Tue·Aug 5, 2014Tuesday·August 5, 2014

1. 01*

   Transverse Energy ($E_T$) distributions at mid-rapidity in $p$$+$$p$, $d$$+$Au and Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}$=200 GeV and implications for particle production models

   M. J. Tannenbaum (for the PHENIX Collaboration)🇺🇸

   Measurements of the midrapidity transverse energy distribution $d{\mathrm{E}}_T/d\eta$ are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au Collisions at $\sqrt{s_{{}_{NN}}}$=62.4--200 GeV. The ${\mathrm{E}}_T$ distributions are compared with the number of participants, $N_{\mathrm{part}}$, the number of constituent-quark participants, $N_{qp}$, and the number of color-strings (Additive Quark Model-AQM) calculated from a Glauber model. For Au$+$Au, $⟨d{\mathrm{E}}_T/d\eta /(0.5N_{\mathrm{part}})⟩$ increases with $N_{\mathrm{part}}$, while $⟨d{\mathrm{E}}_T/d\eta /N_{qp}⟩$ is approximately constant vs. centrality for $\sqrt{s_{{}_{NN}}}\ge 62.4$ GeV. This indicates that the two component ansatz, $d{\mathrm{E}}_T^{\mathrm{AA}}/d\eta =(d{\mathrm{E}}_T^{\mathrm{pp}}/d\eta )[(1-x)N_{\mathrm{part}}/2+x{N}_{\mathrm{coll}}]$, which has been used to represent ${\mathrm{E}}_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\mathrm{coll}}$ term does not represent a hard-scattering component in ${\mathrm{E}}_T$ distributions. The $d{\mathrm{E}}_T/d\eta$ distributions of $d$$+$Au, and Au$+$Au are calculated from the measured $p$$+$$p$ ${\mathrm{E}}_T$ distribution using two models (AQM and $N_{qp}$) that both reproduce the Au$+$Au data. For the asymmetric $d$$+$Au system, the $N_{qp}$ model reproduces the data while the AQM does not.

   nucl-exNPA(2014)·1 citation
2. 02*

   Overview of ALICE Results at Quark Matter 2014

   Jan Fiete Grosse-Oetringhaus (for the ALICE collaboration)🇨🇭

   The results released by the ALICE collaboration at Quark Matter 2014 address topics from identified-particle jet fragmentation functions in pp collisions, to the search for collective signatures in p-Pb collisions to precision measurements of jet quenching with D mesons in Pb-Pb collisions. This paper gives an overview of the contributions (31 parallel talks, 2 flash talks and 80 posters) by the ALICE collaboration at Quark Matter 2014.

   nucl-exhep-exNPA(2014)·18 citations
3. 03*

   Systematic studies of the centrality dependence of soft photon production in Au+Au collision with PHENIX

   Benjamin Bannier🇺🇸

   Since the earliest days of Heavy Ion Physics thermal soft photon radiation emitted during the reaction had been theorized as a smoking gun signal for formation of a quark-gluon plasma and as a tool to characterize its properties. In recent years the existence of excess photon radiation in heavy ion collisions over the expectation from initial hard interactions has been confirmed at both RHIC and LHC energies by PHENIX and ALICE respectively. There the radiation has been found to exhibit elliptic flow $v_2$ well above what can currently be reconciled with a picture of early emission from a plasma phase. During the 2007 and 2010 Au+Au runs PHENIX has measured a high purity sample of soft photons down to $p_T>0.4\text{GeV}/c$ using an external conversion method. We present recent systematic studies by PHENIX from that sample on the centrality dependence of the soft photon yield, and elliptic and triangular flow $v_2$ and $v_3$ in Au+Au collisions which fill in the experimental picture and enable discrimination of competing soft photon production scenarios.

   nucl-exNPA(2014)·13 citations
4. 04*

   Measurement of jet $p_{\mathrm{T}}$ spectra and $R_{\mathrm{AA}}$ in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV with the ALICE detector

