### Regular Series

#### Conference Strangeness in Quark Matter 2011

ALICE Overview

Acta Phys. Pol. B 43, 497 (2012)

page 497 •

abstract

A general overview of the results obtained by the ALICE experiment from the analysis of the Pb–Pb data sample collected at the end of 2010 during the first heavy-ion run at the LHC is presented.

Heavy Ion Results with the ATLAS Experiment at the LHC

Acta Phys. Pol. B 43, 507 (2012)

page 507 •

abstract

An overview of the first results on particle production in lead–lead collisions at $\sqrt {s_{_{NN}}}=2.76$ TeV obtained with the ATLAS detector is presented. The results were obtained from the sample of minimum bias lead–lead collision data from the 2010 LHC run, with an integrated luminosity up to 9 $\mu$b$^{-1}$. The measurements of global and collective features of lead–lead collisions are shown and complemented with studies of high-transverse momentum probes, including charged hadron suppression, jet quenching, dijet energy imbalance and di-lepton final states.

Heavy-flavor Production in the CMS

Acta Phys. Pol. B 43, 517 (2012)

page 517 •

abstract

The compact muon solenoid (CMS) detector at the large hadron collider (LHC) is ideal to measure the heavy flavor production, especially, in the dimuon channels in high-multiplicity environment. Compared to the $pp$ data scaled by the number of binary collisions, the yields of prompt and non-prompt $J/\psi$ and ${\mit \Upsilon }$(1$S$) in Pb–Pb collisions are strongly suppressed at $\sqrt {s_{NN}}=2.76$ TeV. In addition, the excited ${\mit \Upsilon }$(2$S$+3$S$) states are also suppressed relative to the ground ${\mit \Upsilon }$(1$S$) state in Pb–Pb collisions. These results consistently indicate a significant medium effect on the heavy-flavor production in heavy-ion collisions at LHC.

Heavy Flavor Measurements in PHENIX

Acta Phys. Pol. B 43, 527 (2012)

page 527 •

abstract

Heavy quarkonia suppression is one of the highly cited signatures of quark-gluon plasma (QGP) formed in relativistic heavy ion collisions. However, theoretical predictions remain diverse due to lack of precise knowledge of heavy flavor meson production, suppression, regeneration in hot and dense medium and other cold nuclear effects. PHENIX has carried out a comprehensive study of heavy flavors which includes baseline measurements of heavy flavor, $J/\psi$ and Upsilon in $p+p$ collisions, and the measurements from $d$+Au, Cu+Cu and Au+Au collisions over the past decade. This paper will give an overview of the PHENIX heavy flavor measurements with a focus on the most recent and exciting results from PHENIX. An outlook of the PHENIX effort on heavy flavor studies will also be presented in this talk.

Highlights from the STAR Experiment at RHIC

Acta Phys. Pol. B 43, 535 (2012)

page 535 •

abstract

Experiments using heavy ion collisions at ultrarelativistic energies aim to explore the QCD phase transition and map out the QCD phase diagram. A wealth of remarkable results in this field have been reported recently, for example the ${\mit \Upsilon }$ suppression discovered recently. We discuss recent results from the STAR experiment focusing on strangeness, charm and beauty production.

Heavy Flavor Results at RHIC — A Comparative Overview

Acta Phys. Pol. B 43, 545 (2012)

page 545 •

abstract

I review the latest heavy flavor measurements at RHIC experiments. Measurements from RHIC together with preliminary results from LHC offer us an opportunity to systematically study the sQGP medium properties. In the end, I will outlook a prospective future on precision heavy flavor measurements with detector upgrades at RHIC.

