Hot Quarks 2016

12 Sept 2016, 01:00 → 17 Sept 2016, 23:30 US/Eastern

Jana Bielcikova (Acad. of Sciences of the Czech Rep. (CZ)), Rainer Fries (Texas A&M University), Sevil Salur (Rutgers, State Univ. of New Jersey (US))

^7th Workshop for young scientists on the physics of ultrarelativistic nucleus-nucleus collisions

If you would like to attend the workshop please submit your proposed talk topic together with an abstract through the "Submit Abstract" link and upload your contact information by completing the registration form found under the "Registration" link. The deadline is June 3, 2016.

NEW: The proceedings submission deadline is October 31, 2016.

 

Monday, 12 September

08:30 → 12:10 Monday Morning

Convener: Jana Bielcikova (Acad. of Sciences of the Czech Rep. (CZ))

08:30 Welcoming remarks

Speaker: Rainer Fries (Texas A&M University)

08:40 Overview of jet studies

Speaker: Christine Nattrass (University of Tennessee (US))

NattrassHotQuarks2016.pdf

09:15 Event-by-event hydrodynamics + jet energy loss: A solution to the $R_{AA} \otimes v_2$ puzzle

High $p_T > 10$ GeV elliptic flow, which is experimentally measured via the correlation between soft and hard hadrons, receives competing contributions from event-by-event fluctuations of the low $p_T$ elliptic flow and event plane angle fluctuations in the soft sector. In this paper, a proper account of these event-by-event fluctuations in the soft sector, modeled via viscous hydrodynamics, is combined with a jet energy loss model to reveal that the positive contribution from low $p_T$ $v_2$ fluctuations overwhelms the negative contributions from event plane fluctuations. This leads to an enhancement of high $p_T > 10$ GeV elliptic flow in comparison to previous calculations and provides a natural solution to the decade long high $p_T$ $R_{AA} \otimes v_2$ puzzle. We also present the first theoretical calculation of high $p_T$ $v_3$, which is shown to be compatible with current LHC data. Furthermore, we discuss how short wavelength jet-medium physics can be deconvoluted from the physics of soft, bulk event-by-event flow observables using event shape engineering techniques.

Speaker: Jorge Noronha (University of Sao Paulo)

Noronha_hotquarks_2016.pdf

09:35 Direct photon-hadron correlation measurement at RHIC

The study of direct-photon-triggered away-side jets was proposed [1]
as a good probe of parton energy loss because the direct photon
transverse momentum ($p_{T}$) approximates that of recoil parton before
traversing the medium created in heavy-ion collisions. On the other
hand, comparison between the suppression of direct photon- and $\pi^{0}$-
triggered
away-side hadron yields can give information about the path-length and
color-factor dependence of parton energy loss. We report the results of
direct photon-hadron and $\pi^{0}$-hadron azimuthal correlations as a measure of
the away-side jet-like correlated yields in central Au+Au and p+p
collisions at
$\sqrt{s_{NN}}$ 200 GeV in the STAR experiment. The charged-hadron
per-trigger yields at
mid-rapidity ($|\eta| < $1) and for transverse momenta $p_{T}^{assoc} >$ 1.2
GeV/c associated with direct photon and $\pi^{0}$ (for 12 $< p_{T}^{trig} <$ 20 GeV/c)
in central Au+Au
collisions are compared with p+p collisions. The same $z_{T}$
(~$\frac{p_{T}^{assoc}}{p_{T}^{trig}}$) dependence of the suppression is observed for
direct photon and $\pi^{0}$ triggers, within uncertainties. The results are compared with energy-loss-inspired theoretical model predictions.

[1] X.-N. Wang, Z. Huang, and I. Sarcevic, Phys. Rev. Lett. 77, 231
(1996).

Speaker: Dr Nihar Sahoo (Texas A&M University)

hotquarks2016_nihar.pdf

09:55 Coffee break

10:25 Latest results with JEWEL

We present new results with the latest version of the JEWEL monte carlo event generator. The correlation of photons and vector bosons with the jets produced in heavy ion environment at 2.76 TeV and 5 TeV are studied including comparisons with data. These electro weak interacting bosons leave the medium unmodified and hence provide the perfect tool to study the modification of the recoil jets through the medium. Further detailed studies of the modified jet tomographical properties are presented to help us gain both a qualitative and quantitative picture of jet-medium interactions in heavy ion collisions.

Speaker: Raghav Kunnawalkam Elayavalli (Rutgers, State Univ. of New Jersey (US))

HQ_Sept2016_raghav_jewel_v2.pdf

10:45 Jet suppression measurement with the ATLAS detector

In relativistic heavy ion collisions, a hot medium with a high density of unscreened color charges is produced. Jets are produced at the early stages of this collision and are known to become attenuated as they propagate through the hot matter. One manifestation of this energy loss is a lower yield of jets emerging from the medium than expected in the absence of medium effects. Another manifestation of the energy loss is the modification of the dijet balance and the modification of fragmentation functions. In this talk, the latest ATLAS results on single jet suppression, dijet suppression, and modification of the jet internal structure in Pb+Pb collisions will be presented.

Speaker: Radim Slovak (Charles University (CZ))

HotQuarks_SLOVAK_JetSupp.pdf

11:05 Cold nuclear matter effects on jet suppression in heavy-ion collisions

High $p_\mathrm{T}$ jet suppression in ultra-relativistic heavy-ion (AA) collisions is a key signature of the formation of a deconfined phase (QGP).
To attribute this suppression uniquely to a hot and dense QGP medium, reference measurements are necessary to quantify the cold nuclear matter effects.
\par
An ideal way to study the influence of cold nuclear matter on the observed jet yield is to measure jet production in a \ensuremath{\mathrm {p\kern-0.05em A}} reference system. For this purpose, the ALICE Collaboration has collected data at \ensuremath{\sqrt{s_\mathrm{NN}}}=5.02\,TeV in the p--Pb collision system. In this system we have measured charged and full jets ($p_\mathrm{T}$=20-120 and 20-90\,\ensuremath{\mathrm{GeV}\kern-0.05em/\kern-0.02em c}, respectively). We will present their measured yields and their comparison to expectations in \pp from next to leading order (NLO) calculations and scaled \ensuremath{\mathrm {p\kern-0.05em p}} measurements. We observe that the resultant \RpPb ratio is consistent with unity for all centralities.
We have further studied possible cold nuclear matter effects on the jet structure by calculating the ratio of jet yields with different resolution parameters (R = 0.2 and 0.4). This ratio is found to be consistent with that for \ensuremath{\mathrm {p\kern-0.05em p}} collisions at \ensuremath{\sqrt{s_\mathrm{NN}}}=5.02\,TeV from a NLO calculation.
\par
These measurements suggest that in the accessible kinematic range no significant modification of jets is caused by cold nuclear matter effects.
This provides strong support for a hot and deconfined phase being the cause of jet suppression in Pb--Pb collisions at the LHC.

Speaker: Eliane Epple (Yale University)

HotQuarks2016_Epple_V3.pptx

11:25 Discussion session

12:10 → 16:30 Lunch and afternoon break

16:30 → 20:00 Monday afternoon

Convener: Sevil Salur (Rutgers, State Univ. of New Jersey (US))

16:30 Dijet asymmetry in PbPb collisions with the ATLAS detector

The phenomenon of events containing highly asymmetric dijet pairs is one of the most striking results in heavy ion physics. It has provided the first direct observation of in-medium jet energy loss at the LHC. Detailed measurements of centrality-dependent dijet imbalance in sqrt(sNN)=2.76 TeV \PbPb collisions using data collected in the 2011 LHC heavy ion run are presented. The new analysis fully corrects to the particle level. The results show a centrality-dependent modification of the dijet asymmetry distribution accompanied by an unmodified angular correlation between two jets in the dijet system. Detailed studies of the dijet asymmetry as a function of the leading jet transverse momentum and jet radius are presented. The reference measurement of the dijet asymmetry in the \pp collisions at the same center of mass energy is also shown.

Speaker: Laura Brittany Havener (Columbia University (US))

Havener_HotQuarks2016_v5.pdf

16:50 Quark-antiquark antenna splitting in a medium

Estudiamos la configuración en la cuál un par quark-antiquark con un ángulo de apertura fijo emite un gluón dentro del medio, y este mismo gluón realiza una segunda emisión fuera del medio. Los resultados nos permiten discutir los efectos de coherencia de color basándonos en la probabilidad de supervivencia $ \Big(1-\Delta_{med}(t)\Big) $, donde $ \Delta_{med} $ es el parámetro de decoherencia, que nos proporciona información sobre la decoherencia del par $ q \bar{q} $. Este escenario particular nos permite discutir la decoherencia del par debido a las interacciones de color con el medio.

Actualmente estamos trabajando en el cálculo de la emisión de dos gluones (con una primera emisión gluónica de un quark y una segunda emisión gluónica del gluón emitido por el quark) por un quark hard que se propaga a través de un medio.

