Thermal electromagnetic radiation in heavy-ion collisions

  • R. Rapp
  • H. van HeesEmail author
Part of the following topical collections:
  1. Exploring strongly interacting matter at high densities - NICA White Paper


We review the potential of precise measurements of electromagnetic probes in relativistic heavy-ion collisions for the theoretical understanding of strongly interacting matter. The penetrating nature of photons and dileptons implies that they can carry undistorted information about the hot and dense regions of the fireballs formed in these reactions and thus provide a unique opportunity to measure the electromagnetic spectral function of QCD matter as a function of both invariant mass and momentum. In particular we report on recent progress on how the medium modifications of the (dominant) isovector part of the vector current correlator (\( \rho\) channel) can shed light on the mechanism of chiral symmetry restoration in the hot and/or dense environment. In addition, thermal dilepton radiation enables novel access to a) the fireball lifetime through the dilepton yield in the low invariant-mass window 0.3 GeV \(\leq M \leq\) 0.7 GeV, and b) the early temperatures of the fireball through the slope of the invariant-mass spectrum in the intermediate-mass region (1.5 GeV \(< M <\) 2.5 GeV). The investigation of the pertinent excitation function suggests that the beam energies provided by the NICA and FAIR projects are in a promising range for a potential discovery of the onset of a first-order phase transition, as signaled by a non-monotonous behavior of both low-mass yields and temperature slopes.


  1. 1.
    L.D. McLerran, T. Toimela, Phys. Rev. D 31, 545 (1985)ADSCrossRefGoogle Scholar
  2. 2.
    C. Gale, J.I. Kapusta, Nucl. Phys. B 357, 65 (1991)ADSCrossRefGoogle Scholar
  3. 3.
    Particle Data Group (K. Nakamura et al.), J. Phys. G 37, 075021 (2010)ADSCrossRefGoogle Scholar
  4. 4.
    Y. Aoki, Z. Fodor, S.D. Katz, K.K. Szabo, Phys. Lett. B 643, 46 (2006)ADSCrossRefGoogle Scholar
  5. 5.
    T. Bhattacharya et al., Phys. Rev. Lett. 113, 082001 (2014)ADSCrossRefGoogle Scholar
  6. 6.
    E.V. Shuryak, Phys. Rep. 61, 71 (1980)ADSMathSciNetCrossRefGoogle Scholar
  7. 7.
    R. Rapp, Acta Phys. Pol. B 42, 2823 (2011)CrossRefGoogle Scholar
  8. 8.
    H. van Hees, C. Gale, R. Rapp, Phys. Rev. C 84, 054906 (2011)ADSCrossRefGoogle Scholar
  9. 9.
    G.J. Gounaris, J.J. Sakurai, Phys. Rev. Lett. 21, 244 (1968)ADSCrossRefGoogle Scholar
  10. 10.
    N.M. Kroll, T.D. Lee, B. Zumino, Phys. Rev. 157, 1376 (1967)ADSCrossRefGoogle Scholar
  11. 11.
    P.M. Hohler, R. Rapp, Phys. Lett. B 731, 103 (2014)ADSCrossRefGoogle Scholar
  12. 12.
    R. Rapp, J. Wambach, Eur. Phys. J. A 6, 415 (1999)ADSCrossRefGoogle Scholar
  13. 13.
    R. Rapp, J. Wambach, Adv. Nucl. Phys. 25, 1 (2000)CrossRefGoogle Scholar
  14. 14.
    T. Hatsuda, Y. Koike, S.-H. Lee, Nucl. Phys. B 394, 221 (1993)ADSCrossRefGoogle Scholar
  15. 15.
    J.I. Kapusta, E.V. Shuryak, Phys. Rev. D 49, 4694 (1994)ADSCrossRefGoogle Scholar
  16. 16.
    P.M. Hohler, R. Rapp, Ann. Phys. 368, 70 (2016)ADSMathSciNetCrossRefGoogle Scholar
  17. 17.
    P.M. Hohler, R. Rapp, Phys. Rev. D 89, 125013 (2014)ADSCrossRefGoogle Scholar
  18. 18.
    G. Aarts, C. Allton, S. Hands, B. Jäger, C. Praki, J.-I. Skullerud, Phys. Rev. D 92, 014503 (2015)ADSCrossRefGoogle Scholar
  19. 19.
    NA60 Collaboration (H.J. Specht), AIP Conf. Proc. 1322, 1 (2010)Google Scholar
  20. 20.
    CERES/NA45 Collaboration (D. Adamova et al.), Phys. Rev. Lett. 91, 042301 (2003)ADSCrossRefGoogle Scholar
  21. 21.
    CERES/NA45 Collaboration (G. Agakichiev et al.), Eur. Phys. J. C 41, 475 (2005)ADSCrossRefGoogle Scholar
  22. 22.
    STAR Collaboration (P. Huck), Nucl. Phys. A 931, 659 (2014)CrossRefGoogle Scholar
  23. 23.
    STAR Collaboration (L. Adamczyk et al.), Phys. Rev. C 92, 024912 (2015)ADSCrossRefGoogle Scholar
  24. 24.
    R. Rapp, Adv. High Energy Phys. 2013, 148253 (2013)CrossRefGoogle Scholar
  25. 25.
    S. Endres, H. van Hees, J. Weil, M. Bleicher, Phys. Rev. C 91, 054911 (2015)ADSCrossRefGoogle Scholar
  26. 26.
    S. Endres, H. van Hees, J. Weil, M. Bleicher, Phys. Rev. C 92, 014911 (2015)ADSCrossRefGoogle Scholar
  27. 27.
    PHENIX Collaboration (A. Adare et al.), Phys. Rev. C 81, 034911 (2010)ADSCrossRefGoogle Scholar
  28. 28.
    R. Rapp, H. van Hees, Phys. Lett. B 753, 586 (2016)ADSCrossRefGoogle Scholar
  29. 29.
    PHENIX Collaboration (A. Adare et al.), Phys. Rev. C 93, 014904 (2016)ADSCrossRefGoogle Scholar

Copyright information

© SIF, Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Cyclotron Institute and Department of Physics & AstronomyTexas A&M UniversityCollege StationUSA
  2. 2.Institut für Theoretische PhysikGoethe-Universität FrankfurtFrankfurtGermany
  3. 3.Frankfurt Institute of Advanced Studies (FIAS)FrankfurtGermany

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