Identified-particle Production and Spectra with the ALICE Detector in $pp$ and Pb–Pb Collisions at the LHC

Acta Phys. Pol. B 43, 555 (2012)

page 555 •

abstract

Thanks to its unique capabilities the ALICE experiment can measure the production of identified particles and resonances over a wide momentum range both in $pp$ and Pb–Pb collisions at the LHC. In this report, particle-identification detectors and techniques, as well as achieved performance, are shortly reviewed. The current results on hadron transverse momentum spectra measured in $pp$ collisions at $\sqrt {s}=0.9$ TeV and 7 TeV, and in Pb–Pb collisions at $\sqrt {s_{NN}}=2.76$ TeV are shown. In particular, proton–proton results on particle production yields, spectral shapes and particle ratios are presented as a function of the collision energy and compared to previous experiments and commonly-used Monte Carlo models. Particle spectra, yields and ratios in Pb–Pb are measured as a function of the collision centrality and the results are compared with published RHIC data in Au–Au collisions at $\sqrt {s_{NN}}=0.2$ TeV and predictions for the LHC.

The Thermal Model at the Large Hadron Collider

Acta Phys. Pol. B 43, 563 (2012)

page 563 •

abstract

A discussion is presented of results with identified particles at the Large Hadron Collider. Possible deviations from the standard statistical distributions are investigated by considering in detail results obtained using the Tsallis distribution. Matter–antimatter production is discussed within the framework of chemical equilibrium in $p$–$p$ and heavy ion collisions.

Statistical Hadronization with Exclusive Channels in ${e}^+{e}^-$ Annihilation

Acta Phys. Pol. B 43, 571 (2012)

page 571 •

abstract

We present a systematic analysis of exclusive hadronic channels in $e^+e^-$ collisions at centre-of-mass energies between 2.1 and 2.6 GeV within the statistical hadronization model. Because of the low multiplicities involved, calculations have been carried out in the full microcanonical ensemble, including conservation of energy-momentum, angular momentum, parity, isospin, and all relevant charges. We show that the data is in an overall good agreement with the model for an energy density of about 0.5 GeV/fm$^3$ and an extra strangeness suppression parameter $\gamma _{\rm S} \sim 0.7$, essentially the same values found with fits to inclusive multiplicities at higher energy.

Is There Life After Hadronization? An Experimental Overview

Acta Phys. Pol. B 43, 577 (2012)

page 577 •

abstract

Recent experimental findings on the properties of the chemical and kinetic freeze-out are reviewed, including data from low energies (SPS) over RHIC, up to recent results from the LHC. We discuss whether chemical freeze-out coincides with hadronization or if there is evidence for a “life after hadronization” which might significantly change particle abundances.

The Phase Structure of Strongly Interacting Matter

Acta Phys. Pol. B 43, 587 (2012)

page 587 •

abstract

With increasing temperature and density, strongly interacting matter will undergo two transitions: deconfinement and chiral symmetry restoration. While at low baryon density the two coincide, at high baryon density chiral symmetry can remain broken in a deconfined state. This leads to a phase diagram of three basic states: hadronic matter, a plasma of massive colored quarks, and a quark-gluon plasma.

Strangeness Measurements with HADES

Acta Phys. Pol. B 43, 601 (2012)

page 601 •

abstract

We present strangeness data taken with the High Acceptance Di-Electron Spectrometer (HADES) at the SchwerIonenSynchrotron SIS18 at the GSI Helmholtzzentrum Darmstadt. HADES, primarily designed to measure dielectrons, offers excellent hadron identification capabilities, too. Yields and phase-space distributions have been determined for the collision system Ar+KCl at 1.76$A$ GeV and for strange particle species, with a substantial number of them being produced well below the production threshold in elementary nucleon–nucleon collisions. Here, sub-threshold production of $\phi$ mesons appeared to contribute substantially to the $K^-$ yield. Confronting the $K^0_{\rm S}$ spectra, measured over a wide range in momentum and rapidity, to predictions of the IQMD transport model points to a repulsive in-medium $K^0$ potential of about 40 MeV. Furthermore, we present our results on ${\mit \Lambda }$–$p$ intensity interferometry in Ar+KCl and compare them to other data.

