Dr. Stefan Floerchinger bio photo

Dr. Stefan Floerchinger

Theoretical physicist at Heidelberg University.

Email InspireHEP arXiv


Physics of the quark-gluon plasma



  • Prof. Dr. Carlo Ewerz (ITP Heidelberg & EMMI/GSI & FIAS)
    AdS/CFT and its application to heavy quarks in hot plasmas

    [Wednesday, July 20, 16:15 h, Physikalisches Institut, INF 226, SR 01.106]

    One of the most surprising findings in string theory is the AdS/CFT correspondence (or gauge/gravity correspondence) which establishes a new holographic relation between gauge theories and gravitational theories. In particular, a strongly coupled gauge theory can be equivalently described by weakly coupled gravity in a higher-dimensional space. This opens a revolutionary new way to address complicated dynamical problems in strongly coupled systems and has contributed to the discovery of universal behavior in many strongly coupled quantum systems. In this talk I will give an introduction to the AdS/CFT correspondence and some of its generalizations. I will then discuss some recent results concerning the physics of heavy quarks in a hot plasma.

  • Prof. Dr. Johanna Stachel (PI Heidelberg) & Dr. Alexander Rothkopf (ITP Heidelberg)
    Quarkonia as probes of deconfinement at the LHC

    [Wednesday, July 6, 16:15 h, Physikalisches Institut, INF 226, SR 01.106]
    [slides of J. Stachel], [slides of A. Rothkopf]

    Experimental data on quarkonia at the LHC, including the very recently released first results from run 2, are summarized. The focus will be on PbPb collisions, but the most relevant data from pp and pPb collisions will be included. Data will be compared to the statistical hadronization model and to some transport model calculations. The theory part presents the latest results on kinetically thermalized heavy quark-antiquark bound states using lattice QCD input. Based on the lattice in-medium heavy-quark potential, we compute and discuss finite temperature spectral functions for Charmonium and Bottomonium. These form the basis for estimating e.g. the J/Psi / Psi’ ratio at freezeout or the modification of feed-down fractions from the P-wave to the S-wave states.

  • Prof. Dr. Peter Braun-Munzinger (GSI Darmstadt & PI Heidelberg) & Dr. Stefan Floerchinger (ITP Heidelberg)
    Probability distributions and moments of hadron production in relativistic nuclear collisions: theoretical perspectives and experimental challenges

    [Wednesday, June 22, 16:15 h, Physikalisches Institut, INF 226, SR 01.106]
    [sildes of P. Braun-Munzinger], [slides of S. Floerchinger]

    Introduction and perspective
    Hadron production, Lattice QCD and the QCD phase structure
    Susceptibilities and 1st moments
    Higher moments – the experimental challenges
    Experimental outlook
    Theory of fluctuations and correlations in QCD matter
    Freeze-out with correlations
    Theoretical challenges

  • Prof. Dr. Raju Venugopalan (BNL Brookhaven & ITP Heidelberg)
    Kibble-Zurek dynamics and universal off-equilibrium scaling of critical cumulants in the QCD phase diagram

    [Wednesday, June 8, 16:15 h, Physikalisches Institut, INF 226, SR 01.106]

    We exploit the universality between the QCD critical point and the three dimensional Ising model to derive closed form expressions for non-equilibrium critical cumulants on the crossover side of the critical point. Novel expressions are obtained for the non-Gaussian Skewness and Kurtosis cumulants; our results reveal that they can differ both in magnitude and sign from equilibrium expectations. We show further that key elements of the Kibble-Zurek framework of non-equilibrium phase transitions can be employed to describe the dynamics of these critical cumulants. As a consequence, observables sensitive to critical dynamics in heavy-ion collisions are expressible as universal scaling functions and thereby provide powerful model independent guidance in searches for the QCD critical point.

  • Prof. Dr. Klaus Reygers (PI Heidelberg) & Dr. Naoto Tanji (ITP Heidelberg)
    Pre-equilibrium photon production and the direct-photon puzzle

    [Wednesday, May 11, 16:15 h, Physikalisches Institut, INF 226, SR 01.106]
    [sildes of K. Reygers], [slides of N. Tanji]

    The observed yield and azimuthal anisotropy of direct photons in heavy-ion collisions are not well described by hydrodynamic models which nicely fit hadronic observables. This so-called direct-photon puzzle challenges the standard model of the space-time evolution of these collisions. We discuss possible ways to solve this puzzle. In particular, we focus on direct-photon Hanbury Brown-Twiss correlations as a tool to investigate whether direct photons mostly come from the early or late stage of the collision. On the theoretical side, a better understanding of photon production in the pre-equilibrium stage of the collisions might help solve the puzzle. Aiming at a first-principle-based study of the pre-equilibrium photon production, the quark production in inhomogeneous classical gauge fields has been calculated by using real-time lattice simulation technique. It will be shown that photons emitted from the produced quarks by a classical process exhibit a thermal-like exponential spectrum though the system is far away from equilibrium.

  • Prof. Dr. Charles Gale (McGill U., Montreal)
    QCD under extreme conditions: Hot, shiny fluids and sticky business

    [Wednesday, April 27, 17:00 h, Kirchhoff Institute for Physics, INF 227, HS 2]

    The phase diagram of Quantum Chromodynamics (QCD, the theory of the strong interaction) is only poorly known. There is currently a vibrant experimental and theoretical program that concentrate on the study and the characterization of the quark-gluon plasma, a fundamental state of matter that existed a few microseconds after the Big Bang. I will describe the theoretical aspects of this endeavour, and highlight some of the surprises uncovered along the way. In particular, I will spend some time reviewing what can be learned from the study of electromagnetic radiation from those high-energy collisions.