MIAPP Programme 2018 Heavy Ion

27 Aug 2018, 09:00 → 21 Sept 2018, 17:00 Europe/Berlin

MIAPP

Torsten Dahms (TUM), Laura Fabbietti (TUM), Jean-Philippe Lansberg (IPNO - Paris-Saclay U. - CNRS/IN2P3), Jean-Yves Ollitrault (Institut de physique theorique, Saclay)

Experiments at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC) study the properties of the quark-gluon plasma (QGP) produced in ultrarelativistic heavy-ion collisions. The QGP is an extreme state of matter comprising deconfined quarks and gluons (partons) that exists only at temperatures above approximately 160 MeV, a condition met for last time a few microseconds after the Big Bang, or at baryon densities five times higher than normal nuclear densities, speculated to exist inside the core of neutron stars.

Measurements of collective phenomena and heavy quarks have fundamentally changed our understanding of the QGP. There is overwhelming evidence that the QGP, while composed of deconfined partons, still remains a strongly coupled system. The QGP is also dense and hot enough to cause significant energy loss to the heavy charm and bottom quarks as well as dissociate even the strongest bound heavy quarkonium states.

With the LHC Run-2 nearing its completion and the second RHIC beam energy scan programme upcoming, this MIAPP programme will provide an excellent opportunity to bring together experts in the community to review the progress, discuss open questions and foster new collaborations.

It is foreseen that the first half of the programme will then be dedicated to collective phenomena while the second half will focus more on heavy quarks.

 

Monday 27 August

09:00 → 09:15 Welcome: Start of the Programme

09:15 → 12:45 Week 1: Day 1

09:15 Dynamical core-corona initialization in hydro models

One of the important findings in small colliding systems at the LHC energies is that yields of (multi-)strange hadrons enhance more rapidly than those of charged pions as functions of multiplicity. To interpret this, we develop a dynamical initialization model with core-corona picture in hydrodynamic models. We generate the initial partons using some event generator. We put them in the source terms of relativistic hydrodynamic equations to generate the QGP fluids. Some of the initial partons with high pT or those isolated from the others are able to survive after dynamical initialization and form a hadronic string to decay into hadrons. Thus, in this framework, final hadrons come from either chemically equilibrated fluids (core) or string fragmentation (corona). By using this model, we reasonably reproduce the yield ratio of (multi-)strange hadrons to charged pions as a function of multiplicity observed by the ALICE Collaboration. We claim that hydrodynamic analysis of experimental data requires this kind of core-corona picture for better understanding of the whole reaction process of high-energy nuclear collisions.

Speaker: Tetsufumi Hirano (Sophia Univ.)

hirano.pptx

10:45 Coffee Break

11:15 Pre-equilibrium stages with QCD kinetic theory

The produced matter in the high energy nuclear collisions reinteracts and form a plasma which ultimately equilibrates and exhibits collective hydrodynamic flow.
The connection between the early gluon production in classical field simulations and hydrodynamic expansion at later times is given by the QCD kinetic theory.
I will discuss the recent progress on smooth matching between these three stages, including the hydrodynamization and chemical equilibration of Quark-Gluon Plasma.

Speaker: Aleksas Mazeliauskas (Heidelberg University)

Mazeliauskas_MIAPP_v2.pdf

12:45 → 14:00 Lunch

15:30 → 16:00 Coffee Break

Tuesday 28 August

09:30 → 13:00 Week 1: Day 2

09:30 Some results and challenges for hydro modelling at RHIC BES

In this talk I overview the results of our studies of heavy ion collisions at RHIC BES energies in the framework of a viscous hydro + cascade model, vHLLE+UrQMD, focusing on the following phenomena:

• Lambda polarization - from RHIC BES to LHC energies
• Femtoscopic observables at RHIC BES

And discuss challenges for hydrodynamic modelling at the lower collision energies (RHIC BES, FAIR, NICA energies)

Speaker: Iurii Karpenko (SUBATECH Nantes)

MIAPP2018.pdf

11:00 Coffee Break

11:30 A new relativistic viscous hydrodynamics code for high-energy heavy-ion collisions

A relativistic viscous hydrodynamic model plays an important role in the quantitative
understanding of the QGP bulk property.
In spite of the success of hydrodynamic models in high-energy heavy-ion collisions,
there are still several issues under discussion.
In particular, we emphasize that a numerical algorithm for solving the relativistic hydrodynamic
equation is one of the important ingredients in developing the hydrodynamic models.
Recent high statistical experimental data at RHIC and the LHC imposed a more rigorous
numerical treatment on the hydrodynamical models.

