Hirschegg 2010:

Strongly Interacting Matter under Extreme Conditions

International Workshop XXXVIII on Gross Properties of Nuclei and Nuclear Excitations
Hirschegg, Kleinwalsertal, Austria, January 17 - 23, 2010


Quark spectral functions from Dyson-Schwinger equations
Müller, Jens (TU Darmstadt), Fischer, Christian (TU Darmstadt, GSI Darmstadt), Nickel, Dominik (Univ. Seattle)
We investigate spectral functions of quarks at finite temperature within the framework of Dyson-Schwinger equations. As an input we use quenched lattice data for the gluon propagator. To investigate the spectral properties of the quarks we use different ansaetze for the spectral functions and fit these to the data. We compare results below and above the deconfinement phase transition as well as at finite quark mass and in the chiral limit. We analyse quasiparticle properties in the deconfined, chirally symmetric limit.
P- and CP-odd effects in heavy ion collisions
Warringa, Harmen
Fluctuations of topological charge give rise to P- and CP-odd effects by inducing an imbalance in the number of right-hand and left-handed quarks. In this talk I will explain that due to enormous magnetic fields created in heavy ion collisions such imbalance naturally leads to separation of electric charge along the direction of angular momentum of the collision. This separation can in principle be addressed experimentally by measuring specific charge correlations. As such these correlations could be a probe for P- and CP-odd effects. I will discuss exciting results from the STAR collaboration on such charge correlations.
Cold quarks stars from hot lattice QCD
Schulze, R. (FZ Dresden-Rossendorf, TU Dresden), Kaempfer, B. (FZ Dresden-Rossendorf)
At small net baryon densities ab initio lattice QCD provides valuable information on the finite-temperature equation of state of strongly interacting matter. Our phenomenological quasiparticle model provides a means to map such lattice results to regions relevant for future heavy-ion experiments at large baryon density; even the cool equation of state can be inferred to address the issue of quark stars. We report on (i) the side conditions (charge neutrality, beta equilibrium) in mapping latest lattice QCD results to large baryon density and (ii) scaling properties of emerging strange quark stars.
Collective effects in pp scattering
Werner, K (Subatech)
We discuss the importance of multiple scattering in pp collisions at LHC energies. Large numbers of elementary scatterings will lead to energy densities comparable to the ones obtained in AuAu at RHIC. Similar collective effects will therefore be observed, like hydrodynamical expansion and collective radial flow. We will discuss the results of the corresponding calculations, based on EPOS initial conditions and a 3D hydrodynamical evolution.
Strongly Interaction Matter under Extreme Conditions
Prof. Stoecker
will follow
Dilepton production as probe to dense matter EOS
Qun Wang (USTC), Jian Deng (USTC), Nu Xu (LBL), Peng-fei Zhuang (Tsinghua)
We study di-lepton production in Au+Au collisions at 200 AGeV. The space-time evolution of the medium is described by a $2+1$ dimensional ideal fluid hydrodynamic model. Different equations of state are employed to compare the contribution from quark-gluon-plasma and hadronic gas. Di-lepton spectra are sensitive to how the dense matter evolves in space-time. The slope parameters in transverse mass spectra and elliptic flows in non-central collisions show distinct features from two emission sources, which can be tested for the picture we have for the dense matter created in ultra-relativistic heavy ion collisions.
