SPS and RHIC energies, respectively, are analysed within a two-source statistical model of an ideal hadron gas. These two sources represent the expanding system of colliding heavy ions, where the hot central fireball is embedded in a larger but cooler fireball. The volume of the central source increases with rising bombarding energy. Results of the two-source model fit to RHIC experimental data at midra...
Hypertriton and light nuclei production at A-production subthreshold energy in heavy-ion collisions
Institute of Scientific and Technical Information of China (English)
ZHANG Song; CHEN Jin-Hui; MA Yu-Gang; XU Zhang-Bu; CAI Xiang-Zhou; MA Guo-Liang; ZHONG Chen
2011-01-01
High-energy heavy-ion collisions produce abundant hyperons and nucleons. A dynamical coalescence model coupled with the ART model is employed to study the production probabilities of light clusters,deuteron (d), triton (t), helion (3 He), and hypertriton(∧3H) at subthreshold energy of ∧ production(≈1 GeV per nucleon). We study the dependence on the reaction system size of the coalescence penalty factor per additional nucleon and entropy per nucleon.The Strangeness Population Factor (S3 =∧3H/(3He×p/∧))shows an extra suppression of hypertriton comparing to light clusters of the same mass number. This model predicts a hypertriton production cross-section of a few μb in 36Ar+36Ar, 40 Ca+4o Ca and 56Ni+56Ni in 1 A GeV reactions. The production rate is as high as a few hypertritons per million collisions, which shows that the fixed-target heavy-ion collisions at CSR (Lanzhou/China) at A subthreshold energy are suitable for breaking new ground in hypernuclear physics.
Net-Baryon and Net-Kaon Rapidity Distributions in Ultrarelativistic Heavy-Ion Collisions
Institute of Scientific and Technical Information of China (English)
王宏民; 侯召宇; 孙献静
2012-01-01
In this paper, the gluon distribution is extracted from the KLR-AdS/CFT saturation model and used to investigate net-baryon and net-kaon rapidity distributions in ultrarelativistic heavy-ion collisions. With the same parameters of the saturation model fitting to HERA data and an χ^2 analysis of the overall constant C, the theoretical results are in good agreement with RHIC data in Au＋Au collisions at √s = 0.2 TeV. Then, we present the predictive results for net-baryon rapidity distributions in central Pb＋Pb collisions at LHC energies of √s = 2.76, 3.94, and 5.52 TeV, and give the corresponding values of dN/ dy for net-baryon at y = 0.
Photoproduction of vector mesons: from ultraperipheral to semi-central heavy ion collisions
Klusek-Gawenda, M
2016-01-01
We discuss nuclear cross sections for $AA \\to AAV$ and $AA \\to AAVV$ reactions with one or two vector mesons in the final state. Our analysis is done in the impact parameter space equivalent photon approximation. This approach allows to consider the above processes taking into account distance between colliding nuclei. We consider both ultraperipheral and semi-central collisions. We are a first group which undertook a study of single $J/\\psi$ photoproduction for different centrality bins. We show that one can describe new ALICE experimental data by including geometrical effects of collisions in the flux factor. Next, total and differential cross section for double-scattering mechanism in the exclusive $AA \\to AAVV$ reaction in ultrarelativistic ultraperipheral heavy ion collisions is presented. In this context we consider double photoproduction and photon-photon processes. Simultaneously, we get very good agreement of our results with STAR (RHIC), CMS and ALICE (LHC) experimental data for single $\\rho^0$ and ...
Dipolar degrees of freedom and Isospin equilibration processes in Heavy Ion collisions
Papa, M; Acosta, L; Amorini, F; Agodi, C; Anzalone, A; Auditore, L; Cardella, G; Cavallaro, S; Chatterjee, M B; De Filippo, E; Francalanza, L; Geraci, E; Grassi, L; Gnoffo, B; Han, J; La Guidara, E; Lanzalone, G; Lombardo, I; Pagano, C Maiolino T Minniti A; Pagano, E V; Pirrone, S; Politi, G; Porto, F; Quattrocchi, L; Rizzo, F; Rosato, E; Russotto, P; Trifirò, A; Trimarchi, M; Verde, G; Vigilante, and M
2015-01-01
Background: In heavy ion collision at the Fermi energies Isospin equilibration processes occur- ring when nuclei with different charge/mass asymmetries interacts have been investigated to get information on the nucleon-nucleon Iso-vectorial effective interaction. Purpose: In this paper, for the system 48Ca +27 Al at 40 MeV/nucleon, we investigate on this process by means of an observable tightly linked to isospin equilibration processes and sensitive in exclusive way to the dynamical stage of the collision. From the comparison with dynamical model calculations we want also to obtain information on the Iso-vectorial effective microscopic interaction. Method: The average time derivative of the total dipole associated to the relative motion of all emitted charged particles and fragments has been determined from the measured charges and velocities by using the 4? multi-detector CHIMERA. The average has been determined for semi- peripheral collisions and for different charges Zb of the biggest produced fragment. E...
{gamma}-radiation of excited nuclear discrete levels in peripheral heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Korotkikh, V.L.; Chikin, K.A. [Scobeltsyn Institute of Nuclear Physics, Moscow State University (Russian Federation)
2002-06-01
A new process of a nuclear excitation to discrete states in peripheral heavy ion collisions is studied. High-energy photons are emitted by the exited nuclei with energies up to a few tens of GeV at angles of a few hundred microradians with respect to the beam direction. We show that a two-stage process, where an electron-positron pair is produced by virtual photons emitted by nuclei and then the electron or positron excites the nucleus, has a large cross-section. It is equal to about 5 b for CaCa collisions. On the one hand, it produces a significant {gamma}-rays background in the nuclear fragmentation region but, on the other hand, it could be used for monitoring the nuclear beam intensity at the LHC. These secondary nuclear photons could be a good signal for triggering peripheral nuclear collisions. (orig.)
On energy densities reached in heavy-ion collisions at the CERN SPS
Pisút, J; Tomasik, Boris; Pisut, Jan; Pisutova, Neva; Tomasik, Boris
2003-01-01
We present a few estimates of energy densities reached in heavy-ion collisions at the CERN SPS. The estimates are based on data and models of proton-nucleus and nucleus-nucleus interactions. In all of these estimates the maximum energy density in central Pb+Pb interactions is larger than the critical energy density of about 0.7 GeV/fm^3 following from lattice gauge theory computations. In estimates which we consider as realistic the maximum energy density is about twice the critical value. In this way our analysis gives some support to claims that deconfined matter has been produced at the CERN SPS. Any definite statement requires a deeper understanding of formation times of partons and hadrons in nuclear collisions. We also compare our results with implicit energy estimates contained in earlier models of anomalous J/psi suppression in nuclear collisions.
Light-by-light scattering in ultraperipheral heavy-ion collisions at the LHC
Szczurek, Antoni; Lebiedowicz, Piotr
2016-01-01
We present cross sections for diphoton production in (semi)exclusive $PbPb$ collisions, relevant for the LHC. The calculation is based on equivalent photon approximation in the impact parameter space. The cross sections for elementary elastic scattering $\\gamma \\gamma \\to \\gamma \\gamma$ subprocess are calculated including two mechanisms: box diagrams with leptons and quarks in the loops and a mechanism based on vector-meson dominance (VDM-Regge) model with virtual intermediate vector-like excitations of the photons. We get measureable cross sections in $PbPb$ collisions. We present many interesting differential distributions which could be measured by the ALICE, CMS or ATLAS Collaborations at the LHC. We study whether a separation of box and VDM-Regge contributions is possible. We find that the cross section for elastic $\\gamma \\gamma$ scattering could be measured in the heavy-ion collisions for subprocess energies smaller than $W_{\\gamma\\gamma} \\approx 15-20$~GeV.
Event-by-event fluctuations in heavy-ion collisions and the quark-gluon string model
Capella, A.; Ferreiro, E. G.; Kaidalov, A. B.
1999-01-01
We apply dynamical string models of heavy-ions collisions at high energies to the analysis of event-by-event fluctuations. Main attention is devoted to a new variable proposed to study "equilibration" in heavy-ions collisions. Recent results of the NA49 collaboration at CERN SPS are compared with predictions of the Quark-Gluon String Model (QGSM), which gives a good description of different aspects of multiparticle production for collisions of nucleons and nuclei. It is shown that the new obs...