Here we construct a new relativistic viscous hydrodynamics code optimized in
the Milne coordinates. We split the conservation equations into an ideal part and
a viscous part, using the Strang spitting method. In the code a Riemann solver
based on the two-shock approximation is utilized for the ideal part and the Piecewise
Exact Solution (PES) method is applied for the viscous part.
We check the validity of our numerical calculations by comparing analytical solutions,
the viscous Bjorken’s flow and the Israel–Stewart theory in Gubser flow regime.

Using our developed new relativistic viscous hydrodynamics code, we investigate
the temperature dependence of shear and bulk viscosities from comparison with the
ALICE data; single particle spectra and collective flows at Pb+Pb $\sqrt{s_{NN}} = 2.76$ TeV
collisions at the Large Hadron Collider. We find that from the comprehensive analyses
of centrality dependence of single particle spectra and collective flows, we can extract
the detailed information of the QGP bulk property, without being smeared by the final state
interactions.

Speaker: Prof. Chiho Nonaka (Nagoya University)

2018_MIAPP_nonaka.pptx

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

18:00 → 20:00 BBQ

Wednesday 29 August

09:30 → 13:00 Week 1: Day 3

09:30 Convergence of the Method of moments and Attractor Solutions of the Boltzmann Equation

Relativistic hydrodynamics has played a key role in our understanding of the novel properties of quark-gluon plasma. However, the validity of hydrodynamical models in describing the extreme conditions produced in heavy ion collisions has still not been properly justified theoretically. Even more, the gradient expansion, commonly used to derive hydrodynamics from microscopic theory, has been recently shown to diverge for conformal fluids or relativistic gases undergoing Bjorken flow [1,2], putting under question the definition of hydrodynamics itself.

In this contribution, another approach to derive relativistic hydrodynamics from the Boltzmann equation is discussed: the method of moments [3]. We investigate the convergence of this approximation scheme under Bjorken flow and Gubser flow and show that, in contrast to the gradient expansion, the method of moments appears to be convergent. Finally, we discuss whether there is an attractor for solutions of the full Boltzmann equation, both in the relaxation time approximation and for a collision term including elasctic 2-to-2 collisions.

[1] M. P. Heller and M. Spalinski, "Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation," Phys. Rev. Lett. 115, no. 7, 072501 (2015).
[2] G. S. Denicol and J. Noronha, "Analytical attractor and the divergence of the slow-roll expansion in relativistic hydrodynamics,'' Phys.Rev. D97 (2018) no.5, 056021.
[3] G. S. Denicol, H. Niemi, E. Molnar, and D. H. Rischke, "Derivation of transient relativistic fluid dynamics from the Boltzmann equation," Phys. Rev. D 85, 114047 (2012).

Speaker: Gabriel Silveira Denicol (Universidade Federal Fluminense)

Talk_MIAPP2.pdf

11:00 Coffee Break

11:30 Hydrodynamic flow in small systems?

The "unreasonable effectiveness" of relativistic fluid dynamics in describing high energy heavy-ion and even proton-proton collisions will be demonstrated and discussed. Several recent ideas of optimizing relativistic fluid dynamics for the specific challenges posed by such collisions will be presented, and some thoughts will be offered why the framework works better than originally expected. I will also address the unresolved question where exactly hydrodynamics breaks down, and why.

Speaker: Ulrich Heinz (The Ohio State University)

Heinz_MIAPP_29Aug2018.pdf

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Thursday 30 August

09:30 → 13:00 Week 1: Day 4

09:30 Connecting rapidity-dependent hydrodynamic flow to initial conditions

Relativistic viscous hydrodynamics consists of a set of complicated nonlinear differential equations. Nevertheless, it is possible to find simple relations between particular aspects of the initial conditions and final observables in hydrodynamic simulations of relativistic heavy ion collisions. The canonical example is the event-by-event proportionality between elliptic flow and initial eccentricity. These relations provide a powerful tool for understanding the behavior of the collision system, separating properties of the initial stages and of the QGP medium, and directly accessing such properties from experimental data.

