Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session DL: Mini-Symposium: Collectivity from Small to Large Colliding Systems |
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Chair: Tetsufumi Hirano, Sophia University Room: Hilton Queen's 5 |
Thursday, October 25, 2018 9:00AM - 9:30AM |
DL.00001: Dynamical modeling from small to large colliding systems Invited Speaker: Koichi Murase In this talk, recent development of dynamical modeling of high-energy nuclear collisions, including large colliding systems such as Pb+Pb as well as small systems such as p+Pb, d+Au, 3He+Au, p+p, etc., will be reviewed. After collective behavior was experimentally found in small colliding systems, dynamical models have been extended to investigate the origin of the collectivity in the small systems. For the large systems, flow fluctuations are measured in detail through event-plane decorrelation, flow correlation, etc. To establish a consistent understanding on collectivity from small to large systems, we need to develop dynamical models that can describe various sizes of systems in a consistent way. The fluctuations in final observables are understood mainly by the initial state fluctuations. While event-by-event distributions of wounded nucleon positions are important in the large systems, fluctuations of proton shape and structure become important in the initial state of the small systems. The effects of longitudinal initial fluctuations to flow decorrelation are investigated as well. Also, in the small systems, non-flow contributions to observables, which are the effects from the non-equilibrated components of the system such as jets, become relatively important since the fluid size and lifetime are smaller compared to the large systems. The core-corona picture can be used to separate the system into the equilibrated matter which is described by hydrodynamics (core), and the other parts described by some microscopic models (corona). Recently several dynamical initial state models are proposed to describe such heterogeneous systems consistently, which are also important in lower energy collisions for high-baryon density. Other sources of flow fluctuations and correlations include hydrodynamic fluctuations, i.e., the thermal fluctuations of hydrodynamics, medium response to jets and mini-jets, etc. |
Thursday, October 25, 2018 9:30AM - 9:45AM |
DL.00002: Effects of hydrodynamic fluctuations in heavy ion collisions Azumi Sakai, Koichi Murase, Tetsufumi Hirano Fluctuations have been playing an important role in understanding observables in high-energy nuclear collisions. For example, event-by-event initial fluctuations of transverse profiles are discussed to understand higher harmonics of azimuthal angle distributions. Recently, to understand the rapidity decorrelation, initial fluctuations in longitudinal direction and thermal fluctuations during hydrodynamic evolution of the QGP fluids are studied. In this presentation, we focus on the effect of thermal fluctuations on rapidity decorrelation. We employ an integrated dynamical model which combines full three-dimensional relativistic hydrodynamics with a Monte-Carlo version of the Glauber model for event-by-event initialization and the hadronic cascade model in the late rescattering stage. By using this model, we first tune initial parameters and transport coefficients to reproduce pseudorapidity distribution, and centrality dependence of integrated elliptic flow coefficients in Pb+Pb collisions at the LHC energy. We next analyze the n-th order factorization ratios, which quantify rapidity decorrelation. By switching on and off hydrodynamic fluctuations in the hydrodynamic stage, we see how hydrodynamic fluctuations affect rapidity decorrelation. |
Thursday, October 25, 2018 9:45AM - 10:00AM |
DL.00003: Comparisons between p+p and p+A at forward rapidity at STAR Branden Summa The Solenoid Tracker at RHIC (STAR) experiment has already released preliminary results for transverse single spin asymmetries ( AN) for π0 production, comparing proton-proton (p+p) and proton-gold (p+Au) collisions at forward rapidity (η∼3.0) at √s =200 GeV. This presentation will include an update on related studies of the ratio of the p+p and p+Au cross sections in the same kinematic region as the previous AN measurements, using data from the STAR Forward Meson Spectrometer (FMS). The data were from the 2015 RHIC run to study p+p, p+Au, and p+Al collisions. The presentation will discuss progress toward a measurement of cross section ratios between p+p and p+A. The asymmetry measurements and associated cross section ratios may provide insight into nuclear modification in the kinematic region where gluon saturation effects might be present. |
