Thu·Jun 30, 2011Thursday·June 30, 2011

1. 01*

   Gluon polarization measurements with inclusive jets at STAR

   Pibero Djawotho (for the STAR Collaboration)🇺🇸

   At RHIC kinematics, polarized jet hadroproduction is dominated by $gg$ and $qg$ scattering, making the jet double longitudinal spin asymmetry, $A_{LL}$, sensitive to gluon polarization in the nucleon. I will present STAR results of $A_{LL}$ from inclusive jet measurements for the RHIC 2006 run at center-of-mass energy 200 GeV. I will also discuss the current status of the analysis of data from the 2009 run, also at center-of-mass energy 200 GeV. The results are compared with theoretical calculations of $A_{LL}$ based on various models of the gluon density in the nucleon. The STAR data place significant constraints on allowed theoretical models.

   nucl-ex13 citations
2. 02*

   Quarkonium production measurements with the ALICE detector at the LHC

   Ginés Martínez García (for the ALICE Collaboration)🇫🇷

   In this new energy regime, quarkonium provides a unique probe to study the properties of the high-density, strongly interacting system formed in the early stages of high-energy heavy-ion collisions. In ALICE, quarkonium states are reconstructed down to p_T=0 via their mu+mu- decay channel in the muon spectrometer (2.5<y<4.0) and via their e+e- channel in the central barrel (|y|<0.9). Measurement of the transverse momentum and rapidity distributions of inclusive J/psi production cross section in proton-proton collisions at sqrt{s}=2.76 and 7 TeV will be presented. We will discuss the dependence on charged particle multiplicity of the inclusive J/psi yield in proton-proton collisions at sqrt{s}=7 TeV. Finally, the analysis of the inclusive J/psi production in Pb-Pb collisions at sqrt{s_NN}=2.76 TeV will be described. Preliminary results on the nuclear modification factor (R_AA) and the central to peripheral nuclear modification factor (R_CP) will be discussed.

   nucl-exhep-exJ.Phys.G(2011)·31 citations
3. 03*

   STAR experiment results from the beam energy scan program at RHIC

   Bedangadas Mohanty🇮🇳

   We present the first results using the STAR detector from the Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC). In this program, Au ion collisions at center of mass energies (\sqrt{s_{NN}}) of 7.7, 11.5 and 39 GeV allowed RHIC to extend the study of the QCD phase diagram from baryonic chemical potential values of 20 MeV to about 400 MeV. For the high net-baryon density matter at midrapidity, formed in these collisions, we report several interesting measurements. These include the observation of difference between anti-particle and particle elliptic flow, disappearance of the difference in dynamical azimuthal correlations with respect to event plane between same and opposite signed charged particles, change in slope of eccentricity at freeze-out and directed flow of protons as a function of \sqrt{s_{NN}} and the deviation of higher order fluctuations from hadron resonance gas and Poissonian expectations. Possible interpretations of these observations are also discussed.

   nucl-exhep-exhep-phnucl-thJ.Phys.G(2011)·153 citations
4. 04*

   The flow of heavy flavor in hydrodynamics

   Taesoo Song🇺🇸 · Woosung Park🇰🇷 · Su Houng Lee🇰🇷

   The flow of charm is calculated in 2+1 ideal hydrodynamics by introducing the charge of $c\bar{c}$ pair assuming that the number of $c\bar{c}$ pairs is conserved in relativistic heavy-ion collisions. It is found that the mean radial flow velocity of charm quarks is smaller than that of bulk matter by 10$\sim$15 \% and the measured $v_2$ of heavy-flavor electrons is reproduced up to $p_T^e=$ 1.5 GeV/c in Au+Au collision at RHIC. The same flow is applied to regenerated $J/\psi$ and its $v_2$ is discussed.

   ↳ nucl-thnucl-exPRC(2011)·9 citations
5. 05*

   ALICE detector upgrades

   Thomas Peitzmann (for the ALICE collaboration)🇳🇱

   The LHC with its unprecedented energy offers unique opportunities for groundbreaking measurements in p+p, p+A and A+A collisions even beyond the baseline experimental designs. ALICE is setting up a program of detector upgrades, which could to a large extent be installed in the LHC shutdown planned for 2017/18, to address the new scientific challenges. We will discuss examples of the scientific frontiers and will present the corresponding upgrade projects under study for the ALICE experiment.

   ↳ physics.ins-dethep-exnucl-exJ.Phys.G(2011)·2 citations
6. 06*

   Can transport peak explain the low-mass enhancement of dileptons at RHIC?

   Yukinao Akamatsu🇯🇵 · Hideki Hamagaki🇯🇵 · Tetsuo Hatsuda🇯🇵 · Tetsufumi Hirano🇯🇵

   We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIX and transport coefficients of QGP such as the charge diffusion constant $D$ and the relaxation time ${\tau }_{\mathrm{J}}$. We parameterize the transport peak in the spectral function using the second-order relativistic dissipative hydrodynamics by Israel and Stewart. Combining the spectral function and the full (3+1)-dimensional hydrodynamical evolution with the lattice EoS, theoretical dielectron spectra and the experimental data are compared. Detailed analysis suggests that the low-mass dilepton enhancement originates mainly from the high-temperature QGP phase where there is a large electric charge fluctuation as obtained from lattice QCD simulations.