Report from NA49

Acta Phys. Pol. B 43, 609 (2012)

page 609 •

abstract

The signatures of the onset of deconfinement, found by the NA49 experiment at low SPS energies, are confronted with new results from the Beam Energy Scan (BES) program at BNL RHIC and CERN LHC results. Additionally, new NA49 results on chemical (particle ratio) fluctuations, azimuthal angle fluctuations, intermittency of di-pions, etc. are presented.

full authors' list

J. Steinheimer, A. Botvina, K. Gudima, I. Mishustin, S. Schramm, M. Bleicher, H. Stöcker

From FAIR to RHIC, Hyper Clusters and an Effective Strange EoS for QCD

Acta Phys. Pol. B 43, 619 (2012)

page 619 •

abstract

Two major aspects of strange particle physics at the upcoming FAIR and NICA facilities and the RHIC low energy scan will be discussed. A new distinct production mechanism for hypernuclei will be presented, namely the production abundances for hypernuclei from ${\mit \Lambda }$s absorbed in the spectator matter in peripheral heavy ion collisions. As strangeness is not uniformly distributed in the fireball of a heavy ion collision, the properties of the equation of state therefore depend on the local strangeness fraction. Similarly, inside neutron stars strangeness is not conserved and lattice studies on the properties of finite density QCD usually rely on an expansion of thermodynamic quantities at zero strange chemical potential, hence at non-zero strange-densities. We will, therefore, discuss recent investigations on the EoS of strange-QCD and present results from an effective EoS of QCD that includes the correct asymptotic degrees of freedom and a deconfinement and chiral phase transition.

Search for the Critical Point of the Nuclear Matter Phase Diagram. First Results from the Beam Energy Scan Program at RHIC

Acta Phys. Pol. B 43, 627 (2012)

page 627 •

abstract

In 2010, the Relativistic Heavy Ion Collider (RHIC) launched a multi-step experimental program to investigate the QCD Phase Diagram in general, and to search for the QCD Critical Point (CP) and/or 1st order phase transition in particular. The BES (Beam Energy Scan) program involves an “energy scan” of Au+Au collisions from the top RHIC energy ($\sqrt {s} = 200$ GeV) down to energies as low as 5 GeV in $NN$ center of mass. During the first BES run (2010), data were collected at 7.7, 11.5 and 39 GeV. It was complemented in 2011 by two other data sets at 27 and 19.6 GeV. The preparations for the remaining data taking at $\sqrt {s} = 5$ GeV are in progress. The overview of the BES program and the first experimental results are presented and discussed.

NA61/SHINE at the CERN SPS: Plans, Status and First Results

Acta Phys. Pol. B 43, 635 (2012)

page 635 •

abstract

The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study properties of the onset of deconfinement. It also performs precise hadron production measurements for the neutrino and cosmic rays experiments. These goals will be achieved by measurements of hadron production properties in nucleus–nucleus, proton–proton and proton–nucleus interactions as a function of collision energy and size of the colliding nuclei, as well as pion–nucleus interactions. This contribution summarises the arguments of the ion program as well as presents the first physics results of the NA61 experiment.

Strange and Multi-strange Particle Production at the LHC Energies with ALICE

Acta Phys. Pol. B 43, 645 (2012)

page 645 •

abstract

Strange quark and particle production is studied at the LHC with unprecedented high beam energies in both heavy-ion and proton–proton collisions: on the one hand, strangeness is used for investigating chemical equilibration and bulk properties; on the other hand, strange particles contribute to probe different kinematical domains, from the one where collective phenomena are at play up to the region dominated by pQCD-calculable processes. We highlight the suitability of the ALICE experiment for this topic, presenting our latest measurements and comparing them to models.

Radiative and Collisional Energy Loss of Heavy Quarks in Deconfined Matter

Acta Phys. Pol. B 43, 655 (2012)

page 655 •

abstract

We extend our recently advanced model on collisional energy loss of heavy quarks in a quark-gluon plasma (QGP) by including radiative energy loss. We discuss the approach and present calculations for PbPb collisions at $\sqrt {s}=2.76$ TeV. The transverse momentum spectra, $R_{AA}$, and the elliptic flow $v_2$ of heavy quarks have been obtained using the model of Kolb and Heinz for the hydrodynamical expansion of the plasma.

