Mon·Apr 17, 2017Monday·April 17, 2017

1. 01*

   Beam energy dependence of $d$ and $\bar{d}$ productions in Au+Au collisions at RHIC

   Ning Yu (for the STAR Collaboration)🇨🇳

   Light nuclei have much smaller binding energy compared to the temperature of the system created in heavy-ion collisions. Consequently, the distributions of light nuclei can be used to probe the freeze-out properties, such as correlation volume and local baryon density of the medium created in high-energy nuclear collisions. In this paper, we report the results of deuteron and anti-deuteron production in Au+Au collision at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by STAR at RHIC. The collision energy, centrality and transverse momentum dependence of the coalescence parameter $B_2$ for deuteron and anti-deuteron production are discussed. We find the values of $B_2$ for anti-deuteron are systematically lower than those for deuterons indicating the correlation volume of anti-baryon are larger than that of baryon. In addition, the values of $B_2$ are found to decrease with increasing collision energy and reach a minimum around $\sqrt{s_{\mathrm{NN}}}$ = 20 GeV implying a change of the equation of state of the medium in these collisions.

   nucl-exhep-exNPA(2017)·14 citations
2. 02*

   ${\Lambda }_c$ Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV measured by the STAR experiment

   Guannan Xie (for the STAR Collaboration)🇨🇳

   At RHIC, enhancements in the baryon-to-meson ratio for light hadrons and hadrons containing strange quarks have been observed in central heavy-ion collisions compared to those in p+p and peripheral heavy-ion collisions in the intermediate transverse momentum ($p_T$) range (2 $<$ $p_T$ $<$ 6 GeV/$c$). This can be explained by the hadronization mechanism involving multi-parton coalescence. ${\Lambda }_c$ is the lightest charmed baryon with mass close to that of $D^0$ meson, and has an extremely short life time (c$\tau$$\sim$60 $\mu$m). Different models predict different magnitudes of enhancement in the ${\Lambda }_c$/$D^0$ ratio depending on the degree to which charm quarks are thermalized in the medium and how the coalescence mechanism is implemented. In these proceedings, we report the first measurement of ${\Lambda }_c$ production in heavy-ion collisions using the Heavy Flavor Tracker at STAR. The invariant yield of ${\Lambda }_c$ for 3 $<$ $p_T$ $<$ 6 GeV/$c$ is measured in 10-60% central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The ${\Lambda }_c$/$D^0$ ratio is compared to different model calculations, and the physics implications are discussed.

   nucl-exNPA(2017)·27 citations
3. 03*

   Measurements of ${\Lambda }_c^{+}$ and $D_s^{+}$ productions in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from STAR

   Long Zhou (for the STAR Collaboration)🇨🇳

   We report the first measurement of ${\Lambda }_c^{+}$ (average of ${\Lambda }_c^{+}$ and ${\bar{\Lambda }}_c^{-}$) baryon production and significantly improved measurement of $D_s^{+}$ (average of $D_s^{+}$ and $D_s^{-}$) meson production, within the rapidity range of $\left|y\right|<1$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV from the STAR experiment. The transverse momentum spectra of ${\Lambda }_c^{+}$ and $D_s^{+}$ as well as their yield ratios to that of $D^0$ meson are also presented and compared to theoretical calculations.Both the ${\Lambda }_c^{+}/D^0$ and $D_s^{+}/D^0$ ratios are found to be significantly enhanced in Au+Au collisions with respect to those in p+p collisions predicted by PYTHIA. A model calculation including coalescence hadronization and thermalized charm quarks is consistent with the measured ${\Lambda }_c^{+}/D^0$ ratio. On the other hand, the TAMU model seems to underestimate the $D_s^{+}/D^0$ ratio measured in Au+Au collisions in the applicable kinematic region.

   nucl-exNPA(2017)·44 citations
4. 04*

   Study of cold and hot nuclear matter effects on jets with direct photon triggered correlations from PHENIX

