31st International Workshop on Deep Inelastic Scattering

K+K− photoproduction in ultra-peripheral Pb–Pb collisions with ALICE

Non programmé

20m

Maison MINATEC, Grenoble, FRANCE

Regular parallel talk WG2: Small-x, Diffraction and Vector Mesons

Orateur

Minjung Kim (UC Berkeley)

Description

In ultra-peripheral collisions (UPCs), the photon fluctuates to a quark-antiquark dipole which then elastically scatters off the nucleus, emerging as vector meson  or an oppositely charged pseudoscalar meson pair.
The powerful particle identification capability of ALICE allows the study of photoproduced ${\pi }^{+}{\pi }^{-}$ pairs and $K^{+}{K}^{-}$ pairs at midrapidity in Pb--Pb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 5.02 TeV. We will present the exclusive $K^{+}{K}^{-}$ photoproduction cross section in ALICE, measured for the first time in UPCs. We will discuss the interference between the resonance contribution of $\varphi (1020)\to K^{+}{K}^{-}$ and direct oppositely charged pair production, obtained from a fit to the invariant mass spectrum of $K^{+}{K}^{-}$ pairs, with comparison to the ${\pi }^{+}{\pi }^{-}$ system.