Measurement of $J/\psi$, $W$ Boson and $Z$ Boson in Pb–Pb Collisions at ATLAS

Acta Phys. Pol. B 43, 663 (2012)

page 663 •

abstract

A broad program of measurements using heavy ion collisions is underway in ATLAS, with the aim of studying the properties of QCD matter at high temperatures and densities. Heavy ion collisions produce a very large number of particles in the Inner Detector, but only muons traverse the calorimeter and leave tracks in the Muon Spectrometer, making muons essential tools for the study of heavy ion collisions. The centrality dependence of $J/\psi \to \mu ^+\mu ^-$ yields allow the study of modification production of heavy quarkonium states. $W$ boson and $Z$ boson measurements are also possible using their decay leptons, and provide another handle on the initial state, and in particular the nuclear PDFs. This document describes measurements performed using 5–6.7 pb$^{-1}$ of Pb–Pb collision data provided at a nucleon–nucleon center-of-mass energy of 2.76 GeV by the Large Hadron Collider and collected by the ATLAS Detector during November and December 2010.

Study of Production of Open Heavy Flavor Hadrons Through Their Semi-leptonic Decays at RHIC and LHC

Acta Phys. Pol. B 43, 671 (2012)

page 671 •

abstract

I review the status of studying open heavy flavor production at RHIC and the LHC focusing on the results from non-photonic electron production. I compare the measurements with theoretical predictions and discuss the current understanding of heavy quark production in the strongly-coupled QGP produced in heavy-ion collisions.

The SuperB Project

Acta Phys. Pol. B 43, 679 (2012)

page 679 •

abstract

The SuperB is a new generation flavour factory. This paper comprises a review of the project, covering the highlights of the broad physics programme and the conceptual design of the accelerator and detector.

Hydrodynamic Flow from RHIC to LHC

Acta Phys. Pol. B 43, 689 (2012)

page 689 •

abstract

The hydrodynamic model for the expansion of the fireball in relativistic heavy-ion collisions is presented. Calculations using relativistic hydrodynamics of a fluid with small viscosity yield a satisfactory description of the experimental data on the particle spectra, the elliptic flow or the interferometry radii.

Comparative Study of Hadron- and $\gamma$-triggered Azimuthal Correlations in Relativistic Heavy-ion Collisions

Acta Phys. Pol. B 43, 697 (2012)

page 697 •

abstract

In the framework of a multi-phase transport model, initial fluctuations in the transverse parton density lead to all orders of harmonic flows. Hadron-triggered azimuthal correlations include all contributions from harmonic flows, hot spots, and jet-medium excitations, which are isolated by using different initial conditions. We found that different physical components dominate different pseudorapidity ranges of dihadron correlations. Because $\gamma$-triggered azimuthal correlations can only be caused by jet-medium interactions, a comparative study of hadron- and $\gamma$-triggered azimuthal correlations can reveal more dynamics about jet-medium interactions.

The Ridge Effect from $p$–$p$ to Pb–Pb (and Back)

Acta Phys. Pol. B 43, 705 (2012)

page 705 •

abstract

The long-range near-side correlation investigated in heavy-ion collisions at RHIC has turned up, unexpectedly, in high-multiplicity $pp$ collisions studied by the CMS experiment at the LHC. This effect in now also observed in Pb–Pb collisions. A spectrum of many recent interpretations concerning the effect is presented.

