Conveners
Parallel Session 2.3: Electromagnetic Probes (II)
- Hideki Hamagaki (Nagasaki Inst. of Applied Science (JP))
Direct photon measurement in heavy-ion collisions provides a valuable set of observables to study the hot QCD medium since these photons are
produced at different stages of the collision and escape the medium unaffected. In pp collisions,
the direct photon yield at high transverse momentum ($p_T$) are produced in hard scattering (prompt photons),
but also in the fragmentation of high $p_T$...
PHENIX has discovered a large yield of low momentum direct photons emitted with large azimuthal anisotropy in 200 GeV Au+Au collisions. The large yield suggests early emission at high temperature, while the large anisotropy points towards late emission when the radial flow of the matter is fully developed, but the temperature is already reduced. This apparent contradiction poses a significant...
We discuss photon emission at the stage of hadronization as a possible resolution to the direct-photon puzzle. In an ordinary plasma, it is well known that photon emission occurs when a plasma goes back to a normal state through recombination processes such as $e^- + p^+ \to H + \gamma$ for an electron-proton plasma. This is called the “radiative recombination”. A similar process should take...
Large scale classical statistical simulations confirm [1] that the correct kinetic theory describing the off-equilibrium Glasma is the "bottom-up” thermalization scenario [2]. Detailed simulations demonstrate that the bottom-up results match on to relativistic viscous hydrodynamics on time scales of order 1 Fermi for realistic values of the coupling [3]. We explore the detailed implications of...
The polarization of direct photons
produced in an ultrarelativistic heavy-ion collision reflects the
anisotropy of the quark-gluon plasma created in the collision. We describe a general framework, based on the photon spectral functions in the plasma, for analyzing the angular distribution and thus the polarization of dileptons in terms of the plasma anisotropies. The rates of dilepton...