However, these relations have only been developed in a 2-dimensional context, relating initial and final quantities that have been averaged over rapidity. In this talk I will discus extending to rapidity dependent relations -- how to define rapidity-dependent eccentricities and related quantities, to what extent rapidity-dependent flow can be estimated from these eccentricities, and how to extend to non-local relations. These relations will be useful for analyzing various rapidity-dependent correlation observables and using them to determine properties of the collision system, in a similar way to what was done in the rapidity-independent case.

Speaker: Matthew Luzum (Universidade de São Paulo)

LuzumMIAPP.pdf

11:00 Coffee Break

11:30 Longitudinal structure, correlated gluonic hot spots and hadronic dynamics

Longitudinal fluctuations originating from strings in the initial state of high-energy heavy ion collisions are investigated within an AMPT+CLVIsc relativistic fluid dynamics calculation. The results are compared to CMS and STAR data on the decorrelation of event planes.
The sub-structure of protons is crucial to understand collective effects in small systems. In this work, correlations between gluonic hot spots are investigated and in particular the effect of the correlations on flow correlation observables. First, this is evaluated in coordinate space and first results for the corresponding final state momentum space structures after a hydrodynamic evolution are also shown.
A new hadron transport approach (SMASH) is introduced and validated against bulk observables at SIS energies. The hadron gas viscosity as a function of temperature and baryon chemical potential has been calculated within this approach, highlighting the influence of resonance lifetimes on the relaxation dynamics of the system. The effect of hadronic rescattering on flow and correlation observables at high energies is assessed. In addition, this approach is applied to study the initial collisions at intermediate beam energies to understand the baryon stopping dynamics that is highly relevant for the beam energy scan program at RHIC and future FAIR.
Since heavy ion collisions are complex and the modelling contains many uncertainties, we have applied deep learning techniques to assess sensitivities in the transverse momentum - azimuthal angle plane of final state particles to the equation of state. I will report on a proof-of-principle study employing fluid dynamics for the dynamical evolution of the system.

Speaker: Hannah Petersen

Elfner_MIAPP.pdf

13:00 → 14:30 Lunch

15:30 → 17:00 Collectivity in small systems with IP-Jazma

Discussion of arxiv:1808.01276

Speaker: James Nagle (University of Colorado Boulder)

nagle_miapp_explanations_discussion_2018.pptx

16:00 → 16:30 Coffee Break

Friday 31 August

09:30 → 13:00 Week 1: Day 5

09:30 Centrality fluctuation in heavy-ion collisions

Centrality fluctuations (CF) is one of the main uncertainties for interpreting the centrality dependence of many experimental observables. The influence of CF for any bulk observable can be studied from the multi-particle cumulants of its event by event distribution. Using a Glauber-based independent source model, we study the influence of CF on several distributions of multiplicity N and eccentricities e_n: p(N), p(e_n,e_m), p(N,e_n). In ultra-central collisions, where distribution of particle production sources is strongly distorted, we find these cumulants exhibit rich sign-change patterns, due to observable-dependent non-Gaussianity in the underlying distributions. The details of sign- change pattern change with the size of the collision systems. Simultaneous comparison on these different types cumulants between model prediction and experimental data can be used to constrain the CF and particle production mechanism in heavy-ion collisions. Since the concept of centrality and CF are expected to fluctuate in the longitudinal direction within a single event, we propose to use pseudorapidity-separated subevent cumulant method to explore the nature of intra-event fluctuations of centrality and collective dynamics. The subevent method has the potential to separate different mechanisms for multiplicity and flow fluctuations happening at different time scales. The forward detector upgrades at RHIC and LHC will greatly enhance such studies in the future.

Speaker: Jia Jiangyong

Jiangyong_centrality_MIAPP.pdf

11:00 Coffee Break

11:30 Electromagnetic radiation and hydrodynamic modelling of heavy-ion collisions

Most of the information we have about the phases modelled by hydrodynamics in relativistic nuclear collisions comes from the analyses of hadronic collectivity. However, electromagnetic radiation (real and virtual photons) can be both penetrating and soft, and as such opens a unique window to the space-time regions that are opaque to hadrons. In this talk, we will review how measurements of photons and leptons can inform our knowledge of the dynamics of relativistic hadronic reactions at RHIC, LHC, and BES energies, as well as our understanding of the transport coefficients of strongly interacting matter.