High-$p_{\rm T}$ Processes Measured with ALICE at the LHC

Acta Phys. Pol. B 43, 713 (2012)

page 713 •

abstract

From studies of single-particle spectra, particle correlations, and jet production in heavy-ion collisions we can obtain information about the density and the dynamic properties of the Quark-Gluon Plasma (QGP). The observed suppression of high-$p_{\rm T}$ particle production ($R_{AA}$) and away-side jets ($I_{AA}$) is generally attributed to energy loss of partons as they propagate through the plasma. We present the results obtained from the analysis of Pb–Pb collisions at $\sqrt {s_{NN}} = 2.76$ TeV recorded by ALICE in November 2010. The nuclear modification factors $R_{AA}$ and $I_{AA}$, and the status of full jet reconstruction in Pb–Pb is presented. Comparison with the RHIC measurements at lower collision energy and with theory models is shown.

QCD Critical Point: Synergy of Lattice and Experiments

Acta Phys. Pol. B 43, 723 (2012)

page 723 •

abstract

The freeze-out curve, which describes a vast amount of precise experimental data in heavy ion collisions, provides a relation between the colliding energy and the thermodynamical parameters of the fireball. The variance, skew and kurtosis of the event distribution of baryon number are studied at several energies of interest through Padé resummations of our Lattice QCD results. A smooth behaviour is predicted for three ratios of these quantities at current RHIC and future LHC energies. Any deviations from these at the RHIC energy scan would signal the presence of a nearby critical point. Our lattice results on the critical point do show such a behaviour.

Physics Prospects at FAIR

Acta Phys. Pol. B 43, 731 (2012)

page 731 •

abstract

We review the physics potential at FAIR in the light of the existing data of the RHIC-BES program and the NA49/NA61 beam and system size scan. Special emphasis will be put on the potential of fluctuations, as well as dilepton observables.

full authors' list

I. Sagert, T. Fischer, M. Hempel, G. Pagliara, J. Schaffner-Bielich, F.-K. Thielemann, M. Liebendörfer

Strange Matter in Core-collapse Supernovae

Acta Phys. Pol. B 43, 741 (2012)

page 741 •

abstract

We discuss the possible impact of strange quark matter on the evolution of core-collapse supernovae with emphasis on low critical densities for the quark–hadron phase transition. For such cases the hot proto-neutron star can collapse to a more compact hybrid star configuration hundreds of milliseconds after core-bounce. The collapse triggers the formation of a second shock wave. The latter leads to a successful supernova explosion and leaves an imprint on the neutrino signal. These dynamical features are discussed with respect to their compatibility with recent neutron star mass measurements which indicate a stiff high density nuclear matter equation of state.

Properties and Stability of Hybrid Stars

Acta Phys. Pol. B 43, 749 (2012)

page 749 •

abstract

We discuss the properties of neutron stars and their modifications due to the occurrence of hyperons and quarks in the core of the star. More specifically, we consider the general problem of exotic particles inside compact stars in light of the observed two-solar mass pulsar. In addition, we investigate neutron star cooling and a possible explanation of the recently measured cooling curve of the neutron star in the supernova remnant Cas A.

Strangeness and the Quark-Gluon Plasma: Thirty Years of Discovery

Acta Phys. Pol. B 43, 761 (2012)

page 761 •

abstract

I review the role of strange quarks as probes of hot QCD matter.

Four Heavy-ion Experiments at the CERN-SPS — A Trip Down Memory Lane

Acta Phys. Pol. B 43, 771 (2012)

page 771 •

abstract

After a brief review of the first steps towards high-energy nuclear beams at CERN, the heavy-ion experiments at the OMEGA Spectrometer, WA85, WA94, WA97, are introduced together with their North-Area successor, NA57. In particular, the experimental solutions adopted to cope with very high-multiplicity events are described, as well as the main results obtained in the pursuit of the Quark-Gluon Plasma. The inspiring role played by Johann Rafelski is underlined.

Relativistic Noise

Acta Phys. Pol. B 43, 781 (2012)

page 781 •

abstract

The relativistic theory of hydrodynamic fluctuations, or noise, is derived and applied to high energy heavy ion collisions. These fluctuations are inherent in any space-time varying system and are present in addition to initial state fluctuations. We illustrate the effects with the boost-invariant Bjorken solution to the hydrodynamic equations. Long range correlations in rapidity are induced by propagation of sound modes. The magnitude of these correlations is directly proportional to the viscosities. These fluctuations should be enhanced near a phase transition or rapid crossover.

