Graviton and Radion Production at LHC: From pp and PbPb Collisions
  If the Planck scale is around a TeV in theories with large extra dimension, then gravitons should be produced in high energy hadronic collisions at the LHC. In this paper we compute the direct graviton production cross section in a pp and PbPb collision at LHC at \sqrt s^{NN}= 14 TeV and 5.5 TeV respectively. The graviton production cross section in a lead-lead collision is enhanced in comparison to a pp collision at LHC depending upon the minimum transverse energy of the jet E_{T,jet}^{min} above which the graviton production cross section is computed. For two extra dimensions and above E_{T,jet}^{min} = 100, 500, 1000, 1500 GeV the ratio of graviton production cross sections in a PbPb collision to that in a pp collision is found to be 2220, 400, 43, 2. For four extra dimensions this ratio is found to be 470, 100, 10, 0.5. In the Randall-Sundrum model the radion production cross section is also found to be enhanced in a lead-lead collision over that in a pp collision at LHC. The ratio of the radion production cross sections in a PbPb collision to that in a pp collision at LHC is found to be 1650, 460, 180, 67, 23, 1 for radion of masses 100, 500, 1000, 1500, 2000, 3000 GeV respectively. 
Gouranga C. Nayak (LANL)