   J. D. Osborn (for the PHENIX Collaboration)🇺🇸

   Direct photons, being colorless objects, provide an unmodified control particle that can be used in conjunction with jets to probe the quark-gluon plasma. To leading order the direct photon momentum balances the momentum of opposing jets and can therefore provide a clean handle on the jet energy. Therefore, angular correlations with direct photons provide a mechanism to study the fragmentation of the opposing jet without performing jet reconstruction. Jet fragmentation modification has been measured previously in PHENIX in central Au+Au collisions. Recent RHIC runs offer the potential to study these observables in heavy ion collisions with greater statistics and over different collision systems including asymmetric collision geometries. In this talk we present results of isolated direct photon-triggered correlations in d+Au collisions and discuss the constraints of cold nuclear matter effects on the fragmentation functions. We also present the latest results with higher statistics on direct photon-triggered correlations in Au+Au collisions including differential measurements of fragmentation function modification. Finally, we present the status of the centrality and collision species dependence of these observables, including comparisons to related dihadron correlations. Together these results can give a view of jet modification going from small to large system size.

   nucl-exhep-exNPA(2017)·2 citations
5. 05*

   Evolving theoretical descriptions of heavy-ion fusion :from phenomenological to microscopic approaches

   K. Hagino

   We overview the current status of theoretical approaches for heavy-ion fusion reactions at subbarrier energies. We particularly discuss theoretical challenges in the coupled-channels approach, that include i) a description of deep subbarrier hindrance of fusion cross sections, ii) the role of nuclear dissipation, iii) fusion of unstable nuclei, and iv) an interplay between fusion and multi-nucleon transfer processes. We also present results of a semi-microscopic approach to heavy-ion fusion reactions, that combines the coupled-channels approach with state-of-the-art microscopic nuclear structure calculations.

   ↳ nucl-thnucl-exEPJ Web Conf.(2017)·1 citation
6. 06*

   Chiral magnetic effect in isobaric collisions

   Xu-Guang Huang🇨🇳 · Wei-Tian Deng🇨🇳 · Guo-Liang Ma🇨🇳 · Gang Wang🇺🇸

   We give a numerical simulation of the generation of the magnetic field and the charge-separation signal due to the chiral magnetic effect (CME) --- the induction of an electric current by the magnetic field in a parity-odd matter --- in the collisions of isobaric nuclei, ${}_{44}^{96}$Ru + ${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr + ${}_{40}^{96}$Zr, at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. We show that such collisions provide an ideal tool to disentangle the CME signal from the possible elliptic-flow driven background effects. We also discuss some other effects that can be tested by using the isobaric collisions.

   ↳ nucl-thnucl-exNPA(2017)·12 citations
7. 07*

   Characterization of the initial state and QGP medium from a combined Bayesian analysis of LHC data at 2.76 and 5.02 TeV

   Jonah E. Bernhard🇺🇸 · J. Scott Moreland🇺🇸 · Steffen A. Bass🇺🇸

   We perform a global Bayesian analysis of a modern event-by-event heavy-ion collision model and LHC data at $\sqrt{s}$ = 2.76 and 5.02 TeV. After calibration, the model simultaneously describes multiplicity, transverse momentum, and flow data at both beam energies. We report new constraints on the scaling of initial-state entropy deposition and QGP transport coefficients, including a quantitative estimate of the temperature-dependent shear viscosity $(\eta /s)(T)$.

   ↳ nucl-thhep-phnucl-exNPA(2017)·21 citations
8. 08*

   Flow in small and large quark-gluon plasma droplets: the role of nucleon substructure

   J. Scott Moreland🇺🇸 · Jonah E. Bernhard🇺🇸 · Weiyao Ke🇺🇸 · Steffen A. Bass🇺🇸

   We study the effects of nucleon substructure on bulk observables in proton-lead collisions at the LHC using Bayesian methodology. Substructure is added to the TRENTO parametric initial condition model using Gaussian nucleons with a variable number of Gaussian partons. We vary the number and width of these partons while recovering the desired inelastic proton-proton cross section and ensemble averaged proton density. We then run the model through a large number of minimum bias hydrodynamic simulations and measure the response of final particle production and azimuthal particle correlations to initial state properties. Once these response functions are determined, we calibrate free parameters of the model using established Bayesian methodology. We comment on the implied viability of the partonic model for describing hydrodynamic behavior in small systems.

   ↳ nucl-thnucl-exNPA(2017)·13 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.