   ↳ nucl-thhep-phnucl-exJ.Phys.G(2011)·13 citations
7. 07*

   Performance simulation of a MRPC-based PET Imaging System

   A. Banerjee · S. Chattopadhyay🇮🇳

   The low cost and high resolution gas-based Multi-gap Resistive Plate Chamber (MRPC) opens a new possibility to find an efficient alternative detector for Time of Flight (TOF) based Positron Emission Tomography, where the sensitivity of the system depends largely on the time resolution of the detector. Suitable converters can be used to increase the efficiency of detection of photons from annihilation. In this work, we perform a detailed GEANT4 simulation to optimize the converter thickness thereby improving the efficiency of photon conversion. Also we have developed a Monte Carlo based simulation of MRPC response thereby obtaining the intrinsic time resolution of the detector, making it possible to simulate the final response of MRPC-based systems for PET imaging. The result of the cosmic ray test of a four-gap Bakelite-based MRPC operating in streamer mode is discussed.

   ↳ physics.ins-dethep-exnucl-exphysics.med-ph2 citations
8. 08*

   D meson nuclear modification factors in Pb-Pb collisions at {\surd}sNN = 2.76 TeV, measured with the ALICE detector

   Andrea Rossi (for the ALICE Collaboration)🇮🇹

   The ALICE experiment has measured the D meson production in pp and Pb-Pb collisions at the LHC at {\surd}s = 7 and 2.76 TeV and {\surd}sNN = 2.76 TeV respectively, via the exclusive reconstruction of hadronic decay channels. The analyses of the D0{\to}K-pi+ and D+{\to}K-pi+pi+ channels will be described and the preliminary results for the D0 and D+ nuclear modification factor will be presented.

   ↳ hep-exnucl-exJ.Phys.G(2011)·18 citations
9. 09*

   Production of Neutral Pions and Eta-mesons in pp Collisions Measured with ALICE

   Klaus Reygers (for the ALICE Collaboration)🇩🇪

   Invariant cross sections for neutral pions and eta mesons in pp collisions at sqrt(s) = 0.9, 2.76, and 7 TeV were measured by the ALICE detector at the Large Hadron Collider. Next-to-leading order (NLO) perturbative QCD calculations describe the pi0 and eta spectra at 0.9 TeV, but overestimate the measured cross sections at 2.76 TeV and 7 TeV. The measured eta/pi0 ratio is consistent with mT scaling at 2.76 TeV. At 7 TeV indications for a violation of mT scaling were found.

   ↳ hep-exnucl-exJ.Phys.G(2011)·14 citations
10. 10*

    Spectra, flow and HBT in Pb-Pb collisions at the LHC

    Piotr Bozek🇵🇱

    The transverse momentum spectra, elliptic flow and interferometry radii for Pb-Pb collisions at the LHC are calculated in relativistic viscous hydrodynamics. For Glauber model initial conditions, we find that the data can be described using a small value of shear viscosity eta/s=0.08. The viscosities and the equation of state are the same as used for RHIC energies.

    ↳ nucl-thnucl-exJ.Phys.G(2011)·7 citations
11. 11*

    The $\Delta (1232)$ axial charge and form factors from lattice QCD

    C. Alexandrou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · E. B. Gregory (Univ. of Cyprus)🇨🇾 · T. Korzec (Humboldt Univ. Berlin)🇩🇪 · G. Koutsou (Cyprus Inst.)🇨🇾 · J. W. Negele (MIT)🇺🇸 · T. Sato (Osaka Univ.)🇯🇵 · A. Tsapalis (Hellenic Naval Acad. & National Tech. Univ. of Athens)🇬🇷

    We present the first calculation on the $\Delta$ axial-vector and pseudoscalar form factors using lattice QCD. Two Goldberger-Treiman relations are derived and examined. A combined chiral fit is performed to the nucleon axial charge, N to $\Delta$ axial transition coupling constant and $\Delta$ axial charge.

    ↳ hep-lathep-phnucl-exnucl-thPRL(2011)·19 citations
12. 12*

    Heavy-Quark Diffusion and Hadronization in Quark-Gluon Plasma

    Min He🇺🇸 · Rainer J. Fries🇺🇸 · Ralf Rapp🇺🇸

    We calculate diffusion and hadronization of heavy quarks in high-energy heavy-ion collisions implementing the notion of a strongly coupled quark-gluon plasma in both micro- and macroscopic components. The diffusion process is simulated using relativistic Fokker-Planck dynamics for elastic scattering in a hydrodynamic background. The heavy-quark transport coefficients in the medium are obtained from non-perturbative $T$-matrix interactions which build up resonant correlations close to the transition temperature. The latter also form the basis for hadronization of heavy quarks into heavy-flavor mesons via recombination with light quarks from the medium. The pertinent resonance recombination satisfies energy conservation and provides an equilibrium mapping between quark and meson distributions. The recombination probability is derived from the resonant heavy-quark scattering rate. Consequently, recombination dominates at low transverse momentum ($p_T$) and yields to fragmentation at high $p_T$. Our approach thus emphasizes the role of resonance correlations in the diffusion and hadronization processes. We calculate the nuclear modification factor and elliptic flow of $D$- and $B$-mesons for Au-Au collisions at the Relativistic Heavy Ion Collider, and compare their decay-electron spectra to available data. We also find that a realistic description of the medium flow is essential for a quantitative interpretation of the data.

    ↳ nucl-thhep-phnucl-exPRC(2012)·273 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.