Speaker: Víctor Vila (Universidade de Santiago de Compostela)

VilaV_Talk.pdf

17:10 Suppression of baryon diffusion in a baryon rich strongly coupled quark-gluon plasma

Five dimensional black hole geometries describing the QCD crossover transition seen in (2+1)-flavor lattice QCD calculations at zero and nonzero baryon densities are used to obtain holographic predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures 130  MeV ≤ T ≤ 300  MeV and baryon chemical potentials 0 ≤ μB ≤ 400  MeV. Diffusive transport is predicted to be suppressed in this region of the QCD phase diagram, which is consistent with the existence of a critical end point at larger baryon densities. We also calculate the fourth-order baryon susceptibility at zero baryon chemical potential and find quantitative agreement with recent lattice results. The baryon transport coefficients computed in this work can be readily implemented in hydrodynamic codes used to investigate the hot and baryon dense QGP produced at RHIC’s beam energy scan.

Speaker: Dr Romulo Rougemont (University of Sao Paulo)

romulo_baryon_diff_HQ2016.pdf

17:30 Coffee break

18:00 Non-equilibrium properties of the QGP with a magnetic field: a holographic approach

Lattice data for the QCD equation of state and magnetic susceptibility at zero magnetic field are used to engineer a holographic system dual to the QGP with a magnetic field near the crossover region. This holographic setup is a five dimensional black hole whose dynamics is given by an Einstein-Maxwell-Dilaton action. Our results for equilibrium quantities such as entropy density and pressure at finite magnetic field are in quantitative agreement with current lattice data. We then proceed to compute how the inclusion of the magnetic field alters the momentum transport (non-equilibrium quantities that are currently out of reach of lattice QCD), such as viscosity and the drag force experienced by a heavy quark, in the QGP.

Speaker: Renato Critelli (University of Sao Paulo - Institute of Physics)

Critelli HotQuarks16 v4.pdf

18:20 Jet quenching in strongly magnetized QGP: pQCD vs. AdS/CFT

We study the jet quenching parameter $\hat q$ of QCD plasma in the presence of strong magnetic field in both weakly and strongly
coupled regimes. In weakly coupled regime, we compute $\hat q$ in perturbative QCD at complete leading order (that is, leading log as well as the constant under the log) in QCD coupling constant $\alpha_s$, assuming the hierarchy of scales $\alpha_s eB\ll T^2\ll eB$.
We consider two cases of jet orientations with respect to the magnetic field: 1) the case of jet moving parallel to the magnetic field, 2) the case jet moving perpendicular to the magnetic field. In the former case, we find $\hat q\sim \alpha_s^2 (eB)T\log(1/\alpha_s)$, while in the latter we have $\hat q\sim \alpha_s^2 (eB)T\log(T^2/\alpha_seB)$. In both cases, this leading order result arises from the scatterings with thermally populated lowest Landau level quarks. In strongly coupled regime described by AdS/CFT correspondence,
we find $\hat q\sim \sqrt{\lambda}(eB)T$ or $\hat q\sim \sqrt{\lambda}\sqrt{eB}T^2$ in the same hierarchy of $T^2\ll eB$ depending on whether the jet is moving parallel or perpendicular to the magnetic field, respectively, which indicates a universal dependence of $\hat q$ on $(eB)T$ in both regimes for the parallel case, the origin of which should be the transverse density of lowest Landau level states proportional to $eB$.
Finally, the asymmetric transverse momentum diffusion in the case of jet moving perpendicular to the magnetic field may give an interesting azimuthal asymmetry of the gluon Bremsstrahlung spectrum in the BDMPS-Z formalism.

Speaker: Kiminad Mamo (University of Illinois at Chicago)

qhatwithB-texas-mamo.pdf

18:40 Jet-Hadron correlations at the LHC with ALICE

The hot, dense and strongly interacting medium known as the Quark Gluon Plasma (QGP) is produced in relativistic heavy-ion collisions at the Large Hadron Collider (LHC). Early in the collisions, quarks and gluons from the incoming nuclei collide to produce high momentum partons which fragment into collimated sprays of hadrons called "jets". In pp collisions, jet production is well understood within the framework of perturbative QCD and acts as a rigorous baseline measurement for jet quenching measurements. Using pp as a reference, we can compare to heavy-ion collision systems, and study the modification of the $p_{T}$ or angular distributions of jet fragments. A recently developed background subtraction method to remove the complex, flow dominated, heavy-ion background will be used in this analysis.
Azimuthal angular correlations of charged hadrons with respect to the axis of a full (charged + neutral) reconstructed 'trigger' jet in Pb--Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV in ALICE will be presented here. The analysis of angular correlations for different orientations of the trigger relative to the event plane allows for the study of the path length dependence of medium modifications to jets. The status of studies of the event plane dependence of angular correlations will be presented.

Speaker: Joel Anthony Mazer (University of Tennessee (US))

HotQuarks_September12_2016_JMazer.pdf

19:00 Discussion session

Tuesday, 13 September

08:30 → 12:00 Tuesday morning

Convener: Hannah Petersen

08:30 Overview of hydrodynamical studies

Speaker: Jacquelyn Noronha-Hostler (University of Houston)

HotQuarks.pdf

09:05 Anisotropic flow and related phenomena in Pb-Pb collisions at $\sqrt{s_\text{NN}} = 5.02$ TeV with ALICE

The ALICE experiment is designed and optimised to study the properties of the Quark-Gluon Plasma (QGP), a new state of matter, which is expected to be created at the high energy densities reached at the LHC. One of the key observables used to characterize the transport properties and the equation of state of the QGP is the azimuthal anisotropy in particle production, which is usually called anisotropic flow. In this presentation, we report the first measurements of anisotropic flow in Pb–Pb collisions at $\sqrt{s_\text{NN}} = 5.02$ TeV, the highest energy ever achieved in heavy–ion collisions, and compare them with both theoretical predictions and experimental measurements at lower energies and other collision systems. This provides a unique opportunity to test the validity of the hydrodynamic paradigm at new energies and to further constraint key transport parameters of the QGP, such as the shear viscosity over entropy ratio.

Speaker: Jacopo Margutti (Utrecht University (NL))

jmargutti_11092016_v1.pdf

09:25 Fluid dynamics for the anisotropically expanding quark-gluon plasma

Local momentum anisotropies become large in the early stages of the quark-gluon plasma created in relativistic heavy-ion collisions, due to the extreme difference in the longitudinal and transverse expansion rates. In such situations, fluid dynamics derived from an expansion around an isotropic local equilibrium state is bound to break down. Instead, we subsume the slowest nonhydrodynamic degree of freedom (associated with the deviation from momentum isotropy) at leading order defining a local anisoptropic quasi-equilibrium state, thereby treating the longitudinal/transverse pressure anisotropy nonperturbatively. Perturbative transport equations are then derived to deal with the remaining residual momentum anisotropies creating a complete transient effective theory called viscous anisotropic hydrodynamics. This approach has been shown to dramatically outperform viscous hydrodynamics in several simplified situations for which exact solutions exits but which share with realistic expansion scenarios the problem of large dissipative currents. We will discuss the present status of applying viscous anisotropic hydrodynamics to the phenomenological description of the quark-gluon plasma in realistic expansion scenarios.

Speaker: Dennis Bazow (The Ohio State University)

Bazow.pdf

09:45 Coffee break

10:15 Quasiparticle anisotropic hydrodynamics for central collisions

We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost- invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasi- particle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results ob- tained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio η/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, η/s, but differ at large η/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative at large pT which is clearly unphysical. Such a behavior is not seen in either anisotropic hydrodynamics approach, irrespective of the value of η/s.

Speaker: Mubarak Alqahtani (Kent State University)

qpaHydro_Mubarak.pdf

10:35 Dynamical coupling of hydrodynamics and transport for heavy ion collisions

The theoretical description of heavy ion collisions based on hydrodynamics allows to investigate the Equation of State (EoS) of strongly-interacting matter. This benefit comes with assumptions, such as rapid thermalization [2], negligible backflow to hydrodynamics (also known as negative Cooper-frye contributions), existence of a sharp freeze-out hypersurface and possibility to determine it aposteriori from only hydrodynamical evolution. At low collision energies, as well as in event-by-event simulations, these assumptions are violated, in particular the backflow becomes large [1].

In this talk a simple method is suggested to partially relax the above mentioned assumptions, while keeping the same advantages: in a pure transport simulation forced thermalization is performed in regions with high energy density. The backflow is then automatically taken into account by the transport, the transition hypersurface is determined dynamically and, most remarkably, it is possible to plug in an arbitrary EoS, with or without phase transition, directly in the transport. Instead of a sharp freeze-out hypersurface a gradual transition can be constructed by assigning space-time dependent probabilities for particles to be thermalized.

We demonstrate the suggested method using the SMASH (Simulating Multiple Accelerated Strongly-interacting Hadrons) hadronic transport approach and show that forced thermalization leads to a longer lifetime of the system, increases the multiplicity of strange particles and affects anisotropic flow. Finally, the outcome of dynamically coupled approach with different EoS is compared - hadron gas EoS versus chiral EoS with the first order phase transition.