   Salvatore Aiola (for the ALICE Collaboration)🇺🇸

   Hard-scattered partons provide an ideal probe for the study of the Quark-Gluon Plasma because they are produced prior to the formation of the QCD medium in heavy-ion collisions. Jet production is therefore susceptible to modifications induced by the presence of the medium ("jet quenching"). Both RHIC and LHC experiments have provided compelling evidence of jet quenching. Jets are reconstructed in ALICE utilizing the central tracking system for the charged constituents and the Electromagnetic Calorimeter for the neutral constituents. Jet spectra are reported for central (0-10%) and semi-central (10-30%) Pb-Pb events at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The nuclear modification factor, determined using a pp baseline measured at the same collisional energy, shows a strong suppression of jet production in central Pb-Pb collisions with the expected centrality ordering. Observations are in qualitative agreement with medium-induced energy loss models. Furthermore, indication of a path-length dependence of jet suppression is inferred from measurements of the yields relative to the orientation of the event plane.

   nucl-exNPA(2014)·13 citations
5. 05*

   Baseline for the cumulants of net-proton distributions at STAR

   Xiaofeng Luo🇨🇳 · Bedangadas Mohanty🇮🇳 · Nu Xu🇺🇸

   We present a systematic comparison between the recently measured cumulants of the net-proton distributions by STAR for 0-5% central Au+Au collisions at $\sqrt{s_{NN}}$=7.7-200 GeV and two kinds of possible baseline measures, the Poisson and Binomial baselines. These baseline measures are assuming that the proton and anti-proton distributions independently follow Poisson statistics or Binomial statistics. The higher order cumulant net-proton data are observed to deviate from all the baseline measures studied at 19.6 and 27 GeV. We also compare the net-proton with net-baryon fluctuations in UrQMD and AMPT model, and convert the net-proton fluctuations to net-baryon fluctuations in AMPT model by using a set of formula.

   nucl-exhep-exhep-lathep-ph+1NPA(2014)·24 citations
6. 06*

   Azimuthal elliptic anisotropy ($v_{{}_2}$) of high-$p_{{}_T}$ direct $\gamma$ in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV

   Ahmed M. Hamed🇺🇸

   Preliminary results from the STAR collaboration for the azimuthal elliptic anisotropy $(v_{{}_2})$ of high transverse momentum ($p_{{}_T}$) direct photons (${\gamma }_{{}_{dir}}$) produced at mid-rapidity ($|{\eta }^{{\gamma }_{{}_{dir}}}|<1$) in Au+Au collisions at center-of-mass energy $\sqrt{s_{{}_{NN}}}=200$~GeV are presented, and compared to the measured $(v_{{}_2})$ of neutral pions (${\pi }^0$) in the same kinematic range. The electromagnetic transverse shower profile is used to distinguish ${\pi }^0$ from direct photons. The measured $v_{{}_2}^{{\gamma }_{{}_{dir}}}(p_{{}_T})$ at high $p_{{}_T}$ ($8<p_{{}_T}^{{\gamma }_{{}_{dir}}}<20$~GeV/$c$) is found to be smaller than that of ${\pi }^0$ and consistent with zero when using the forward detectors in determining the event plane.

   nucl-exJ.Phys.Conf.Ser.(2015)·1 citation
7. 07*

   Present status of nuclear cluster physics and experimental perspectives

   C. Beck (Departement de Recherches Subatomiques, Institut Pluridisciplinaire Hubert Curien, IN2P3-CNRS and Universite de Strasbourg)🇫🇷

   Knowledge on nuclear cluster physics has increased considerably as nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes in light N=Z alpha-like nuclei and the evolution of clustering from stability to the drip-lines are being investigated more and more accurately both theoretically and experimentally. Experimental progresses in understanding these questions were recently examined and will be further revisited in this introductory talk: clustering aspects are, in particular, discussed for light exotic nuclei with a large neutron excess such as neutron-rich Oxygen isotopes with their complete spectrocopy.

