Mon·Jul 16, 2018Monday·July 16, 2018

1. 01*

   Measurements of directed and elliptic flow for $D^0$ and $\overline{D^0}$ mesons using the STAR detector at RHIC

   Subhash Singha (for the STAR Collaboration)🇺🇸

   We report on the first evidence for a non-zero rapidity-odd directed flow ($v_1$) for $D^0$ and $\overline{D^0}$ mesons in 10-80\% centrality Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200~GeV measured with the STAR detector at RHIC. The slope of the $v_1$ rapidity dependence ($d{v}_1/dy$) averaged over $D^0$ and $\overline{D^0}$ mesons is -0.081 $\pm$ 0.021 $\pm$ 0.017, while that of charged kaons is -0.0030 $\pm$ 0.0001 $\pm$ 0.0002, suggesting significantly larger slope for the $D^0$ mesons. Models indicate that the large $d{v}_1/dy$ of $D^0$ mesons is sensitive to the initially tilted source. We also present a new measurement of the $D^0$ meson elliptic flow ($v_2$) as a function of transverse momentum ($p_T$) in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200~GeV with an improved precision with respect to the previously published results.The $D^0$ $v_2$ results are compared to those of light-flavor hadrons to test the number-of-constituent-quark (NCQ) scaling. Both the $v_1$ and $v_2$ results are compared to recent hydrodynamic and transport model calculations.

   nucl-exhep-exhep-phnucl-thNPA(2019)·7 citations
2. 02*

   Factorization of two-particle distributions in AMPT simulations of Pb-Pb collisions at $\sqrt{{\mathbf{s}}_{\text{NN}}}$ = 5.02 TeV

   Christian Bourjau (for the ALICE Collaboration)🇩🇰

   The flow ansatz states that the single-particle distribution of a given event can be described in terms of the complex flow coefficients $V_n$. Multi-particle distributions can therefore be expressed as products of these single-particle coefficients; a property commonly referred to as factorization. The amplitudes and phases of the coefficients fluctuate from event to event, possibly breaking the factorization assumption for event-sample averaged multi-particle distributions. Furthermore, non-flow effects such as di-jets may also break the factorization assumption. The factorization breaking with respect to pseudorapidity $\eta$ provides insights into the fluctuations of the initial conditions of heavy ion collisions and can simultaneously be used to identify regions of the phase space which exhibit non-flow effects. These proceedings present a method to perform a factorization of the two-particle Fourier coefficients $V_{n\Delta }({\eta }_a,{\eta }_b)$ which is largely independent of detector effects. AMPT model calculations of Pb-Pb collisions at $\sqrt{s_{\text{NN}}}=5.02$ TeV are used to identify the smallest $|\Delta \eta |$-gap necessary for the factorization assumption to hold. Furthermore, a possible $\Delta \eta$-dependent decorrelation effect in the simulated data is quantified using the empirical parameter $F_2^{\eta }$. The decorrelation effect observed in the AMPT calculations is compared to results by the CMS collaboration for Pb-Pb collisions at $\sqrt{s_{\text{NN}}}=2.76$ TeV.

   nucl-exJ.Phys.Conf.Ser.(2018)·1 citation
3. 03*

   Prompt and non-prompt $J/\psi$ elliptic flow in Pb+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV with the ATLAS detector

   ATLAS Collaboration

   The elliptic flow of prompt and non-prompt $J/\psi$ was measured in the dimuon decay channel in Pb+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV with an integrated luminosity of $0.42{\mathrm{nb}}^{-1}$ with the ATLAS detector at the LHC. The prompt and non-prompt signals are separated using a two-dimensional simultaneous fit of the invariant mass and pseudo-proper decay time of the dimuon system from the $J/\psi$ decay. The measurement is performed in the kinematic range of dimuon transverse momentum and rapidity $9<p_{\mathrm{T}}<30$ GeV, $|y|<2$, and 0-60% collision centrality. The elliptic flow coefficient, $v_2$, is evaluated relative to the event plane and the results are presented as a function of transverse momentum, rapidity and centrality. It is found that prompt and non-prompt $J/\psi$ mesons have non-zero elliptic flow. Prompt $J/\psi$ $v_2$ decreases as a function of $p_{\mathrm{T}}$, while non-prompt $J/\psi$ it is, with limited statistical significance, consistent with a flat behaviour over the studied kinematic region. There is no observed dependence on rapidity or centrality.

   nucl-exhep-exEPJC(2018)·56 citations
4. 04*

   Heavy-flavor nuclear modification factor and event-by-event azimuthal anisotropy correlations in heavy ion collisions

