Variable Energy Cyclotron Centre

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.

Identified charged-particle spectra of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ifmmode\pm\else\textpm\fi{}}$, $p$, and $\overline{p}$ at midrapidity ($|y|<0.1$) measured by the $\mathit{dE}/\mathit{dx}$ method in the STAR (solenoidal tracker at the BNL Relativistic Heavy Ion Collider) time projection chamber are reported for $\mathit{pp}$ and $d+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV and for $\mathrm{Au}+\mathrm{Au}$ collisions at 62.4, 130, and 200 GeV. Average transverse momenta, total particle production, particle yield ratios, strangeness, and baryon production rates are investigated as a function of the collision system and centrality. The transverse momentum spectra are found to be flatter for heavy particles than for light particles in all collision systems; the effect is more prominent for more central collisions. The extracted average transverse momentum of each particle species follows a trend determined by the total charged-particle multiplicity density. The Bjorken energy density estimate is at least several GeV/${\mathrm{fm}}^{3}$ for a formation time less than 1 fm/$c$. A significantly larger net-baryon density and a stronger increase of the net-baryon density with centrality are found in $\mathrm{Au}+\mathrm{Au}$ collisions at 62.4 GeV than at the two higher energies. Antibaryon production relative to total particle multiplicity is found to be constant over centrality, but increases with the collision energy. Strangeness production relative to total particle multiplicity is similar at the three measured RHIC energies. Relative strangeness production increases quickly with centrality in peripheral $\mathrm{Au}+\mathrm{Au}$ collisions, to a value about 50% above the $\mathit{pp}$ value, and remains rather constant in more central collisions. Bulk freeze-out properties are extracted from thermal equilibrium model and hydrodynamics-motivated blast-wave model fits to the data. Resonance decays are found to have little effect on the extracted kinetic freeze-out parameters because of the transverse momentum range of our measurements. The extracted chemical freeze-out temperature is constant, independent of collision system or centrality; its value is close to the predicted phase-transition temperature, suggesting that chemical freeze-out happens in the vicinity of hadronization and the chemical freeze-out temperature is universal despite the vastly different initial conditions in the collision systems. The extracted kinetic freeze-out temperature, while similar to the chemical freeze-out temperature in $\mathit{pp}$, $d+\mathrm{Au}$, and peripheral $\mathrm{Au}+\mathrm{Au}$ collisions, drops significantly with centrality in $\mathrm{Au}+\mathrm{Au}$ collisions, whereas the extracted transverse radial flow velocity increases rapidly with centrality. There appears to be a prolonged period of particle elastic scatterings from chemical to kinetic freeze-out in central $\mathrm{Au}+\mathrm{Au}$ collisions. The bulk properties extracted at chemical and kinetic freeze-out are observed to evolve smoothly over the measured energy range, collision systems, and collision centralities.

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at sqrt[S(NN)] =2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (|η|<0.8) and transverse momentum range 0.2<p t<5.0 GeV/c. The elliptic flow signal v₂, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 ± 0.002(stat) ± 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v₂ p t reaches a maximum of 0.2 near p t =3 GeV/c. Compared to RHIC Au-Au collisions at sqrt[S(NN)] 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

We report high statistics measurements of inclusive charged hadron production in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ and $p+p$ collisions at $\sqrt{{s}_{\mathrm{N}\mathrm{N}}}=200\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$. A large, approximately constant hadron suppression is observed in central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions for $5\mathrm{&lt;}{p}_{T}\mathrm{&lt;}12\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$. The collision energy dependence of the yields and the centrality and ${p}_{T}$ dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of ${p}_{T}$-dependent suppression, which may be expected from models incorporating jet attenuation in cold nuclear matter or scattering of fragmentation hadrons.

Abstract At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark–gluon plasma (QGP) 1 . Such an exotic state of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed 2,3,4,5,6 . Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions 7 , is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton–proton (pp) collisions 8,9 , but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton–proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p–Pb collision results 10,11 , indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb–Pb collisions, where a QGP is formed.