Particle Fluctuations in STAR
Westfall, G.D., for the STAR Collaboration
The freeze-out of an extended, strongly-interacting system created in a relativistic heavy ion collision near the QCD critical endpoint could create observable non-statistical fluctuations in net charge, strangeness and baryon number. We present results for $K/\pi$, $p/\pi$, and $p/K$ fluctuations from central Au+Au collisions at $\sqrt{s_{NN}}$ = 20, 62.4, 130, and 200 GeV in terms of the variable $\sigma_{\rm dyn}$. We compare these results with recent data from NA49 for central Pb-Pb collisions at $\sqrt{s_{NN}}$ = 6.3, 7.6, 8.7, 12.3, and 17.3 GeV. We present the centrality dependence of $K/\pi$, $p/\pi$ and $p/K$ fluctuations from Au+Au collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV in terms of the variable $\nu_{{\rm dyn},K\pi}$. To minimize contributions from background protons, we restrict our measurements for $p$ and $\overline{p}$ to the transverse momentum range $0.4 < p_{t} < 1.0$ GeV/c. We present results for $K/\pi$, $p/\pi$, and $p/K$ fluctuations separated by sign as a function of centrality. In addition, we present results for net charge fluctuations ($\pi^+/\pi^-$), net strangeness fluctuations ($K^+/K^-$), and net baryon fluctuations ($p/\overline{p}$). We compare our results with the predictions of the Statistical Hadronization, HIJING, UrQMD, and HSD models.
Heavy-Flavour Production in Nucleus-Nucleus Collisions: From RHIC to LHC
Andre Mischke (Utrecht University)
Calculations from Lattice-QCD predict that at high energy densities a phase transition between hadronic matter and a deconfined state formed by quarks and gluons, the Quark-Gluon Plasma (QGP), occurs. Measurements from the SPS and RHIC facilities have yielded compelling evidence for the formation of this novel state of matter in nucleus-nucleus collisions. At RHIC, hard probes and in particular jets provided profound insight into the properties of the strongly interacting matter produced. Due to their large mass, heavy quarks (charm and bottom) are believed to be predominantly produced in the initial state of the collision by gluon fusion processes so that they probe the entire lifetime of the QGP. Thus, the investigation of heavy-flavour production in nucleus-nucleus collisions provides key tests of parton energy-loss models with an emphasis on the colour charge and mass dependence of the quenching effect. The expected large heavy-quark production cross sections at LHC will allow performing precision measurements of both open and hidden heavy-flavour particles. A review on charm and bottom production at RHIC and perspectives at LHC will be presented. --- *Supported by the European Research Council (ERC) under the European Community's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement no 210223.
Astrophysics implication of dense matter phase diagram
A. Sedrakian
I will discuss the ways that astrophysics can help us to understand the phase diagram of dense matter. The examples will include gravitational wave from compact stars, cooling of compact stars, and effects on vorticity on compact star dynamics.
Chiral phase transition: the role of scalar fields
Francesco Giacosa, Achim Heinz, Stefan Strueber, Dirk H. Rischke
The interpretation of scalar mesons in the vacuum is a highly debated topic. In the context of a linear sigma model it is not clear which is the scalar resonance listed in the PDG which should be identified with the sigma field of the model. This identification is not only an issue of vacuum\'s phenomenology: in fact, it has a strong influence on the properties of the system at nonzero temperature and density, most notably on the chiral phase transition. In this talk different scenarios are presented and discussed. Also, the inclusion of an additional, light scalar field in the Lagrangian, to be interpreted as a tetraquark field as suggested by many studies in the vacuum, is here investigated at nonzero T with special attention to its role on the chiral phase transition.
Hadronic matter at high baryon density
Höhne, C. (GSI), NA49 and CBM collaboration
The investigation of hadronic matter at high baryon density is of particular interest in order to study the intermediate range of the QCD phase diagram where structures such as a first order phase transition between hadronic and partonic matter or a critical point are expected. Furthermore, hadronic properties are expected to chance and chiral symmetry to be restored. This range of the phase diagramm has been addressed by experiments at the CERN-SPS and will be investigated in detail with the future CBM experiment at FAIR. Results from the SPS experiments, in particular from NA49 will be discussed and prospects of the CBM experiment will be given in this talk.
