by Dr. K. Sridhar, Azim Premji University, Bangalore

Abstract:

Non-Relativistic QCD (NRQCD) has been used with considerable success for understanding charmonium production and decays but the true tests of NRQCD -- the parameter-free predictions that rely on the heavy-quark symmetry of the NRQCD Lagrangian viz., the polarisation of J/psi and psi' and the prediction of the eta_c cross section -- fail miserably to conform with experiment. This has provoked us to propose a modification of NQRCD where we invoke soft, perturbative gluon emission from the intermediate colour-octet c c(bar) states. This model is able to
i) provide very good fits to Tevatron data on J/psi, psi' and chi production,
ii) provide parameter-free predictions for J/psi, psi' and chi production which are in excellent agreement with the data from LHC, and
iii) provide a complete resolution of the LHCb eta_c anomaly. Results on bottomonium production at the LHC and on quarkonia production in nucleus-nucleus collisions will also be presented.