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high ${p}_{T}$) in minimum bias and central $d+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$. The inclusive yield is enhanced in $d+\mathrm{A}\mathrm{u}$ collisions relative to binary-scaled $p+p$ collisions, while the two-particle azimuthal distributions are very similar to those observed in $p+p$ collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high ${p}_{T}$ previously observed in central $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions are due to final-state interactions with the dense medium generated in such collisions.

In this paper measurements are presented of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ifmmode\pm\else\textpm\fi{}}$, $p$, and $\overline{p}$ production at midrapidity ($|y|&lt;0.5$), in Pb-Pb collisions at $\sqrt{{s}_{NN}}=2.76$ TeV as a function of centrality. The measurement covers the transverse-momentum (${p}_{T}$) range from 100, 200, and 300 MeV/$c$ up to 3, 3, and 4.6 GeV/$c$ for $\ensuremath{\pi}$, $K$, and $p$, respectively. The measured ${p}_{T}$ distributions and yields are compared to expectations based on hydrodynamic, thermal and recombination models. The spectral shapes of central collisions show a stronger radial flow than measured at lower energies, which can be described in hydrodynamic models. In peripheral collisions, the ${p}_{T}$ distributions are not well reproduced by hydrodynamic models. Ratios of integrated particle yields are found to be nearly independent of centrality. The yield of protons normalized to pions is a factor $\ensuremath{\sim}$1.5 lower than the expectation from thermal models.

The centrality dependence of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor of 2 from peripheral (70%-80%) to central (0%-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.

The results from the STAR Collaboration on directed flow (${v}_{1}$), elliptic flow (${v}_{2}$), and the fourth harmonic (${v}_{4}$) in the anisotropic azimuthal distribution of particles from Au+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a blast-wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For ${v}_{2}$, scaling with the number of constituent quarks and parton coalescence are discussed. For ${v}_{4}$, scaling with ${v}_{2}^{2}$ and quark coalescence are discussed.

We report on the first measurement of the triangular v3, quadrangular v4, and pentagonal v5 charged particle flow in Pb-Pb collisions at sqrt(s(NN)) = 2.76 TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow v2 and v3 have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.

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 Q(s). The model naturally produces initial energy fluctuations that are described by a negative binomial distribution. The ratio of triangularity to eccentricity ε(3)/ε(2) 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.

The beam-energy scan at RHIC aims to discover whether a critical point exists in the phase diagram of QCD. This paper reports on the most comprehensive measurement of single-particle spectra for a multitude of hadrons from the first run, taken with the STAR experiment. From these the authors infer the kinetic and chemical freeze-out temperatures and the baryon chemical potential as functions of beam energy and centrality. The results provide an opportunity for the beam-energy scan program at RHIC to enlarge the ($T,\ensuremath{\mu}\phantom{\rule{0}{0ex}}B$) region of the phase diagram to search for the QCD critical point.

Anisotropic flow coefficients v(1)-v(5) in heavy ion collisions are computed by combining a classical Yang-Mills description of the early time Glasma flow with the subsequent relativistic viscous hydrodynamic evolution of matter through the quark-gluon plasma and hadron gas phases. The Glasma dynamics, as realized in the impact parameter dependent Glasma (IP-Glasma) model, takes into account event-by-event geometric fluctuations in nucleon positions and intrinsic subnucleon scale color charge fluctuations; the preequilibrium flow of matter is then matched to the music algorithm describing viscous hydrodynamic flow and particle production at freeze-out. The IP-Glasma+MUSIC model describes well both transverse momentum dependent and integrated v(n) data measured at the Large Hadron Collider and the Relativistic Heavy Ion Collider. The model also reproduces the event-by-event distributions of v(2), v(3) and v(4) measured by the ATLAS Collaboration. The implications of our results for better understanding of the dynamics of the Glasma and for the extraction of transport properties of the quark-gluon plasma are outlined.