   Caio Alves Garcia Prado🇧🇷

   Relativistic heavy ion collisions, which are performed at large experimental programs such as Relativistic Heavy Ion Collider's (RHIC) STAR experiment and the Large Hadron Collider's (LHC) experiments, can create an extremely hot and dense state of the matter known as the quark gluon plasma (QGP). A huge amount of sub-nucleonic particles are created in the collision processes and their interaction and subsequent evolution after the collision takes place is at the core of the understanding of the matter that builds up the Universe. It has recently been shown that event-by-event fluctuations in the spatial distribution between different collision events have great impact on the particle distributions that are measured after the evolution of the created system. Specifically, these distributions are greatly responsible for generating the observed azimuthal anisotropy in measurements. Furthermore, the eventual cooling and expansion of the fluctuating system can become very complex due to lumps of energy density and temperature, which affects the interaction of the particles that traverse the medium. In this configuration, heavy flavor particles play a special role, as they are generally created at the initial stages of the process and have properties that allow them to retain "memory" from the interactions within the whole evolution of the system. However, the comparison between experimental data and theoretical or phenomenological predictions on the heavy flavor sector cannot fully explain the heavy quarks coupling with the medium and their subsequent hadronization process. [Full abstract in file]

   ↳ nucl-thhep-phnucl-ex2 citations
5. 05*

   Longitudinal fluctuations and decorrelations of anisotropic flows in relativistic heavy-ion collisions

   Xiang-Yu Wu🇨🇳 · Long-Gang Pang🇺🇸 · Guang-You Qin🇨🇳 · Xin-Nian Wang🇨🇳

   We study the longitudinal decorrelations of elliptic, triangular and quadrangular flows in heavy-ion collisions at the LHC and RHIC energies. The event-by-event CLVisc (3+1)-dimensional hydrodynamics model, combined with the fully fluctuating AMPT initial conditions, is utilized to simulate the space-time evolution of the strongly-coupled quark-gluon plasma. Detailed analysis is performed for the longitudinal decorrelations of flow vectors, flow magnitudes and flow orientations. We find strong correlations between final-state longitudinal decorrelations of anisotropic flows and initial-state longitudinal structures and collision geometry: while the decorrelation of elliptic flow shows a non-monotonic centrality dependence due to initial elliptic geometry, typically the longitudinal flow decorrelations are larger in lower energy and less central collisions where the mean lengths of the string structure are shorter in the initial states.

   ↳ nucl-thnucl-exNPA(2019)·2 citations
6. 06*

   PHENIX results on jet modification with ${\pi }^0$- and photon-triggered two particle correlations in $p$$+$$p$, $p(d)$+Au, and Au+Au collisions

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

   As a colorless probe, direct photons balance the $p_T$ of the away-side jet at leading order. Direct photon-hadron correlations are thus an excellent probe for nuclear structure and QCD effects, including parton energy loss in the Quark-Gluon Plasma. PHENIX has measured ${\pi }^0$ and direct photon-triggered two-particle azimuthal correlations in a variety of collision systems ranging from $p$$+$$p$ to Au+Au at 200 GeV. In $p$$+$Au and $d$$+$Au collisions, no modification of the per-trigger jet yield or away-side correlation width compared to $p$$+$$p$ collisions is observed for direct photon triggered correlations while an increase in the away-side width for ${\pi }^0$ triggered correlations in $p$$+$Au has been measured. In Au+Au collisions, direct photons have been identified statistically as well as using an isolation cut. Combining data sets from different collision systems allows us to quantify the transition from suppression at high $z_T$ $(p_{T,h}/p_{T,\gamma })$ to the enhancement of low $z_T$ particles relative to $p$$+$$p$, and to study this transition as a function of trigger $p_T$.

   ↳ hep-exnucl-exNPA(2019)·5 citations
7. 07*

   Theoretical study of the ${\Delta }^{++}-{\Delta }^{-}$ configuration in the deuteron using antiproton beam

   A.B. Larionov🇩🇪 · A. Gillitzer🇩🇪 · J. Haidenbauer🇩🇪 · M. Strikman🇺🇸

   We study the manifestation of the ${\Delta }^{++}-{\Delta }^{-}$ component of the deuteron wave function in the exclusive reaction $\bar{p}d\to {\pi }^{-}{\pi }^{-}{\Delta }^{++}$. Due to the large binding energy the internal motion in the $\Delta -\Delta$ system is relativistic. We take this into account within the light-cone (LC) wave function formalism and, indeed, found large differences between calculations based on the LC and non-relativistic (NR) wave functions. We demonstrate, that the consistent LC treatment of the $\Delta -\Delta$ system plays the key role in the separation of the signal and background. Within the LC approach, the characteristic shape of the momentum distribution of the $\Delta -\Delta$ bound system predicted by the meson-exchange model is well visible on the background of usual annihilations at beam momenta between 10 and 15 GeV/c.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·8 citations
8. 08*

   Dynamical initialization and hydrodynamic modeling of relativistic heavy-ion collisions

   Chun Shen🇺🇸 · Björn Schenke🇺🇸

   We present a fully three-dimensional model providing initial conditions for energy and conserved charge density distributions in heavy ion collisions at RHIC Beam Energy Scan (BES) collision energies. The model includes the dynamical deceleration of participating nucleons or valence quarks. It provides a realistic estimation of the initial baryon stopping during the early stage of collisions. We also present the implementation of the model with 3+1 dimensional hydrodynamics, which involves the addition of source terms that deposit energy and net-baryon densities produced by the initial state model at proper times greater than the initial time for the hydrodynamic simulation. The importance of this dynamical initialization stage on hadronic flow observables at the RHIC BES is quantified.

   ↳ nucl-thhep-phnucl-exNPA(2019)·35 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.