Speaker: Prof. Charles Gale (McGill University)

Gale_MIAPP_2018.key

Gale_MIAPP_2018.pdf

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Monday 3 September

09:30 → 13:00 Week 2: Day 6

09:30 Determination of Quark-Gluon-Plasma properties via Bayesian analysis

A primary goal of heavy-ion physics is the measurement of the fundamental properties of the quark-gluon plasma (QGP), notably its transport coefficients and initial state properties. Since these properties are not directly measurable, one relies on a comparison of experimental data to computational models of the time-evolution of the collision to connect measured observables to the properties of the transient QGP state. These model-to-data comparisons are non-trivial due to the large number of model parameters and the non-factorizing sensitivity of measured observables to multiple parameters.

Over the last few years the Duke QCD group has developed techniques based on Bayesian statistics that allow for the simultaneous calibration of a large number of model parameters and the precision extraction of QGP properties including their quantified uncertainties. The computational model used is based on the Trento initial condition model, viscous relativistic hydrodynamics and a microscopic hadronic transport to describe the off-equilibrium late stage hadronic evolution. The analysis starts by selecting a set of salient model parameters - including physical properties such as temperature and/or momentum dependent transport coefficients - then evaluates the event-by-event heavy-ion collision model at a small set of points in the multidimensional parameter space, varying all parameters simultaneously. Gaussian process emulators are used to non-parametrically interpolate the parameter space, providing fast predictions at any point in parameter space with quantitative uncertainty. Finally, the parameter space is systematically explored using a Markov chain Monte Carlo (MCMC) to obtain rigorous constraints on all parameters simultaneously, including all correlations among the parameters.

In this talk I will review the basic components of the Bayesian analysis and discuss recent progress in the determination of QGP initial conditions and transport coefficients with special emphasis on flow observables and the specific shear and bulk viscosity of the QGP.

Speaker: Prof. Steffen Bass (Duke University)

Bass_MIAPP_2018.pdf

10:45 Coffee Break

11:15 Polarization in relativistic fluids

The observation of a finite global polarization in agreement with
theoretical predictions has opened a new dimension in relativistic
heavy ion physics as well as in relativistic hydrodynamics, with
several intriguing connections to chiral and electromagnetic effects.
Very recent experimental observations seem to challenge the
hydrodynamic predictions. In this talk, the status of the theory of
polarization in relativistic fluids is reviewed and possible
developments in the field are discussed.

Speaker: Francesco Becattini (University of Florence (IT))

becattini.pdf

13:00 → 14:00 Lunch

14:30 → 16:00 Week 2: Day 6: Afternoon

14:30 One particle distribution function and shear viscosity in magnetic field: a relaxation time approach

We calculate the $\delta f$ correction to the one particle distribution function in
presence of magnetic field and non-zero shear viscosity within the relaxation time approximation. The $\delta f$ correction is found to be electric charge dependent. Subsequently, we also calculate one longitudinal and four transverse shear viscous coefficients as a function of dimensionless Hall parameter $\chi_{H}$ in presence of the magnetic field. Calculation of invariant yield of $\pi^{-}$ in a simple Bjorken expansion in longitudinal direction along with a realistic transverse expansion of fluid shows that both $p_{T}$ spectra and elliptic flow is altered due to the $\delta f$ correction for a realistic values of the magnetic field and relaxation time.

Speaker: Dr Victor Roy (NISER, India)

MIAPP2018_Victor.pdf

16:00 → 16:30 Coffee Break

Tuesday 4 September

09:30 → 13:00 Week 2: Day 7

09:30 Elliptic flow with polarized beams

We discuss https://arxiv.org/abs/1808.09840

Speaker: Wojciech Broniowski (IFJ PAN)

Broniowski_MIAPP.pdf

10:45 Coffee Break

11:15 Ultracentral heavy-ion collisions as a probe of nuclear structure

In recent years heavy-ion collisions have noted that a preference for both a deformed proton and deformed nuclei are seen in comparing flow observables to relativistic viscous hydrodynamic calculations. Thus far, all deformations of nuclei have only considered the ground state of the nucleus. In the case of XeXe collisions, it was found that the deformed Xenon nucleus increase elliptical flow in very central collisions ~0-5%. In PbPb collisions a similar discrepancy was also found where triangular flow is consistently under-predicted by hydrodynamics calculations. In this talk, the first excited state of Pb nuclei that has a pear shape is considered, which has the effect of increasing triangular flow in central PbPb collisions, which aids in understanding the v3 puzzle in ultracentral PbPb collisions at the LHC.