Quarkyonic Chiral Spirals
Toru, Kojo (RBRC), Robert, Pisarski (BNL), Larry McLerran (RBRC/BNL)
We argue the properties of confining dense quark matter, "quarkyonic" matter, from the viewpoint of both bulk properties and excitation modes. After a brief review of confining aspects, the chiral breaking/restoration will be discussed. We argue that the strong infrared correlations induce the chiral spiral, i.e., the spatial modulation of the chiral condensate which breaks the chiral symmetry locally but restore it globally. The effective dimensional reduction takes place, allowing us to analyzing the system as 2D model in which several exact results can be explicitly derived. We also discuss the excitation spectra, both mesonic and baryonic ones, on the chiral spiral.
Minimum of eta/s and the phase transition of the Linear Sigma Model in the large-N limit.
Felipe J. Llanes-Estrada, Antonio Dobado, Juan M. Torres-Rincon (U. Complutense)
We reexamine the possibility of employing the viscosity over entropy density ratio as a diagnostic tool to identify a phase transition in hadron physics to the strongly coupled quark-gluon plasma and other circumstances where direct measurement of the order parameter or the free energy may be difficult. It has been conjectured that the minimum of eta/s does indeed occur at the phase transition. We now make a careful assessment in a controled theoretical framework, the Linear Sigma Model at large-N, and indeed find that the minimum of eta/s occurs near the second order phase transition of the model due to the rapid variation of the order parameter (here the sigma vacuum expectation value) at a temperature slightly smaller than the critical one.
Hydrodynamical description of first-order phase transitions
V. Skokov
Solutions of hydrodynamical equations are presented for an equation of state allowing for a first-order phase transition. The numerical analysis is supplemented by analytical treatment provided the system is close to the critical point. The processes of growth and dissolution of seeds of various sizes and shapes in meta-stable phases (like super-cooled vapor and super-heated liquid) are studied, as well as the dynamics of unstable modes in the spinodal region. We show that initially nonspherical seeds acquire spherical shape with passage of time. Applications to the description of the first-order phase transitions in nuclear systems, such as the nuclear gas-liquid transition occurring in low energy heavy-ion collisions and the hadron-quark transition in the high energy heavy-ion collisions are discussed. In both cases we point out the important role played by effects of viscosity and surface tension. It is shown that fluctuations dissolve and grow as if the fluid were effectively very viscous. Even in the spinodal region seeds may grow slowly due to viscosity and critical slowing down. This prevents the enhancement of fluctuations in the near-critical region, which is frequently considered as a signal of the critical point in heavy-ion collisions.
Chiral and deconfinement transition from Dyson-Schwinger equations
Fischer, C.S. (TUD), Mueller, J.A. (TUD)
I summarise recent results on the chiral and deconfinement phase transitions from Dyson-Schwinger equations. In particular I discuss transition temperatures and spectral properties of quarks.
Heavy Flavor Physics in Heavy-Ion Collisions with STAR Heavy Flavor Tracker
Yifei Zhang, (for the STAR Collaboration)
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 ($p_{T}$) 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. But due to the absence of the measurement of B-mesons and precise measurement of D-mesons, it is difficult to separate bottom and charm contributions experimentally in current non-photonic electron measurements for both spectra and elliptic flow $v_2$. 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 study on the open charm nuclear modification factor, elliptic flow $v_2$ and $\Lambda_{c}$ measurement as well as the measurement of bottom mesons via a semi-leptonic decay.
Quark Susceptibilities from the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model
Klein, B (Technische Universität München), Cristoforetti, M, Hell, T, Weise, W (Technische Universität München)
We investigate thermodynamic susceptibilities with regard to the quark flavor chemical potentials in a Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with two quark flavors. Going beyond a saddle-point approximation, we find that the flavor non-diagonal susceptibilities show significant contributions from pionic zero-mode fluctuations, in addition to effects due to the Polyakov loop. These fluctuations appear only in finite volumes and can be understood in terms of a chiral effective Lagrangian. Our results show good agreement with the results of QCD lattice simulations at the corresponding volume size and suggest that such pionic zero-mode fluctuations play a role in lattice simulations as well.