[1] D. Oliinychenko, P. Huovinen, H. Petersen, "Systematic Investigation of Negative Cooper-Frye Contributions in Heavy Ion Collisions Using Coarse-grained Molecular Dynamics", Phys.Rev. C91 (2015) no.2, 024906

[2] D. Oliinychenko, H. Petersen, "Deviations of the Energy-Momentum Tensor from Equilibrium in the Initial State for Hydrodynamics from Transport Approaches",
Phys.Rev. C93 (2016) no.3, 034905

Speaker: Dmytro Oliinychenko (Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main, Germany)

Oliinychenko_HotQuarks2016.pdf

10:55 Momentum anisotropy at kinetic freeze out

The transition from a hydrodynamical modeling to a particle-based approach is a crucial element of the description of high-energy heavy-ion collisions. Assuming this "freeze out" happens instantaneously at each point of the expanding medium, we argue that the local phase-space distribution of the emitted particles is asymmetric in momentum space. This suggests the use of anisotropic hydrodynamics for the last stages of the fluid evolution. We show how observables depend on the amount of momentum-space anisotropy at freeze out and how smaller or larger anisotropies allow for different values of the freeze-out temperature.

Speaker: Steffen Feld (Universität Bielefeld)

presentation hot quark 2016.pdf

11:15 Discussion session

12:00 → 16:30 Lunch and afternoon break

16:30 → 20:05 Tuesday afternoon

Convener: Rainer Fries (Texas A&M University)

16:30 Phenomenological predictions of 3+1d anisotropic hydrodynamics

We make phenomenological predictions for particle spectra and flow in heavy-ion collisions using 3+1d anisotropic hydrodynamics (aHydro) including the effects of both bulk and shear viscosities. The dynamical equations necessary are derived by taking moments of Boltzmann equation allowing for three distinct momentum-space anisotropy parameters. The formulation is based on relaxation-time approximation for the collisional kernel and a lattice-QCD-based equation of state. Evolving the system to late times, we calculate particle production using THERMINATOR modified to account for an ellipsoidal distribution function. We obtain particle spectra for different particle types such as pions, kaons, and protons and elliptic flow, $v_2$ as a function of centrality, transverse momentum, and rapidity. In our model, we have four free parameters, i.e. freeze-out temperature, initial energy density, initial momentum-space anisotropy, and shear viscosity to entropy density ratio. Using a multidimensional fit to LHC experimental data, we extract these parameters. We find good agreement between 3+1d aHydro and available experimental data.

Speaker: Mohammad Nopoush (Kent State University)

HQ2016-pres.pdf

16:50 Measurements of azimuthal anisotropy for high $p_T$ charged hadrons in Au+Au collisions at ${\sqrt{s_{NN}}}$ = 200GeV at RHIC-PHENIX

The azimuthal anisotropy coefficient $v_2$ is a good tool to investigate
properties of the QGP not only to study collective flow, but also the energy loss of hard scattered partons. For non-central collisions,
the collision area has an elliptic shape. When the hard scattered partons
created in the collision are emitted, they have different path-lengths
interacting with QGP depending on the orientation with respect
to the reaction plane, azimuth, which results in the difference of the yields
of high transverse momentum ($p_T$) particles in in-plane and out-of-plane.
Therefore, the energy loss mechanism can be investigated by measuring
the $v_2$ at high $p_T$.

We have recently improved the precision of the $v_2$ measurement by
reducing background tracks using the silicon vertex tracker installed in
PHENIX. In this presentation, I discuss the collision centrality dependence
and $p_T$ dependence of charged hadron $v_2$ in Au+Au collisions
at ${\sqrt{s_{NN}}}$=200GeV from the data collected by PHENIX during the
RHIC Year-2011 run.

Speaker: Akari Takeda (Nara Women's University)

HQ_Akari.pdf

17:10 A blast wave model with viscous corrections

Experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) probe the properties of nuclear matter at extremely high temperatures and densities. Hadronic observables in the final stage of the heavy ion collision can be described well by fluid dynamics or blast wave parameterizations. We improve existing blast wave models by adding shear viscous corrections to the particle distributions in the Navier-Stokes approximation. The specific shear viscosity of a hadron gas at the freeze-out temperature is a new parameter in this model. We extract the blast wave parameters with viscous corrections from experimental data which leads to constraints on the specific shear viscosity.

Speaker: Mr Zhidong Yang (Texas A&M University)

HQ16_Blast Wave_Zhidong.pdf

17:30 Coffee break

18:00 Anomalous transport model study of chiral magnetic effects in heavy ion collisions

Using an anomalous transport model for massless quarks, we study the effect of magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in non-central heavy ion collisions can last for a sufficiently long time, we obtain a substantial electric quadrupole moment in the transverse plane of a heavy ion collision, which subsequently leads to an appreciable splitting between the elliptic flows of quarks and antiquarks as expected from the chiral magnetic wave and observed in experiments at the Relativistic Heavy Ion Collider (RHIC).

Speaker: Yifeng Sun (Texas A&M University)

CME.pdf

18:20 Rapidity Correlation Structure in Nuclear Collisions

The forces that drive the nuclear collision system towards local thermal equilibrium leave few observable traces. Heavy ion experiments report a range of features widely attributed to the hydrodynamic flow of a near-equilibrium quark gluon plasma. In particular, measurements of azimuthal anisotropy provide the most comprehensive support for the hydrodynamic description of these systems. In search of the source of this flow, we turned to smaller proton-proton, proton-nucleus and deuterium-nucleus collisions, expecting to find this effect absent. Instead, these collisions show an azimuthal anisotropy that is comparable to the larger ion-ion systems. How can we learn about the mechanisms that give rise to hydrodynamics if every available collision system exhibits flow?

We show that measurements of the rapidity dependence of transverse momentum correlations can be used to determine the characteristic time $\tau_\pi$ that dictates the rate of isotropization of the stress energy tensor, as well as the shear viscosity $\nu = \eta/sT$. We formulate methods for computing these correlations using second order dissipative hydrodynamics with noise. Current data are consistent with $\tau_\pi/\nu \sim 10$ but targeted measurements can improve this precision.

Speaker: Christopher Zin (Wayne State University)

Hot Quarks - Rapidity Correlation Structure in Nuclear Collisions - Chris Zin.pdf

18:40 J/𝜓 azimuthal anisotropy in Au+Au collisions at sqrt(s_{NN}) = 200 GeV

In relativistic heavy-ion collisions, J/𝜓 mesons can be produced via different mechanisms, and the large mass of the charm quark makes these mesons a valuable probe to the thermalization of the medium. The study of J/𝜓 azimuthal anisotropy allows for a disentanglement of various production processes and access to charm quark azimuthal anisotropy. J/𝜓 produced from direct pQCD processes have little azimuthal anisotropy due to the lack of collectivity and initial emitting azimuthal preference, while J/𝜓 produced from recombination of charm quarks in the medium are expected to inherit considerable azimuthal anisotropy of the constituent charm quarks (assuming they are well thermalized).
In this talk, we will present measurements of J/𝜓 azimuthal anisotropy in Au+Au collisions at Sqrt(s_{NN}) = 200 GeV, using data taken by STAR during RHIC operations in the years 2010 and 2011. J/𝜓 mesons are reconstructed via the di-electron channel. The anisotropy will be presented as a function of the event centrality and J/𝜓 transverse momentum.

Speaker: Chensheng Zhou (Brookhaven National Laboratory)

zhouchensheng_hotquarks2016.pdf

19:00 Discussion session

Wednesday, 14 September

08:30 → 12:00 Wednesday morning

Convener: Jean-Francois Paquet (Stony Brook University)

08:30 Heavy flavor overview

Speaker: Alessandro Grelli (Utrecht University (NL))

Overview_grelli_HF_HQ2016.pdf

09:05 HEAVY QUARK DYNAMICS IN THE QGP WITHIN A BOLTZMANN TRANSPORT MODEL: Radiative vs Collisional Energy Loss

Heavy quarks represent a fundamental probe for investiganting the properties of hot and dense QCD matter created at Ultra-Relativistic Heavy Ion Collisions.
They are created at early stages of collisions and due to their large masses they do no thermalize with the bulk medium. Thus they conserve memory of propagation throw the entire space-time evolution of the QGP.
The two key observables for heavy quarks are the nuclear suppression factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$. The challenge of each theoretical framework is to give a consistent description of both quantities at RHIC and LHC energies, hence solving the so called $R_{AA} - v_2$ puzzle for $D$ mesons.
We discuss the propagation of heavy quarks through the QGP by means of a relativistic Boltzmann transport approach including both collisional and radiative energy loss mechanisms.
In particular we investigate the impact of induced gluon radiation by dynamical QCD medium implementing in our transport model a formula for the emitted gluon spectrum calculated in a higher-twist scheme.
We notice that in the high $p_T$ region ($p_T > 10 $ GeV) radiative processes play an essential role giving a significant contribution to the generation of $R_{AA}$ and $v_2$ at momentum values for which the energy loss by collisions is in the perturbative regime, hence less effective with respect to the low $p_T$ region in reproducing the experimental data for these two observables.

Speaker: Mr Gabriele Coci (INFN - National Institute for Nuclear Physics)

Coci_HotQuarks2016.pdf

09:25 Open-charm meson measurements in pp and Pb-Pb collisions at central rapidity with ALICE

Heavy quarks (charm and beauty) are interesting probes for the study of the properties of the hot and dense matter created in ultra-relativistic heavy-ion collisions, known as the Quark-Gluon Plasma. Indeed, being mainly produced at the early stage of the collision, they experience the whole collision history. For this purpose, the production of several heavy-flavour mesons, $\mathrm{D^{0}}$, $\mathrm{D^{+}}$, $\mathrm{D^{*+}}$ and $\mathrm{D^{+}_{s}}$, has been measured by ALICE over a wide transverse momentum range. In this presentation, an overview of the main ALICE results on open-charm mesons at central rapidity will be given for pp and Pb-Pb collisions recorded at LHC Run I energies. Recent measurements of the nuclear modification factor and elliptic flow will be presented and will be compared with theoretical model predictions. An emphasis will be put on the discussion on the theoretical predictions of $\mathrm{D^{+}_{s}}$ with respect to other D mesons. Finally, prospects for future open-charm studies will be discussed.

