Speaker
Michal Broz
(Czech Technical University (CZ))
Description
Vector mesons are copiously produced in ultra-peripheral nucleus-nucleus collisions
In these collisions, the nuclei are separated by an impact parameter
larger than the sum of the nuclear radii.
The interaction proceeds through the emission of a photon, generated by the electromagnetic field of one of the two nuclei, fluctuating into a quark-antiquark pair,that interacts with the target nucleus.
The cross section for this process is sensitive to the gluon
distribution in the nucleus and can therefore probe the nuclear gluon shadowing.
The ALICE Collaboration has performed the first measurement of the
coherent $\psi$(2S) photoproduction cross section in Pb-Pb collisions at the LHC.
This charmonium excited state is tagged via the $\psi(2S) \rightarrow
l^{+} l^{-}$ and $\psi(2S) \rightarrow J/\psi\pi^{+}\pi^{-}$ decays,
where the $J/\psi$ decays into two leptons.
The measured cross section and its ratio to the $J/\psi$ cross
section are compared to predictions from theoretical models.
| On behalf of collaboration: | ALICE |
|---|
Author
Michal Broz
(Czech Technical University (CZ))