Behera, Nirbhay K; Naik, Bharati; Nandi, Basanta K; Pani, Tanmay
2016-01-01
The charged particle multiplicity distribution and the transverse energy distribution measured in heavy-ion collisions at top RHIC and LHC energies are described using the two-component model approach based on convolution of Monte Carlo Glauber model with the Weibull model for particle production. The model successfully describes the multiplicity and transverse energy distribution of minimum bias collision data for a wide range of energies. We also propose that Weibull-Glauber model can be used to determine the centrality classes in heavy-ion collision as an alternative to the conventional Negative Binomial distribution for particle production.
Probing Multi-Strange Dibaryon with Proton-Omega Correlation in High-energy Heavy Ion Collisions
Morita, Kenji; Etminan, Faisal; Hatsuda, Tetsuo
2016-01-01
Two-particle intensity correlation between the proton ($p$) and the Omega-baryon ($\\Omega$) in high-energy heavy ion collisions is studied to unravel the possible spin-2 $p\\Omega$ dibaryon recently suggested by lattice QCD simulations. The ratio of correlation functions between small and large collision systems, $C_{\\rm SL}(Q)$, is proposed to be a new measure to extract the strong $p\\Omega$ interaction without much contamination from the Coulomb attraction. Relevance of this quantity to the experimental observables in heavy-ion collisions is also discussed.
Lokhtin, Igor P; Sarycheva, L I; Snigirev, A M
2002-01-01
The possibility for the appearance of azimuthal asymmetry of hadron jet spectra due to rescattering and energy loss of hard produced partons in dense quark-gluon matter, created initially in nuclear overlap zone in collisions with nonzero impact parameter is investigated. The methods of determination of reaction plane angle in ultrarelativistic heavy-ion collisions using semi-hard particle flow are discussed
Formation and collapse of false vacuum bubbles in relativistic heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Ray, Rajarshi E-mail: rajarshi@iopb.res.in; Sanyal, Soma E-mail: sanyal@iopb.res.in; Srivastava, Ajit M. E-mail: ajit@iopb.res.in
2002-12-30
It is possible that under certain situations, in a relativistic heavy-ion collision, partons may expand out forming a shell like structure. We analyze the process of hadronization in such a picture for the case when the quark-hadron transition is of first order, and argue that the inside region of such a shell must correspond to a supercooled (to T=0) deconfined vacuum. Hadrons from that region escape out, leaving a bubble of pure deconfined vacuum with large vacuum energy. This bubble undergoes relativistic collapse, with highly Lorentz contracted bubble walls, and may concentrate the entire energy into extremely small regions. Eventually different portions of bubble wall collide, with the energy being released in the form of particle production. Thermalization of this system can lead to very high temperatures. With a reasonably conservative set of parameters, at LHC, the temperature of the hot spot can reach as high as 3 GeV, and well above it with more optimistic parameters. Such a hot spot can leave signals like large P{sub T} partons, dileptons, and enhanced production of heavy quarks. We also briefly discuss a speculative possibility where the electroweak symmetry may get restored in the highly dense region resulting from the decay of the bubble wall via the phenomenon of non-thermal symmetry restoration (which is usually employed in models of pre-heating after inflation). If that could happen then the possibility may arise of observing sphaleron induced baryon number violation in relativistic heavy-ion collisions.
Early Time Dynamics in Heavy Ion Collisions from AdS/CFT Correspondence
Kovchegov, Yuri V
2007-01-01
We study the matter produced in heavy ion collisions assuming that this matter is strongly interacting and employing AdS/CFT correspondence to investigate its dynamics. At late proper times we show that Bjorken hydrodynamics solution, obtained recently by Janik and Peschanski using gauge-gravity duality [hep-th/0512162], can be singled out by simply requiring that the metric tensor is a real and single-valued function of the coordinates everywhere in the bulk, without imposing any constraints on the curvature invariant. At early proper times we use similar strategy to show that the energy density approaches a constant as proper time goes to zero. We therefore demonstrate that the strong coupling dynamics incorporates the isotropization transition in heavy ion collisions. By matching our early-time regime with the late-time one of Janik and Peschanski we estimate the isotropization time at RHIC to be approximately 0.3 fm/c, in good agreement with results of hydrodynamic simulations.
Heavy Flavor Physics in Heavy-Ion Collisions with STAR Heavy Flavor Tracker
Zhang, Yifei
2010-02-01
Heavy quarks are a unique tool to probe the strongly interacting matter created in relativistic heavy-ion collisions at RHIC energies. Due to their large mass, energetic heavy quarks are predicted to lose less energy than light quarks by gluon radiation when they traverse a Quark-Gluon Plasma. In contrast, recent measurements of non-photonic electrons from heavy quark decays at high transverse momentum (pT) show a jet quenching level similar to that of the light hadrons. Heavy quark are produced mainly at early stage in heavy-ion collisions, thus they are proposed to probe the QCD medium and to be sensitive to bulk medium properties. Ultimately, their flow behavior may help establish whether light quarks thermalize. Therefore, topological reconstruction of D-mesons and identification of electrons from charm and bottom decays are crucial to understand the heavy flavor production and their in medium properties. The Heavy Flavor Tracker (HFT) is a micro-vertex detector utilizing active pixel sensors and silicon strip technology. The HFT will significantly extend the physics reach of the STAR experiment for precise measurement of charmed and bottom hadrons. We present a performance study with full detector on the open charm nuclear modification factor, elliptic flow v2 and λc measurement as well as the measurement of bottom mesons via a semi-leptonic decay. )
Constraining the in-medium hyperon-nucleon interaction in heavy-ion collisions
International Nuclear Information System (INIS)
The knowledge of the strangeness sector of strong interactions is important for our understanding of hadron dynamics. It is still a widely debated topic how the hyperon-nucleon interaction is modified inside a dense hadronic environment. From our recent in-medium T-matrix calculations for hyperon-nucleon scattering with strangeness exchange, e.g., Σ+n→Σ0p,Λp, we determine the in-medium modifications of cross sections at finite baryon density. The results are used in intermediate energy heavy-ion collisions, which offer an unique opportunity to investigate this issue in the laboratory. Indeed, precise data on K0,+ and Λ+Σ0 production exist and can help us to study the in-medium modifications of the hyperon-nucleon interaction with strangeness exchange. We apply a relativistic Boltzmann-like transport approach, which incorporates a perturbative propagation of particles with finite strangeness (positive and neutral kaons with S=1 and hyperons with S=-1) under the influence of chiral potentials for the kaons and hyperons self-energies. Our calculations shows that strangeness production in heavy-ion collisions is a sensitive tool for investigations of in-medium YN- and YY-interactions. We compare transport theoretical results on strangeness yields and their rapidity distributions with data and discuss in particular the high density properties of YN-interactions, entering e.g. also into neutron star calculations.
Li, Ming
2016-01-01
In very high energy collisions nuclei are practically tranparent to each other but produce very hot, nearly baryon-free, matter in the so-called central rapidity region. The energy in the central rapidity region comes from the kinetic energy of the colliding nuclei. We calculate the energy and rapidity loss of the nuclei using the color glass condensate model. This model also predicts the excitation energy of the nuclear fragments. Using a space-time picture of the collision we calculate the baryon and energy densities of the receding baryonic fireballs. For central collisions of gold nuclei at the highest energy attainable at the Relativistic Heavy Ion Collider, for example, we find baryon densities more than ten times that of atomic nuclei over a large volume.
