Speaker
Prof.
Ulrich Heinz
(The Ohio State University)
Description
Azimuthally sensitive HBT interferometry can complement
elliptic flow measurements by constraining the spatial deformation
of the source and its time evolution. Performing these measurements on
photons allows us to access the fireball evolution at earlier times than
with hadrons. Using ideal hydrodynamics to model the space-time
evolution of the collision fireball, we explore theoretically various
aspects of 2-photon intensity interferometry with transverse momenta
up to 2 GeV, in particular the azimuthal angle dependence of the HBT
radii in non-central collisions. We find interesting differences in the
structure of the photon correlation function when compared to that of
hadrons, caused by the masslessness of the photon. We highlight the
dual nature of thermal photon emission, in both central and non-central
collisions, resulting from the superposition of QGP and hadron resonance
gas photon production. This signature is present in both the thermal
photon source function and the HBT radii extracted from Gaussian fits
of the 2-photon correlation function. We find that the azimuthal oscillation
amplitude of the sideward HBT radius for photons tracks the source
eccentricity not only at KT=0 (as is the case for pions), but for all KT.
This allows to reconstruct the time-evolution of the source eccentricity
from the KT-dependence of the sideward oscillation amplitude.
Primary author
Prof.
Ulrich Heinz
(The Ohio State University)
Co-author
Dr
Evan Frodermann
(University of Minnesota)
