Quark Matter 2018

Session

Initial state physics and approach to equilibrium

14 May 2018, 16:30

Sala Volpi, 1st Floor (Palazzo del Casinò)

Conveners

Initial state physics and approach to equilibrium: I

• Bolek Wyslouch (Massachusetts Inst. of Technology (US))

Initial state physics and approach to equilibrium: II

• Kari J. Eskola (University of Jyvaskyla)

Initial state physics and approach to equilibrium: III

• Peter Alan Steinberg (Brookhaven National Laboratory (US))

474. Measurement of exclusive Upsilon photoproduction off protons in pPb collisions at sqrt(s_NN) = 5.02 TeV with CMS

Ruchi Chudasama (Bhabha Atomic Research Centre (IN))

14/05/2018, 16:30

Initial state physics and approach to equilibrium

Parallel Talk

Exclusive photoproduction of Upsilon(nS) meson states off protons is measured in ultraperipheral pPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The measurement is carried out in the $\Upsilon (nS)\to\mu^+\mu^-$ decay modes, with data collected by the CMS experiment corresponding to an integrated luminosity of $32.6$~nb$^{-1}$. Differential cross sections, as a function...

725. Breaking Boost Invariance: IP-Glasma Phenomenology Beyond 2D

Scott McDonald (McGill University)

14/05/2018, 16:50

Initial state physics and approach to equilibrium

Parallel Talk

We present a novel formulation of the IP-Glasma initial state model in 3+1D, where the 2D boost invariant IP-Glasma is generalized to 3D through JIMWLK rapidity evolution of the pre-collision Wilson lines [1]. By breaking boost invariance, the 3D model no longer trivially satisfies Gauss' law at the initial time, and we now enforce it locally. We compare the time evolution of the...

140. Nonequilibrium quark production in the expanding QCD plasma

Naoto Tanji (ECT*)

14/05/2018, 17:10

Initial state physics and approach to equilibrium

Parallel Talk

In the high-energy limit of heavy-ion collisions, the system right after a collision is described as an over-occupied gluon plasma expanding in the beam direction. Its space-time evolution can be studied by means of real-time lattice gauge theory simulation techniques with dynamical quarks. To find observable consequences of such nonequilibrium evolution, the understanding of quark dynamics is...

35. Charmonium production in ultra-peripheral heavy-ion collisions at LHCb

Albert Bursche (Universita e INFN, Cagliari (IT))

14/05/2018, 17:30

Initial state physics and approach to equilibrium

Parallel Talk

At the LHC, in ultra-peripheral heavy-ion collisions the highly boosted electromagnetic field of the Pb ions represents a source of quasi-real photon. Vector meson photo-production measurements in p-Pb (Pb-Pb) collisions are sensitive to the gluon parton distribution functions in the proton
(nucleus). LHCb results on charmonium production in ultra-peripheral p-Pb and Pb-Pb collisions will be...

479. Measurements of nuclear parton distribution functions using dijets, forward jets, and photo-nuclear jets at the CMS detector

Prof. Daniel Tapia Takaki (University of Kansas)

14/05/2018, 17:50

Initial state physics and approach to equilibrium

Parallel Talk

Measurements of dijet production and photo-nuclear interactions in heavy-ion collisions probe several nuclear mechanisms. In particular, dijet measurements in pPb collisions have been shown to be one of the most important tools for constraining the gluon nuclear parton distribution functions (PDFs) at large Bjorken-x. Dijet production in pp and pPb collisions at a nucleon-nucleon centre-of-...

359. Charmonium photoproduction in ultraperipheral and peripheral Pb-Pb collisions with ALICE at the LHC

Christoph Mayer (Polish Academy of Sciences (PL))

14/05/2018, 18:10

Initial state physics and approach to equilibrium

Parallel Talk

The electromagnetic field of relativistic heavy ions can be described by a flux of virtual photons. In ultraperipheral collisions (UPC), where the impact parameter is larger than the sum of nuclei radii, the interaction of these photons with the nucleus can provide insight into its structure and allow us to probe nuclear shadowing via photoproduction of charmonia.

Extensive efforts on this...

38. Prompt photon production in p-Pb collisions at $\sqrt{s_{NN}}=5$TeV

Thomas Julian Boettcher (Massachusetts Inst. of Technology (US))

15/05/2018, 11:10

Initial state physics and approach to equilibrium

Parallel Talk

At very small fractional momentum of the nucleon, the increase of the gluon density is expected to saturate, but no experimental measurements have yet shown this saturation effect without ambiguity. Measurements of prompt photon production at forward rapidity in p-Pb collisions represent suitable tests for the onset of the gluon saturation.
The LHCb experiment is well suited for prompt photon...

588. Collision System Dependence of Anisotropic Flow, Flow Fluctuations and Mixed Harmonic Correlations at STAR Energies

Niseem Abdelrahman"Magdy" (Stony Brook University)

15/05/2018, 11:30

Initial state physics and approach to equilibrium

Parallel Talk

We present new symmetric cumulant measurements, as well as two-, four- and six-particle $v_n$ measurements (and their ratios) for charged and particle identified hadrons. These measurements will be presented for a broad range of transverse momenta and centrality intervals in U+U collisions at $\sqrt{s_{NN}}$= 193 GeV and Au+Au, Cu+Au, Cu+Cu, d+Au and p+Au collisions at $\sqrt{s_{NN}}$=200 GeV....