We present STAR measurements of the azimuthal anisotropy parameter ${v}_{2}$ and the binary-collision scaled centrality ratio ${R}_{\mathrm{C}\mathrm{P}}$ for kaons and lambdas ($\ensuremath{\Lambda}+\overline{\ensuremath{\Lambda}}$) at midrapidity in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$. In combination, the ${v}_{2}$ and ${R}_{\mathrm{C}\mathrm{P}}$ particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish ${p}_{T}\ensuremath{\approx}5\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ as the value where the centrality dependent baryon enhancement ends. The ${K}_{S}^{0}$ and $\ensuremath{\Lambda}+\overline{\ensuremath{\Lambda}}$ ${v}_{2}$ values are consistent with expectations of constituent-quark-number scaling from models of hadron formation by parton coalescence or recombination.

Alessandro, B; Antinori, F; Belikov, J A; Blume, C; Dainese, A; Foka, P; Giubellino, P; Hippolyte, B; Kuhn, C; Martínez, G; Monteno, M; Morsch, A; Nayak, T K; Nystrand, J; López Noriega, M; Paic, G; Pluta, J; Ramello, L; Revol, J-P; Safarík, K; Schukraft, J; Schutz, Y; Scomparin, E; Snellings, R; Villalobos Baillie, O; Vercellin, E; Cortese, P; Dellacasa, G; Ramello, L; Sitta, M; Ahmad, N; Ahmad, S; Ahmad, T; Bari, W; Irfan, M; Zafar, M; Botje, M; Kuijer, P G; Snellings, R; Belogianni, A; Christakoglou, P; Ganoti, P; Petridis, A; Roukoutakis, F; Spyropoulou-Stassinaki, M; Vassiliou, M; Bruno, G E; Cali, I A; Caselle, M; De Cataldo, G; Di Bari, D; Elia, D; Fini, R A; Ghidini, B; Lenti, V; Manzari, V; Mastroserio, A; Minafra, F; Nappi, E; Navach, F; Pastore, C; Paticchio, V; Perrino, D; Posa, F; Santoro, R; Sgura, I; Volpe, G; Corsi, F; De Venuto, D; Fratino, U; Marzocca, C; Tauro, A; Li, X; Liu, Z; Lu, S; Lu, Z; Meng, Q; Sa, B; Yuan, J; Zhou, J; Zhou, S; Alme, J; Bablok, S; Klovning, A; Nystrand, J; Pommeresche, B; Richter, M; Röhrich, D; Ullaland, K; Yang, H; Helstrup, H; F Hetland, K; Kileng, B; Røed, K; Choudhury, R K; Dash, S; Mahapatra, D P; Mishra, D; Phatak, S C; Sahoo, R; Daniel, L; Evans, D; Jones, G T; Jovanovic, P; Jusko, A; Kinson, J B; Platt, R; Lietava, R; Tapia Takaki, J D; Villalobos Baillie, O; Alici, A; Antinori, S; Antonioli, P; Arcelli, S; Bari, G; Basile, M; Cara Romeo, G; Cifarelli, L; Cindolo, F; Falchieri, D; Gabrielli, A; Gandolfi, E; Hatzifotiadou, D; Laurenti, G; L Luvisetto, M; Margotti, A; Masetti, M; Nania, R; Noferini, F; Palmonari, F; Pesci, A; Sartorelli, G; Scapparone, E; Scioli, G; Vacca, G P; Valenti, G; Venturi, G; Williams, M C S; Zampolli, C; Zichichi, A; Cerný, V; Janik, R; Lúcan, L; Pikna, M; Pisút, J; Pisútová, N; Sitár, B; Strmen, P; Szarka, I; Zagiba, M; Aiftimiei, C; Catanescu, V; Legrand, C I; Petrovici, M; Pop, A; Schiaua, C; Simion, V; Barnaföldi, G; Boldizsár, L; Dénes, E; Fodor, Z; Futó, E; Kiss, T; Lévai, P; Pálla, G; Zimányi, J; Atanassov, I; Basciu, S; Cicalo, C; De Falco, A; Floris, M; Masoni, A; Mura, D; Puddu, G; Serci, S; Siddi, E; Usai, G; Badalà, A C; Barbera, R; Lo Re, G; Palmeri, A; Pappalardo, G S; Pulvirenti, A; Riggi, F; Anelli, G; Augustin, I; Augustinus, A; Baechler, J; Belikov, J A; Betev, L; Boccardi, A; Brun, R; Burns, M; Buncic, P; Campagnolo, R; Campbell, M; Carena, F; Carena, W; Carminati, F; Chapeland, S; Cheshkov, C; Chochula, P; Christiansen, P; Colla, A; Conrad, J; Correia Belbute, B F; Davenport, M; de Groot, J; Di