Author
A. V. Alakhverdyants
Bio: A. V. Alakhverdyants is an academic researcher from Joint Institute for Nuclear Research. The author has contributed to research in topics: Relativistic Heavy Ion Collider & Pseudorapidity. The author has an hindex of 36, co-authored 82 publications receiving 5957 citations.
Papers
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B. I. Abelev1, Madan M. Aggarwal2, Zubayer Ahammed3, A. V. Alakhverdyants4 +345 more•Institutions (49)
1,696 citations
B. I. Abelev1, Madan M. Aggarwal2, Zubayer Ahammed3, A. V. Alakhverdyants4 +372 more•Institutions (48)
TL;DR: In this article, the authors investigate a three-particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect, and report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at s(NN)=200 GeV using the STAR detector.
Abstract: Parity-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three-particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at s(NN)=200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.
454 citations
B. I. Abelev1, Madan M. Aggarwal2, Zubayer Ahammed3, A. V. Alakhverdyants4 +372 more•Institutions (49)
TL;DR: In this paper, a three-particle mixed-harmonic azimuthal correlator is investigated, which is a P-even observable, but directly sensitive to the charge-separation effect.
Abstract: Parity (P)-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in noncentral collisions. To study this effect, we investigate a three-particle mixed-harmonics azimuthal correlator which is a P-even observable, but directly sensitive to the charge-separation effect. We report measurements of this observable using the STAR detector in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators and discuss in detail possible contributions from other effects that are not related to P violation.
308 citations
Madan M. Aggarwal1, Zubayer Ahammed2, A. V. Alakhverdyants3, I. G. Alekseev +380 more•Institutions (50)
TL;DR: From the measurements at the three beam energies, no evidence for a critical point in the QCD phase diagram for μB below 200 MeV is found and the products κσ2 and Sσ are constant as functions of collision centrality.
Abstract: 200 GeV corresponding to baryon chemical potentials (mu(B)) between 200 and 20 MeV. Our measurements of the products kappa sigma(2) and S sigma, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long-range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the root s(NN) dependence of kappa sigma(2). From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for mu(B) below 200 MeV.
306 citations
B. I. Abelev1, Madan M. Aggarwal2, Zubayer Ahammed3, A. V. Alakhverdyants4 +387 more•Institutions (50)
TL;DR: The authors reported the observation of antihypertritons-comprising an antiproton, an antineutron, and an antilambda hyperon-produced by colliding gold nuclei at high energy.
Abstract: Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons-comprising an antiproton, an antineutron, and an antilambda hyperon-produced by colliding gold nuclei at high energy. Our analysis yields 70 +/- 17 antihypertritons (3/Lambda(H) over bar) and 157 +/- 30 hypertritons ((3)(Lambda)H). The measured yields of (3)(Lambda)H (3/Lambda(H) over bar) and (3)He ((3)(He) over bar) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and of nuclei containing strange quarks, have implications spanning nuclear and particle physics, astrophysics, and cosmology.
242 citations
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Journal Article•
28,685 citations
Technische Universität München1, Novosibirsk State University2, Cornell University3, Lawrence Livermore National Laboratory4, University of California, Davis5, Argonne National Laboratory6, Fermilab7, Florida State University8, Indiana University9, Brookhaven National Laboratory10, Wayne State University11, University of Paris-Sud12, GSI Helmholtz Centre for Heavy Ion Research13, Ohio State University14, University of Regensburg15, University of Ferrara16, Polish Academy of Sciences17, University of Bari18, Max Planck Society19, Lancaster University20, Peking University21, Thomas Jefferson National Accelerator Facility22, University of Auvergne23, University of Cincinnati24, Stanford University25, University of Alberta26, Forschungszentrum Jülich27, University of Hawaii28, Illinois Institute of Technology29, Lawrence Berkeley National Laboratory30, École Polytechnique31, Budker Institute of Nuclear Physics32, CERN33, Université catholique de Louvain34, Pratt Institute35, University of São Paulo36, Seoul National University37, Tsinghua University38, Stony Brook University39, University of Valencia40, University of Milan41, Tohoku University42, University of Minnesota43
TL;DR: The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress as mentioned in this paper.
Abstract: A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the B-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau-Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include h(c)(1P), chi(c2)(2P), B-c(+), and eta(b)(1S). In addition, the unexpected and still-fascinating X(3872) has been joined by more than a dozen other charmonium- and bottomonium-like "XYZ" states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c (c) over bar, b (b) over bar, and b (c) over bar bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.
1,354 citations
TL;DR: In this paper, the production of mesons containing strange quarks (KS, φ) and both singly and doubly strange baryons (,, and − + +) are measured at mid-rapidity in pp collisions at √ s = 0.9 TeV with the ALICE experiment at the LHC.
1,176 citations
CERN1
TL;DR: In this article, the p{sub perpendicular}-ordered shower and underlying event model in Pythia 6.4 is updated and supersede the older "S0" family, and a set of 8 related "Perugia variations" that attempt to systematically explore soft, hard, parton density, and color structure variations in the theoretical parameters.
Abstract: We present 9 new tunes of the p{sub perpendicular}-ordered shower and underlying-event model in Pythia 6.4. These 'Perugia' tunes update and supersede the older 'S0' family. The data sets used to constrain the models include hadronic Z{sup 0} decays at LEP, Tevatron min-bias data at 630, 1800, and 1960 GeV, Tevatron Drell-Yan data at 1800 and 1960 GeV, and SPS min-bias data at 200, 546, and 900 GeV. In addition to the central parameter set, called 'Perugia 0', we introduce a set of 8 related 'Perugia variations' that attempt to systematically explore soft, hard, parton density, and color structure variations in the theoretical parameters. Based on these variations, a best-guess prediction of the charged track multiplicity in inelastic, nondiffractive minimum-bias events at the LHC is made. Note that these tunes can only be used with Pythia 6, not with Pythia 8.
1,056 citations
Hampton University1, Thomas Jefferson National Accelerator Facility2, University of Paris-Sud3, University of Santiago, Chile4, Brookhaven National Laboratory5, University of Pavia6, University of Groningen7, Federico Santa María Technical University8, Shandong University9, Goethe University Frankfurt10, Stony Brook University11, Baruch College12, Duke University13, Argonne National Laboratory14, The Catholic University of America15, Old Dominion University16, Lawrence Berkeley National Laboratory17, Ohio State University18, University of Zagreb19, University of Jyväskylä20, Tel Aviv University21, CERN22, Temple University23, Massachusetts Institute of Technology24, Columbia University25, Ruhr University Bochum26, California Institute of Technology27, University of Massachusetts Amherst28, University of Buenos Aires29, University of the Basque Country30, University of Connecticut31, University of Tübingen32, Pennsylvania State University33, Stanford University34, Dalhousie University35, Central China Normal University36
TL;DR: In this article, the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community, is presented.
Abstract: This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.
1,022 citations