Speaker: Julien Charles Hamon (Institut Pluridisciplinaire Hubert Curien (FR))

HQ2016-DmesonsInPbPb-JHamon-FinalVersion.pdf

09:45 Coffee break

10:15 Separation of the charm and beauty production in p--Pb and Pb--Pb collisions with ALICE

In heavy-ion collisions the energy loss of heavy quarks is an interesting quantity for the investigation of the properties of the Quark-Gluon Plasma (QGP). Heavy quarks are produced almost exclusively in the initial hard interactions. Thus, they can interact with the surrounding matter throughout its evolution. A comparison of measurements in Pb--Pb and p--Pb collisions helps to separate initial- and final-state effects. The excellent particle identification properties of the ALICE detector and the large branching ratio ($\approx10\%$) of hadrons containing heavy quarks to a final state containing electrons suggest a measurement of heavy flavours using semielectronic decay channels. In the analyses presented here, the contributions from charm and beauty to the electrons from heavy-flavour hadron decays are separated statistically using their different track impact parameter distributions and empirical estimations of the background. This approach makes use of the larger decay length ($c\tau\approx500\,\mathrm{\mu m}$) of hadrons with beauty quarks compared to those with charm quarks. The current results of the analyses of p--Pb collisions at $\sqrt{s_{\textrm{NN}}}=5.02\,\mathrm{TeV}$ and Pb--Pb collisions at $\sqrt{s_{\textrm{NN}}}=2.76\mathrm{\, TeV}$ are presented.

Speaker: Martin Andreas Volkl (Ruprecht-Karls-Universitaet Heidelberg (DE))

VoelklHotQuarks2016.pdf

10:35 Upsilon production at the STAR experiment

The production of quarkonia in high-energy heavy-ion collisions is
expected to be sensitive to the energy density of the medium due to
color screening of the quark-antiquark binding potential. Sequential
suppression of different quarkonium states may therefore serve as a
thermometer of the medium. Although the suppression of charmonia was
anticipated as a key signature of the quark-gluon plasma formation, the
recombination of uncorrelated $c\bar{c}$ pairs in the medium complicates
the picture. Bottomonia, on the other hand, are less affected by
recombination and thus provide a cleaner probe of the strongly
interacting medium. Recent STAR results show that in central Au+Au
collisions at $\sqrt{s_{NN}}=200$ GeV, the Upsilon 1S state is
suppressed beyond the mere cold nuclear matter effects, and the yields
of the excited states are consistent with a complete suppression.
STAR collected data in U+U collisions at $\sqrt{s_{NN}}=193$ GeV
triggered by high-energy electrons with an integrated luminosity of
263.4 $\mu b^{-1}$. The energy density in central U+U collisions is
estimated to be about 20% higher than that in $\sqrt{s_{NN}}=200$ GeV
central Au+Au data. Studies of quarkonium production in U+U collisions
can therefore serve as further tests of the sequential suppression
hypothesis. The latest results for the nuclear modification factors of
the Upsilon 1S state, as well as all three states together, will be
presented as a function of number of participants in U+U and Au+Au
collisions, and compared to theoretical calculations.
The Muon Telescope Detector (MTD), completed in 2014, allows for
measurements of Upsilon's with better precision through the muon decay
channel. Recent measurements of Upsilon production using the MTD will
also be presented.

Speaker: Robert Vertesi (Nuclear Physics Institute ASCR, Prague/Rez)

vertesi_bottomonium_HQ16.pdf

10:55 $J/\psi$ production in p+p and Au+Au collisions at STAR experiment

The production of heavy quarkonia has been extensively used to probe Quark-Gluon Plasma (QGP) created in heavy ion collisions. The suppression of $J/\psi$ in a deconfined medium due to Debye color screening of the charm quark potential has been proposed as a signature of the QGP formation. Interpretation of $J/\psi$ suppression requires good understandings of both its production mechanism in elementary collisions and contribution from coalescence of uncorrelated c and $\overline{c}$ quraks in the medium. Despite decades of efforts, the $J/\psi$ production mechanism in p+p collisions is still not fully understood. $J/\psi$ measurements in p+p collisions at $\sqrt{s}$ = 500 GeV will provide additional insights into its production mechanism. On the other hand, precise measurements of the nuclear modification factor ($R_{AA}$) and elliptic flow ($v_{2}$) for $J/\psi$ over a broad kinematic range in Au+Au collisions can help better understand the feature of Debye color screening.

We report measurement of $J/\psi$ cross-section and yield dependence on event multiplicity in p+p collisions at $\sqrt{s}$ = 500 GeV using both the di-electron and di-muon channels. $J/\psi$ $R_{AA}$ and $v_{2}$ measurements in the di-muon channel in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV with the full data sample taken during RHIC 2014 run will also be presented.

Speakers: Mr Qian Yang (BNL/USTC), Qian Yang (University of Science and Technology of China)

Hotquark_v2.pdf

11:15 Discussion session

12:00 → 16:30 Lunch and afternoon break

16:30 → 20:00 Wednesday afternoon

Convener: Andre Mischke (Universiteit Utrecht)

16:30 Charmonium production in Pb-Pb collisions at √sNN = 2.76 TeV and √sNN = 5.02 TeV measured with ALICE at the LHC

The production of charmonium states (for instance J/$\psi$ and $\psi(2S)$) is one of the probes studied to investigate the properties of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions. Indeed, the presence of a deconfined medium should modify the charmonium production yield, due to the color screening of the charm quark anti-quark potential. Such a suppression was already observed in heavy-ion collisions at SPS and RHIC energies. In Pb-Pb collisions at $\sqrt{s_{\text{NN}}} = 2.76$ TeV at the LHC, a clear suppression of the J/$\psi$ yield with respect to the one measured in binary-scaled pp collisions was observed, but much smaller than that at lower collision energies. This observation can be explained by the presence of a new production mechanism, the recombination of deconfined charm and anti-charm quarks during the hydrodynamical expansion of the QGP or at the hadronization stage. In this presentation, we will report on the results of the charmonium production in Pb-Pb collisions measured with the ALICE detector. In particular, we will focus on the new measurements obtained at $\sqrt{s_{\text{NN}}} = 5.02$ TeV for the J/$\psi$ at forward rapidity in the dimuon channel and their comparison with previous measurements at lower energy and model calculations.

Speakers: Mr Benjamin Audurier (The Alice Collaboration), Benjamin Audurier (Centre National de la Recherche Scientifique (FR))

audurier_HQ2016_final.pdf

Proceeding_audurier_HQ2016_HQReview.pdf

16:50 Measurements of open charm hadrons at STAR experiment

Charm quarks are predominantly produced in the early stages of the heavy-ion
collisions via hard scattering because of
their high mass. Thus, they experience the entire evolution of the Quark-Gluon Plasma
created in such collisions. Compared to light quarks,
charm quarks thermalize more slowly. The open
charm hadrons present, therefore, a unique probe to the properties of
the hot and dense nuclear matter by measuring their energy loss and
degree of thermalization in the medium. Furthermore, with the combined measurements of
D mesons, D$_\mathrm{s}$, and $\Lambda_\mathrm{c}$, we can study
multiple modes of
coalescence of charm quarks with
light quarks in heavy-ion collisions.

The newly installed Heavy Flavor Tracker at the STAR experiment
enables full topological reconstruction of open charm hadrons. It opens
the door to reconstructing D$_\mathrm{s}$ and $\Lambda_\mathrm{c}$ for the first time at RHIC
and greatly improves measurements of D$^0$ mesons.

In this talk, we present the latest results from the direct reconstruction
of open charm hadrons via hadronic channels at the STAR experiment. In addition,
we discuss comparisons to model calculations of the charm hadron
production and similar measurements of other particle species.

Speaker: Miroslav Simko (Nuclear Physics Institute, Czech Academy of Scinces (cz))

HotQuarksSimko_v7.pdf

17:10 Measurements of J/$\psi$ production in pp collisions at LHC energies with ALICE

Charmonium production in hadronic collisions is a complex process involving both hard scales, i.e. the production of charm-anticharm quark pairs in initial hard collisions, and soft scales, i.e. the subsequent formation of a bound charmonium state. The former can be addressed by perturbative Quantum ChromoDynamics (QCD), whereas the latter fall into the non-perturbative regime of QCD. Theoretical models are not yet able to provide a comprehensive description of all aspects of charmonium production in hadronic collisions. Experimental data on charmonium production in proton-proton collision are relevant to constrain the above mentioned theoretical models; in addition they serve as a crucial baseline for proton-nucleus collisions, in which Cold Nuclear Matter effects can occur, as well as for nucleus-nucleus collisions, where the production of a hot medium is expected, which can lead to suppression or enhancement mechanisms.

ALICE has unique capabilities among the LHC experiments to measure J/$\psi$ production both at forward rapidity in the $\mu^{\rm{+}}\mu^{\rm{-}}$ decay channel and at mid-rapidity in the $e^{\rm{+}}e^{\rm{-}}$ decay channel down to zero transverse momentum.

