Fri·Jul 1, 2011Friday·July 1, 2011

1. 01*

   STAR Measurements of Bottom to Charm Ratio and Heavy Quark Interaction with the QCD Medium through Non-Photonic Electron-Hadron Correlations

   Wenqin Xu (for the STAR Collaboration)🇺🇸

   We present STAR measurements of relative charm and bottom contributions to NPE from $p+p$ collisions at $\sqrt{s}$= 200 and 500 GeV energies. We report the total bottom quark production cross section from p+p collisions at $\sqrt{s}=200$ GeV extracted from NPE spectrum and B to D ratios. We also present the NPE-hadron azimuthal correlations from $Au+Au$ collisions at $\text{sqrtsNN}=200$ GeV from the 2010 RHIC run where we have collected high statistics data set with low photonic conversion background.

   nucl-exhep-exJ.Phys.G(2011)·4 citations
2. 02*

   STAR Highlights

   Hiroshi Masui (for the STAR Collaboration)🇯🇵

   We report selected results from STAR collaboration at RHIC, focusing on jet-hadron and jet-like correlations, quarkonium suppression and collectivity, di-electron spectrum in both p+p and Au+Au, and higher moments of net-protons as well as azimuthal anisotropy from RHIC Beam Energy Scan program.

   nucl-exJ.Phys.G(2011)·15 citations
3. 03*

   Jet-hadron correlations in STAR

   Alice Ohlson (for the STAR Collaboration)🇺🇸

   In recent years, the study of dihadron correlations has been one of the primary methods used to investigate the propagation and modification of hard-scattered partons through the QGP. Due to recent advances in jet-finding algorithms, it is now possible to use reconstructed jets in these correlation studies, extending the kinematic reach compared to dihadron analyses. The results of the jet-hadron correlation analysis indicate a broadening and softening of jets that interact with the medium. Jet-hadron correlations can also be used to assess the systematics of other jet-like correlation analyses, such as 2+1 correlations. It is shown that the jets selected in 2+1 correlations are relatively unmodified. Future work will include an analysis of jet-hadron correlations with respect to the event plane to measure the pathlength dependence of parton energy loss. The first steps in this analysis indicate that complications arise when calculating the event plane in the presence of a jet as well as in calculating jet v2. The data analyzed were collected by the STAR detector in sqrt(s_NN) = 200 GeV Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC).

   nucl-exJ.Phys.Conf.Ser.(2011)·8 citations
4. 04*

   Untriggered di-hadron correlations in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV from ALICE

   Anthony R. Timmins (for the ALICE collaboration)🇺🇸

   We present measurements of untriggered di-hadron correlations as a function of centrality in Pb-Pb \sNN collisions, for charged hadrons with $p_T>0.15$ GeV$/c$. These measurements provide a map of the bulk correlation structures in heavy-ion collisions. Contributions to these structures may come from jets, initial density fluctuations, elliptic flow, resonances, and/or momentum conservation. We decompose the measured correlation functions via a multi-parameter fit in order to extract the nearside Gaussian, the longer range $\Delta \eta$ correlation often referred to as the soft ridge. The effect of including higher harmonics ($v_3$ and $v_4$) in this procedure will be discussed. We investigate how the nearside Gaussian scales with the number of binary collisions. Finally, we show the charge dependence of the nearside Gaussian.

   nucl-exJ.Phys.G(2011)·15 citations
5. 05*

   Identified Hadron Production from the RHIC Beam Energy Scan

   Lokesh Kumar (for the STAR Collaboration)🇺🇸

   A current focus at RHIC is the Beam Energy Scan to study the QCD phase diagram -- temperature ($T$) vs. baryon chemical potential (${\mu }_B$). The STAR experiment has collected data for Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7 GeV, 11.5 GeV, and 39 GeV in the year 2010. We present midrapidity results on rapidity density, average transverse mass, and particle ratios for identified hadrons from the STAR experiment. Collision dynamics are studied in the framework of chemical and kinetic freeze-out conditions.

   nucl-exJ.Phys.G(2011)·67 citations
6. 06*

   Open charm hadron measurement in p+p and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV in STAR

