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Thermal Photons and Dileptons in Heavy-Ion Collisions


As penetrating probes, thermal dileptons and photons (which mostly figure at low transverse momentum (pT)) are prime observables to study the properties and evolution of the strongly interacting medium in heavy-ion collisions. The unique access to an in-medium spectral function (vector channel) is possibly the best window on signatures of chiral symmetry restoration and the expected change from hadronic to partonic degrees of freedom. Intermediate-mass dileptons and direct photons carry unique information about the temperatures attained in the collision. While very challenging, both theoretically and experimentally, there is a rapidly growing interest in thermal electromagnetic radiation in the heavy-ion community. This is reflected -- maybe even somewhat triggered -- by two earlier workshops of similar type held at BNL (December 2011, organized by the Physics Department and December 2012, organized by RBRC), that brought together theorists and experimentalists from SIS and SPS to RHIC and LHC. This past year brought exciting new developments, including the dielectron results from the STAR beam energy scan exhibiting the energy dependence of the low-mass excess, and the extension and corroboration of earlier PHENIX results on radial and elliptic photon flow by ALICE, which remain somewhat controversial in current theoretical models.

Other important analyses are expected to be finished soon, including the extension of the RHIC direct photon spectra to lower pT, additional centralities, Fourier components higher than v2, as well as clarifying the low mass dielectron discrepancy between PHENIX and STAR with new PHENIX HBD results. Dielectrons remain a strong component in the mid-term future plans at STAR. For sPHENIX, the acquisition of the BABAR magnet means that the inner radius doubled. With the earlier design, any sensitive low pT photon and electron measurement was virtually impossible. Despite serious challenges even in the new geometry, it is no longer ab ovo excluded, and certainly worth starting an in-depth discussion (in very general terms it has already been discussed in an Appendixof the sPHENIX proposal).

We believe that these very active developments warrant another low pT dielectron and photon workshop at BNL in August 2014. Reviewing the latest experimental and theoretical developments, the goal is to move forward and merge the understanding of the available data including the most recent information as presented at the upcoming QM14 conference in May. In addition, the workshop will further solidify and expand the group of scientists committed to contribute and push forward the field of soft electromagnetic probes.


Presentations will be mainly by invitation. We expect to be able to accommodate a limited number of contributed talks. If you are interested in presenting a contributed talk, please contact one of the workshop organizers directly.

Evening Events

Registered attendees are invited to attend the optional banquet dinner; free of charge for registered participants.

Thursday Night Dinner
Brookhaven Center, South Room
Building 30, Upton Road
August 21, 2014

Workshop Organizers

  • Gabor David (BNL)
  • Ralf Rapp (Texas A&M)
  • Lijuan Ruan (BNL)
  • Ho-Ung Yee (UIC and RBRC)


Click on the "Workshop Information" tab above to find accommodation information.

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Last Modified: December 27, 2017