Abstract
This thesis presents the analysis of the coherent ρ' mesons photoproduction in ultra-peripheral Pb-Pb collisions at the center of mass energy of √(s_NN ) = 5.02 TeV with the ALICE detector at the Large Hadron Collider. The STAR collaboration has measured the π^+ π^- π^+ π^- decay channel previously in Au-Au collisions at a collision energy of 200 GeV and observed a wide peak at 1.540 GeV/c^2. In contrast, the Particle Data Group lists two separate particles at 1.465 GeV/c^2 and 1.720 GeV/c^2. I have measured the π^+ π^- π^+ π^- decay channel of the ρ' meson at a higher collision energy, with higher statistics to resolve this contradiction.
I have analyzed 4.52 x 10^8 events. Out of that 1.46 x 10^4 events satisfied the selection criteria. The raw ρ' yield was approximately corrected for track reconstruction efficiency, but a full efficiency correction was not done. The detector acceptance was estimated using the STARlight Monte Carlo simulations. The efficiency-corrected
ρ' mass distribution was fit with both a single Breit-Wigner function, to compare with the results obtained by the STAR collaboration and with a combination of two Breit-Wigner functions, as expected based on the Particle Data Group. The results
I obtained favors the two Breit-Wigner interpretation, but this should be confirmed after doing a full efficiency correction