Mauro, A; Divià, R; Engster, C; Evrard, S; Fabjan, C W; Feng, L; Flierl, D; Formenti, F; Fuchs, U; García López, A; Gheata, A; Gheata, M; González-Gutiérrez, C; Grosso, R; Gruwe, M; Gustafsson, H-A; Hoedelmoser, H; Hristov, P; Ivanov, M; Jirden, L; Jorgensen, C; Junique, A; Kapusta, S; Kickinger, W; Klempt, W; Kluge, A; Leistam, L; Lo, J P; López Noriega, M; Lourenço, C; Makhlyueva, I; Marin, J-C; Martinengo, P; Meunier-Picard, D; Meoni, M; Morel, M; Morsch, A; Mota, B; Muller, H; Musa, L; Nayak, T K; Nilsson, P; Nouais, D; Osmic, F; Perini, D; Pestotnik, R; Peters, A; Pinto Morais, V; Popescu, S; Rademakers, F; Revol, J-P; Riedler, P; Riegler, W; Safarík, K; Schossmaier, K; Schukraft, J; Schutz, Y; Silva Loureiro, P A; Soos, C; Stefanini, G; Swoboda, D; Tadel, M; Taureg, H; Tavlet, M; Tissot-Daguette, P; Torcato de Matos, C; Vande Vyvre, P; Vanuxem, J-P; Aggarwal, M M; Bhati, A K; Kumar, A; Sharma, M; Sood, G; Baldit, A; Barret, V; Bastid, N; Blanchard, G; Castor, J; Crochet, P; Daudon, F; Devaux, A; Dupieux, P; Force, P; Grigoryan, S; Guerin, F; Guernane, R; Insa, C; Jouve, F; Lecoq, J; Manso, F; Rosnet, P; Royer, L; Saturnini, P; Savinel, G; Humanic, T J; Kotov, I V; Lisa, M; Nilsen, B S; Truesdale, D; Johnson, D; Bearden, I; Bøggild, H; Christensen, C H; Gaardhøje, J J; Gulbrandtsen, K; Nielsen, B S; Renault, G; Bartke, J; Gladysz-Dziadus, E; Kornas, E; Kowalski, M; Rybicki, A; Wróblewski, A; Andronic, A; Antonczyk, D; Badura, E; Bailhache, R; Berdermann, E; Braun-Munzinger, P; Busch, O; Ciobanu, M; Foka, P; Frankenfeld, U; Garabatos, C; Gutbrod, H; Lippmann, C; Malzacher, P; Marín, A; Miskowiec, D; Radomski, S; Schmidt, H R; Schwarz, K; Sedykh, S; Simon, R S; Soyk, D; Stelzer, H; Stockmeier, M; Tziledakis, G; Vranic, D; Wiechula, J; Bonnes, U; Kraus, I; Oeschler, H; Appelshäuser, H; Blume, C; Dietel, T; Gazdzicki, M; Hartig, M; Kliemant, M; Kniege, S; Kolleger, T; Kramer, F; Lange, S; Loizides, C; Ploskon, M; Renfordt, R; Sommer, W; Stock, R; Ströbele, H; Berdnikov, Ya; Ivanov, V; Khanzadeev, A; Miftakhov, N; Nikoulin, V; Polyakov, V; Rostchin, E; Samsonov, V; Tarasenkova, O; Tarakanov, V; Zhalov, M; López Torres, E; Abrahantes Quintana, A; Díaz Valdes, R; Alt, T; Angelov, V; Cuveland, J; Gutfleisch, M; Kalcher, S; Lindenstruth, V; Panse, R; Reichling, C; Schneider, R; Steinbeck, T; Tilsner, H; Tröger, G; Wiebalck, A; Adler, C; Emschermann, D; Glässel, P; Herrmann, N; Ludolphs, W; Mahmoud, T; Mercado, J; Milosevic, J; Oyama, K; Rusanov, I; Schicker, R; Shukla, P; Soltveit, H C; Stachel, J; Vulpescu, B; Windelband, B; Yurevich, S; Shigaki, K; Sugitate, T; Raniwala, R; Raniwala, S; Badyal, S K; Bala, R; Bhasin, A; Gupta, A; Gupta, V K; Mahajan, S; Mangotra, L K; Potukuchi, B V K S; Sambyal, S S; Akichine, P G; Arefiev, V A; Baatar, Ts; Batiounia, B V; Chepurnov, V F; Chernenko, S A; Dodokhov, V K; Fateev, O V; Fedunov, A G; Haiduc, M; Hasegan, D; Kadychevsky, V G; Kharadze, G; Khurelbaatar, B; Koshurnikov, E K; Lioubochits, V L; Lobanov, V I; Malinina, L V; Minaev, Y I; Nioradze, M; Nomokonov, P V; Panebrattsev, Y A; Penev, V N; Pismennaya, V G; Pocheptsov, T A; Roufanov, I; Shabratova, G S; Shestakov, V; Shklovskaya, A I; Sorin, A S; Suleimanov, M K; Tevzadze, Y; Togoo, R; Vodopianov, A S; Yurevich, V I; Zanevsky, Y V; Zaporojets, S A; Zinchenko, A