Zhong, Yang; Yang, Chun-Bin; Cai, Xu; Feng, Sheng-Qin
2016-08-01
It has been proposed that electric fields may lead to chiral separation in quark-gluon plasma (QGP). This is called the chiral electric separation effect. The strong electromagnetic field and the QCD vacuum can both be completely produced in off-central nuclear-nuclear collision. We use the Woods-Saxon nucleon distribution to calculate the electric field distributions of off-central collisions. The chiral electric field spatial distribution at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energy regions are systematically studied in this paper. The dependence of the electric field produced by the thermal quark in the central position with different impact parameters on the proper time with different collision energies in the RHIC and LHC energy regions are studied in this paper. Supported by National Natural Science Foundation of China (11375069, 11435054, 11075061, 11221504) and Key Laboratory Foundation of Quark and Lepton Physics (Hua-Zhong Normal University)(QLPL2014P01)
International Nuclear Information System (INIS)
Ultra-Relativistic heavy-ion physics is a promising field of high energy physics connecting two fields: nuclear physics and elementary particle physics. Experimental achievements of the last years have provided an opportunity to study the properties of a new state of matter created in heavy-ion collisions called quark-gluon plasma. The initial state of two colliding nuclei is affected by fluctuations coming from wave- functions of nucleons. These fluctuations lead to the momentum anisotropy of the hadronic matter which is observed by the detectors. The system created in the collision behaves like a fluid, so the initial state is connected to the final state via hydrodynamic evolution. In this thesis we model the evolution with relativistic viscous hydrodynamics. Our results, combined with experimental data, give non trivial constraints on the initial state, thus achieving 'reverse engineering' of the heavy-ion collisions. The observable which characterizes the momentum anisotropy is the anisotropic flow vn. We present the first measurements of the first harmonic of the anisotropic flow called directed flow v1 in Pb-Pb collisions at the LHC. We then perform the first viscous hydrodynamic modeling of directed flow and show that it is less sensitive to viscosity than higher harmonics. Comparison of these experimental data with the modeling allows to extract the values of the dipole asymmetry of the initial state, which provides constraints on the models of initial states. A prediction for directed flow v1 in Au-Au collisions is also made for RHIC. We then perform a similar modeling of the second and third harmonics of the anisotropic flow, called respectively elliptic v2 and triangular v3 flow. A combined analysis of the elliptic and triangular flow data compared with viscous hydrodynamic calculations allows us to put constraints on initial ellipticity and triangularity of the system. These constraints are then used as a filter for different models of
Initial state properties in heavy ion collisions at RHIC and LHC energies
Energy Technology Data Exchange (ETDEWEB)
Marty, Rudy; Bratkovskaya, Elena [FIAS, Frankfurt (Germany); ITP, Frankfurt (Germany); Cassing, Wolfgang [ITP, Giessen (Germany); Aichelin, Joerg [SUBATECH, Nantes (France)
2014-07-01
The issue of initial conditions in relativistic heavy ion collisions is a subject of intensive debate. Especially the assumption of thermal equilibrium after ∝1 fm/c is currently not supported by microscopic transport approaches. In our study we compare the Parton-Hadron-String Dynamics (PHSD) with new transport approach RSP based on the Nambu-Jona-Lasinio (NJL) model, applying the same initial conditions from PHSD, which have a 'lumpy' energy density profile. The comparison of final hadronic observables shows that the initial parton distribution must be out of equilibrium in order to reproduce the multiplicity spectra dN/dp{sub T} and dN/dη and the elliptic flow v{sub 2} for Au+Au at RHIC energies. We also discuss the applicability of an equation of state and the applicability of a hydrodynamics for relativistic high energy collisions.
Medium Modification of \\gamma-jets in High-energy Heavy-ion Collisions
Wang, Xin-Nian
2013-01-01
Medium modification of \\gamma-tagged jets in high-energy heavy-ion collisions is investigated within a Linearized Boltzmann Transport model for jet propagation that includes both elastic parton scattering and induced gluon emission. Inclusion of recoiled medium partons in the reconstruction of partonic jets is found to significantly reduce the net jet energy loss. Experimental data on \\gamma-jet asymmetry and survival rate in Pb + Pb collisions at \\sqrt{s}=2.76 TeV can be reproduced. Medium modifications of reconstructed jet fragmentation function, transverse profile and energy flow outside the jet-cone are found to be sizable especially for \\gamma-tagged jets with small values of x=p_T^{jet}/p_T^\\gamma.
Holographic approach to quark–gluon plasma in heavy ion collisions
International Nuclear Information System (INIS)
We review recent applications of the dual holographic approach to describing the quark–gluon plasma observed in high-energy collisions of relativistic heavy nuclei. Holography and AdS/CFT duality provide a means to study the properties of strong-coupling quantum field theories using higher-dimensional gravity theories. The appearance of quark–gluon plasma in heavy ion collisions can be described in dual terms as the formation of a black hole. To illustrate the major achievements of holographic theory, we discuss the calculation of the following quantities: the shear viscosity and other transport coefficients (all calculated by second order hydrodynamic models), the energy dependence of multiplicities, and the anisotropic thermalization and isotropization times. We also compare theoretical predictions with available experimental data, including the recent LHC results. (reviews of topical problems)
Fluctuations in Charged Particle Multiplicities in Relativistic Heavy-Ion Collisions
Mukherjee, Maitreyee; Choudhury, Subikash; Nayak, Tapan K
2016-01-01
Multiplicity distributions of charged particles and their event-by-event fluctuations have been compiled for relativistic heavy-ion collisions from the available experimental data at Brookhaven National Laboratory and CERN and also by the use of an event generator. Multiplicity fluctuations are sensitive to QCD phase transition and to the presence of critical point in the QCD phase diagram. In addition, multiplicity fluctuations provide baselines for other event-by-event measurements. Multiplicity fluctuation expressed in terms of the scaled variance of the multiplicity distribution is an intensive quantity, but is sensitive to the volume fluctuation of the system. The importance of the choice of narrow centrality bins and the corrections of centrality bin width effect for controlling volume fluctuations have been discussed. It is observed that the mean and width of the multiplicity distributions monotonically increase as a function of increasing centrality at all collision energies, whereas the multiplicity ...
Fluctuations of conserved charges in relativistic heavy ion collisions: An introduction
Asakawa, Masayuki; Kitazawa, Masakiyo
2016-09-01
Bulk fluctuations of conserved charges measured by event-by-event analysis in relativistic heavy ion collisions are observables which are believed to carry significant amount of information on the hot medium created by the collisions. Active studies have been done recently experimentally, theoretically, and on the lattice. In particular, non-Gaussianity of the fluctuations has acquired much attention recently. In this review, we give a pedagogical introduction to these issues, and survey recent developments in this field of research. Starting from the definition of cumulants, basic concepts in fluctuation physics, such as thermal fluctuations in statistical mechanics and time evolution of fluctuations in diffusive systems, are described. Phenomena which are expected to occur in finite temperature and/or density QCD matter and their measurement by event-by-event analyses are also elucidated.
Intermediate pT phenomena in relativistic heavy-ion collisions
Ayala, Alejandro
2010-07-01
Particles produced with intermediate values of transverse momentum 1-2≲pT≲4-5 GeV, exhibit both thermal and jet-like features making them an ideal testing ground of the properties of the quark-gluon plasma produced in the aftermath of a relativistic heavy-ion collision, which have been only inferred from the behavior of either soft or hard modes. In this work I discuss two phenomena that that are observed in this transverse momentum window: the suppression of the single, non-photonic electron yield compared to normalized p+p collisions and the spin alignment of vector mesons. I make use of a recombination scenario of either a heavy or a fast quark with thermal ones and show that this way of describing hadron formation can account for the afore mentioned phenomena.
Fluctuations of conserved charges in relativistic heavy ion collisions: An introduction
Asakawa, Masayuki
2015-01-01
Bulk fluctuations of conserved charges measured by event-by-event analysis in relativistic heavy ion collisions are observables which are believed to carry significant information on the primordial thermodynamics of the hot medium created by the collisions. Active studies have been done recently experimentally, theoretically, and on the lattice. In particular, non-Gaussianity of the fluctuations aquires much attention recently. In this review, we give a pedagogical introduction to these physics, and overview recent developments in this field of research. Starting from the definition of cumulants, basic concepts in fluctuation physics, such as thermal fluctuations in statistical mechanics and time evolution of fluctuations in diffusive systems, are described. Physics which are expected to occur in the QCD phase diagram and their measurement by event-by-event analyses are also elucidated.
Hydrodynamic flow amplitude correlations in event-by-event fluctuating heavy-ion collisions
Qian, Jing
2016-01-01
The effects of event-by-event fluctuations in the initial geometry of the colliding nuclei are important in the analysis of final flow observables in relativistic heavy-ion collisions. We use hydrodynamic simulations to study the amplitude correlations between different orders of event-by-event fluctuating anisotropic flow harmonics. While the general trends seen in the experimental data are qualitatively reproduced by the model, deviations in detail, in particular for peripheral collisions, point to the need for more elaborate future calculations with a hybrid approach that describes the late hadronic stage of the evolution microscopically. It is demonstrated explicitly that the observed anti-correlation between $v_2$ and $v_3$ is the consequence of approximately linear hydrodynamic response to a similar anti-correlation of the corresponding initial eccentricities $\\epsilon_2$ and $\\epsilon_3$. For $n{\\,>\\,}3$, the hydrodynamic correlations between $v_{2,3}$ and $v_n$ deviate from the rescaled correlations a...