   Yifei Zhang🇨🇳

   We present the measurements of $D^0$ and $D^{\ast }$ in p+p and $D^0$ in Au+Au collisions via hadronic decays $D^0\to K^{-}{\pi }^{+}$, $D^{\ast +}\to D^0{\pi }^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ in mid-rapidity $|y|<1$ at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 200 GeV, covering $p_T$ from 0.2 to 6 GeV/$c$ in p+p and 0.4 to 5 GeV/$c$ in Au+Au, respectively. The charm pair production cross section per nucleon-nucleon collision at mid rapidity is measured to be 202 $\pm$ 56 (stat.) $\pm$ 40 (sys.) $\pm$ 20 (norm.) $\mu$b in p+p and 186 $\pm$ 22 (stat.) $\pm$ 30 (sys.) $\pm$ 18 (norm.) $\mu$b in Au+Au minimum bias collisions. The number of binary collisions scaling of charm cross section indicates that charm is produced via initial hard scatterings. No suppression of $D^0$ $R_{AA}$ in Au+Au 0-80% minbias collisions is observed at $p_T$ below 3 GeV/$c$. Blast-wave predictions with light-quark hadron parameters are different from data, which may indicate that $D^0$ decouples earlier from the medium than the light-quark hadrons.

   nucl-exJ.Phys.G(2011)·18 citations
7. 07*

   Searching for the QCD Critical Point Using Particle Ratio Fluctuations and Higher Moments of Multiplicity Distributions

   Terence J Tarnowsky (for the STAR Collaboration)🇺🇸

   Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be observed near a QCD critical point. Results from new measurements of dynamical $K/\pi$, $p/\pi$, and $K/p$ ratio fluctuations are presented. The commencing of a QCD critical point search at RHIC has extended the reach of possible measurements of dynamical $K/\pi$, $p/\pi$, and $K/p$ ratio fluctuations from Au+Au collisions to lower energies. The STAR experiment has performed a comprehensive study of the energy dependence of these dynamical fluctuations in Au+Au collisions at the energies $\sqrt{s_{NN}}$ = 7.7, 11.5, 39, 62.4, and 200 GeV. New results are compared to previous measurements and to theoretical predictions from several models. The measured dynamical $K/\pi$ fluctuations are found to be independent of collision energy, while dynamical $p/\pi$ and $K/p$ fluctuations have a negative value that increases toward zero at top RHIC energy. Fluctuations of the higher moments of conserved quantities (net-proton and net-charge) distributions, which are predicted to be sensitive to the presence of a critical point, are also presented.

   nucl-exJ.Phys.G(2011)·28 citations
8. 08*

   A Study of the QCD Critical Point Using Particle Ratio Fluctuations

   Terence J Tarnowsky (for the STAR Collaboration)🇺🇸

   Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be observed near a QCD critical point. Results from new measurements of dynamical $K/\pi$ and $p/\pi$ ratio fluctuations are presented. The commencing of a QCD critical point search at RHIC has extended the reach of possible measurements of dynamical $K/\pi$ and $p/\pi$ ratio fluctuations from Au+Au collisions to lower energies. The STAR experiment has performed a comprehensive study of the energy dependence of these dynamical fluctuations in Au+Au collisions at the energies $\sqrt{s_{NN}}$ = 7.7, 11.5, and 39 GeV. New results are compared to previous measurements and to theoretical predictions from several models.

   nucl-exJ.Phys.Conf.Ser.(2011)·0 citations
9. 09*

   Dielectron continuum production from $\sqrt{s_{NN}}$ = 200 GeV p + p and Au + Au collisions at STAR

   Jie Zhao (for the STAR Collaboration)🇨🇳

   We present the first STAR dielectron measurement in 200 GeV p + p and Au + Au collisions. Results are compared to hadron decay cocktails to search for vector meson in-medium modification in low mass region and quark gluon plasma thermal radiation in the intermediate mass region. The $\omega \to e^{+}{e}^{-}$ spectra and the transverse mass distribution in the intermediate mass region are also discussed.

   nucl-exhep-exComments Nucl.Part.Phys.(2011)·33 citations
10. 10*

    Measurement of the nuclear modification factor of electrons from heavy-flavour decays at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV with ALICE