I; Äysto, J; Bondila, M; Lyapin, V; Oinonen, M; Malkiewicz, T; Ruuskanen, V; Seppänen, H; Trzaska, W; Yamaletkinov, S; Jung, H T; Jung, W; Kim, D-W; Kim, H N; Kim, J S; Lee, K S; Lee, S-C; Blank, T; Gemmeke, H; Bochek, G L; Dovbnya, A N; Kulibaba, V I; Maslov, N I; Naumov, S V; Ovchinnik, V D; Potin, S M; Starodubtsev, A F; Borshchov, V N; Chykalov, O; Kaurova, L; Kiprich, S K; Klymova, L; Listratenko, O M; Mykhaylova, N; Protsenko, M; Reznik, O; Starkov, V E; Kadenko, I; Martynov, Y; Molodtsov, S; Sinyukov, Y; Zinovjev, G; Bhattacharya, P; Bose, S; Chatterjee, S; Chattopadhyay, S; Das, D; Das, I; Dutt-Mazumder, A K; Majumdar, N; Mukhopadhyay, S; Pal, S; Paul, L; Roy, P; Sanyal, A; Sarkar, S; Sen, P; Sen, S K; Sinha, B C; Sinha, T; Ahammed, Z; Bhaskar, P; Chattopadhyay, S; Das, D; Das, S; Dutta Majumdar, M R; Ganti, M S; Ghosh, P; Mohanty, B; Netrakanti, P K; Pal, S; Singaraju, R N; Singhal, V; Sinha, B; Viyogi, Y P; Hartung, G; Krawutschke, T; Bán, J; Bombara, M; Dirner, A; Hnatic, M; Králik, I; Kravcáková, A; Kriván, F; Krivda, M; Martinská, G; Pastircák, B; Sándor, L; Urbán, J; Vrláková, J; Cinausero, M; Fioretto, E; Prete, G; Ricci, R A; Vannucci, L; Branco, P; Carvalho, R; Seixas, J; Vilela Mendes, R; Oskarsson, A; Osterman, L; Otterlund, I; Stenlund, E A; Cheynis, B; Ducroux, L; Grossiord, J Y; Guichard, A; Pillot, P; Rapp, B; Tieulent, R; Alfaro Molina, J R; Ayala, A; Belmont Moreno, E; Contreras, J G; Cuautle, E; D'Olivo, J C; Domínguez, I; Flores, A; Grabski, V; Herrera Corral, G; Linares, M; Martínez, M I; Martínez Dávalos, A; Menchaca-Rocha, A; Montaño Zetina, L M; Nellen, L; Paic, G; del Pino, J; Reyes, P; Sandoval, A; Solano, J; Vergara, S; Zepeda, A; Feshchenko, V A; Golubeva, M B; Gorlychev, V G; Guber, F F; Karavichev, O V; Karavicheva, T L; Karpechev, E V; Kurepin, A B; Maevskaya, A I; Marin, V V; Pshenichnov, I A; Razin, V I; Reshetin, A I; Shileev, K A; Topil'skaia, N S; Akindinov, A N; Golovine, V; Kaidalov, A B; Kats, M M; Kiselev, I T; Kisselev, S M; Lioublev, E; Martemianov, M; Martemiyanov, A N; Polozov, P A; Serov, V S; Smirnitski, A V; Tchoumakov, M M; Vetlitski, I A; Volochine, K G; Vorobiev, L S; Zagreev, B V; Aleksandrov, D; Antonenko, V; Beliaev, S; Fokine, S; Ippolitov, M; Karadjev, K; Koutcheriaev, I; Lebedev, V; Manko, V I; Moukhanova, T; Nianine, A; Nikolaev, S; Nikouline, S; Patarakine, O; Peressounko, D; Sibiriak, I; Tsvetkov, A; Vasiliev, A; Vinogradov, A; Yushmanov, I; Grigoriev, V A; Kaplin, V A; Loginov, V A; Nandi, B K; Varma, R; Chandratre, V; Kataria, V; Baumann, C; Glasow, R; Gottschlag, H; Grosse-Oetringhaus, J F; Heine, N; Klein-Bösing, C; Reygers, K; Santo, R; Verhoeven, W; Wessels, J; Wilk, A; Aphecetche, L; Berny, R; Bouvier, S; Conesa-Balbastre, G; Conesa-del-Valle, Z; Cussonneau, J P; Delagrange, H; Dialinas, M; Finck, Ch; Erazmus, B; Germain, M; Lefèvre, F; Luquin, L; Martínez, G; Renard, Ch; Roy, C; Tournaire, A; Frolov, A R; Pestov, I N; Awes, T; Cherney, M; Gorbunov, Y; Bimbot, L; Chambert, V; Charpy, A; Comets, M P; Courtat, P; Drouet, S; Edelbruck, P; Espagnon, B; Hrivnácová, I; Kunne, R; Le Bornec, Y; Mac Cormick, M; Peyré, J; Pouthas, J; Rousseau, S; Suire, C; Willis, N; Wu, T; Bravina, L; Løvhøiden, G; Skaali, B; Tveter, T S; Vik, T; Antinori, F; Dainese, A; Dima, R; Fabris, D; Faivre, J; Lunardon, M; Morando, M; Moretto, S; Pepato, A; Quercigh, E; Scarlassara, F; Segato, G; Turrisi, R; Viesti, G; Choi, J; Beitlerova, A; Mares, J; Polák, K; Závada, P; Petrácek, V; Pachr, M; Skoda, L; Bogolyubsky, M