In this talk we will present an overview of ALICE results concerning the measurements of J/$\psi$ production in pp collisions at $\sqrt{s}$ = 7 TeV and at $\sqrt{s}$ = 8 TeV collected during the LHC Run-1, as well as first results at forward rapidity from pp collisions at $\sqrt{s}$ = 13 TeV and at $\sqrt{s}$ = 5 TeV collected during the first part of LHC Run-2. In particular, the measurements of J/$\psi$ production as function of transverse momentum, rapidity, and charged-particle multiplicity will be discussed and compared to theoretical models.

Speaker: Steffen Georg Weber (Technische Universitaet Darmstadt (DE))

sweber_HotQuarks.pdf

17:30 Coffee break

18:00 Measurement of D-meson tagged jets in pp collisions at 7 TeV with ALICE

Jets are a fundamental feature of high-energy particle interactions.
They result from the fragmentation of hard-scattered partons,
a key process of Quantum Chromodynamics (QCD).
In particular, the production and the internal properties of heavy-flavor jets
in pp collisions are not yet satisfactorily described by neither analytical nor
phenomenological approaches to QCD. Measurements are needed
in order to provide important constraints to models inspired by perturbative QCD
and Monte-Carlo generators, such as PYTHIA and POWHEG, widely used in high-energy particle physics.

Heavy-flavor jets can also provide important insights into the Quark-Gluon Plasma (QGP)
produced in ultra-relativistic heavy-ion collisions, as heavy quarks are predicted
to interact with the QGP differently compared to light quarks and gluons.
However, their production mechanisms must first be studied in the vacuum,
in order to provide a baseline for the observation of possible modifications induced by the presence of the QGP.

We present the current status of the measurement of jets that contain a D meson (D-tagged jet) with ALICE.
The aim of the analysis is to extract both the $p_{\rm T}$ spectrum of the D-tagged jets and the jet-momentum fraction of the D mesons.
We identify D-meson candidates via their hadronic decay channels using topological selections and particle identification.
These D-meson candidates are combined with the other charged tracks reconstructed by the central tracking system,
using the anti-$k_{\rm T}$ jet-finding algorithm.
We extract the yield of D-tagged jets through an invariant mass analysis of the D-meson candidates associated with each jet,
in bins of jet $p_{\rm T}$ and momentum fraction carried by the D meson. Finally we use a standard unfolding procedure
to correct the jet $p_{\rm T}$ spectrum for detector inefficiencies and momentum resolution. For this analysis we use data collected
by ALICE with minimum bias triggers in pp collisions at 7 TeV. We will discuss also
the perspectives for the same measurement in Pb-Pb and p-Pb collisions.

Speaker: Salvatore Aiola (Yale University (US))

HQ16_DtaggedJets_SAiola.pdf

18:20 Charmonium production in pp and PbPb collisions with the CMS

The Psi prime (Psi(2S)) meson yield in PbPb collisions is of particular interest when compared to the J/psi meson. A variety of effects modify the charmonium production in PbPb collisions with respect to pp collisions, including melting in the quark gluon plasma and statistical recombination, which can have a different impact on the J/psi and the Psi(2S) mesons. Using pp and PbPb data at sqrt(s_NN) = 2.76 TeV, the CMS Collaboration has previously reported that the Psi(2S) meson is more suppressed than the J/psi at midrapidity and high pt (|y|<1.6. pt>6.5), but a hint of less suppression at forward rapidity and intermediate pt (1.6<|y|<2.4, pt>3). New results on the relative J/psi and Psi(2S) modification, based on the pp and PbPb data recently collected at sqrt(s_NN) = 5.02 TeV by the CMS Collaboration, will be reported.

Speaker: Andre Govinda Stahl Leiton (Centre National de la Recherche Scientifique (FR))

HotQuarks.pdf

Proceeding_v3.pdf

18:40 Neutral mesons measurements with the ALICE detector

Adam Matyja
on behalf of the ALICE Collaboration

Institute of Nuclear Physics PAN,
Radzikowskiego 152, 31-342 Kraków, Poland.

The ALICE experiment at LHC is dedicated to studies of the quark-gluon plasma (QGP) state, which is created in heavy-ion collisions. Neutral mesons are excellent probes for QGP formation studies. The medium-induced energy loss of particles can be investigated via the measurement of neutral meson spectra produced in heavy-ion collisions for different centrality classes as well as via neutral meson-hadron correlations. A decrease of the nuclear modification factor ($R_{\rm AA}$) is observed, increasing with the centrality of the collision. The suppression of the per-trigger yield on the away side as measured by the modification factor ($I_{\rm AA}$) shows in a similar way the evidence for parton energy loss in medium. Neutral mesons have been measured by the ALICE experiment. Photons are measured in ALICE directly in the two electromagnetic calorimeters (PHOS and EMCal), as well as via the method of photon conversion (PCM) into electron-positon pairs, where the latter are measured in the inner tracking system (ITS) and the time projection chamber (TPC). Neutral mesons are combined from photon pairs via the invariant mass technique. Results obtained in EMCal, PHOS and PCM are consistent one to the other and allow to measure the spectra of particles with high precision over a wide kinematical range. An overview of the recent results on meson production from ALICE will be shown.

Speaker: Adam Tomasz Matyja (Polish Academy of Sciences (PL))

HQ2016_AM.pdf

19:00 Discussion session

Thursday, 15 September

08:30 → 12:00 Thursday morning

Convener: Prithwish Tribedy (Brookhaven National Lab)

08:30 Overview on electromagnetic probes studies

Speaker: Jean-Francois Paquet (Stony Brook University)

hot_quarks_EM_probes_Paquet.pdf

09:05 Low-Mass Dielectron Production in pp, p-Pb and Pb-Pb Collisions with ALICE

Carsten Klein, Goethe University Frankfurt,
on behalf of the ALICE Collaboration

Electron-positron pairs (dielectrons)
are an excellent experimental probe to investigate the properties of the quark-gluon plasma formed in ultrarelativistic heavy-ion collions. Because they do not interact strongly, their spectra reflect the entire
space-time evolution of the collision. The created medium can modify the dielectron production with respect to the vacuum rate. Therefore, measurements in pp collisions
serve as a medium-free baseline while the measurements in p-Pb collisions help to separate cold nuclear matter effects from
those of the hot and dense medium. In this contribution, dielectron measurements in all collision systems using the central barrel of ALICE are presented. Electrons at mid rapidity
are identified via a combined method using their specific energy loss in the Inner Tracking System (ITS) and Time Projection Chamber (TPC) together with time of flight information of the TOF detector.

Preliminary results on the dielectron production will be compared to the expected contributions from hadronic sources in pp
collisions at $ \sqrt{s}=7 $ TeV, in p-Pb collisions at $ \sqrt{s_{\rm NN}}=5.02 $ TeV and in Pb-Pb collisions at $ \sqrt{s_{\rm NN}}=2.76 $ TeV. Based on those distributions we discuss also constraints on the heavy-flavour production. An outlook for the measurements at $ \sqrt{s_{\rm NN}}=5.5 $ TeV using the upgraded ALICE detector after the second long shutdown of the LHC will also be presented.

Speaker: Carsten Klein (Johann-Wolfgang-Goethe Univ. (DE))

KleinHQ2016LowMassDielectrons-v6.pdf

09:25 Measurements of electron production from heavy flavor decays in p+p and Au+Au collisions at √𝐬NN = 200 GeV at STAR

Heavy quarks are predominantly produced at early stages of high-energy heavy-ion collisions due to their large masses. Studies of interactions between heavy quarks and Quark-Gluon Plasma (QGP) in various collision centralities can provide new insights to the properties of QGP. Heavy quark production in p+p collisions is a baseline to similar measurements in heavy-ion collisions and is expected to be well described by perturbative Quantum Chromodynamics (pQCD) calculations. Thus measurements of heavy quark production via measuring the electrons from semi-leptonic decays of heavy flavor hadrons, also known as Non-Photonic Electron (NPE), in both p+p and Au+Au collisions are crucial.

In this talk, we will present the new results of NPE production in p+p collisions at √s = 200 GeV from the STAR experiment with much improved precision and wider kinematic coverage than previous measurements. We will also report measurements of the nuclear modification factor, RAA, for NPE production in Au+Au collisions at √𝐬NN = 200 GeV.

Speaker: Shenghui Zhang (USTC)

NPE_wd0e_for_Hot_Quark-SHENGHUIZHANG.pdf

09:45 Coffee break

10:15 Non-equilibrium dilepton production in hadronic transport approaches

In this talk the non-equilibrium dilepton production from a hadronic transport approach (SMASH) is presented. The dilepton emission from the hadronic stage is of interest for current HADES results measured at GSI in the beam energy range from 1.25 - 3.5 GeV. Also at high collision energies (RHIC/LHC) the later dilute stages of the reaction are dominated by hadronic dynamics.

First, the employed hadronic transport approach called SMASH (=Simulating Many Accelerated Strongly-interacting Hadrons) is presented. After explaining the basic interaction mechanism, a comparison of elementary cross sections (e.g. pion production) to data is shown.