    Yvonne Pachmayer (for the ALICE Collaboration)🇩🇪

    We present results on inclusive electrons for 1.5 $<p_{\mathrm{T}}<$ 6 GeV/$c$ in {Pb-Pb} collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV measured with ALICE at the LHC and compare these to a cocktail of background electron sources. The excess of electrons beyond the cocktail at high momenta ({$p_{\mathrm{T}}>$ 3.5 GeV/$c$}) is attributed to electrons from heavy-flavour decays. The corresponding nuclear modification factor indicates heavy-flavour suppression by a factor of 1.5-4.

    nucl-exJ.Phys.G(2011)·12 citations
11. 11*

    Anisotropic flow of charged particles at $\sqrt{{\mathbf{s}}_{\mathbf{NN}}}=2.76$ TeV measured with the ALICE detector

    Ante Bilandzic🇳🇱

    Measurements of anisotropic flow in heavy-ion collisions provide evidence for the creation of strongly interacting matter which appears to behave as an almost ideal fluid. Anisotropic flow signals the presence of multiple interactions and is very sensitive to the initial spatial anisotropy of the overlap region in non-central heavy-ion collisions. In this article we report measurements of elliptic $v_2$, triangular $v_3$, quadrangular $v_4$ and pentagonal $v_5$ flow. These measurements have been performed with 2- and multi-particle correlation techniques.

    nucl-exJ.Phys.G(2011)·14 citations
12. 12*

    Identification of the slow E3 transition 136mCs -> 136Cs with conversion electrons

    K. Wimmer🇩🇪 · U. Koester🇫🇷 · P. Hoff🇳🇴 · Th. Kroell🇩🇪 · R. Kruecken🇩🇪 · R. Lutter🇩🇪 · H. Mach🇸🇪 · Th. Morgan🇩🇪 · S. Sarkar🇮🇳 · M. Saha Sarkar · W. Schwerdtfeger🇩🇪 · P. C. Srivastava🇮🇳 · P. G. Thirolf🇩🇪 · P. Van Isacker🇫🇷

    We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in 136Cs by and conversion-electron detection. For the first time the excitation energy of the isomer and the multipolarity of its decay have been measured. The half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer decays via a very slow 518 keV E3 transition to the ground state. In addition to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV E2 transition has been found. Thus we have found a new level at 105 keV with spin 4+ between the isomeric and the ground state. The results are discussed in comparison to shell model calculations.

    nucl-exnucl-thPRC(2011)·14 citations
13. 13*

    Jet-hadron correlations in STAR

    Alice Ohlson (for the STAR Collaboration)🇺🇸

    Advancements in full jet reconstruction have made it possible to use jets as triggers in azimuthal angular correlations to study the modification of hard-scattered partons in the medium created in ultrarelativistic heavy-ion collisions. This increases the range of parton energies accessible in these analyses and improves the signal-to-background ratio compared to dihadron correlations. Results of a systematic study of jet-hadron correlations in central Au-Au collisions at sqrt(s_NN) = 200 GeV are indicative of a broadening and softening of jets which interact with the medium. Furthermore, jet-hadron correlations suggest that the suppression of the associated hadron yield at high-pT is balanced in large part by low-pT enhancement.

    nucl-exJ.Phys.G(2011)·10 citations
14. 14*

    Jets and jet-like correlations studies from STAR

    Helen Caines (the STAR Collaboration)🇺🇸

    I present recent results from jets and jet-like correlation measurements from STAR. The pp data are compared to those from Au-Au collisions to attempt to infer information on the medium produced and how hard scattered partons interact with this matter. Results from d-Au events are utilized to investigate the magnitude of cold nuclear matter effects on hard scatterings. The evolution of the underlying event from pp to d-Au collisions is studied. In heavy-ion collisions, background fluctuations are the major source of systematic uncertainties in jet measurements. Detailed studies are therefore being made of these fluctuations and recent progress in our understanding is reported. Jet and jet-hadron correlations results are presented and give clear indications that partonic fragmentation at RHIC is highly modified in the presence of a strongly coupled coloured medium, resulting in a significant broadening and softening of the jet fragments correlation. Finally di-hadron correlations utilizing identified particles as triggers indicate that the "ridge" is stronger for p+K than for pi but that the near-side peak per-trigger yield remains unaltered from d-Au to Au-Au collisions.

