We review the main results obtained by the BRAHMS Collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A ...particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so-called quark–gluon plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e., the proposed color glass condensate.
In this work, we investigate the freeze-out process in heavy ion collisions at different relativistic energies. We present a study of standard blast-wave fits and Tsallis blast-wave fits performed to ...the transverse momentum spectra obtained in Au+Au collisions at RHIC energies. In addition, comparisons with simulated heavy ion collisions data using the UrQMD code will be presented to provide more detailed insight into the properties of the space-time evolution such as collective dynamics of the dense matter.
In this paper we present a new version of Chaos Many-Body Engine (CMBE) Grossu et al. (2014) 1. Inspired by the Mean Free Path concept, we implemented a new parameter, namely the “Mean Free Time”, ...which is defined as the mean time between one particle’s creation and its stimulated decay. This new parameter should be understood as an effect of the nuclear environment and, as opposed to the particle lifetime, it has the advantage of not being affected by the relativistic dilation. In 2 we presented a toy-model for chaos analysis of relativistic nuclear collisions at 4.5 A GeV/c (the SKM 200 collaboration). In this work, we extended our model to 200 A GeV (the maximum BNL energy).
Program title: Chaos Many-Body Engine v05
Catalogue identifier: AEGH_v5_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGH_v5_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: Microsoft Public License (Ms-PL)
No. of lines in distributed program, including test data, etc.: 638984
No. of bytes in distributed program, including test data, etc.: 15918340
Distribution format: tar.gz
Programming language: Visual C# .Net 2010
Computer: PC
Operating system: .Net Framework 4.0 running on MS Windows
RAM: 128 MB
Classification: 24.60.Lz, 05.45.a
Catalogue identifier of previous version: AEGH_v4_0
Journal reference of previous version: Computer Physics Communications 185 (2014) 1339
Does the new version supersede the previous version?: Yes
Nature of problem: Toy-model for relativistic nuclear collisions at present BNL energies.
Solution method: Relativistic many-body OOP engine, including a reactions module.
Reasons for new version:1.Implementation of the “Mean Free Time” parameter;2.Implementation of a new example of use for relativistic nuclear collisions at present BNL energies.
Summary of revisions:1.Implementation of a new parameter, namely the “Mean Free Time”, defined as the mean time between one particle’s creation and its stimulated decay. The Mean Free Time should be understood as an effect of the nuclear environment and, as opposed to the particle lifetime, it is measured in the observation system (not affected by the relativistic dilation). Following this purpose, a new tag (MeanFreeTime) was added in the “Particles” section of the specific XML reactions input file described in 2.2.Analysis ∖Chaos Analysis ∖Double ∖Other: Implementation of a, more reliable, fuzzy algorithm 3 for probability distributions.3.Math ∖Vector ∖GetRandomVector: Bug correction (the distribution is now isotropic).4.Simulations ∖Collider: New example of use for relativistic nuclear collisions at present BNL energies 4.
Additional comments:
Inspired by existing nuclear billiards 5,6, in 2 we implemented a toy-model for relativistic nuclear collisions at 4.5 A GeV/c (the SKM 200 collaboration 7,8). In this work, we extended our model to higher energies. Following this purpose, we inherited the SimulationCollisionExample class (the SimulationColliderExample class), and employed an extended set of reactions (the ColliderReactions.xml file). The, previously discussed, Mean Free Time concept is also playing an important role in this context. As an exemplification of CMBE capabilities, in Figs. 1–3 we present some preliminary results 9 for 1000 Au–Au events at 200 A GeV (the maximum BNL energy 4), simulated at 0.1 Fm/c temporal resolution. Display omitted Display omitted Display omitted
Experiments at the RHIC and LHC can recreate quark-gluon plasma conditions similar to those when the Universe was less than a few microseconds old, and will offer the best prospects to discover how ...the Universe evolved in early stages. In this work we study the (anti)deuteron-to-(anti)proton ratio obtained in heavy ion collisions at relativistic energies and compare the results with the ratio obtained from Big Bang nucleosynthesis.
Relativistic heavy-ion collisions offer a unique opportunity to study highly excited dense nuclear matter in the laboratory. We present measurements of identified charged hadron production at ...different rapidities from Au+Au and p+p collisions at 200 GeV. Coulomb effects on pion spectra in relativistic nuclear collisions at RHIC energies will be investigated. The nuclear modification factors for identified particles show distinct meson/baryon dependence. At high pT the charged pion yields are suppressed by a factor of ~5, while the baryon production is enhanced in Au+Au collisions, when compared to the binary scaled p+p data from the same energy.
Transverse momentum spectra of protons and anti-protons measured in the rapidity range 0<y<3.1 from 0–10% central Au+Au collisions at sNN=62.4 GeV are presented. The rapidity densities, dN/dy, of ...protons, anti-protons and net-protons (Np–Np¯) have been deduced from the spectra over a rapidity range wide enough to observe the expected maximum net-baryon density. From mid-rapidity to y=1 the net-proton yield is roughly constant (dN/dy∼10), but rises to dN/dy∼25 at 2.3<y<3.1. The mean rapidity loss is 2.01±0.14±0.12 units from beam rapidity. The measured rapidity distributions are compared to model predictions. Systematics of net-baryon distributions and rapidity loss vs. collision energy are discussed.
The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons, and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at s NN =200 GeV. As the collisions become more ...central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and 2.5 GeV/c are suppressed for central collisions relative to scaled p + p collisions. This suppression, which increases as the collisions become more central, is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities, initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. In conclusion, the ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.
Charged-particle pseudorapidity densities are presented for the d + Au reaction at sqrts(NN) = 200 GeV with -4.2 < or = eta < or = 4.2. The results, from the BRAHMS experiment at BNL Relativistic ...Heavy-Ion Collider, are shown for minimum-bias events and 0%-30%, 30%-60%, and 60%-80% centrality classes. Models incorporating both soft physics and hard, perturbative QCD-based scattering physics agree well with the experimental results. The data do not support predictions based on strong-coupling, semiclassical QCD. In the deuteron-fragmentation region the central 200 GeV data show behavior similar to full-overlap d+Au results at sqrts(NN) = 19.4 GeV.
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