On the History of Multi-particle Production in High Energy Collisions

Acta Phys. Pol. B 43, 791 (2012)

page 791 •

abstract

The 60th birthday of Johann Rafelski was celebrated during the Strangeness in Quark Matter 2011 conference in Kraków. Johann was born in Kraków and he initiated the series of the SQM conferences. This report, which briefly presents my personal view on the history of multi-particle production in high energy collisions, is dedicated to Johann.

full authors' list

L.P. Csernai, A.M. Skålvik, D.J. Wang, V.K. Magas, H. Stöcker, D.D. Strottman, Y. Cheng, Y.L. Yan

Flow Components and Initial State CM Fluctuations

Acta Phys. Pol. B 43, 803 (2012)

page 803 •

abstract

At the LHC, the strong collective flow is observed in Pb+Pb collisions, as shown by the azimuthal correlations in the transverse-momentum distributions of the produced particles. We calculate flow components in a relativistic fluid dynamical model at constant time freeze out (FO) for massless equilibrated post FO pion gas. Our results indicate that at the LHC the $v_1$ flow is expected to peak at forward rapidities, at the same side and direction as the projectile residue. The effect of initial state center-of-mass rapidity fluctuations is taken into account. In order to better study the transverse-momentum flow dependence, we suggest a new “symmetrized” $v_1^{\rm S}$ function; and we also propose a new method to disentangle global $v_1$ flow from the contribution generated by the random fluctuations in the initial state. The result is sensitive to the global initial state, where different parameterizations exist.

Non-extensive Statistical Model for Strange and Non-strange Hadron Spectra at RHIC and LHC Energies

Acta Phys. Pol. B 43, 811 (2012)

page 811 •

abstract

We review the basic assumptions, proofs and phenomenological applications of non-extensive thermodynamics and statistical models to high-energy elementary and heavy-ion collisions. We also speculate about physical processes in terms of classical field theory which may mimic a thermal source of the experimentally observed spectra.

My Strange Times with Johann Rafelski

Acta Phys. Pol. B 43, 821 (2012)

page 821 •

abstract

I will give a short review on the physics of strangeness enhancement in quark-gluon plasma, and argue that it is currently the best candidate of a signature of deconfinement. I will also discuss what strangeness abundance can tell us about the bulk properties of the system created in heavy ion collisions.

Strangeness and Quark-Gluon Plasma

Acta Phys. Pol. B 43, 829 (2012)

page 829 •

abstract

I review the foundational motivations which led us to the ultra relativistic heavy ion collision research at SPS, RHIC and now LHC: the quantum vacuum structure; the deconfined nature of the quark-gluon plasma (QGP) phase filling the Universe for the first 30 $\mu$s after the Big Bang; the origin of mass of stable matter; and the origin of flavor. The special roles of strangeness enhancement and strange antibaryon signature are highlighted. It is shown how hadron production can be used to determine the properties of QGP and how the threshold energy for QGP formation is determined.

Strange Quark Matter: Business as Usual or Phase Transition?

Acta Phys. Pol. B 43, 847 (2012)

page 847 •

abstract

We give an overview of some results presented at the Strange Quark Matter 2011 conference in Kraków, and interpret them in light of the search for the deconfinement QCD phase transition in heavy ion collisions.

Experimental Achievements at the Dawn of LHC Era

Acta Phys. Pol. B 43, 867 (2012)

page 867 •

abstract

A summary on experimental achievements in the study of nucleus–nucleus collisions is presented, on the basis of the new results reported at Strangeness in Quark Matter 2011 by the GSI–SIS18, RHIC, and LHC experiments. Ultra-relativistic heavy-ion physics entered the new era with the first LHC Pb–Pb operations.

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