Continuous Decoupling of Dynamically Expanding Systems
Knoll, J. (GSI)
The decoupling and freeze-out of energetic nuclear collisions is analysed in terms of transparent semi-classical decoupling formulae. They provide a smooth transition and generalise frequently employed instantaneous freeze-out procedures. Simple relations between the damping width and the duration of the decoupling process are presented and the implications on various physical phenomena arising from the expansion and decay dynamics of the highly compressed hadronic matter generated in high energy nuclear collisions are discussed. The analytically obtained long freeze-out durations of about 6 to 10 fm/c for SPS to RHIC events are well in agreement with recent transport simulation results. The implied space-time correlations of the freeze-out distribution provides HBT radii with $R_{out}/R_{side} \approx 1.2$ well in agreement with experimental observations. J. Knoll, Nucl.Phys.A821:235,2009; Acta Phys.Polon.B40:1037,2009
Dynamical renormalization group approach to O(N) scalar field theory
Nakano, Eiji
In-medium modification of heavy quarkonia from QCD sum rules
Kenji Morita (GSI), Su Houng Lee (Yonsei University)
We study medium modifications of spectral properties of heavy quarkonia using QCD sum rules. We demonstrate that obtained constraints on the spectral modification, which exhibit critical change due to rapid change of gluon condensates, are consistent with lattice QCD measurements of the Euclidian time correlation function. We also discuss possible extension to finite baryonic chemical cases.
Overview of hot and dense QCD matter
Blaizot, Jean-Paul
Investigation of jet-quenching and elliptic flow within a pQCD-based partonic transport model
Fochler, O., Xu, Z., Greiner, C. (Institut für Theoretische Physik, Goethe Universität Frankfurt)
We apply the fully pQCD-based partonic transport model BAMPS (a Boltzmann approach to multiparton scatterings) including radiative processes as a common and consistent setup to both elliptic flow and jet quenching observed in RHIC experiments. The gluonic contribution to the nuclear modification factor $R_{AA}$ for central b = 0 fm and for non-central b = 7 fm Au + Au collisions at 200 AGeV as calculated within BAMPS is discussed. In addition to the comparison of the elliptic flow parameter $v_{2}$ for low-$p_{T}$ to experimental data we present first results on the elliptic flow of high-$p_{T}$ gluons. To further explore the jet quenching mechanism in BAMPS, we adopt the brick setup as proposed by the TECHQM collaboration for parton cascade models and study the evolution of high energy jets in a static medium, comparing pure collisional energy loss to the case where radiative processes are included. From these calculations the transport parameter $\hat{q}$ is extracted for a static medium of gluons.
Charm Quark Thermodynamics
Hegde, Prasad
Recently, the question of the charm quark contribution to the thermodynamics of the QGP has received some attention. In particular at the high temperatures that can be reached in heavy ion collisions at the LHC a better understanding the thermal contribution of charm to bulk thermodynamics will become relevant. Lattice QCD can provide an answer to this question, but fully dynamical, 4-flavor ensembles do not yet exist. The large charm quark mass also is expected to introduce additional cut-off effects. Nonetheless, as an exploratory study, we recently calculated the second-, fourth- and sixth-order susceptibilities for the charm quark in the partially quenched approximation using the p4 action. We found that our results were in good agreement with perturbative estimates for these quantities. We also studied correlations between charm and the lighter flavors. We compared these quantities to simple quasiparticle and resonance gas models. Lastly, we shall also comment on calculations of the charm's contribution to the pressure within the partially quenched approximation.
Confined but chirally symmetric dense and cold matter
L. Ya. Glozman
We discuss a possibility that at low temperatures and reasonably large density there appears a chirally symmetric but confining phase of the QCD matter.
Universal aspects of the QCD transition at finite temperature and density
Karsch, F (Bielefeld&BNL)
We discuss critical behavior in the chiral limit of QCD and show that QCD with physical values of the light quark mass is sensitive to certain features of the 3-dimensional, O(N) universality class. This allows to determine the curvature of the chiral phase transition line at non vanishing baryon chemical potential.