Speaker: Prof. Jacquelyn Noronha-Hostler (Rutgers University)

MIAPP2018.pdf

13:00 → 14:30 Lunch

15:00 → 15:30 Coffee Break

15:30 → 16:30 Causality and relativistic fluid dynamics

Speaker: Stefan Flörchinger (Heidelberg U.)

FloerchingerMIAPP2018.pdf

Wednesday 5 September

09:30 → 13:00 Week 2: Day 8

09:30 Collectivity of heavy flavor quarks in small collisions system

Recent years, evidence for collective effects has been revealed in small collision systems when looking at events releasing large number of particles. The experimental observations lead to a debate of the formation of strongly coupled Quark-Gluon Plasma in those small collision systems. Azimuthal anisotropy coefficient (vn) of heavy-flavor quarks can shed light on their coupling strength to the hypothesized hydrodynamic medium at a significantly reduces size, and impose further constrains on different interpretations related to the origin of the observed collectivity. In this talk, I will present a review of the most recent experimental results of heavy-flavor quark vn in small collision systems, and discuss their implications, as well as new opportunities and challenges that arise from the results.

Speaker: Zhenyu Chen

11:00 Coffee Break

11:30 Fluctuatioans and long time tails in fluid dynamics

We study the role of fluctuations in relativistic fluid dynamics. We consider two issues, long-time tails in current-current correlation functions, and simulations of baryon diffusion in the vicinity of a critical point.

Speaker: Thomas Schaefer

talk_miapp_2018.pdf

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

18:00 → 20:00 Wine & Cheese

Thursday 6 September

09:00 → 18:00 Topical Workshop

https://indico.ph.tum.de/event/3989/

Friday 7 September

09:00 → 18:00 Topical Workshop

https://indico.ph.tum.de/event/3989/

Saturday 8 September

09:00 → 18:00 Topical Workshop

https://indico.ph.tum.de/event/3989/

Monday 10 September

09:30 → 13:00 Week 3: Day 9

09:30 Open heavy-flavour: present measurements and future directions

Strongly interacting matter at high temperatures and large densities can be created and carefully studied under laboratory conditions in high-energy collisions of heavy atomic nuclei. Especially, heavy quarks (charm and beauty) provide particular good probes to study the QCD plasma and its evolution since they are predominantly produced in initial hard partonic scattering processes in the early stages of the collision.
Both the Large Hadron Collider (LHC) at CERN and the Relativistic Heavy Ion Collider (RHIC) at BNL provide heavy-ion collisions at unprecedented energy densities. The measurement of open heavy-flavour production in such collisions allows the study of the dynamical properties of the plasma phase through the energy loss of heavy quarks.
In this contribution, an overview will be given of current open heavy-flavour measurements from RHIC and the LHC as well as future directions and new observables.

Speaker: Andre Mischke (ERC-Research Group QGP - ALICE, Utrecht University)

MIAPP Munich, Sep.2018, A.Mischke.pdf

MIAPP Munich, Sep.2018, A.Mischke.pptx

11:00 Coffee Break

11:30 Heavy quarkonium dissociation by thermal gluons in the QGP

Using the chromo-electric dipole coupling Hamiltonian from QCD multipole expansion, we derive the dissociation cross sections of heavy quarkonia by thermal gluons at next-to-leading order (NLO, also known as inelastic parton scattering dissociation) in the Quark-Gluon Plasma (QGP) in the framework of second order quantum mechanical perturbation theory. While suffering divergence (infrared and soft-collinear divergences) in vacuum, the cross sections thus derived become finite in the QGP as rendered by the finite thermal gluon masses. In contrast to the leading order (LO, also known as gluo-dissociation) counterparts rapidly dropping off with increasing incident gluon energy, the NLO cross sections exhibits finite value toward high energies because of new phase space being opened up. We then carry out a full calculation of the dissociation rates for various charmonia and bottomonia within a non-relativistic in-medium potential model. The NLO process is shown to dominate the dissociation rate toward high temperatures when the binding energies of heavy quarkonia become smaller relative to the Debye screening mass.

Speaker: Dr Min He (Nanjing University of Science & Technology)

M.He_TU_Munich_Sep.2018.pdf

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Tuesday 11 September

09:30 → 13:00 Week 3: Day 10

09:30 Quarkonium production in p-A collisions: a tool for estimating non-QGP effects in AA,?