Then the description of dilepton production within SMASH is explained in detail. The main contribution to the dilepton spectra in the low energy regime of GSI/FAIR/RHIC-BES originates from resonance decays. Results of the dilepton production with SMASH including dilepton invariant mass spectra are shown and compared to HADES data. The dilepton spectrum also allows access to the electromagnetic transition form factors, which is studied under the hypothesis of vector-meson dominance in a transport picture[1]. The obtained results are compatible with NA60 data.

Furthermore, the possibility of employing the non-equilibrium dilepton production from a hadronic transport approach combined with a hydrodynamic approach (hybrid model) is explored.

ref. [1] J.Weil, J.Staudenmaier and H.Petersen, Dilepton production with the SMASH model, arXiv:1604.07028 [nucl-th], Proceedings Fairness 2016

Speaker: Jan Staudenmaier (Goethe University Frankfurt (FIAS))

HQ_Staudenmaier_2016.pdf

10:35 Open heavy-flavour and electroweak boson measurements via the (di-)muonic decay channel with ALICE at the LHC

Heavy flavours (charm and beauty) and electroweak bosons (W and Z) are produced in initial hard partonic scatterings. The former interact strongly with the medium formed in ultra-relativistic heavy-ion collisions throughout its evolution, thus making them well suited to investigate its properties. Furthermore, heavy-flavour measurements in proton-nucleus collisions can be used to investigate initial-state effects whereas in proton-proton (pp) collisions they are considered an important test for perturbative Quantum ChromoDynamics (pQCD) predictions. In addition, the open heavy-flavour measurements in pp collisions are used as a reference for proton-lead (p--Pb) and lead-lead (Pb--Pb) collisions.
On the other hand, electroweak bosons and their leptonic decay products only interact weakly with the QCD matter and thus are suitable probes to test the validity of binary-collision scaling of hard processes. Moreover, their measurements in p--Pb collisions could help to constrain nuclear parton distribution functions.

The ALICE muon spectrometer allows the measurement of open heavy flavour, W- and Z-boson production at forward rapidity (-4.0$<\eta<$-2.5) exploiting their (di)muonic decay channel. In this talk the results obtained with the LHC Run I data in pp, p--Pb and Pb--Pb collisions will be discussed and compared with theoretical predictions.

Speaker: Kgotlaesele Senosi (University of Cape Town (ZA))

KJSenosi_HFWZ_HQ2016.pdf

10:55 Discussion session

Friday, 16 September

08:30 → 12:00 Friday morning

Convener: Hannah Petersen

08:30 Exploring the Nuclear Phase Diagram with Beam Energy Scans

The nuclear phase diagram is mapped using beam energy scans of relativistic heavy-ion collisions. This mapping is possible because different collision energies develop along different trajectories through the phase diagram. High energy collisions will evolve though a crossover phase transition according to lattice QCD, but lower collision energies may traverse a first order phase transition. There are hints for this first order phase transition and its critical endpoint, but further measurements and theoretical guidance is needed. In addition to mapping the phase transition beam energy scans allow us to see if we can turn off the signatures of deconfinement. If an observable is a real signature for the formation of the deconfined state called quark-gluon plasma, then it should turn off at sufficiently low collision energies. In this summary talk I will show the current state of the field using beam energy scan results from RHIC and SPS, I will show where precise theoretical guidance is needed for understanding recent measurements, and I will motivate the need for more data and new measurements from FAIR, NICA, RHIC, and the SPS.

Speaker: Stephen Horvat (Yale)

BES_overview_updated.pdf

hq16_BES_overview2.pdf

09:05 Phase structure and dynamics of QCD- a functional perspective

I will report on progress towards a
quantitative first-principle continuum approach to QCD, focusing on
results for quenched QCD and Yang-Mills theory at vanishing and finite temperature obtained in the framework of the Functional
Renormalization group.
In the second part of my talk I will sketch how dynamical questions such as the
calculation of spectral functions or transport coefficients can be
addressed within this framework.

Speaker: Dr Nils Strodthoff (LBNL)

2_Strodthoff_Hotquarks2016.pdf

09:25 Susceptibilities from a black hole engineered EoS with a critical point

Currently at the Beam Energy Scan at RHIC experimental efforts are being made to find the QCD critical point. On the theoretical side, the behavior of higher-order susceptibilities of the net-baryon charge from Lattice QCD may allow us to estimate its position via Taylor expansion of the density of states at $\mu_{B}=0$. However, even if the series expansion continues to higher-orders, there is always the possibility to miss the critical point behavior due to truncation errors. An alternative approach to exploring the QCD critical point is using black hole engineering. This method allows us to obtain susceptibilities fitting the lattice data at $\mu_{B}=0$ and it can be used to calculate observables at extremely large baryonic chemical potentials as well. Additionally, in the black hole engineered EoS there is a clear critical point at $\mu_{B}=725$ MeV and $T=80$ MeV. In this talk, we obtain the freeze-out line and compare it with the hadron resonance gas model, lattice calculations, and experimental data. We also explore higher order fluctuations at the lowest energies at the beam energy scan to see if there are signatures of the critical point.

Speaker: Israel Portillo (University of Houston)

Isra_HQ.pdf

09:45 Coffee break

10:15 Femtoscopy with identified charged pions in proton-lead collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~\mathrm{TeV}$ with the ATLAS detector

Bose-Einstein correlations between identified charged pions are measured for p+Pb collisions at √sNN=5.02 TeV with the ATLAS detector with a total integrated luminosity of 28 nb−1. Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of average transverse pair momentum (kT) and rapidity (y∗k) as well as collision centrality. Pairs are selected with a rapidity −2<y∗k<1 and with an average transverse momentum 0.1<kT<0.8 GeV. The effect on the two-particle correlation function from jet fragmentation is studied, and a new method for constraining its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair kT. A correlation with the local multiplicity dN/dy∗ is demonstrated. The scaling of the extracted radii with the mean number of participants is also used to compare a selection of initial-geometry models. The cross term Rol is measured as a function of rapidity, and a departure from zero is observed with 4.8 σ combined significance in the proton-going side of the most central events.

Speaker: Michael Ryan Clark (Columbia University (US))

clark_hq_slides.pdf

10:35 Kaon femtoscopy at the STAR experiment

The properties of the quark-gluon plasma have been extensively studied in high-energy nuclear collisions at RHIC. In particular the Beam Energy Scan, a research program capitalizing on RHIC’s unique capability to vary the collision energy from 7.7 to 200GeV, presents an unprecedented opportunity to study the phase diagram of the strongly interacting matter.

Femtoscopic measurements of two-particle correlations at small relative momenta reveal the space-time characteristics of the system at the moment of particle emission.
In comparison to analyses using the most abundant pions, like-sign kaons provide a cleaner probe of the emission source as they less frequently result from resonance weak decays. Additionally, kaons contain strange quarks so these measurements can be sensitive to different effects and earlier collision stages.

Pairs of like-sign kaons exhibit correlations due to Coulomb interactions and Bose-Einstein quantum statistics. The system of unlike-sign kaons contains a narrow $\phi$(1020) resonance in the final state. Femtoscopic measurements have been predicted to be particularly sensitive to the source size and momentum-space correlations in the region of this resonance.

In this talk I will present the STAR preliminary results on femtoscopic correlations of like-sign kaons in Au+Au collisions from the RHIC Beam Energy
Scan program. I will also report on STAR analysis of unlike-sign kaons femtoscopic correlations in Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV. The experimental results will be compared to theoretical predictions.

Speaker: Jindřich Lidrych (Czech Technical University in Prague)

HQ_KK_femto_Lidrych.pdf

10:55 Calculation of the Electric Conductivity of Hot Hadronic Matter

Using hadronic many-body theory, the author calculates the rho meson self-energy in a pion gas. Previously the effects of in medium nucleons and delta particles (which have a large coupling to the rho) on the rho propagator, have been calculated. However the effects of in-medium pions were not included. Calculation of the electric conductivity requires one to consider the zero momentum and low energy limit of the rho spectral function. In this limit and at small temperatures, the effects of high mass particles like nucleons and deltas will be suppressed and the effects of the lower mass pion will become significant. Thus, the author has calculated the effects of in-medium pions on the rho self-energy, assuring that these calculations preserve gauge invariance. This requires the determination of the significant interactions between in-medium pions and the rho meson, and the calculation of these interactions. This calculation requires the dressing of the pion propagators in the rho self-energy with pion-rho loops. However, this violates gauge invariance. To correct for this one must calculate vertex corrections to the rho self-energy loops. Using guidance from previous works, the author calculates these vertex corrections. The author then combines the results with the results for nucleon and delta particles to obtain an improved calculation of the rho self-energy and spectral function in hadronic matter. The resulting spectral function was used to calculate the electric conductivity of hot hadronic matter.