Electromagnetic fields with electric and chiral magnetic conductivities in heavy ion collisions
Li, Hui; Wang, Qun
2016-01-01
We derive analytic formula for electric and magnetic fields produced by a moving charged particle in a conducting medium with the electric conductivity \\sigma and the chiral magnetic conductivity \\sigma_{\\chi}. We use the Green function method and assume that \\sigma_{\\chi} is much smaller than \\sigma. The compact algebraic expressions for electric and magnetic fields without any integrals are obtained. They recover the Lienard-Wiechert formula at vanishing conductivities. Exact numerical solutions are also found for any values of \\sigma and \\sigma_{\\chi} and are compared to analytic results. Both numerical and analytic results agree very well for the scale of high energy heavy ion collisions. The space-time profiles of electromagnetic fields in non-central Au+Au collisions have been calculated based on these analytic formula as well as exact numerical solutions.
D0 Meson Production in Heavy Ion Collisions in CMS experiment
Wang, Jing
2016-01-01
The measurement of heavy flavour production is a powerful tool to study the properties of the high-density QCD medium created in heavy-ion collisions as heavy quarks are sensitive to the transport properties of the medium and may interact with the QCD matter differently from light quarks. In particular, the comparison between the nuclear modification factors of light and heavy flavoured particles provides insights into the expected flavour dependence of in-medium parton energy loss. With the CMS detector, the D0 meson production is studied in pp and PbPb collisions at 2.76 and 5.02 TeV. In this talk, the nuclear modification factor of D0 meson are presented and compared to the charged hadron nuclear modification factor and theoretical calculations.
Spatial Wilson loops in the classical field of high-energy heavy-ion collisions
Petreska, Elena
2013-01-01
It has been previously shown numerically that the expectation value of the magnetic Wilson loop at the initial time of a heavy-ion collision exhibits area law scaling. This was obtained for a classical non-Abelian gauge field in the forward light cone and for loops of area $A\\gsim 2/Q_s^2$. Here, we present an analytic calculation of the spatial Wilson loop evaluated in the classical field of a collision within perturbation theory. We show that the leading diagram corresponds to two sources, for both projectile and target, whose field is evaluated at second order in the gauge potential. We find that in ``naive'' perturbation theory without screening the magnetic flux through a loop is proportional to the square of its area.
A viscous blast-wave model for high energy heavy-ion collisions
Directory of Open Access Journals (Sweden)
Jaiswal Amaresh
2016-01-01
Full Text Available Employing a viscosity-based survival scale for initial geometrical perturbations formed in relativistic heavy-ion collisions, we model the radial flow velocity at freeze-out. Subsequently, we use the Cooper-Frye freeze-out prescription, with viscous corrections to the distribution function, to extract the transverse momentum dependence of particle yields and flow harmonics. We fit the model parameters for central collisions, by fitting the spectra of identified particles at the Large Hadron Collider (LHC, and estimate them for other centralities using simple hydrodynamic relations. We use the results of Monte Carlo Glauber model for initial eccentricities. We demonstrate that this improved viscous blast-wave model leads to good agreement with transverse momentum distribution of elliptic and triangular flow for all centralities and estimate the shear viscosity to entropy density ratio η/s ≃ 0.24 at the LHC.
Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
Mehtar-Tani, Yacine
2016-01-01
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.
A viscous blast-wave model for high energy heavy-ion collisions
Jaiswal, Amaresh; Koch, Volker
2016-07-01
Employing a viscosity-based survival scale for initial geometrical perturbations formed in relativistic heavy-ion collisions, we model the radial flow velocity at freeze-out. Subsequently, we use the Cooper-Frye freeze-out prescription, with viscous corrections to the distribution function, to extract the transverse momentum dependence of particle yields and flow harmonics. We fit the model parameters for central collisions, by fitting the spectra of identified particles at the Large Hadron Collider (LHC), and estimate them for other centralities using simple hydrodynamic relations. We use the results of Monte Carlo Glauber model for initial eccentricities. We demonstrate that this improved viscous blast-wave model leads to good agreement with transverse momentum distribution of elliptic and triangular flow for all centralities and estimate the shear viscosity to entropy density ratio η/s ≃ 0.24 at the LHC.
Inclusion of the diffuseness in the schematic model of heavy ion collisions
International Nuclear Information System (INIS)
The schematic model of central heavy ion collisions developed by Swiatecki includes the Coulomb and surface contributions to the potential energy of the system and one-body dissipation. This model is extended by considering the diffuseness of the nuclear surface; this has the implication that we must consider the proximity forces in the dynamics of the collisions. For the sake of simplicity we work with symmetrical systems. The results of the model studied are compared with experimental data and with other theoretical calculations. We conclude that the detailed consideration of the diffuseness of the nuclear surfaces does not substantially change the results of the schematic model for sharp surfaces in which the diffuseness is considered only through the parameters. (author)
Studying the interplay of strong and electromagnetic forces in heavy-ion collisions with NICA
Rybicki, A.; Szczurek, A.; Kłusek-Gawenda, M.; Sputowska, I.
2016-08-01
In the following we stress the advantages of the NICA research programme in the context of studying the spectator-induced electromagnetic phenomena present in heavy-ion collisions. We point at the specific interest of using these phenomena as a new, independent source of information on the space-time evolution of the reaction and of the non-perturbative process of particle production. We propose an extended series of measurements of well-defined observables to be performed in different types of nuclear reactions and in the whole range of collision energies available to NICA. We expect these measurements to bring very valuable new insight into the mechanism of non-perturbative strong interactions, complementary to the studies made at the SPS at CERN, RHIC at BNL, and the LHC.
Strangeness production in heavy ion collisions -Constraining the KN – potential in medium
International Nuclear Information System (INIS)
We review the strangeness production in heavy ion collisions at energies around the NN production threshold and discuss recent measurements of the FOPI collaboration on charged kaon flow over a wide impact parameter range. The data are compared to comprehensive state-of-the-art transport models. The dense nuclear matter environment produced in those collisions may provide unique opportunities to form strange few body systems. The FOPI detector is especially suited to reconstruct such states by their charged particle decays. Apart from strongly decaying states special emphasis will be put on the search for long living weakly decaying states, i.e. Hyper-Nuclei. Light hyper nuclei are reconstructed by their two body decay channels and the production of Hyper-Tritons is studied with respect to Λ and t(3He).
Strangeness production in heavy ion collisions -Constraining the KN - potential in medium
Leifels, Yvonne; FOPI Collaboration
2013-03-01
We review the strangeness production in heavy ion collisions at energies around the NN production threshold and discuss recent measurements of the FOPI collaboration on charged kaon flow over a wide impact parameter range. The data are compared to comprehensive state-of-the-art transport models. The dense nuclear matter environment produced in those collisions may provide unique opportunities to form strange few body systems. The FOPI detector is especially suited to reconstruct such states by their charged particle decays. Apart from strongly decaying states special emphasis will be put on the search for long living weakly decaying states, i.e. Hyper-Nuclei. Light hyper nuclei are reconstructed by their two body decay channels and the production of Hyper-Tritons is studied with respect to Λ and t(3He).