QCD Thermodynamics with Highly Improved Staggered Quark (HISQ) action
P. Petreczky (BNL), HotQCD Collaboration
I will discuss the QCD transition in terms of renormalized Polyakov loop and chiral condensate using the Highly Improved Staggered Quark (HISQ) action. Numerical caluclation have been performed on 32^3x8 lattices at the physical value of the light quark masses. It was found that the chiral transition shifts to considerably smaller temperatures compared to the previous results obtained with p4 and asqtad. Equation of State and quark number susceptibilities have also been calculated.
Transport Coefficients of Nambu-Jona-Lasinio Model: Symmetry Broken Phase
Xu-Guang Huang, Shijun Mao, Dirk H. Rischke, and Pengfei Zhuang
In the frame of Nambu-Jona-Lasinio model, we calculated the transport coefficients (shear viscosity, bulk viscosity and heat conductivity) of quark matter. The feedback effects of composite mesons (RPA mesons) to quarks are essential, which lead to the following behaviors of transport coefficients: in symmetry broken phase, near T_c, \eta/s decreases, \zeta/s increases, and \kai decreasees with temperature increases.
Viscosity and HBT
Miskowiec, Dariusz
Recent results of two-particle correlation analysis of nuclear collision data will be presented. The emphasis will be put on the collision energy dependence.
Bulk and Shear Viscosities of the Gluon Plasma
Bluhm, M. (Forschungszentrum Dresden-Rossendorf & CERN), Kämpfer, B. (FZD & TU Dresden), Redlich, K. (University of Wroclaw)
With emphasis on the deconfined gluon medium, bulk and shear viscosities are derived within an effective kinetic theory approach for quasiparticle excitations with medium-dependent self-energies. The temperature dependence of these transport coefficients is shown to be in agreement with general expectations and available lattice QCD results. The inclusion of quark degrees of freedom is discussed.
Phase Diagram Evolution with Increasing $6/g^2$ in Strong Coupling Lattice QCD
Kohtaroh Miura (Kyoto Univ.), Takashi Z. Nakano (Kyoto Univ.), Akira Ohnishi (Kyoto Univ.), and Noboru Kawamoto (Hokkaido Univ.)
We investigate a QCD phase diagram by utilizing a strong coupling lattice QCD with one species of staggered fermion. We evaluate the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of the strong coupling expansion, and eluscidate the phase diagram evolution at finite coupling 6/g^2. A partially chiral restored phase appears via NLO effects, and survives in the NNLO cases. We also investigate a critical point flow resulting from 6/g^2 variations.
Chiral and Deconfinement Aspects of (2+1)-flavor QCD
Schaefer, B.-J. (KFU Graz)
Coalesence models for hadronization in uRHIC
V. Greco
Heavy quark production and elliptic flow at RHIC and LHC
Uphoff, J. (Uni Frankfurt), Fochler, O. (Uni Frankfurt), Xu, Z. (Uni Frankfurt), Greiner, C. (Uni Frankfurt)
We investigate heavy quark production and space-time evolution in nucleus-nucleus collisions at RHIC and LHC with the partonic transport model BAMPS. Heavy quarks, produced in primary hard parton scatterings during nucleon-nucleon collisions, are sampled using the Monte Carlo event generator PYTHIA, comparing various parton distribution functions. In a comprehensive study with different charm masses, K factors, and initial gluon conditions, secondary production via $g+g \rightarrow Q + \overline{Q}$ and the evolution of heavy quarks are examined within a fully dynamic BAMPS simulation for central heavy-ion collisions at RHIC and LHC. In addition, we estimate the chemical equilibration time from box calculations and compare it to the simulated charm fugacity at RHIC. Furthermore, we take a look at elliptic flow and energy loss of charm quarks.
