### Speakers

Antoni Szczurek
(Institute of Nuclear Physics)
Mariola Jadwiga Klusek-Gawenda
(Polish Academy of Sciences (PL))

### Description

We present, for the first time, differential distributions for two $\rho^0$ meson
production in exclusive ultraperipheral, ultrarelativistic collisions
via a double scattering mechanism. The calculations are done in the impact
parameter space. The cross section for $\gamma A \to \rho^0 A$ is
parametrized based on an existing calculation. Smearing of $\rho^0$ masses
is taken into account. The results of calculations are compared at the RHIC
and LHC energies.
The cross section for the double scattering mechanism
is an order of magnitude larger at $M_{\rho \rho} <$ 2 GeV
and more than two orders of magnitude at $M_{\rho \rho} >$ 3 GeV,
than that for the photon-photon mechanism.
The double scattering mechanism populates somewhat larger $\rho^0 \rho^0$
invariant masses and larger rapidity distances between the two $\rho^0$
mesons compared to the two-photon mechanism. The mechanism considered gives a
significant contribution to the $A A \to A A \pi^+ \pi^- \pi^+ \pi^-$
reaction.
Some observables related to charged pions are presented too.
We compare results of our calculation with the STAR collaboration
results on four charged pion production.
The shape in invariant mass of the four-pion system is very
similar to the measured one.
We discuss a possibility of identifying the double scattering mechanism at the LHC.
Literature:
M. Klusek-Gawenda and A. Szczurek,
Phys. Rev. C89 (2014) 024912.

### Primary author

Antoni Szczurek
(Institute of Nuclear Physics)

### Co-author

Mariola Jadwiga Klusek-Gawenda
(Polish Academy of Sciences (PL))