Study of flow as a function of centrality in heavy ion collisions at ultrarelativistic energies
International Nuclear Information System (INIS)
The goal of the NA50 experiment which continues the NA38 and NA51 experiments, is to put into evidence the quark gluon plasma (QGP) in ultrarelativistic heavy ion collisions. Up to now, the J/ψ resonance production was used as a probe for the QGP formation. According to strong interaction, quark gluon plasma is supposed to reach a thermal equilibrium, at least locally. An evidence of this thermalization of the matter coming from the collision would appear in the transverse plane as an elliptic flow in the direction of the reaction plane. The analysis developed in this thesis is a study of the elliptic flow in neutral transverse energy as a function centrality in S-S, S-Cu, S-U and Pb-Pb collisions. Flow study is realized using data coming from the electromagnetic calorimeter. An elliptic flow in neutral transverse energy is observed in Pb-Pb interactions. Its maximum value is about 2% for semi-central collisions and it vanishes for central collisions. This is the expected behaviour for a thermalized medium. The same analysis has been done in S-S, S-Cu collisions which provides no evidence for the existence of an elliptic flow. Furthermore, the J/ψ production as a function of the angle between J/ψ direction and impact parameter direction could be analyzed. The results seems to show that J/ψ interaction with produced particles is small. (author)
Nuclear quantum many-body dynamics: from collective vibrations to heavy-ion collisions
International Nuclear Information System (INIS)
This report gives a summary of my research on nuclear dynamics during the past ten years. The choice of this field has been motivated by the desire to understand the physics of complex systems obeying quantum mechanics. In particular, the interplay between collective motion and single-particle degrees of freedom is a source of complex and fascinating behaviours. For instance, giant resonances are characterised by a collective vibration of many nucleons, but their decay may occur by the emission of a single nucleon. Another example could be taken from the collision of nuclei where the transfer of few nucleons may have a strong impact on the formation of a compound system is non trivial. To describe these complex systems, one needs to solve the quantum many-body problem. The description of the dynamics of composite systems can be very challenging, especially when two such systems interact. An important goal of nuclear physics is to find a unified way to describe the dynamics of nuclear systems. Ultimately, the same theoretical model should be able to describe vibrations, rotations, fission, all the possible outcomes of heavy-ion collisions (elastic and inelastic scattering, particle transfer, fusion, and multifragmentation), and even the dynamics of neutron star crust. This desire for a global approach to nuclear dynamics has strongly influenced my research activities. In particular, all the numerical applications presented in this report have been obtained from few numerical codes solving equations derived from the same variational principle. Beside the quest for a unified model of nuclear dynamics, possible applications of heavy-ion collisions such as the formation of new nuclei is also a strong motivation for the experimental and theoretical studies of reaction mechanisms. This report is not a review article, but should be considered as a reading guide of the main papers my collaborators and myself have published. It also gives the opportunity to detail some
Relativistic heavy ion research
International Nuclear Information System (INIS)
This report discusses the following topics: antiproton production; Bose-Einstein correlations; high-transverse momentum spectra; strangeness enhancement in heavy ion collisions; search for rare negative secondaries of antiprotons and antinuclei produced in heavy ion collisions; quark matter; and time-of-flight systems test at Brookhaven AGS. (LSP)
International Nuclear Information System (INIS)
In a recent paper, a fifth order polynomial curve was presented which fits very well to the existing experimental data on K-shell ionization cross-sections induced by protons. It is a universal curve, in the sense that it includes target atoms of any Z number at any projectile (proton) energy. In principle, it is possible to fit in the same curve the cross-sections obtained with any ion as a projectile, by means of a scaling law derived from the plane wave Born approximation (PWBA) and the binary encounter approximation (BEA) models. Experimental data with deuterons, alpha particles and 3He ions were fit into the same curve, with a good agreement. The agreement was poorer for experimental cross-sections obtained with heavier ions, like 12C, 14N and 40Ar. The discrepancies are attributable to several aspects of the ion-atom interaction, not considered in the derivation of such scaling law. The ECPSSR model has been more successful on predicting the cross-sections for heavy ions. Within the considerations in the ECPSSR and other models, arguments are given to explain the former discrepancies and suggestions are made to generalize the scaling law to fit the heavy ion data in a single curve
The discovery of nuclear compression phenomena in relativistic heavy-ion collisions
International Nuclear Information System (INIS)
This article has attempted to review more than 15 years of research on shock compression phenomena, which is closely related to the goal of determining the nuclear EOS. Exciting progress has been made in this field over the last years and the fundamental physics of relativistic heavy ion-collisions has been well established. Overwhelming experimental evidence for the existence of shock compression has been extracted from the data. While early, inclusive measurements had been rather inconclusive, the advent of 4π-detectors like the GSI-LBL Plastic Ball had enabled the outstanding discovery of collective flow effects, as they were predicted by fluid-dynamical calculations. The particular case of conical Mach shock waves, anticipated for asymmetric collisions, has not been observed. What are the reasons? Surprisingly, the maximum energy of 2.1 GeV/nucleon for heavy ions at the BEVALAC had been found to be too low for Mach shock waves to occur. The small 20Ne-nucleus is stopped in the heavy Au target. A Mach cone, however, if it had developed in the early stage of the collision will be wiped out by thermal motion in the process of slowing the projectile down to rest. A comparison of the data with models hints towards a rather hard EOS, although a soft one cannot be excluded definitively. A quantitative extraction is aggravated by a number in-medium and final-state effects which influence the calculated observables in a similar fashion as different choices of an EOS. Thus, as of now, the precise knowledge of the EOS of hot and dense matter is still an open question and needs further investigation. (orig.)
The High-Energy Limit of Electromagnetic Pair Production in Heavy-Ions Collisions
International Nuclear Information System (INIS)
In recent experiments at the SPS, and in the near future colliding-beam accelerators, such as RHIC and LHC, peripheral heavy-ions collisions produce strong, Lorentz contracted electromagnetic fields. The high charges and high energies of the ions give large cross sections for electromagnetic lepton - antilepton pair production. In this work, a non-perturbative treatment of pair production under these extreme conditions is considered. The two-center Dirac equation for an electron in the external electromagnetic field of two colliding heavy ions in the limit in which the ions are moving at the speed of light is exactly solved off the light fronts using light-front variables and a light-fronts representation. The electromagnetic fields of the ions are confined to the light fronts by the extreme Lorentz contraction and by a choice of gauge designed to incorporate the long-range Coulomb effects into the definition of the asymptotic states. After the peripheral collision, as the ions move apart, the solution in the space between them is determined by the non-trivial boundary conditions at the light fronts. An exact integral representation for the free pair creation amplitudes off the light fronts is obtained by calculating the transition currents flowing from the light fronts into the space between the separating ions. The condition for the applicability of this nonperturbative solution for large but finite collision energy is found, and used to explain recent experimental results according to which the measured production rates scale as the square of the projectile and target charges, even for large charges. It is shown that this observed scaling of positron yields is a result of an exact cancellation of a nonperturbative charge dependence. Nonperturbative effects may contribute significantly to the small-momentum-transfer regime, and to asymptotic states on the light fronts, as well as to results for multiple pair-production, and for correlations between the produced
Chiral symmetry restoration versus deconfinement in heavy-ion collisions at high baryon density
Cassing, W.; Palmese, A.; Moreau, P.; Bratkovskaya, E. L.
2016-01-01
We study the production of strange hadrons in nucleus-nucleus collisions from 4 to 160 A GeV within the parton-hadron-string dynamics (PHSD) transport approach that is extended to incorporate essentials aspects of chiral symmetry restoration (CSR) in the hadronic sector (via the Schwinger mechanism) on top of the deconfinement phase transition as implemented in PHSD. Especially the K+/π+ and the (Λ +Σ0) /π- ratios in central Au+Au collisions are found to provide information on the relative importance of both transitions. The modeling of chiral symmetry restoration is driven by the pion-nucleon Σ term in the computation of the quark scalar condensate that serves as an order parameter for CSR and also scales approximately with the effective quark masses ms and mq. Furthermore, the nucleon scalar density ρs, which also enters the computation of , is evaluated within the nonlinear σ -ω model which is constrained by Dirac-Brueckner calculations and low-energy heavy-ion reactions. The Schwinger mechanism (for string decay) fixes the ratio of strange to light quark production in the hadronic medium. We find that above ˜80 A GeV the reaction dynamics of heavy nuclei is dominantly driven by partonic degrees of freedom such that traces of the chiral symmetry restoration are hard to identify. Our studies support the conjecture of "quarkyonic matter" in heavy-ion collisions from about 5 to 40 A GeV and provide a microscopic explanation for the maximum in the K+/π+ ratio at about 30 A GeV, which only shows up if a transition to partonic degrees of freedom is incorporated in the reaction dynamics and is discarded in the traditional hadron-string models.
A Hydrodynamic Analysis of Collective Flow in Heavy-Ion Collisions
Yan, Li
Recent progress in the hydrodynamic simulation of heavy-ion collisions have characterized the fluctuating initial state and the viscous corrections to the corresponding collective flow. These fluctuations naturally explain the "ridge" and "shoulder" structure of the measured two-particle correlation functions at RHIC and the LHC. We introduce a cumulant expansion for analyzing the azimuthal fluctuations in the initial state. The cumulant definitions systematically describe the azimuthal anisotropy order by order. In particular, the dipole asymmetry epsilon 1 appears at third order in the expansion, and the response to this initial fluctuation produces a radipity even dipole flow v 1, which has been subsequently confirmed by experiment. In addition, the cumulant expansion organizes the study of the nonlinear response to the initial conditions. The linear and nonlinear response coefficients to a given initial state were calculated with ideal and viscous hydrodynamic simulations. The collective flow is generated either linearly or nonlinearly, and the relative contribution of these two mechanisms to the observed flow pattern is calculated as a function of harmonic order, collision centrality, and the shear viscosity. For non-central collisions and high harmonic orders n ≥ 4, the nonlinear response is the dominant mechanism. This result is also seen in event-by-event hydrodynamic simulations. Using the cumulant expansion and the corresponding linear and nonlinear response coefficients, we determine the event plane correlations and compare to first measurements of this type. The observed event plane correlations are rooted in the initial state participant plane correlations, but a large fraction of the observed correlations are determined by harmonic mixing during the bulk expansion. Viscous corrections to the hydrodynamic formulation of collective flow are reflected in hydrodynamic equations of motion, as well as the correction to the distribution function at freeze
Testing Dirac-Brueckner models in collective flow of heavy-ion collisions
International Nuclear Information System (INIS)
We investigate differential in-plane and out-of-plane flow observables in heavy-ion reactions at intermediate energies from 0.2-2 AGeV within the framework of relativistic BUU transport calculations. The mean field is based on microscopic Dirac-Brueckner-Hartree-Fock (DB) calculations. We apply two different sets of DB predictions, those of ter Haar and Malfliet and more recent ones from the Tuebingen group, which are similar in general but differ in details. The latter DB calculations exclude spurious contributions from the negative-energy sector to the mean field which results in a slightly softer equation of state and a less repulsive momentum dependence of the nucleon-nucleus potential at high densities and high momenta. For the application to heavy-ion collisions in both cases non-equilibrium features of the phase space are taken into account on the level of the effective interaction. The systematic comparison to experimental data favours the less repulsive and softer model. Relative to non-relativistic approaches one obtains larger values of the effective nucleon mass. This produces a sufficient amount of repulsion to describe the differential flow data reasonably well. (orig.)