Speaker: Joseph Atchison (Texas A&M University)

Hot Quarks.pdf

Hot Quarks.pptx

11:15 Discussion session

12:00 → 16:30 Lunch and afternoon break

16:30 → 20:00 Friday afternoon

Convener: Jacquelyn Noronha-Hostler (University of Houston)

16:30 Production of Σ(1385)± and Ξ(1530)0 in p–Pb collisions at √sNN = 5.02 TeV measured by ALICE at the LHC

In order to study the hot hadronic matter created in heavy ion collisions it is important to compare particle production in such collisions with particle production in other, smaller systems, such as proton-proton (pp) and proton-lead (p--Pb) collisions. In particular, hyperon resonances with different lifetimes are good candidates to probe the interplay of particle re-scattering and regeneration in the hadronic phase. The yields of the strange and double-strange hyperon resonances $\Sigma(1385)^{\pm}$ and $\Xi(1530)^{0}$ are measured in the rapidity range $-0.5 < y < 0$ in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ALICE detector at the LHC. We report on the transverse momentum distributions and mean transverse momentum as a function of the charged-particle multiplicity. These results complement the information deriving from the measurements of other resonances such as K*(892)$^{0}$ and $\Phi$(1020). The multiplicity dependence of the integrated yield ratios of excited hyperons to longer-lived particles is discussed and compared to model predictions from pQCD-inspired models such as PYTHIA8 as well as statistical hadronization models.

Speaker: Jihye Song (Pusan National University (KR))

HQ2016_JHSONG.pdf

16:50 (Hyper-)nuclei and exotica production measured with ALICE at the LHC

The high collision energies reached at the Large Hadron Collider (LHC) lead to significant production of light (anti-)(hyper-)nuclei in proton-proton (pp), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions.

The excellent particle identification (PID) capabilities of the ALICE detector are exploited to identify rarely produced particles such as deuterons, $\rm ^{3}{H}$, $\rm ^{3}{He}$, $\rm ^{4}{He}$ and their antiparticles, in addition to light hadrons.
PID is performed by measuring the specific energy loss in the Time Projection Chamber (TPC) and the particle velocity with the Time-Of-Flight (TOF) detector.

In addition, the high-resolution vertexing provided by the Inner Tracking System (ITS) allows for the separation of primary and secondary vertices.

The precise secondary vertex reconstruction allows one to study the (anti-)$\rm ^{3}_{\Lambda}H$ production via its mesonic weak decay channel ($\rm ^{3}_{\Lambda}H \rightarrow\ ^{3}{He}+\pi^{-}$) and the search for weakly bound states containing a $\Lambda$ hyperon, such as the H-dibaryon (H$\rightarrow \Lambda$+p+$\pi^{-}$) and $\Lambda$n ($\Lambda$n $\rightarrow$ d+$\pi^{-}$).

We present the results on the production yields of light nuclei and anti-nuclei in the following collision systems: pp at $\sqrt{s}$= 7 TeV, p-Pb at $\sqrt{s}$= 5.02 TeV and Pb-Pb at $\sqrt{s_{NN}}$= 2.76 TeV.

The measurement of production rates and lifetime of the hypertriton in Pb-Pb together with the upper limits on the production of exotic bound states will also be shown.

The experimental results will be compared with the prediction of thermal (statistical) and coalescence models.

Speaker: Stefano Trogolo (Universita e INFN Torino (IT))

Trogolo_HQ2016_Final.pdf

17:10 Light flavour hadron production in pp collisions at $\sqrt{s} =$ 13 TeV with ALICE

We report on the measurement of identified particle production at mid-rapidity in pp collisions at the highest centre-of-mass energy, $\sqrt{s}$ = 13 TeV, ever reached in the laboratory. The measurements extend from pions to multi-strange hyperons and cover the range in $p_{\rm{T}}$ from 100
MeV/c to 20 GeV/c, depending on the species. The data are compared to models commonly employed at the LHC such as EPOS and PYTHIA, and to results at lower energies. The key question of whether or not the observed evolution of identified particle production with increasing $\sqrt{s}$ is mostly driven by an increase in charged particle density is also addressed.

Speakers: Mr Raúl Tonatiuh Jimenez Bustamante (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH), Tonatiuh Jimenez (Ruprecht-Karls-Universitaet Heidelberg (DE))

HQ2016_Bustamante_FINAL.pdf

17:30 Coffee break

18:00 Testing the hadronic spectrum in the strange sector

Heavier resonances are continually being added to the hadronic spectrum from the Particle Data
Group [1]. The existence of additional states is predicted by relativistic quark models [2, 3]. It has
been suggested [4, 5] that further states might need to be included in the hadronic spectrum in order
to improve the agreement between the hadron resonance gas model predictions and lattice QCD
data. However, for some selected observables, the inclusion of these states worsens the agreement
with the lattice results. We propose a new set of observables which allow us to test the predictions
of the quark model, by dividing the new states according to their quantum numbers. This will help
to clarify the situation and determine how many new states are needed.

[1] K. A. Olive et al. [Particle Data Group Collaboration],
Chin. Phys. C 38, 090001 (2014). doi:10.1088/1674-
1137/38/9/090001
[2] S. Godfrey and N. Isgur, Phys. Rev. D 32, 189 (1985).
doi:10.1103/PhysRevD.32.189
[3] S. Capstick and N. Isgur, Phys. Rev. D 34,
2809 (1986) [AIP Conf. Proc. 132, 267 (1985)].
doi:10.1103/PhysRevD.34.2809, 10.1063/1.35361
[4] A. Majumder and B. Muller, Phys. Rev. Lett.
105, 252002 (2010) doi:10.1103/PhysRevLett.105.252002
[arXiv:1008.1747 [hep-ph]].
[5] A. Bazavov et al., Phys. Rev. Lett. 113, no.
7, 072001 (2014) doi:10.1103/PhysRevLett.113.072001
[arXiv:1404.6511 [hep-lat]].

Speaker: Paolo Parotto (University of houston)

HQ16_Parotto.pdf

18:20 Transverse momentum spectra and the nuclear modification factor of charged particles with ALICE

The observed suppression of particle production at high transverse momentum in nucleus-nucleus collisions at high energies is an effect of the energy loss of partons as they propagate through the hot and dense QCD medium. The measurement of transverse momentum spectra of primary charged particles in Pb-Pb collisions and the comparison to the measurement in pp collisions are important to quantify the properties of the deconfined medium. In 2015, pp and Pb-Pb collisions have been recorded at the LHC at the record energies of $\sqrt{s}=13 $ and $\sqrt{s_{NN}}=5.02$ TeV, respectively. The inclusive charged particle production is measured with the ALICE detector in the pseudo-rapidity range $|\eta|<0.8$ and in the transverse momentum range 0.15 < p$_{\rm T}$ < 40 GeV/$c$. The spectra in Pb-Pb, determined for several centrality intervals, is compared to the reference spectrum in pp collisions by calculating the nuclear modification factor R$_{AA}$. We observe that the suppression of high-$p_{\rm T}$ particles strongly depends on the event centrality. The data are compared to measurements at the lower collision energy of 2.76 TeV and to model predictions.

Speaker: Edgar Perez Lezama (Johann-Wolfgang-Goethe Univ. (DE))

Edgar_HotQuarks2016.pdf

18:40 sPHENIX: the next generation heavy ion detector at RHIC

sPHENIX is a new collaboration and future detector project at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC). It seeks to answer fundamental questions on the nature of the quark gluon plasma (QGP), including its temperature dependence and coupling strength, by using a suite of precision jet and upsilon measurements that the probe different length scales of the QGP. This will be achieved with large acceptance, |$\eta$| < 1 and $2\pi$ in $\phi$, electromagentic and hadronic calorimeters and precision tracking enabled by a 1.5T superconducting magnet. With the increased luminosity afforded by accelerator upgrades, sPHENIX will perform high statistics measurements extending the kinematic reach at RHIC to overlap the LHC's. This overlap with the LHC will facilitate better understanding of the role of temperature, density and parton virtuality in QGP dynamics and for jet quenching in particular. This talk will focus on key future sPHENIX measurements and the current state of the sPHENIX project.

Speaker: Sarah Campbell (Columbia University (US))

HotQuarks2016.pdf

19:00 Discussion session

Saturday, 17 September

08:30 → 12:00 Saturday morning

Convener: Christine Nattrass (University of Tennessee (US))

08:30 The Initial Stage of Colliding Nuclei and Hadrons

In this talk I will go through some recent developments in the description of the initial stages of hadronic and heavy ion collisions.

Speaker: Prithwish Tribedy (Brookhaven National Lab)

hotquarks2016_Tribedy_short.pdf

talk_tribedy_hotquarks16.pdf

09:05 Achieving High Baryon Densities in the Fragmentation Region in Heavy Ion Collisions at Top RHIC Energy

In very high energy collisions nuclei are practically transparent to each other but produce very hot, nearly baryon-free, matter in the so-called central rapidity region. The energy in the central rapidity region comes from the kinetic energy of the colliding nuclei. We calculate the energy and rapidity loss of the nuclei using the Color Glass Condensate model. This model also predicts the excitation energy of the nuclear fragments. Using a space-time picture of the collision we calculate the baryon and energy densities of the receding baryonic fireballs. For central collisions of Gold nuclei at the highest energy attainable at the Relativistic Heavy Ion Collider, for example, we find baryon densities more than ten times that of atomic nuclei over a large volume. (arXiv:1604.08525)

Speaker: Ming Li (University of Minnesota, Twin Cities)

HQ2016_Ming_Li.pdf

09:25 Initial conditions for hydrodynamics from weakly coupled pre-equilibrium evolution

Initial state of heavy ion collision and subsequent hydrodynamic evolution are separated by a short phase of fast equilibration of underlying degrees of freedom. We use effective kinetic theory, accurate at weak coupling, to simulate the pre-equilibrium evolution of transverse energy and flow perturbations. We construct a Green function which propagates the initial perturbations to the energy-momentum tensor at a time when hydrodynamics becomes applicable.
This allows the complete pre-thermal evolution from saturated nuclei to hydrodynamics to be modelled in a perturbatively controlled way.