Thursday, October 25, 2018 10:00AM - 10:15AM |
DL.00004: Hydrodynamic collectivity and viscosities in high-energy heavy-ion collisions Chiho Nonaka Using our developed new relativistic viscous hydrodynamics code, we investigate the temperature dependence of shear and bulk viscosities from comparison with the ALICE data; single particle spectra and collective flows at Pb+Pb $\sqrt{s_{\rm NN}}=2.76$ TeV collisions at the Large Hadron Collider. Furthermore we apply our hydrodynamic model to the small systems such as p+p and p+Pb collisions We find that from the comprehensive analyses of centrality dependence of single particle spectra and collective flows, we can extract the detailed information of the QGP bulk property, without being smeared by the final state interactions. and discuss applicability of the hydrodynamics to the systems from quantitative analyses of single particle spectra and collective flows. |
Thursday, October 25, 2018 10:15AM - 10:30AM |
DL.00005: Long range angular correlations in p-Pb collisions with ALICE Yuko Sekiguchi Measurements of particle correlations as a function of relative azimuthal angle |
Thursday, October 25, 2018 10:30AM - 10:45AM |
DL.00006: Strangeness enhancement at the LHC energies from dynamical core-corona initialization Kanakubo Yuuka, Michito Okai, Yasuki Tachibana, Tetsufumi Hirano We study the enhancement of yields of strange and multi-strange baryons in small and large colliding systems. We previously proposed an idea of dynamically initializing hydrodynamic fields by utilizing source terms in hydrodynamic equations [1]. In this study, we further introduce the core-corona picture by considering spatial density of the initially produced partons. Under this idea, we calculate the ratios of strange hadron yields to charged pion yields as functions of multiplicity and compare our results with the ALICE data [2]. Our results describe the tendencies of increasing behavior of the ratios seen in ALICE data. From this analysis, we find the ALICE data indicate a continuous change of hadronization process from string fragmentation to particlization from fluids as a function of multiplicity. |
Thursday, October 25, 2018 10:45AM - 11:00AM |
DL.00007: PHENIX results on elliptic and triangular flow with geometry-engineered small systems at 200 GeV Sylvia Irene Morrow To investigate the role of the initial spatial distribution of the collision system in driving final-state particle distributions, RHIC operated with three different collision species, p/d/3He+Au, which have intrinsic circularity, ellipticity, and triangularity, respectively, at 200 GeV center-of-mass energy. We present the 5% most central events in each system which were analyzed using the event plane method to determine the flow coefficients, vn, for the second and third harmonics. To investigate the role of the local particle density, we also study the flow correlations comparing these systems for events with the same average number of participants. |
Thursday, October 25, 2018 11:00AM - 11:15AM |
DL.00008: Di-hadron correlations with event shape engineering in Au+Au collisions at STAR Ryo Aoyama Jets present excellent probes to study the properties of the Quark Gluon Plasma in relativistic heavy ion collisions. |
Thursday, October 25, 2018 11:15AM - 11:30AM |
DL.00009: Gluon saturation search using photon+hadron correlations in LHCb Cesar Luiz Da Silva Gluon saturation in high-energy collisions is expected to explain several observations in nuclear collisions such as particle collectivity and depleted yields of particle coming from soft gluons. Previous DIS results from HERA show a fast increase of gluons as their fractional momentum x decreases. The size of gluons is inversely proportional to the Q^2 scale of the process. The saturation scale Qs^2(x) is still to be determined experimentally. The LHCb experiment is a forward spectrometer with vertexing, tracking, p, K, pi, e, mu identification and calorimetry in the region 1.6<eta<4.9. LHCb is the only experiment in the world which can probe x between 1e-6 and 1e-4, up to two orders of magnitude smaller than HERA. A direct probe of gluons can be performed with photon+hadron correlation measurements. This talk is going to report the status of the analysis efforts aimed of finding evidences of gluon saturation and its scale Qs^2(x) at LHCb. Future improvements in these measurements with additional triggers and a soft particle tracker in LHCb are also going to be discussed.
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