Polyakov-Nambu-Jona Lasinio model in external fields
Marco Ruggieri, MR, Yukawa Institute for Theoretical Physics
The thermal phase transition of the Polyakov-Nambu-Jona Lasinio model under the influence of an external field (magnetic as well as chromomagnetic) is investigated. Relevance quantities for heavy ions collisions are computed.
Fluctuations of from initial size fluctuations
Chojnacki, M. (IFJ PAN, Krakow, PL), Broniowski, W. (IFJ PAN, Krakow, PL), Obara L. (Jan Kochanowski University, Kielce, PL)
We investigate the initial transverse size of the source, which comes directly from the Glauber treatment of the earliest stage of relativistic heavy-ion collisions. After the hydrodynamic evolution stage the fluctuations in the transverse velocity flow at the hadronic freeze-out are transformed into the even-by-event fluctuations of the average transverse momentum. The Glauber phase is simulated by GLISSANDO and followed by a realistic hydrodynamic evolution stage. The statistical hadronization is performed by the THERMINATOR. We describe the pT fluctuations at RHIC, in particular the magnitude of the effect, its centrality dependence, and the weak dependence on the incident energy. The results show that the observed event-by-event p_T fluctuations are mainly caused by the initial source size fluctuations.
Perfect-fluid hydrodynamics for RHIC: successes and problems
Florkowski, Wojciech
The short review of the applications of the perfect-fluid hydrodynamics to describe the soft-hadronic RHIC data will be given. The emphasis will be put on still open problems such as the HBT and early-thermalization puzzles. Possible solutions to these puzzles will be suggested.
Femtoscopy in Relativistic Heavy-Ion Collisions as a probe of system collectivity
Kisiel A. (CERN)
The collision of ultrarelativistic heavy-ions creates a system that rapidly evolves and emits a significant number of hadrons. The femtoscopy technique is able, through the analysis of two-particle correlations, to measure the space-time extent of the system at the point of this emission. I will show how these results can then be used to probe the dynamics of the system and, in particular, provide evidence that it behaves collectively, as a single piece of matter. This is especially interesting at the SPS and RHIC energies, where the system is predicted to go through a deconfined state and will continue to be relevant in PbPb collisions at the LHC. Hydrodynamic models aim to describe the behaviour of the system and provide predictions for both the system size and its dependence on the evolution dynamics. I present experimental femtoscopic results and confront them with hydrodynamic predictions and discuss their validity. I also show extrapolations to the LHC regime both for heav-ion and proton-proton collisions.
Charmonia in Heavy Ion Collisions
Roberta Arnaldi (INFN Torino, Italy)
The understanding of J/psi production is an extremely complicate issue. On one hand, charmonia suppression represents one of the main signatures for the formation of a deconfined medium in A-A collisions. On the other hand, also nuclear effects, not related to the production of a hot medium, may affect the J/psi yield. Therefore, the understanding of charmonia behaviour in p-A or d-A collisions is extremely important to quantify the amount of suppression due to the deconfined medium. In this talk recent results obtained from SPS and RHIC experiments with p-A, d-A and A-A collisions will be reviewed. Expectations for the incoming LHC charmonia measurements will also be presented.
Hydrodynamics, flow, and flow fluctuations
Jean-Yves Ollitrault, Clément Gombeaud
The matter formed in heavy-ion collisions has been shown to interact so strongly that it behaves like a relativistic fluid during its expansion. I show that initial-state fluctuations, due to the nucleonic structure of incoming nuclei, have a large effect of flow observables. I argue that these fluctuations do not reduce to eccentricity fluctuations.
Electromagnetic Probes in Ultrarelatistic Heavy-Ion Collisions
van Hees, H. (JLU Giessen)
The invariant-mass spectra of lepton pairs are an important probe for the electromagnetic properties of the hot and dense medium created in ultrarelativistich heavy-ion collisions since the leptons leave the medium with negligible final-state interactions. In the low-mass region (M<1 GeV) the signal is dominated by the contributions from the vector mesons, rho, omega, and phi. Thus, the dilepton signal provides a direct insight in their spectral properties, particularly in their in-medium mass shifts and broadening. In the intermediate-mass range the spectrum becomes continuum like and can be described with multi-pion processes in the hadronic and quark-antiquark annihilation in the partonic phase of the fireball evolution. In this talk, I will summarize our current understanding of recent dilepton data from the SPS and RHIC in terms of effective hadronic (and partonic) models for the in-medium properties of the electromagnetic current-correlation function.