Speaker: Aleksas Mazeliauskas

Aleksas_Mazeliauskas_HQ16.pdf

hotquarks_talk.pdf

09:45 Coffee break

10:15 Study of Drell-Yan pair production on nuclear targets

Drell-Yan pair production off nuclei is an ideal tool to test the initial state nuclear effects occurring before a hard collision since no interaction in the final state is expected, either energy loss or absorption. We present for the first time a comprehensive study of the nucleus-to-nucleon production ratio (the nuclear modification factor) within the color dipole approach using the Green function formalism, which naturally incorporates for the color transparency and quantum coherence (QC) effects. We study a different onset of nuclear shadowing in various kinematical regions. At large values of the Feynman variable $x_F$ and dilepton invariant mass $M$ we include also a suppression factor due to restrictions caused by the energy conservation induced by multiple initial state interactions (ISI effects). The corresponding numerical results for the nuclear modification factor are compared with available data. Besides, we present a variety of predictions for the nuclear suppression as a function of $x_F$ and $M$ that can be verified by experiments at RHIC and LHC. The mixing of QC with ISI effects can be eliminated going to large values of the dilepton inveriant mass. Then predictions for the nuclear suppression is a direct manifestation for the onset of net ISI effects that can be verified by the future measurements.

Speaker: Mr Michal Krelina (FNSPE, Czech Technical University in Prague)

krelina-HQ2016_v4.pdf

10:35 Event-By-Event Initial Conditions for Heavy Ion Collisions

The early time dynamics of heavy ion collisions can be described by classical fields in an approximation of Quantum ChromoDynamics (QCD) called Color Glass Condensate (CGC). Monte-Carlo sampling of the color charge for the incoming nuclei are used to calculate their classical gluon fields. We use the recent work by Chen et. al. (Phys. Rev. C 92, 064912, 2015) to calculate the energy momentum tensor at early times in the collision event-by-event. This can then be used for subsequent hydrodynamic evolution of the single events.

Speaker: Steven Rose (Texas A&M University)

EnergyDensityEvolotuion.avi

EnergyDensityEvolotuion.gif

SRHQ2016.pdf

SRHQ2016.pptx

10:55 Quark mass thresholds in QCD thermodynamics and charm fluctuations in QGP

The heavy quark degrees of freedom of the QGP with special focus on mass effects are investigated. A next-to-leading-order perturbation theory approach with bare quark mass dependence is applied and compared to Lattice results with physical bare quark masses. The susceptibilities and ratios of it appear to be the most interesting quantities and show a good agreement with lattice data.

Speaker: Dr Thorben Graf (SUBATECH Nantes)

HotQuarks2016_ThorbenGraf.pdf

11:15 Discussion session

12:00 → 16:30 Lunch and afternoon break

16:30 → 20:00 Saturday afternoon

Convener: Jorge Noronha (University of Sao Paulo)

16:30 Deciphering the Charge Production Dynamics with General Charge Balance Functions at ALICE

The two-wave quark production scenario, proposed by Scott Pratt in 2012 as a signature of the production of quark-gluon plasma in high energy heavy ion collisions, can be studied with balance functions of identified particle pairs. We present measurements of such balance functions based on an analysis of data acquired at the Large Hadron Collider (LHC) by the ALICE detector. Balance functions have been measured for identified charged-pion pairs and for identified charged-kaon pairs in Pb-Pb collisions at √sNN = 2.76 TeV. These balance functions are presented in relative rapidity Δy and relative azimuthal angle Δϕ. We observe that the relative rapidity width of the charged-pion balance functions exhibits a strong dependence on the Pb-Pb collision centrality, while the balance functions for charged kaons show little centrality dependence. These findings are consistent with the effects of delayed hadronization and radial flow, as well as the two-wave scenario, but further analyses of the data, including a measurement of proton balance functions and detailed model comparisons are required to draw more significant conclusions.

Speaker: Jinjin Pan (Wayne State University (US))

AuAu_20160917_HQ16_PID_BF_Final.pdf

16:50 Impact of early stage non-equilibrium dynamics on photon production in relativistic heavy ion collisions

Radiation of photons is a promising and efficient tool to study the initial state of heavy-ion collisions. Unlike hadrons, photons are emitted during all stages of the expanding fireball and, due to their electromagnetic nature, they do not suffer further interaction with the medium, carrying undistorted information about the circumstances of their production. In this talk we discuss spectrum and elliptic flow of photons emitted from the quark-gluon plasma produced in heavy ion collisions, both at LHC and RHIC energies. Simulating the space-time evolution of the fireball by solving the relativistic Boltzmann transport equation and including two particle scattering processes with photon emission allows as to make a first step in the description of thermal photons from the QGP as well as of those produced in the pre-equilibrium stage. Indeed, we consider not only a standard Glauber initial condition but also a model in which partons are produced through the Schwinger mechanism by the decay of an initial color-electric field. In the latter approach relativistic kinetic equations are coupled in a self-consistent way to the chromo-electric field equations. We aim at spotting the impact of early stage non-equilibrium dynamics on the photon production.

Speaker: Lucia Oliva (INFN - National Institute for Nuclear Physics)

Oliva - Impact of early stage on photon prduction.pdf

17:10 Measurement of long-range azimuthal anisotropies in $pp$ and $p$+Pb collisions with the ATLAS detector

ATLAS measurements of correlations between particle pairs in relative azimuthal angle (Δϕ) and pseudorapidity separation (Δη), in pp collisions at √s=2.76, 5.02 and 13~TeV, and in p+Pb collisions at √sNN=5.02~TeV are presented. Prior measurements have shown that in pp collisions with a large multiplicity of produced particles, a long-range structure,commonly called the ``ridge'', develops along Δη at Δϕ∼0. However, due to the presence of the large away-side jet, the full Δϕ dependence of the long-range correlation could not be studied previously. In this analysis, a template fitting procedure is implemented to determine the contributions from dijets to the correlations, using low-multiplicity events, and extract the genuine long-range correlation. The Fourier harmonics of the genuine long-range correlation for orders n=2--4 are extracted, and their dependence on pT, event-multiplicity and collision energy are studied. It is shown that the second Fourier coefficient, v2,2, dominates the long range correlation, with small but significant contributions from v3,3 and v4,4. The v2,2 is shown to factorize into the product of single-particle anisotropies v2. A large v2 is shown to be present even in events with a small multiplicity of produced particles, implying that the long-range correlations are not unique to rare high multiplicity events, but are present even in low multiplicity pp collisions. Comparisons to the vn,n and vn obtained when applying the template fitting procedure to p+Pb collisions are also presented. These measurements can help determine if the long range correlations in pp and p+Pb collisions arise from similar mechanisms or not.

Speaker: Soumya Mohapatra (Columbia University (US))

HQ_Talk.pdf

17:30 Coffee break

18:00 Multiplicity dependence of light flavour hadrons in small systems with the ALICE experiment

Measurements obtained in high-multiplicity proton-proton (pp) and proton-lead (p--Pb) collisions at the Large Hadron Collider have exhibited features that are similar to what was observed in lead-lead (Pb--Pb) collisions, where they are usually interpreted as signs of collective behaviour.
These observations warrant a comprehensive study of the production of identified particles which are important probes to investigate the dynamics of the small systems.
Thanks to the excellent particle identification performance of the ALICE detector the measurement of identified particles is possible over a wide range of transverse momentum ($p_{\mathrm{T}}$).
\
We report on the $p_{\mathrm{T}}$ distributions of $\pi$, $K$, $p$, $K^0_{s}$, $K^{*}$, $\phi$, $\Lambda$, $\Xi$ and $\Omega$ measured as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}=7$ TeV.
Special attention will be given to particle ratios and comparisons to the Monte Carlo models.
\
In order to discuss the similarities between the different collision systems, the results obtained in p--Pb and Pb--Pb collisions will also be reviewed.

Speaker: Nicolo Jacazio (Universita e INFN, Bologna (IT))

HQjacazio.pdf

18:20 Spinodal instability of baryon-rich quark matter

The spinodal instability of a baryon-rich quark matter is studied in both the Nambu-Jona-Lasino (NJL) and the Polyakov-Nambu-Jona-Lasino (PNJL) model. We first obtain via the linear response theory the boundary of the spinodal region and calculate the growth rate of unstable modes. We find that at the mean-field level, the boundary of spinodal instability shrinks with the wave number of unstable modes and is also reduced by both the vector interaction and quantum effect. We then numerically solve the transport equations derived from the NJL Lagrangian to study density fluctuations in a quark matter that is confined in a static box. Appreciable higher-order density moments are seen as a result of the first-order phase transition in the baryon-rich quark matter. Also, the skewness of the quark number event-by-event distribution for quarks in a small sub-volume of the system becomes appreciable. Allowing the quark matter to expand as in heavy ion collisions, we find the presence of a first-order phase transition slows down the expansion and result in the appearance of density clumps that can lead to enhancements in density moments, anisotropic flows, and the dilepton yield.

Speaker: Feng Li (Texas A&M University)

hot_quark_2016.pdf

hot_quark_2016.pptx

18:40 Discussion session