   nucl-exnucl-thJ.Phys.Conf.Ser.(2014)·8 citations
8. 08*

   Measuring and interpreting charge dependent anisotropic flow

   Sergei A. Voloshin🇺🇸 · Ronald Belmont🇺🇸

   The Chiral Magnetic Wave (CMW) [1] predicts a dependence of the positive and negative particle elliptic flow on the event charge asymmetry. Such a dependence has been observed by the STAR Collaboration [2]. However, it is rather difficult to interpret the results of this measurement, as well as to perform cross-experiment comparisons, due to the dependence of the observable on experimental inefficiencies and the kinematic acceptance used to determine the net asymmetry. We propose another observable that is free from these deficiencies. It also provides possibilities for differential measurements clarifying the interpretation of the results. We use this new observable to study the effect of the local charge conservation that can mimic the effect of the CMW in charge dependent flow measurements.

   nucl-exnucl-thNPA(2014)·19 citations
9. 09*

   High-$p_{{}_T}$ Direct Photon Azimuthal Correlation Measurements

   Ahmed M. Hamed🇺🇸

   The azimuthal correlations of direct photons (${\gamma }_{{}_{dir}}$) with high transverse momentum ($p_{{}_T}$), produced at mid-rapidity ($|{\eta }^{{\gamma }_{{}_{dir}}}|<1$) in Au+Au collisions at center-of-mass energy $\sqrt{s_{{}_{NN}}}=200$~GeV, are measured and compared to those of neutral pions (${\pi }^0$) in the same kinematic range. The measured azimuthal elliptic anisotropy of direct photon, $v_{{}_2}^{{\gamma }_{{}_{dir}}}(p_{{}_T})$, at high $p_{{}_T}$ ($8<p_{{}_T}^{{\gamma }_{{}_{dir}}}<20$~GeV/$c$) is found to be smaller than that of ${\pi }^0$ and consistent with zero when using the forward detectors ($2.4<|\eta |<4.0$) in reconstructing the event plane. The associated charged hadron spectra recoiled from ${\gamma }_{{}_{dir}}$ show more suppression than those recoiled from ${\pi }^0$ $(I_{AA}^{{\gamma }_{{}_{dir}}-h^{\pm }}<I_{AA}^{{\pi }^0-h^{\pm }})$ in the new measured kinematic range $12<p_{{}_T}^{{\gamma }_{{}_{dir}},{\pi }^0}<24$~GeV/$c$ and $3<p_{{}_T}^{assoc}<24$~GeV/$c$.

   nucl-exNPA(2014)·4 citations
10. 10*

    RFQ Cooler SHIRaC developent

    Ramzi Boussaid

    The development of a new RFQ Cooler, named SHIRaC, was carried out to handle and cool typical SPIRAL 2 beams of large emittances (up to 80 {\pi}.mm.mrad) and high currents (up to 1 {\micro}A). SHIRaC is a part of SPIRAL 2 facility at GANIL laboratory in France. Its purposes are to enhance as much as possible the beam quality: transverse geometric emittance of less than 3 {\pi}.mm.mrad and a longitudinal energy spread close to 1 eV, and to transmit more than 60 % of ions. Numerical simulations and experimental studies have shown that the required beam quality can be reached only in the term of the emittance. The energy spread is very far from expected values. It is sensitive to the space charge and buffer gas diffusion and more importantly to the RF field derivative effect. The latter arises at the RFQ exit and increases with the following RF parameters: the frequency and the amplitude of the RF voltage applied to the RFQ electrodes. Studies allowing to enhance the cooled beam quality, mainly the energy spread reduction, are presented and discussed along this paper. They consist in implementing a miniature RFQ at the RFQ exit. Using the development of these studies, it becomes possible to enhance the cooled beam quality and to reach 1 eV of longitudinal energy spread and less than 1.8 {\pi}.mm.mrad of transverse geometric emittance for beam currents going up to 1 {\micro}A. The transport of the cooled beam from the exit of the extraction section towards a HRS has been done with an electrostatic quadrupole triplet. Simulations and first experimental tests showed that more than 95 % of cooled beams can reach the HRS. Finally, developments related to the nuclearization protection methods aimed to avoid the escape of any nuclear matter from the SHIRaC beamline are studied

    ↳ physics.acc-phnucl-ex0 citations
11. 11*

    Is $d^{\ast }$ a candidate of hexaquark-dominated exotic state?