Results on quarkonium production in p-Pb collisions from LHC run-1 and run-2 have now reached a considerable accuracy and represent, together with RHIC findings, an important tool for the study of cold nuclear matter effects. While for strongly bound states those effects are probably dominated by nuclear shadowing, excited quarkonium states have been shown to be affected by additional mechanisms, likely related to final state dissociation. As the size of these effects is not negligible, their contribution can be significant and in principle affect our interpretation of A-A results.
It remains to be seen if the information gained via the study of p-A collisions can be effectively used to extract information on the contribution of non-QGP effects to quarkonium production in A-A interactions.

In this contribution, the main results obtained at the LHC from the study of p-Pb collisions will be critically reviewed and possible extrapolations of the presently available data to the conditions of nucleus-nucleus collisions will be discussed. In this way, it could be possible to provide clues to some of the present issues in the field, as the evidence for direct suppression of the bottomonium 1$^{--}$ ground state ($\Upsilon(1S)$) in A-A collisions, as well as more precise insights on the size of the recombination mechanisms for J/$\psi$ production at low $p_{\rm T}$.

Speaker: Enrico Scomparin (INFN Torino (Italy))

Enrico_MIAPP18_seminar.pdf

11:00 Coffee Break

11:30 Potential of LHCb in heavy-ion collisions

LHCb is one of the four large experiments at the LHC. It has taken ion-ion collisions and dedicated fixed-target data samples for the first time in 2015. In this contribution, we will discuss not yet exploited experimental possibilities for this forward acceptance detector both in the correlation as well as in the heavy-flavour sector. The goal is to trigger an open discussion on new ideas that are not exclusively directed towards LHCb.

Speaker: Michael Winn (Paris-Saclay)

MIAPP_mwinn.pdf

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Wednesday 12 September

09:30 → 13:00 Week 3: Day 11

09:30 Heavy Flavor Azimuthal Correlations in Cold Nuclear Matter

It has been proposed that the azimuthal distributions of heavy flavor quark-antiquark pairs may be modified in the medium of a heavy-ion collision. This assumption is tested through next-to-leading order (NLO) calculations of the azimuthal distribution, $d\sigma/d\phi$, including transverse momentum broadening, employing $\langle k_T^2 \rangle$ and fragmentation in exclusive $Q \overline Q$ pair production. The differences between NLO calculations and heavy $Q \overline Q$ pair production in event generators are also discusssed.

First, single inclusive $p_T$ distributions calculated with the exclusive HVQMNR code are compared to those calculated in the fixed-order next-to-leading logarithm approach. Next the azimuthal distributions are calculated and sensitivities to $\langle k_T^2 \rangle$, $p_T$ cut, and rapidity are studied at $\sqrt{s} = 7$ TeV. Finally, calculations are compared to $Q \overline Q$ data in elementary $p+p$ and $p + \overline p$ collisions at $\sqrt{s} = 7$ TeV and 1.96 TeV as well as to the nuclear modification factor $R_{p {\rm Pb}}(p_T)$ in $p+$Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV measured by ALICE. While these studies were done for $p+p$, $p + \overline p$ and $p+$Pb collisions, understanding azimuthal angle correlations between heavy quarks in these smaller, colder systems is important for their interpretation in heavy-ion collisions.

The low $p_T$ ($p_T < 10$ GeV) azimuthal distributions are very sensitive to the $k_T$ broadening and rather insensitive to the fragmentation function. The NLO contributions can result in an enhancement at $\phi \sim 0$ absent any other effects. Agreement with the data was found to be good.

The NLO calculations, assuming collinear factorization and introducing $k_T$ broadening, result in significant modifications of the azimuthal distribution at low $p_T$ which must be taken into account in calculations of these distributions in heavy-ion collisions.

Speaker: Ramona Vogt (LLNL and UC Davis)

MIAPP_talk.pdf

MIAPP_talk (small).pdf

11:00 Coffee Break

11:30 Reсent results on low-mass dielectron production in pp and Pb--Pb collisions with ALICE

Low-mass e$^+$e$^−$ pairs are a particularly useful probe to study the hot and dense medium created in ultra-relativistic heavy-ion collisions. Such pairs are produced during all stages of the collision and carry information about the whole space-time evolution of the system, unperturbed by strong final-state interactions.