Particle production in Ultra-relativistic Heavy-Ion Collisions : A Statistical-Thermal Model Review
Tiwari, S K
2013-01-01
The current status of various thermal and statistical descriptions of particle production in the ultra-relativistic heavy-ion collisions experiments is presented in detail. We discuss the formulation of various types of thermal models of a hot and dense hadron gas (HG) and the methods incorporated in implementing the interactions between hadrons. We first obtain the parametrizations of center-of-mass energy ($\\sqrt{s_{NN}}$) in terms of temperature ($T$) and baryon chemical potential ($\\mu_B$) obtained by analyzing the particle ratios at the freeze-out over a broad energy range from the lowest Alternating Gradient Synchrotron (AGS) energy to the highest Relativistic Heavy-Ion Collider (RHIC) energies. The results of various thermal models together with the experimental results for the various ratios of particles are then compared. We have derived some new universal conditions emerging at the chemical freeze-out of HG fireball which demonstrate the independence with respect to the energy as well as the structu...
Directory of Open Access Journals (Sweden)
Jing Yang
2015-01-01
Full Text Available We systematically investigate the pion transverse momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss (HBT interferometry in the granular source model for the heavy ion collisions of Au-Au at sNN=200 GeV and Pb-Pb at sNN=2.76 TeV with different centralities. The granular source model can well reproduce the experimental results of the heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC and the Large Hadron Collider (LHC. We examine the parameters involved in the granular source model. The experimental data of the momentum spectrum, elliptic flow, and HBT radii for the two collision energies and different centralities impose very strict constraints on the model parameters. They exhibit certain regularities for collision centrality and energy. The space-time structure and expansion velocities of the granular sources for the heavy ion collisions at the RHIC and LHC energies with different centralities are investigated.
Institute of Scientific and Technical Information of China (English)
张松; 陈金辉; 马余刚; 许长补; 蔡翔舟; 马国亮; 钟晨
2011-01-01
High-energy heavy-ion collisions produce abundant hyperons and nucleons. A dynamical coales- cence model coupled with the ART model is employed to study the production probabilities of light clusters, deuteron （d）, triton （t）, helion （3He）, and hypertrito
Characteristic X-ray emission in close collisions between heavy ions and atoms
International Nuclear Information System (INIS)
In this paper an attempt is given to answer the question of how far the inner-shell vacancy production in very heavy ion-atom collisions is influenced by the electronic configuration of the projectile prepared prior to the collision producing the observed vacancy. The variation of this configuration has been induced by changing the primary charge state of the projectile, the target density and thickness or by inverting the collision system. It turns out from the performed analysis of the experimental data that the excitation of even most strongly bound MO's can be easily dependent on these factors which have been ignored until now, especially in discussions of the 1sσ or 2pσ vacancy production at ZUA > 130. Experiments performed for the first time with gaseous targets for such heavy systems show very convincingly the influence of the outer-shell configuration on the vacancy production in inner shells. The analysis of the data has been performed in terms of electronic transitions among MO's transiently formed during the collision. In many cases a satisfactory agreement between theoretical predictions and experiment has been achieved. (orig./HSI)
Measurements of Upsilon meson suppression in heavy ion collisions with the CMS experiment at the LHC
Filipovic, Nicolas
Measurements of Upsilon suppression in ultra relativistic heavy ion collisions are key to understanding the hot and deconfined phase of matter called Quark-Gluon Plasma (QGP). The cross section of Upsilon states Y(nS) are measured in proton-proton collisions and in lead-lead collisions at the centre-of-mass energy of 2.76 TeV per nucleon pair. Individual states are measured through their dimuon decay channel using the Compact Muon Solenoid (CMS) at CERN. The cross sections measured in pp and PbPb are compared thanks to the nuclear modification factor, $R_{AA}$. This observable is computed for Upsilon(1S) and Upsilon(2S) in several bins of transverse momentum,rapidity and centrality of the collision. An upper limit on the production of Upsilon(3S) in PbPb is estimated. These measurements exhibit a clear and ordered suppression pattern, consistent with the hypothesis of sequential melting of quarkonia in the QGP. The measured Upsilon(1S) and Upsilon(2S) suppressions are observed to be independent of transverse ...
Central collisions of heavy ions. Progress report, October 1, 1992--August 31, 1993
Energy Technology Data Exchange (ETDEWEB)
Fung, Sun-yiu
1993-08-01
This report describes the activities of the Heavy Ion Physics Group at the University of California, Riverside from October 1, 1992 to August 31, 1993. During this period, our AGS E802/E859/E866 experiments focused on strange particle production, and the fluctuation phenomenon associated with correlation studies in nucleus nucleus central collisions. We have designed and are implementing a new detector to replace the Target Multiplicity Array (TMA) for the E866 runs. As part of the PHENIX collaboration, we contributed to the Conceptual Design Report (CDR), and worked on a RHIC silicon microstrip detector R&D project, the central core of the multiplicity-vertex detector (MVD). In the coming year, we planned to complete the New Multiplicity Array (NMA) detector for the gold projectile E866 experiment, and analyzed the data associated with this new system. We are continuing our efforts in the preparation of the PHENIX detector system.
Isospin Effect on Nuclear Stopping in Intermediate Energy Heavy Ion Collisions
Institute of Scientific and Technical Information of China (English)
李庆峰; 李祝霞
2002-01-01
By using the isospin-dependent quantum molecular dynamics model, we study the dependence of nuclear stopping Qzz/A and R in intermediate energy heavy ion collisions on system size, initial N/Z, isospin symmetry potential and the medium correction of two-body cross sections. We find the effect of the initial N/Z ratio and isospinsymmetry potential on stopping is weak. The excitation function of Qzz/A and R depends on the form of medium correction of two-body cross sections, the equation ofstate of nuclear matter. Our results show that the behaviour of the excitation function of Qzz/A and R can provide clearer information of the isospin dependence of the medium correction of two-body cross sections
Electromagnetic heavy-lepton pair production in relativistic heavy-ion collisions
Şengül, M. Y.; Güçlü, M. C.; Mercan, Ö.; Karakuş, N. G.
2016-08-01
We calculate the cross sections of electromagnetic productions of muon- and tauon-pair productions from the ultra-relativistic heavy ion collisions. Since the Compton wavelengths of muon and tauon are comparable to the radius of the colliding ions, nuclear form factors play important roles for calculating the cross sections. Recent measurement (Abrahamyan et al., Phys Rev Lett 108:112502, 2012) indicates that the neutrons are differently distributed from the protons; therefore this affects the cross section of the heavy-lepton pair production. In order to see the effects of the neutron distributions in the nucleus, we used analytical expression of the Fourier transforms of the Wood-Saxon distribution. Cross section calculations show that the Wood-Saxon distribution function is more sensitive to the parameter R compared to the parameter a.
Bożek, Piotr
2008-03-01
The longitudinal hydrodynamic expansion of the fluid created in relativistic heavy-ion collisions is considered taking into account shear viscosity. We consider the dynamics of a non-boost-invariant energy density of the fluid in 1+1 dimensions, using the proper time and the space-time rapidity. Both a nonvanishing viscosity and a soft equation of state make the final particle distributions in rapidity narrower. The width of the initial Gaussian rapidity distribution and its central energy density are fitted to reproduce the rapidity distributions of pions and kaons as measured by the BRAHMS Collaboration. The presence of viscosity has dramatic consequences on the value of the initial energy density. Dissipative processes and the reduction of the longitudinal work due to the shear viscosity increase the total entropy and the particle multiplicity at central rapidities. Viscous corrections make the longitudinal velocity of the fluid stay close to the Bjorken scaling flow vz=z/t through the evolution.
