Fotoproducción coherente de $\rho^{0}$ en el LHC

Coherent photoproduction of ½0 mesons in ultra-peripheral Pb-Pb collisions at p sNN = 2.76 TeV is measured for the first time at the LHC and also we show the preliminary results for p-Pb collisions at p sNN = 5.02 TeV. In Pb-Pb collisions the invariant mass and transverse momentum distributions for ½0 production are studied in the ¼+¼¡ decay channel at mid-rapidity. The production cross section in the rapidity range |y|<0.5 is found to be d¾/dy=425§10(est.)+42 ¡50(sist.) mb. Coherent ½0 production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. The results are compared with those from lower energies and with model predictions. In p-Pb collisions the invariant mass and transverse momentum distributions for ½0 production are studied in the ¼+¼¡ decay channel on 7 different rapidity bins corresponding to different energies (Pb-p), also a measurement is made in the rapidity range |y|<0.5 at hW°pi= 82 GeV for both samples (Pb-p and p-Pb). The measured cross section is in agreement with the HERA results. The production cross section in the diferent rapidity bins is found to be: ¾°p = 8.441§0.390(est.); 9.026§0.277(est.); 9.973§0.341(est.); 10.354§0.341(est.); 11.855§0.421(est.); 12.092§0.478(est.); 9.203§0.544(est.) ¹b, at energies hW°pi=59, 69, 78, 86, 95, 105, y 119 GeV, respectively. While at the rapidity range |y|<0.5, where two data sample were analized from two different triggers, the cross section is found to be: ¾°p=11.190§0.369(est.) ¹b (p-Pb), and 10.486§0.163(est.) ¹b (Pb-p).