227. Measurements of the photo-production of jets in ultra-peripheral heavy ion collisions with the ATLAS detector at the LHC

Peter Alan Steinberg (Brookhaven National Laboratory (US))

15/05/2018, 11:50

Initial state physics and approach to equilibrium

Parallel Talk

Ultra-peripheral heavy ion collisions occur when the nuclei have large impact parameter and interact through photon-induced reactions. These include processes in which an energetic photon emitted by one nucleus resolves the partonic structure of the other and stimulates jet production. Much like deep inelastic scattering, such processes provide a clean probe of the nuclear parton...

325. Hadronic observables in small collisions systems from classical Yang-Mills dynamics + Lund string fragmentation

Prithwish Tribedy (Brookhaven National Lab)

15/05/2018, 12:10

Initial state physics and approach to equilibrium

Parallel Talk

We present calculations of hadron production from gluon dominated non-equilibrium matter in various small collision systems using the IP-Glasma model combined with a state-of-the-art fragmentation prescription based on the Lund model. We study bulk observables such as particle spectra, nuclear modification factors (R_{pA}), proton-to-pion ratios and multi-particle azimuthal angular...

610. Isolated photon production in proton-nucleus collisions at forward rapidity

Tuomas Lappi (University of Jyvaskyla)

15/05/2018, 12:30

Initial state physics and approach to equilibrium

Parallel Talk

We calculate isolated photon production at forward rapidities in proton-nucleus collisions in the Color Glass Condensate framework [1]. Our calculation uses dipole cross sections solved from the running coupling Balitsky-Kovchegov equation with an initial condition fit to deep inelastic scattering data and extended to nuclei with an optical Glauber procedure that introduces no additional...

362. Forward particle production in proton-nucleus collisions at next-to-leading order: solving the running-coupling puzzle

Bertrand Ducloue (IPhT Saclay)

15/05/2018, 12:50

Initial state physics and approach to equilibrium

Parallel Talk

Reaching next-to-leading order (NLO) accuracy in perturbative calculations of particle production in QCD at high energy is essential for reliable phenomenological applications. In recent years, the Color Glass Condensate effective theory (the natural framework for such calculations) has indeed been promoted to NLO accuracy. However, the first NLO calculations met with unexpected difficulties,...

570. PHENIX study of the initial state with forward hadron measurements in 200 GeV p(d)+A and $^{3}$He$+$Au collisions

Dr Jason Bryslawskyj

16/05/2018, 16:50

Initial state physics and approach to equilibrium

Parallel Talk

Forward hadron measurements in p(d)+A provide a signal to study nuclear
shadowing, initial state energy loss and/or gluon saturation effects as a function of rapidity, centrality and energy. High $p_T$ identified $\pi^{0}$ measurements are also an essential first step toward measuring prompt photon production. The $\pi^{0}$ measurements are enabled by the PHENIX MPC-EX detector, a Si-W...

393. ALICE results on system-size dependence of the charged-particle multiplicity density in p-Pb, Pb-Pb and Xe-Xe collisions

Beomkyu Kim (Inha University (KR))

16/05/2018, 17:10

Initial state physics and approach to equilibrium

Parallel Talk

Particle production at LHC energies involves the interplay of perturbative (hard) and non-perturbative (soft) QCD processes. Global variables, such as the charged particle multiplicity, related to the initial geometry and the energy density produced in the collision, are important observables to characterize relativistic heavy-ion collisions and to constrain model calculations.
The LHC has...

230. Energy and system size dependence of the subnucleonic fluctuations

Dr Heikki Mäntysaari (University of Jyväskylä)

16/05/2018, 17:30

Initial state physics and approach to equilibrium

Parallel Talk

Understanding the geometric eventy-by-event distribution of gluons in protons and nuclei is a fundamentally interesting task. Moreover, their fluctuating structure has a significant effect on the outcome of hydrodynamical simulations of e.g. proton-nucleus collisions. Thus, it is of utmost interest to determine both the average geometrical structure, and its event-by-event fluctuations, for...

506. Multiplicity and transverse energy measurements from pp, pPb, PbPb and XeXe collisions with the CMS experiment

Ran Bi (Massachusetts Inst. of Technology (US))

16/05/2018, 17:50

Initial state physics and approach to equilibrium

Parallel Talk

One of Richard Feynmans shortest and most cited papers concerns his prediction that for very high energy collisions, the analyticity condition for quantum fields should cause the fragmentation of a nuclear target to become independent of the collision energy. CMS has measured the pseudrapidity dependence of charged hadron multiplicity and transverse energy for a wide range of energies and...

306. Thermalization and hydrodynamics in Bjorken and Gubser flows

Ulrich Heinz (The Ohio State University)

16/05/2018, 18:10

Initial state physics and approach to equilibrium

Parallel Talk

Rapid and strongly anisotropic expansion throughout its evolution keeps the hot and dense medium created in relativistic heavy-ion collisions from ever reaching a state of local momentum isotropy and thermal equilibrium. Still, hydrodynamic descriptions of heavy-ion collisions are phenomenologically very successful. To elucidate the origin of this success we explore exactly solvable...

71. Forward di-hadron back-to-back correlations in p+A collisions at RHIC and the LHC

Cyrille Marquet (CPHT - Ecole Polytechnique)

16/05/2018, 18:30

Initial state physics and approach to equilibrium

Parallel Talk

The suppression of the away-side peak in azimuthal correlations of forward di-hadrons in d+Au vs. p+p collisions observed at RHIC remains one of the most striking experimental evidences supporting the saturation regime of quantum chromodynamics. Within the Color Glass Condensate (CGC) framework, we improve the state-of-the-art description of this observable, by deriving a cross section for the...