    F. Huang🇨🇳 · Z. Y. Zhang🇨🇳 · P. N. Shen🇨🇳 · W. L. Wang🇨🇳

    We confirm our previous prediction of a $d^{\ast }$ state with $I(J^P)=0(3^{+})$ [Phys. Rev. C 60, 045203 (1999)] and report for the first time based on a microscopic calculation that $d^{\ast }$ is a hexaquark dominated exotic state as it has about 2/3 hidden color (CC) configurations. By performing a more elaborate dynamical coupled-channels investigation of the $\Delta \Delta$-CC system within the framework of resonating group method (RGM) in a chiral quark model, we found that the $d^{\ast }$ state has a mass of about 2.38-2.42 GeV, a root-mean-square radius (RMS) of 0.76-0.88 fm, and a CC fraction of 66%-68%. The last ensures that the $d^{\ast }$ has a rather narrow width which, together with the quantum numbers and our calculated mass, is consistent with the newly observed resonance-like structure ($M\approx 2380$ MeV, $\Gamma \approx 70$ MeV) in double-pionic fusion reactions reported by WASA-at-COSY Collaboration.

    ↳ nucl-thhep-phnucl-exCPC(2015)·75 citations
12. 12*

    Mirror symmetry breaking in He isotopes and their mirror nuclei

    Takayuki Myo🇯🇵 · Kiyoshi Kato

    We study the mirror symmetry breaking of ${}^6$He-${}^6$Be and ${}^8$He-${}^8$C using the ${}^4$He + $X$N ($X$=2, 4) cluster model. The many-body resonances are treated for the correct boundary condition using the complex scaling method. We find that the ground state radius of ${}^8$C is larger than that of ${}^8$He due to the Coulomb repulsion in ${}^8$C. On the other hand, the $0_2^{+}$ resonances of the two nuclei exhibit the inverse relation; the ${}^8$C radius is smaller than the ${}^8$He radius. This is due to the Coulomb barrier of the valence protons around the ${}^4$He cluster core in ${}^8$C, which breaks the mirror symmetry of the radius in the two nuclei. A similar variation in the radius is obtained in the mirror nuclei, ${}^6$He and ${}^6$Be. A very large spatial extension of valence nucleons is observed in the $0_2^{+}$ states of ${}^8$He and ${}^8$C. This property is related to the dominance of the $(p_{3/2}{)}^2(p_{1/2}{)}^2$ configuration for four valence nucleons, which is understood from the reduction in the strength of the couplings to other configurations by involving the spatially extended components of valence nucleons.

    ↳ nucl-thnucl-exPTEP(2014)·12 citations
13. 13*

    Heavy Flavor Dynamics in QGP and Hadron Gas

    Shanshan Cao🇺🇸 · Guang-You Qin🇨🇳 · Steffen Bass🇺🇸

    We study heavy flavor evolution in the quark-gluon plasma matter and the subsequent hadron gas created in ultrarelativistic heavy-ion collisions. The motion of heavy quarks inside the QGP is described using our modified Langevin framework that incorporates both collisional and radiative energy loss mechanisms; and the scatterings between heavy mesons and the hadron gas are simulated with the UrQMD model. We find that the hadronic interaction further suppresses the $D$ meson $R_{\mathrm{AA}}$ at high $p_{\mathrm{T}}$ and enhances its $v_2$. And our calculations provide good descriptions of experimental data from both RHIC and LHC. In addition, we explore the heavy-flavor-tagged angular correlation functions and find them to be a potential candidate for distinguishing different energy loss mechanisms of heavy quarks inside the QGP.