The Quark Propagator in a self-consistent 1/Nc Expansion in the NJL Model
D. Mueller, M. Buballa, J. Wambach (TU Darmstadt)
The quark propagator is calculated in the Nambu-Jona-Lasinio (NJL) model in a self-consistent $1/N_c$ expansion at next-to-leading order. The chiral quark condensate and its dependence on temperature and chemical potential is calculated directly and compared with meanfield results. By using the Maximum-Entropy-Method (MEM) spectral functions are determined from the Euclidean propagators. We find a second order phase transition for the quark condensate at finite temperature whereas the critical temperature is reduced in comparison with meanfield results.
Challenges for secondary vertex reconstruction in CBM at SIS100 and SIS300 at FAIR
Lymanets, A. (FIAS), Kotynia, A. (HIC4FAIR) and Heuser, J. (GSI) for the CBM Collaboration
The CBM experiment at FAIR will explore the QCD phase diagram in the region of highest baryon densities. In contrast to other experimental programs in the same energy domain, CBM will be able to explore rare probes such as charm and dileptons due to its capability of running at interaction rates as high as 10 MHz. In order to cope with the related experimental challenges detailed simulations studies as well as extensive R&D activities on the detector and readout systems are ongoing. In this contribution, the challenges of open charm measurement in pA collisions, e.g. already at SIS100, and in AA collisions at SIS300 will be investigated. In order to extract open charm decays from the large background of produced charged particles, secondary vertex reconstruction with a precision of less than 0.1 mm is required. The involved tracking and reconstruction procedures have to be fast in order to allow their implementation already on the trigger level. Prerequisit for this are ultra-low mass, fast and radiation tolerant silicon detectors. These two aspects of a finally successful measurement, hardware development and reconstruction routines, are being developed in close contact to each other and their status is demonstrated in this talk.
Hadron yields and the QCD phase diagram
Stachel, Johanna
Heavy quark(onium) at LHC: the statistical hadronization case
Andronic, A. (GSI), Braun-Munzinger, P. (GSI, EMMI, TU Darmstadt, FIAS), Redlich, K. (U. Wroclaw, EMMI), Stachel, J. (U. Heidelberg)
Novel diagrammatic method for computing transport coefficients --- beyond the Boltzmann approximation ---
Hidaka, Y (Kyoto); Kunihiro, T (Kyoto)
We propose a novel diagrammatic method for computing transport coefficients in relativistic quantum field theory. Our method is based on a reformulation and extension of the diagrammatic method by Eliashberg given in the imaginary-time formalism to the relativistic quantum field theory in the real-time formalism, in which the cumbersome analytical continuation problem can be avoided. The transport coefficients are obtained from a two-point function via Kubo formula. It is know that naive perturbation theory breaks down owing to a so called pinch singularity, and hence a resummation is required for getting a finite and sensible result. As a novel resummation method, we first decompose the two point function into the singular part and the regular part, and then reconstruct the diagrams. We find that a self-consistent equation for the two-point function has the same structure as the linearized Boltzmann equation. It is known that the two-point function at the leading order is equivalent to the linearized Boltzmann equation. We find the higher order corrections are nicely summarized as a renormalization of the vertex function, spectral function, and collision term. We also discuss the critical behavior of the transport coefficients near a phase transition, applying our method.
Can we locate the QCD critical endpoint with the Taylor expansion ?