Yu; Khaoustov, G V; Kharlov, Yu V; Minaev, N G; Petrov, V S; Polichtchouk, B V; Sadovsky, S A; Senko, V A; Soloviev, A S; Stolpovsky, P V; Victorov, V A; Férnandez Téllez, A; Gamez Flores, E; López-Ramírez, R; Ortiz-Velczquez, A; Pagliarone, C; Román-López, S; Tejeda-Muñoz, G; Vargas, A; Villaseñor Cendejas, L; Adamová, D; Kouchpil, S; Kouchpil, V; Kugler, A; Sumbera, M; Wagner, V; Di Liberto, S; Mazzoni, M A; Meddi, F; Urciuoli, G M; Cleymans, J; de Vaux, G; Fearick, R W; Szostak, A; Vilakazi, Z Z; Anfreville, M; Baldisseri, A; Becker, B; Borel, H; Castillo, J; Charvet, J-L; Combet, M; Gosset, J; Hardy, P; Herlant, S; Orsini, F; Pénichot, Y; Pereira, H; Staley, F M; Usseglio, M; De Caro, A; De Gruttola, D; De Pasquale, S; Di Bartolomeo, A; Fusco Girard, M; Grella, G; Guarnaccia, C; Guida, M; Romano, G; Sellitto, S; Silvestri, R; Virgili, T; Basmanov, V; Budnikov, D; Demanov, V; Ianowski, V; Ilkaev, R; Ilkaeva, L; Ivanov, A; Khlebnikov, A; Kouryakin, A; Mikhailov, E; Nazarenko, S; Pavlov, V; Philchagin, S; Punin, A; Punin, V; Poutevskoi, S; Rybin, A; Selin, I; Smetanin, M; Telnov, A; Treskov, S; Vikhlyantsev, O; Vinogradov, I; Vyushin, A; Zavyalov, N; Zhelezov, S; Zhitnik, A; Gotovac, S; Mudnic, E; Vidak, L; Asryan, A G; Braun, M A; Derkach, D A; Feofilov, G A; Igolkin, S N; Ivanov, A S; Kolevatov, R S; Kolojvari, A A; Kondratiev, V P; Naumenko, P A; Toulina, T A; Valiev, F F; Vechernin, V V; Vinogradov, L I; Baudot, J; Bonnet, D; Coffin, J P; Estienne, M; Hippolyte, B; Kuhn, C; Lutz, J R; Vernet, R; Hamagaki, H; Ozawa, K; Bonvicini, V; Borysov, O; Bosisio, L; Bregant, M; Camerini, P; Contin, G; Faleschini, F; Fragiacomo, E; Grion, N; Margagliotti, G; Piano, S; Rachevskaya, I; Rachevski, A; Rui, R; Vacchi, A; Alessandro, B; Arnaldi, R; Bagnasco, S; Batigne, G; Beolé, S; Bruna, E; Cerello, P; Chiavassa, E; Cobanoglu, O; Coli, S; Crescio, E; De Marco, N; De Remigis, P; Ferretti, A; Gagliardi, M; Gallio, M; Gaudichet, L; Gemme, R; Giraudo, G; Giubellino, P; Idzik, M; Martoiu, S; Marzari Chiesa, A; Masera, M; Mazza, G; Mereu, P; Monteno, M; Musso, A; Oppedisano, C; Piccotti, A; Poggio, F; Prino, F; Riccati, L; Rivetti, A; Scomparin, E; Stocco, D; Tosello, F; Toscano, L; Travaglia, G; Vercellin, E; Werbrouck, A; Wheadon, R; Yermia, F; Miake, Y; Esumi, S; Buskop, J J F; De Haas, A P; Ivan, C; Kamermans, R; Mischke, A; Nooren, G; Oskamp, C J; Peitzmann, Th; Simili, E; Sokolov, O; Van Den Brink, A; Van Eijndhoven, N; Enyo, H; Fujiwara, K; Kano, H; Onishi, H; Deloff, A; Dobrowolski, T; Karpio, K; Malek, M; Malinowski, H; Redlich, K; Siemiarczuk, T; Stefanek, G; Tykarski, L; Wilk, G; Chajecki, Z; Gos, H; Janik, M; Jedynak, M; Kisiel, A; Pawlak, T J; Peryt, W S; Pluta, J; Skowronski, P; Slodkowski, M; Szuba, P; Traczyk, T; Conner, E S; Keidel, R; Cai, X; Ding, H T; Liu, H; Wang, X R; Yang, H Y; Yin, Z B; Zhou, D C; Cao, X; Li, Q; Liu, Y Z; Su, G; Tan, L; Zhu, G X; Atayan, M; Grigoryan, A; Gulkanyan, H; Harutyunyan, A; Hayrapetyan, A; Kakoyan, V; Poghosyan, M; Sargsyan, G; Anticic, T; Kadija, K; Susa, T; Arleo, F; Armesto, N; Aurenche, P; Benhabib, L; Bogdanov, A; Borghini, N; Carrer, N; Csörgo, T; Gupta, S; Heinz, U W; Jacobs, P M; Lednický, R; Letessier, J; Mrówczynski, S; Rafelski, J; Ranft, J; Silvermyr, D; Wiedemann, U A