    ↳ nucl-thnucl-exNPA(2014)·15 citations
14. 14*

    First Measurement of Neutrino and Antineutrino Coherent Charged Pion Production on Argon

    R. Acciarri🇺🇸 · C. Adams🇺🇸 · J. Asaadi🇺🇸 · B. Baller🇺🇸 · T.Bolton🇺🇸 · C. Bromberg🇺🇸 · F. Cavanna🇺🇸 · E. Church🇺🇸 · D. Edmunds🇺🇸 · A. Ereditato🇨🇭 · S. Farooq🇺🇸 · B. Fleming🇺🇸 and 20 other authors

    We report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be $2.6_{-1.0}^{+1.2}(stat{)}_{-0.4}^{+0.3}(syst)\times 10^{-38}{\text{cm}}^2/\text{Ar}$ for neutrinos at a mean energy of $9.6$ GeV and $5.5_{-2.1}^{+2.6}(stat{)}_{-0.7}^{+0.6}(syst)\times 10^{-39}{\text{cm}}^2/\text{Ar}$ for antineutrinos at a mean energy of $3.6$ GeV.

    ↳ hep-exnucl-exPRL(2014)·81 citations
15. 15*

    Properties of Thermal Photons at RHIC and LHC

    R. Rapp🇺🇸 · H. van Hees🇩🇪 · M. He🇨🇳

    We study the emission characteristics of thermal photons at RHIC and LHC as affected by both the space-time evolution of the bulk medium and the thermal emission rates. For the former we compare the results of two evolution models (expanding fireball and hydrodynamics). For the latter, we detail the influence of hadronic emission components and study a speculative scenario by upscaling the default QGP and hadronic rates around the pseudo-critical region.

    ↳ nucl-thhep-phnucl-exNPA(2014)·20 citations
16. 16*

    Clustering structure of nuclei in deep inelastic processes

    M. Hirai🇯🇵 · S. Kumano🇯🇵 · K. Saito🇯🇵 · T. Watanabe🇯🇵

    A clustering aspect is explained for the ${}^9$Be nucleus in charged-lepton deep inelastic scattering. Nuclear modifications of the structure function $F_2$ are studied by the ratio $R_{\mathrm{EMC}}=F_2^A/F_2^D$, where $A$ and $D$ are a nucleus and the deuteron, respectively. In a JLab experiment, an unexpectedly large nuclear modification slope $|d{R}_{\mathrm{EMC}}/dx|$ was found for ${}^9$Be, which could be related to its clustering structure. We investigated a mean conventional part of a nuclear structure function $F_2^A$ by a convolution description with nucleon momentum distributions calculated by antisymmetrized (or fermionic) molecular dynamics (AMD) and also by a simple shell model. We found that clustering effects are small in the conventional part, so that the JLab result could be associated with an internal nucleon modification or a short-range nuclear correlation which is caused by high densities due to cluster formation.

    ↳ hep-phhep-exnucl-exnucl-thJ.Phys.Conf.Ser.(2014)·0 citations
17. 17*

    Event activity dependence of inclusive J/{\psi} production in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with ALICE at the LHC

    Igor Lakomov (for the ALICE collaboration)🇫🇷

    Studying p-Pb collisions at LHC energies allows a quantitative evaluation of the cold nuclear matter (CNM) effects. Event activity dependence of the J/{\psi} production is under intense studies both theoretically and experimentally and is expected to provide important insights on the influence of CNM. This paper presents the first results on event activity dependence of the inclusive J/{\psi} production at backward (-4.46 < $y_{cms}$ < -2.96) and forward (2.03 < $y_{cms}$ < 3.53) rapidity in ALICE for p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.

    ↳ hep-exnucl-exNPA(2014)·24 citations
18. 18*

    Universal parameterization of initial-state fluctuations and its applications to event-by-event anisotropy

    Li Yan🇫🇷 · Jean-Yves Ollitrault🇫🇷 · Art M. Poskanzer🇺🇸

    We propose Elliptic Power and Power parameterizations for the probability distribution of initial state anisotropies in heavy-ion collisions. By assuming a linear eccentricity scaling, the new parameterizations can also be applied to fluctuations of harmonic flow. In particular, we analyze flow multi-particle cumulants and event-by-event distributions, both of which are recently measured at the LHC.

    ↳ nucl-thhep-phnucl-exNPA(2014)·3 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.