Isospin dynamics on the production of pions and preequilibrium particles in heavy-ion collisions
Feng, Zhao-Qing
2016-01-01
Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, pion dynamics in heavy-ion collisions near threshold energies and the emission of preequilibrium particles (nucleons and light clusters) have been investigated. A density, momentum and isospin dependent pion-nucleon potential based on the $\\Delta$-hole model is implemented in the transport approach, which slightly increases the $\\pi^{-}/\\pi^{+}$ ratio, but reduces the total pion yields. A bump structure of the $\\pi^{-}/\\pi^{+}$ ratio in the kinetic energy spectra appears at the pion energy close to the $\\Delta$(1232) resonance region. The yield ratios of neutrons to protons from the squeeze-out particles perpendicular to the reaction plane are sensitive to the stiffness of nuclear symmetry energy, in particular at the high-momentum (kinetic energy) tails.
The topological long range order in QCD. Applications to heavy ion collisions and cosmology
Directory of Open Access Journals (Sweden)
Zhitnitsky Ariel R.
2015-01-01
Full Text Available We argue that the local violation of P invariance in heavy ion collisions is a consequence of the long range topological order which is inherent feature of strongly coupled QCD. A similar phenomenon is known to occur in some topologically ordered condensed matter systems with a gap. We also discuss possible cosmological applications of this long range order in strongly coupled gauge theories. In particular, we argue that the de Sitter behaviour might be dynamically generated as a result of the long range order. In this framework the inflaton is an auxiliary field which effectively describes the dynamics of topological sectors in a gauge theory in the expanding universe, rather than a new dynamical degree of freedom.
Techniques in the Moment Analysis of Net-proton Multiplicity Distributions in Heavy-Ion Collisions
Luo, Xiaofeng; Mohanty, Bedangadas; Xu, Nu
2013-01-01
Moments (Variance ($\\sigma^2$), Skewness($S$), Kurtosis($\\kappa$)) of multiplicity distributions of conserved quantities, such as net-baryon,net-charge and net-strangeness, are predicted to be sensitive to the correlation length of the system and connected to the thermodynamic susceptibilities computed in Lattice QCD and Hadron Resonance Gas (HRG) model. In this paper, we point out several measurement artifacts like centrality bin width effect, auto-correlation and centrality resolution effect in the moment analysis of net-proton multiplicity distributions in high energy heavy-ion collisions using the UrQMD model. We present methods to overcome these artifacts so that the extracted moments could be used to obtain physical conclusions. In addition we present methods to properly estimate the statistical errors in moment analysis.
Analyzing flow anisotropies with excursion sets in relativistic heavy-ion collisions
Mohapatra, Ranjita K; Srivastava, Ajit M
2011-01-01
We show that flow anisotropies in relativistic heavy-ion collisions can be analyzed using a certain technique of shape analysis of excursion sets recently proposed by us for CMBR fluctuations to investigate anisotropic expansion history of the universe. The technique analyzes shapes (sizes) of patches above (below) certain threshold value for transverse energy/particle number (the excursion sets) as a function of the azimuthal angle and rapidity. Modeling flow by imparting extra anisotropic momentum to the momentum distribution of particles from HIJING, we compare the resulting distributions for excursion sets at two different azimuthal angles. Angles with maximum difference in the two distributions identify the event plane, and the magnitude of difference in the two distributions relates to the magnitude of momentum anisotropy, i.e. elliptic flow.
Kinetic evolution of the glasma and thermalization in heavy ion collisions
Huang, Xu-Guang
2014-01-01
In relativistic heavy ion collisions, a highly occupied gluonic matter is created shortly after initial impact, which is in a non-thermal state and often referred to as the Glasma. Successful phenomenology suggests that the glasma evolves rather quickly toward the thermal quark-gluon plasma and a hydrodynamic behavior emerges at very early time $\\sim \\hat{o}(1)$ fm/c. Exactly how such "apparent thermalization" occurs and connects the initial conditions to the hydrodynamic onset, remains a significant challenge for theory as well as phenomenology. We briefly review various ideas and recent progress in understanding the approach of the glasma to the thermalized quark-gluon plasma, with an emphasis on the kinetic theory description for the evolution of such far-from-equilibrium and highly overpopulated, thus weakly-coupled yet strongly interacting glasma.
Chiral symmetry restoration in heavy-ion collisions at intermediate energies
Palmese, A; Seifert, E; Steinert, T; Moreau, P; Bratkovskaya, E L
2016-01-01
We study the effect of the chiral symmetry restoration (CSR) on heavy-ion collisions observables in the energy range $\\sqrt{s_{NN}}$=3-20 GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach. The PHSD includes the deconfinement phase transition as well as essential aspects of CSR in the dense and hot hadronic medium, which are incorporated in the Schwinger mechanism for the hadronic particle production. We adopt different parametrizations of the nuclear equation of state from the non-linear $\\sigma-\\omega$ model, which enter in the computation of the quark scalar density for the CSR mechanism, in order to estimate the uncertainty in our calculations.
Direct photon production in high-energy heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Manko, V.; Aggarwal, M.M.; Agnihotri, A.; Ahammed, Z.; Angelis, A.L.S.; Antonenko, V.; Arefiev, V.; Astakhov, V.; Avdeitchikov, V.; Awes, T.C.; Baba, P.V.K.S.; Badyal, S.K.; Baldine, A.; Barabach, L.; Barlag, C.; Bathe, S.; Batiounia, B.; Bernier, T.; Bhalla, K.B.; Bhatia, V.S.; Blume, C.; Bock, R.; Bohne, E.-M.; Boeroecz, Z.; Bucher, D.; Buijs, A.; Buesching, H.; Carlen, L.; Chalyshev, V.; Chattopadhyay, S.; Cherbatchev, R.; Chujo, T.; Claussen, A.; Das, A.C.; Decowski, M.P.; Djordjadze, V.; Donni, P.; Doubovik, I.; Dutt, S.; Majumdar, M.R. Dutta; El Chenawi, K.; Eliseev, S.; Enosawa, K.; Foka, P.; Fokin, S.; Frolov, V.; Ganti, M.S.; Garpman, S.; Gavrischuk, O.; Geurts, F.J.M.; Ghosh, T.K.; Glasow, R.; Gupta, S. K.; Guskov, B.; Gustafsson, H. A.; Gutbrod, H. H.; Higuchi, R.; Hrivnacova, I.; Ippolitov, M.; Kalechofsky, H.; Kamermans, R.; Kampert, K.-H.; Karadjev, K.; Karpio, K.; Kato, S.; Kees, S.; Kim, H.; Kolb, B. W.; Kosarev, I.; Koutcheryaev, I.; Kruempel, T.; Kugler, A.; Kulinich, P.; Kurata, M.; Kurita, K.; Kuzmin, N.; Langbein, I.; Lebedev, A.; Lee, Y.Y.; Loehner, H.; Luquin, L.; Mahapatra, D.P.; Martin, M.; Maximov, A.; Mehdiyev, R.; Mgebrichvili, G.; Miake, Y.; Mikhalev, D.; Mir, Md.F.; Mishra, G.C.; Miyamoto, Y.; Morrison, D.; Mukhopadhyay, D. S.; Myalkovski, V.; Naef, H.; Nandi, B. K.; Nayak, S. K.; Nayak, T. K.; Neumaier, S.; Nianine, A.; Nikitine, V.; Nikolaev, S.; Nilsson, P.; Nishimura, S.; Nomokonov, P.; Nystrand, J.; Obenshain, F.E.; Oskarsson, A.; Otterlund, I.; Pachr, M.; Parfenov, A.; Pavliouk, S.; Peitzmann, T.; Petracek, V.; Plasil, F.; Pinanaud, W.; Purschke, M.L.; Raeven, B.; Rak, J.; Raniwala, R.; Raniwala, S.; Ramamurthy, V.S.; Rao, N.K.; Retiere, F.; Reygers, K.; Roland, G.; Rosselet, L.; Roufanov, I.; Roy, C.; Rubio, J.M.; Sako, H.; Sambyal, S.S.; Santo, R.; Sato, S.; Schlagheck, H.; Schmidt, H.-R.; Shabratova, G.; Shah, T.H.; Sibiriak, I.; Siemiarczuk, T.; Silvermyr, D.; Sinha, B.C.; Slavine, N.; Soederstroem, K. [and others
1999-07-26
Direct thermal photons in the p{sub t} range of 0 - 5 GeV/c are expected to provide a sensitive probe of the hot dense matter formed in the early stage of relativistic heavy ion collisions. The production of single photons in 158 AGeV Pb+Pb interactions has been studied with the 10080 detector lead glass calorimeter of the WA98 experiment at CERN. Neutral {pi}{sup 0} cross section has been measured via its two-photon decay branch. At p{sub t} {>=}{approx}GeV/c single photon yields of {approx}20% of the decay photon yields are observed consistently with different photon identification criteria both for the peripheral and central events.