    nucl-exhep-exJ.Phys.G(2011)·10 citations
15. 15*

    Anisotropic flow at the LHC measured with the ALICE detector

    Raimond Snellings (for the ALICE Collaboration)🇳🇱

    The ALICE detector at the LHC recorded first Pb-Pb collisions at 2.76 TeV in November and December of 2010. We report on the measurements of anisotropic flow for charged and identified particles. From the comparison with measurements at lower energies and with model predictions we find that the system created at these collision energies is described well by hydrodynamical model calculations and behaves like an almost perfect fluid.

    nucl-exhep-exJ.Phys.G(2011)·48 citations
16. 16*

    Evidence of theta(13)>0 from global neutrino data analysis

    G. L. Fogli🇮🇹 · E. Lisi🇮🇹 · A. Marrone🇮🇹 · A. Palazzo🇩🇪 · A. M. Rotunno🇮🇹

    The neutrino mixing angle theta(13) is at the focus of current neutrino research. From a global analysis of the available oscillation data in a 3-neutrino framework, we previously reported [Phys. Rev. Lett. 101, 141801 (2008)] hints in favor of theta(13)>0 at the 90 % C.L. Such hints are consistent with the recent indications of nu(mu)-->nu(e) appearance in the T2K and MINOS long-baseline accelerator experiments. Our global analysis of all the available data currently provides >3 sigma evidence for nonzero theta(13), with 1-sigma ranges sin^2 theta(13) = 0.021+-0.007 or 0.025+-0.007, depending on reactor neutrino flux systematics. Updated ranges are also reported for the other 3-neutrino oscillation parameters (delta m^2, sin^2 theta(12)) and (Delta m^2, sin^2 theta(23)).

    ↳ hep-phastro-ph.SRhep-exnucl-exPRD(2011)·409 citations
17. 17*

    Pion productions by proton and Helium-3 on Au197 target at beam energies of 2.8, 5, 10 and 16.587 GeV/nucleon

    Gao-Chan Yong🇨🇳 · Xurong Chen🇨🇳 · Hu-Shan Xu🇨🇳 · Wei Zuo🇨🇳

    Based on a Relativistic Boltzmann-Uehling- Uhlenbeck transport model, proton and ${}^3$He induced reactions on ${}^{197}$Au target at beam energies of 2.8, 5, 10 and 16.587 GeV/nucleon are studied. It is found that compared with proton induced reactions, ${}^3$He induced reactions give larger cross sections of pion production, about 5 times those of the proton induced reactions. And more importantly, pion production from ${}^3$He induced reaction is more inclined to low-angle emission. Neutrino production via positively charged pion is also discussed accordingly.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2012)·0 citations
18. 18*

    Initial fluctuations and dihadron and $\gamma$-hadron correlations in high-energy heavy ion collisions

    Guo-Liang Ma🇨🇳 · Xin-Nian Wang🇨🇳

    Jets, jet-medium interaction and hydrodynamic evolution of fluctuations in initial parton density all lead to the final anisotropic dihadron azimuthal correlations in high-energy heavy-ion collisions. We remove the harmonic flow background and study the net correlations from different sources with different initial conditions within the AMPT model. We also study $\gamma$-hadron correlations which are only influenced by jet-medium interactions.

    ↳ nucl-thhep-phnucl-exJ.Phys.G(2011)·2 citations
19. 19*

    Equation of state at finite baryon density based on lattice QCD

    Pasi Huovinen🇩🇪 · Peter Petreczky🇺🇸

    We employ the lattice QCD data on Taylor expansion coefficients to extend our previous parametrization of the equation of state to finite baryon density. When we take into account lattice spacing and quark mass dependence of the hadron masses, the Taylor coefficients at low temperature are equal to those of hadron resonance gas. Thus the equation of state is smoothly connected to the hadron resonance gas equation of state at low temperatures. We also show how the elliptic flow is affected by this equation of state at the maximum SPS energy.

    ↳ nucl-thhep-lathep-phnucl-exJ.Phys.G(2011)·25 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.