The invariant-mass ($m_{ee}$) continuum of dielectrons is extremely rich in physics sources: on top of Dalitz and resonance decays of pseudoscalar and vector mesons, heavy-flavour hadron decays and thermal radiation from the medium contribute to the dielectron continuum. In particular the production of thermal radiation and the possible modification of the spectral function of the short-lived rho meson, decaying into dielectrons, are of great interest. The latter is an especially well suited probe of chiral symmetry restoration, which is predicted to be restored at the high temperatures reached in ultra-relativistic heavy-ion collisions. In the intermediate-mass region, the early temperature of the system can be extracted from the $m_{ee}$-spectrum of its thermal black-body radiation. However, it is first necessary to understand the very large background of correlated dielectron pairs from semi-leptonic charm and beauty hadron decays.

The measurement of dielectron production in inelastic proton--proton collisions serves as crucial vacuum reference needed for the heavy-ion studies. In particular, the intermediate-mass region provides insight into heavy-flavour production complementary to single heavy-flavour hadron measurements. Recently, proton--proton collisions with high charged particle multiplicities have been found to exhibit phenomena similar to those attributed to the quark--gluon plasma formation in heavy-ion collisions. Dielectron measurements may contribute to a better understanding of the underlying physics processes in such collisions.

We present the latest results on low-mass dielectron production from the ALICE Collaboration in pp collisions at $\sqrt{s}$ = 7 TeV and 13 TeV and in central Pb--Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The implications for heavy-flavour and (thermal) direct photon production will be discussed. Furthermore, the results in pp collisions at $\sqrt{s}$ = 13 TeV will be shown as a function of the charged-particle event multiplicity. Finally, perspectives for the LHC Run-3 will be shortly mentioned.

Speaker: Ivan Vorobyev (TUM)

MIAPP_20180912_LMeeVorobyev_wide.pdf

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

18:00 → 20:00 BBQ

Thursday 13 September

09:30 → 13:00 Week 3: Day 12

09:30 Physics opportunities with A high luminosity Fixed Target ExpeRiment at the LHC (AFTER@LHC)

By extracting the beam with a bent crystal or by using an internal gas target, the multi-TeV proton and lead LHC beams allow one to perform the most energetic fixed-target experiments ever and to study pp, pd and pA collisions at sqrt(sNN)=115 GeV and Pbp and PbA collisions at sqrt(sNN)=72 GeV with high precision and modern detection techniques. A broad programme, covering the large-x frontier for particle and astroparticle physics, spin and heavy-ion physics will greatly complement collider experiments, in particular those of RHIC and the EIC project.

In this talk, we will first discuss the possible implementations of a high-luminosity fixed-target experiment at the LHC, by using the ALICE and LHCb detectors, and then present our latest feasibilities studies with an emphasis on heavy-flavor production.

Speaker: Cynthia Hadjidakis (Centre National de la Recherche Scientifique (FR))

MIAPP-AFTER-09-2018.pdf

11:00 Coffee Break

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Friday 14 September

09:30 → 13:00 Week 3: Day 13

09:30 Loop functions in thermal QCD

We present recent computations of loop functions in thermal QCD like the Polyakov loop, correlators of Polyakov loops and Wilson lines, and the cyclic Wilson loop. We discuss divergences and how to renormalize them. Finally we compare with lattice data.

Speaker: Antonio Vairo (TUM)

MIAPP18.pdf

11:00 Coffee Break

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Monday 17 September

09:30 → 13:00 Week 4: Day 14

09:30 Quarkonium production in the Statistical Hadronization Model

Assuming full screening of quarkonia in QGP as well as full thermalization of charm quarks in QGP, quarkonium production in the Statistical Hadronization Model occurs at chemical freeze-out (which, for high energies, likely coincides with the QCD phase boundary). The model describes very well the LHC J/psi data on centrality, transverse momentum and rapidity dependence and gives definite predictions for psi(2S) production.
Whether the same generation mechanism applies for the bottomonium is not incontroversial, but remains a tantalizing possibility, which will be presented as well.

Speaker: Anton Andronic (Muenster University)

andronic_miapp18.pdf

11:00 Coffee Break

11:30 From Heavy-Flavor Transport to Microscopic Properties of the Quark-Gluon Plasma

Heavy-flavor particles are believed to be versatile probes of the medium produced in high-energy nuclear collisions. Their masses provide a large scale which implies several benefits in the theoretical and phenomenological analysis of their vacuum and in-medium properties. We discuss a selfconsistent many-body approach that allows for a comprehensive description of both bound and scattering states, encompassing quarkonia and the diffusion of open heavy flavor in the quark-gluon plasma and through hadronization. We address the problem of extracting the underlying potential interaction using constraints from lattice QCD results on the heavy-quark free energy and quarkonium correlators. We then examine in how far the properties of the heavy-quark interactions can be utilized to understand the bulk, spectral and transport properties of the quark-gluon plasma, to do justice to the original idea of using the heavy-quark systems as a probe of the medium.