A Tale of Tails: Photon Rates and Flow in Ultra-Relativistic Heavy Ion Collisions
McLerran, Larry
2015-01-01
We consider the possibility that quark and gluon distributions in the medium created in high energy heavy ion collisions may be modified by a power law tail at energies much higher than the temperature. We parametrize such a tail by Tsallis distributions with an exponent motivated by phenomenology. These distributions are characterized by an effective temperature scale that we assume to evolve in time like the temperature for thermal distributions. We find that including such a tail increases the rates for photon production and significantly delays the emission times for photons of a fixed energy. We argue that these effects are sufficiently large that they should be able to account for photon yields and flow patterns seen in LHC and RHIC experiments.
Energy- Angular Correlation of Medium Energy Particles Produced in Heavy Ion Collisions
Hussein, M T; Sadek, N M; Elsweedy, J; Elsweedy, Jamila
2004-01-01
The nuclear photo-emulsion technique is used to study the information carried by the medium energy nucleons produced in heavy ion collisions. Multiplicity, energies as well as the angular distribution of this type of particles are measured. Due to the difficulties in measuring the energy only some particles having special criteria could be selected to measure their energy with consenting accuracy. A hypothetical model is proposed to correlate the energy of the produced particles to their emission angles so that it becomes easy to estimate the energy distribution in terms of measured emission angle. The proposed model is constructed upon statistical thermodynamic assumptions. Moreover, two additional base functions are originated that play the role of the statistical angular weight factor and the nuclear density of the compressed nuclear matter at the moment of particle emission. The prediction of the model are compared with complete set of measured data of the reactions of proton, helium, carbon and neon nucl...
Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion Collisions
Simenel, Cédric
2012-01-01
A summary of recent researches on nuclear dynamics with realistic microscopic quantum approaches is presented. The Balian-V\\'en\\'eroni variational principle is used to derive the time-dependent Hartree-Fock (TDHF) equation describing the dynamics at the mean-field level, as well as an extension including small-amplitude quantum fluctuations which is equivalent to the time-dependent random-phase approximation (TDRPA). Such formalisms as well as their practical implementation in the nuclear physics framework with modern three-dimensional codes are discussed. Recent applications to nuclear dynamics, from collective vibrations to heavy-ion collisions are presented. A particular attention is devoted to the interplay between collective motions and internal degrees of freedom. For instance, the harmonic nature of collective vibrations is questioned. Nuclei are also known to exhibit superfluidity due to pairing residual interaction. Extensions of the theoretical approach to study such pairing vibrations are now avail...
Collective flows in high-energy heavy-ion collisions at AGS and SPS energies
Indian Academy of Sciences (India)
A Ohnishi; M Isse; N Otuka; P K Sahu; Y Nara
2006-04-01
Proton collective flows in heavy-ion collisions from AGS ((2–11) A GeV) to SPS ((40, 158) A GeV) energies are investigated in a nonequilibrium transport model with nuclear mean-field (MF). Sideward , directed 1, and elliptic 2 flows are systematically studied with different assumptions on the nuclear equation of state (EoS). We find that momentum dependence in the nuclear MF is important for understanding the proton collective flows at AGS and SPS energies. Calculated results with momentum-dependent MF qualitatively reproduce the experimental data of proton sideward, directed, and elliptic flows in an incident energy range of (2–158) A GeV.
Electromagnetic Heavy Lepton Pair Production in Relativistic Heavy-Ion Collisions
Sengul, M Y; Mercan, O; Karakus, N G
2015-01-01
We calculate the cross sections of electromagnetic productions of muon and tauon pair productions from the ultra-relativistic heavy ion collisions. Since the Compton wavelengths of muon and tauon are comparable to the radius of the colliding ions, nuclear form factors play important roles for calculating the cross sections. Recent measurement [1] indicates that the neutrons are differently distributed from the protons therefore this affects the cross section of the heavy lepton pair production. In order to see the effects of the neutron distributions in the nucleus, we used analytical expression of the Fourier transforms of the Wood-Saxon distribution. Cross section calculations show that Wood-Saxon distribution function is more sensitive to the parameter R compare to the parameter a.
A viscous blast-wave model for relativistic heavy-ion collisions
Jaiswal, Amaresh
2015-01-01
Using a viscosity-based survival scale for geometrical perturbations formed in the early stages of relativistic heavy-ion collisions, we model the radial flow velocity during freeze-out. Subsequently, we employ the Cooper-Frye freeze-out prescription, with first-order viscous corrections to the distribution function, to obtain the transverse momentum distribution of particle yields and flow harmonics. For initial eccentricities, we use the results of Monte Carlo Glauber model. We fix the blast-wave model parameters by fitting the transverse momentum spectra of identified particles at the Large Hadron Collider (LHC) and demonstrate that this leads to a fairly good agreement with transverse momentum distribution of elliptic and triangular flow for various centralities. Within this viscous blast-wave model, we estimate the shear viscosity to entropy density ratio $\\eta/s\\simeq 0.24$ at the LHC.
Effects of $\\rho$-meson width on pion distributions in heavy-ion collisions
Huovinen, Pasi; Marczenko, Michał; Morita, Kenji; Redlich, Krzysztof; Sasaki, Chihiro
2016-01-01
The influence of the finite width of $\\rho$ meson on the pion momentum distribution is studied quantitatively in the framework of the S-matrix approach combined with a blast-wave model to describe particle emissions from an expanding fireball. We find that the proper treatment of resonances which accounts for their production dynamics encoded in data for partial wave scattering amplitudes can substantially modify spectra of daughter particles originating in their two body decays. In particular, it results in an enhancement of the low-$p_T$ pions from the decays of $\\rho$ mesons which improves the quantitative description of the pion spectra in heavy ion collisions obtained by the ALICE collaboration at the LHC energy.
Jet energy loss in heavy ion collisions from RHIC to LHC energies
Levai, Peter
2011-01-01
The suppression of hadron production originated from the induced jet energy loss is one of the most accepted and well understood phenomena in heavy ion collisions, which indicates the formation of color deconfined matter consists of quarks, antiquarks and gluons. This phenomena has been seen at RHIC energies and now the first LHC results display a very similar effect. In fact, the suppression is so close to each other at 200 AGeV and 2.76 ATeV, that it is interesting to investigate if such a suppression pattern can exist at all. We use the Gyulassy-Levai-Vitev description of induced jet energy loss combined with different nuclear shadowing functions and describe the experimental data. We claim that a consistent picture can be obtained for the produced hot matter with a weak nuclear shadowing. The interplay between nuclear shadowing and jet energy loss playes a crucial role in the understanding of the experimental data.
Double scattering production of two positron-electron pairs in ultraperipheral heavy-ion collisions
Klusek-Gawenda, Mariola
2016-01-01
We present first measurable predictions for electromagnetic (two-photon) double scattering production of two positron-electron pairs in ultraperipheral heavy-ion collisions at LHC. Measureable cross sections are obtained with realistic cuts on electron/positron (pseudo)rapidities and transverse momenta for the ALICE and ATLAS or CMS experiments. The predictions for total and differential cross sections are presented. We show also two-dimensional distributions in rapidities of the opposite-sign (from the same or different subcollisions) and of the same-sign ($e^+ e^+$ or $e^- e^-$) electrons and in rapidity distance between them. Expected number of events are presented and discussed. Our calculations strongly suggest that relevant measurements with the help of ATLAS, CMS and ALICE detectors are possible in a near future.
Proceedings of the 2nd joint seminar on atomic collisions and heavy ion induced nuclear reactions
International Nuclear Information System (INIS)
The meeting of the 2nd joint seminar on atomic collisions and heavy ion induced nuclear reactions was held at the University of Tokyo, May 13 and 14, 1982. The aim of this seminar has been not only to recognize the common problems lying between above two research fields, but also to obtain an overview of the theoretical and experimental approaches to clear the current problems. In the seminar, more than 50 participants gathered and presented 16 papers. These are two general reviews and fourteen comprehensive surveys on topical subjects which have been developed very intensively in recent years. The editors would like to thank all participants for their assistance and cooperation in making possible a publication of these proceedings. (author)