Wagner, M (TU Darmstadt); Karsch, F. (Bielefeld, BNL, GSI); Schaefer, B.-J. (KFU Graz); Wambach, J (TU Darmstadt)
While lattice QCD simulations are more and more successful at vanishing chemical potential, at finite chemical potential the fermion-sign problem is still a serious problem. Different methods have been proposed to access at least the region at small chemical potential. One such approach is the Taylor expansion. Effective models allow calculations at arbitrary chemical potential. We have developed a novel technique to evaluate the coefficients with high-precision up to 24th order in the PQM model. This model yields a good description of the equation of state at zero chemical potential. We discuss the prospects of the Taylor expansion in particular signal of a possible critical point.
Elliptic Flow: lessons from RHIC, expectations for the LHC
Raimond Snellings
Center vortices, fluxes and the deconfinement transition in QCD-like lattice theories
von Smekal, L. and Edwards, S.R. (TU Darmstadt)
Electromagnetic probes in nuclear collisions
Usai, Gianluca
Among the observables used for the diagnostics of the hot and dense fireball formed in high energy nuclear collisions, lepton pairs are particularly attractive. In contrast to hadrons, they directly probe the entire space-time evolution of the fireball and freely escape from the interaction zone, undisturbed by final-state interactions. This talk will review the present understanding of thermal dilepton production from an experimental point of view focusing on the most recent measurements. A perspective on possible future measurements will be presented as well.
Jet reconstruction
Mateusz Ploskon
Partonic energy loss (jet quenching) within the hot and colored medium created in heavy-ion collisions at Relativistic Heavy-Ion Collider is one of the essential tools to provide quantitative understanding of Quark Gluon Plasma. Measurements of jet quenching via single and di-hadron observables have provided initial estimates of the energy density of this hot QCD medium. However, these hadron-triggered observables suffer from well-known biases since they fold production cross-sections with the energy loss itself, providing limited information on the initial energy of the propagating jet. Fully reconstructed jets - in terms of energy flow - will allow a complete exploration of fragmentation patterns and will not suffer from geometrical biases, providing complementary and perhaps exhaustive understanding of partonic energy loss. In this talk we review the jet reconstruction in experiments at hadron colliders with focus on the complexity and recent progress in full jet reconstruction techniques applied in heavy-ion collisions. We recall the pioneering hadron triggered measurements, summarize their impact and put them in contrast to the first measurements of fully reconstructed jets in heavy-ions at RHIC. In addition we present an outlook towards the full jet reconstruction in heavy-ion collisions at LHC and discuss excellent opportunities for jet quenching measurements at the new energy frontier.
First Physics with ALICE
H. Appelshäuser (Goethe-Universität Frankfurt) for the ALICE Collaboration
In the fall of 2009, first collisions of protons at $\sqrt{s}=900$ GeV are expected to occur at the CERN Large Hadron Collider LHC. The ALICE experiment is the only dedicated heavy-ion detector at LHC, but it is also well suited for detailed studies of pp collisions. In this talk, the status of the experiment and the perspectives for first physics analyses with ALICE will be presented.
Lattice QCD under extreme conditions
Edwin Laermann
The talk attempts to summarize the present knowledge on some key aspects of QCD under extreme conditions as it arises from lattice simulations, and will discuss further prospects.
Dileptons and Charm at RHIC
Thomas K Hemmick, TKH, (PHENIX)
Electro-magnetic probes have long held a place of fascination in studies of nuclear collisions due to their lack of strong interaction and, thereby, their penetrating nature. Ironically, lepton measurements when measured as singles and pairs yield views of opposite characteristics of the colliding system. Singles measurements, dominated at high transverse momentum by semi-leptonic decays of heavy quarks, are the route by which stopping and flow are best characterized and thereby are most influenced by the opacity of the medium to quarks. Pair measurements, on the other hand, yield the most transparent look at the collision zone via virtual direct photon measurements and give access to intriguing in-medium mesonic properties. This talk will present RHIC results in both these extremes.
On the Phase diagram of QCD
Pawlowski, Jan Martin
I review recent work on the phase diagram of QCD with functional methods.