Inclusive transverse momentum spectra of primary charged particles in Pb–Pb collisions at sNN=2.76TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0–5% and 70–80% of the hadronic Pb–Pb cross section. The measured charged particle spectra in |η|<0.8 and 0.3<pT<20GeV/c are compared to the expectation in pp collisions at the same sNN, scaled by the number of underlying nucleon–nucleon collisions. The comparison is expressed in terms of the nuclear modification factor RAA. The result indicates only weak medium effects (RAA≈0.7) in peripheral collisions. In central collisions, RAA reaches a minimum of about 0.14 at pT=6–7GeV/c and increases significantly at larger pT. The measured suppression of high-pT particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb–Pb collisions at the LHC.

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 square root of 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.

Charged hadrons in $0.15&lt;{p}_{\ensuremath{\perp}}&lt;4\text{ }\text{ }\mathrm{GeV}/c$ associated with particles of ${p}_{\ensuremath{\perp}}^{\mathrm{trig}}&gt;4\text{ }\text{ }\mathrm{GeV}/c$ are reconstructed in $pp$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$. The associated multiplicity and ${p}_{\ensuremath{\perp}}$ magnitude sum are found to increase from $pp$ to central $\mathrm{Au}+\mathrm{Au}$ collisions. The associated ${p}_{\ensuremath{\perp}}$ distributions, while similar in shape on the nearside, are significantly softened on the awayside in central $\mathrm{Au}+\mathrm{Au}$ relative to $pp$ and not much harder than that of inclusive hadrons. The results, consistent with jet quenching, suggest that the awayside fragments approach equilibration with the medium traversed.