Speaker: Ralf Rapp (Texas A&M University)

rapp_miapp18.ppt

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Tuesday 18 September

09:30 → 13:00 Week 4: Day 15

09:30 In-medium properties of heavy flavor mesons from lattice QCD

I will review recent progress in studying the in-medium properties of open heavy flavor mesons and quarkonia from lattice QCD. I will report on recent results on in-medium spectral functions for bottomonia and charmonia from non-relativistic
QCD (NRQCD). Discuss new results on the determination of the complex heavy quark potential on the lattice. Furthermore, I will show results on spatial correlation functions of heavy flavor mesons.

Speaker: Peter Petreczky (BNL)

miapp_prog18.pdf

11:00 Coffee Break

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break

Wednesday 19 September

09:30 → 13:00 Week 4: Day 16

09:30 In-medium effects in the spectrum of baryons

Baryons with various strange content are studied across the deconfinement transition using our Nf=2+1 flavour anisotropic FASTSUM lattices. Below Tc we find that the positive-parity states are largely temperature independent, whereas the negative-parity hadron masses decrease as Tc is approached. Near, and above Tc, the parity partners' masses converge, with parity doubling being closest for hadrons with the least strange quark content, a result expected from chiral symmetry arguments

Speaker: Chris Allton (Swansea University)

allton.pdf

11:00 Coffee Break

11:30 Roundtable discussion: quarkonia

13:00 → 14:30 Lunch

16:15 → 16:45 Coffee Break

Thursday 20 September

09:30 → 13:00 Week 4: Day 17

09:30 The static hard-loop gluon propagator to all orders in anisotropy

We calculate the (semi-)static hard-loop self-energy and propagator using the Keldysh formalism in a momentum-space anisotropic quark-gluon plasma. The static retarded, advanced, and Feynman (symmetric) self-energies and propagators are calculated to all orders in the momentum-space anisotropy parameter ξ. For the retarded and advanced self-energies/propagators, we present a concise derivation and comparison with previously-obtained results and extend the calculation of the self-energies to next-to-leading order in the gluon energy, ω. For the Feynman self-energy/propagator, we present new results which are accurate to all orders in ξ. We compare our exact results with prior expressions for the Feynman self-energy/propagator which were obtained using Taylor-expansions around an isotropic state. We show that, unlike the Taylor-expanded results, the all-orders expression for the Feynman propagator is free from infrared singularities. Finally, we discuss the application of our results to the calculation of the imaginary-part of the heavy-quark potential in an anisotropic quark-gluon plasma.

Speaker: Michael Strickland (Kent State University)

strickland.pdf

11:00 Coffee Break

13:00 → 14:30 Lunch

15:30 → 16:15 Tutorial on HELAC-Onia

Speaker: Hua-Sheng Shao (LPTHE Paris)

Shao_MIAPP_2018.pdf

16:15 → 16:45 Coffee Break

18:00 → 20:00 Bavarian Brotzeit

Friday 21 September

09:30 → 13:00 Week 4: Day 18

09:30 Open quantum systems approach to the study of quarkonium suppression

Heavy quarkonium related observables are very useful to obtain information about the medium created in relativistic heavy ion collisions. In recent years the theoretical description of quarkonium in a medium has moved towards a more dynamical picture in which decay and recombination processes are very important. In this talk we will discuss the equations that describe the evolution of the heavy quarks reduced density matrix in different approximations, highlighting the color dynamics that is absent in the Abelian case. Non-relativistic effective field theories are useful tools to study this problem. Using them we will derive the master equation that describes the evolution of quarkonium inside the medium in the case $1/r\gg T$ and we will analyse a specific temperature regime in which all the information needed from the medium can be encoded in two non-perturbative parameters.
We will also discuss the relation with classical equations (Langevin and Boltzmann) and how they can help reducing the computational cost of solving the master equation.

Speaker: Miguel Ángel Escobedo Espinosa (University of Jyväskylä)

miapp_esco.pdf

11:00 Coffee Break

13:00 → 14:30 Lunch

16:00 → 16:30 Coffee Break