# XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS16)

Apr 11 – 15, 2016
DESY Hamburg
Europe/Berlin timezone

## Light-by-light scattering in UPC at the LHC

Apr 13, 2016, 9:00 AM
15m
SR4b (DESY Hamburg)

### SR4b

#### DESY Hamburg

Small-x, Diffraction and Vector Mesons

### Speaker

Dr Mariola Klusek-Gawenda (Institute of Nuclear Physics, Polish Academy of Sciences)

### Description

We will discuss diphoton semi(exclusive) production in ultraperipheral $PbPb$ collisions at energy of $\sqrt{s_{NN}}=$ 5.5 TeV (LHC). The calculation is based on equivalent photon approximation in the impact parameter space. The cross sections for elementary $\gamma \gamma \to \gamma \gamma$ subprocess are calculated including two different mechanisms: \begin{itemize} \item box diagrams with leptons and quarks in the loops and \item a vector-meson dominance (VDM-Regge) contribution with virtual intermediate hadronic (vector-like) excitations of the photons. \end{itemize} We get much higher cross sections in $PbPb$ collisions ($310$ nb) than in earlier calculation from the literature $35 \pm 7$ nb\footnote{D. d'Enterria and G.G. da Silveira, Phys. Rev. Lett. \textbf{111} (2013) 080405}. This opens a possibility to study the $\gamma \gamma \to \gamma \gamma$ (quasi)elastic scattering at the LHC. We will present many interesting differential distributions which could be measured by the ALICE, CMS or ATLAS Collaborations. We will show the range of energy $W_{\gamma\gamma}$ where elastic $\gamma \gamma$ scattering could be measured in the heavy-ion collisions. \vspace{2cm} This talk will be based on our recent paper:\\ - M. K{\l}usek-Gawenda, P. Lebiedowicz and A. Szczurek, arXiv/nucl-th:1601.07001.

### Primary author

Dr Mariola Klusek-Gawenda (Institute of Nuclear Physics, Polish Academy of Sciences)

### Co-authors

Prof. Antoni Szczurek (Institute of Nuclear Physics, Polish Academy of Sciences) Dr Piotr Lebiedowicz (Institute of Nuclear Physics, Polish Academy of Sciences)

 Slides