Speaker
Description
The ALICE detector at the LHC has undergone a major upgrade in the long shutdown 2019-2022 to be able to take data at much higher rates in Run 3 and beyond. I will present the various challenges of this upgrade, and will show first results of pion and kaon pairs in double gap events taken in pp collisions in Run 3. I will discuss the prospects of developing a partial wave analysis for these pairs.
The intense photon fluxes of relativistic nuclei provide an opportunity to study photonuclear interactions in ultra-peripheral collisions. Exclusive final states of vector mesons can be studied in the process $\gamma$ + A → meson + A. The measurement of photoproduced $\pi^+\pi^− \pi^+ \pi^−$ final states in ultra-peripheral Pb–Pb collisions at √sNN = 5.02 TeV is presented for the first time. The cross section, d$\sigma$/dy, times the branching ratio is measured in the rapidity interval |y| < 0.5 and compared to recent theoretical predictions. The invariant mass distribution is not well described with a single Breit-Wigner resonance, so the production of two independent excited resonances, $\rho$(1450) and $\rho$(1700), and their interference is considered. The values of the masses and widths of the resonances are found to be in a good agreement with the PDG values. The mixing angle between the two resonances is also extracted from the fits to the invariant mass spectra.
