Speaker
Sanshiro Mizuno
(University of Tsukuba (JP))
Description
Soft photons are of particular interest since they are unmodified once
produced, and thus carry information about the space-time thermal
properties of the medium. We present new results on the centrality
dependence of soft single photons in Au$+$Au collisions, down to $p_T
= 400$ MeV/$c$ via photon conversions to $e^+e^-$ pairs. These
measurements provide stringent tests of the hydrodynamic space-time
evolution as a detailed function of the collision geometry.
These soft photons have different angular emission patterns depending
on their production mechanism. Previous published PHENIX results
indicate that the second order Fourier coefficient ($v_2$) is postive
for $p_T < 4$ GeV/$c$, which is qualitatively explained by
hydrodynamical model calculations, but not quantitatively. The
3\textsuperscript{rd} order Fourier coefficient ($v_3$) of photons has
been proposed as a critical additional handle to understand the photon
emission. Photons emitted under the presence of strong magnetic field
created in the collision would have a significant influence on $v_2$
while very little on $v_3$. In contrast, hydrodynamical models
predict a sizable photon $v_3$. We report the latest results on the
centrality dependence of the soft photon production and the $v_2$ and
$v_3$ coefficients in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$ GeV.
| On behalf of collaboration: | PHENIX |
|---|
Author
Sanshiro Mizuno
(University of Tsukuba (JP))