We report the beam energy (sqrt[sNN]=7.7-200 GeV) and collision centrality dependence of the mean (M), standard deviation (σ), skewness (S), and kurtosis (κ) of the net-proton multiplicity distributions in Au+Au collisions. The measurements are carried out by the STAR experiment at midrapidity (|y|<0.5) and within the transverse momentum range 0.4<pT<0.8 GeV/c in the first phase of the Beam Energy Scan program at the Relativistic Heavy Ion Collider. These measurements are important for understanding the quantum chromodynamic phase diagram. The products of the moments, Sσ and κσ2, are sensitive to the correlation length of the hot and dense medium created in the collisions and are related to the ratios of baryon number susceptibilities of corresponding orders. The products of moments are found to have values significantly below the Skellam expectation and close to expectations based on independent proton and antiproton production. The measurements are compared to a transport model calculation to understand the effect of acceptance and baryon number conservation and also to a hadron resonance gas model.

The STAR collaboration at the BNL Relativistic Heavy-Ion Collider (RHIC) reports measurements of the inclusive yield of nonphotonic electrons, which arise dominantly from semileptonic decays of heavy flavor mesons, over a broad range of transverse momenta ($1.2&lt;{p}_{T}&lt;10\text{ }\text{ }\mathrm{GeV}/c$) in $p+p$, $d+\mathrm{Au}$, and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathrm{NN}}}=200\text{ }\text{ }\mathrm{GeV}$. The nonphotonic electron yield exhibits an unexpectedly large suppression in central $\mathrm{Au}+\mathrm{Au}$ collisions at high ${p}_{T}$, suggesting substantial heavy-quark energy loss at RHIC. The centrality and ${p}_{T}$ dependences of the suppression provide constraints on theoretical models of suppression.