Speaker
Description
There is serious disagreement between the predictions of Non-Relativistic Quantum Chromodynamics (NRQCD) and the data on $J/\psi$ polarisation which has persisted for almost a quarter of a century. We find that if we account for the effect of perturbative soft gluons on the intermediate charm-anticharm octet states in NRQCD then the polarisation problem can be resolved. In addition, this model, when used to fit the Run 1 data on $J/\psi$, $\psi'$ and $\chi_c$ production from the CDF experiment at Tevatron, gives good fits and yields values of (energy- independent) non-perturbative parameters. These, in turn, can be used to make parameter-free predictions for $J/\psi$ and $\psi'$ data from the CMS experiment at the Large Hadron Collider and the predictions are in excellent agreement with then CMS data. We have also made the predictions for both $\chi_c^1$ and $\chi_c^2$ production at $\sqrt{s}=$7 TeV and find excellent agreement with data from the ATLAS experiment. Furthermore, we have extended our work for $\eta_c$ and made the comparision with LHCb experimental data using the non-perturbative parameter for $J/\psi$ production from the CDF experiment at Tevatron. It also gives a very good agreement with the data from LHCb experiment for $\sqrt{s}=$7 TeV, 8 TeV, 13 TeV.
$\bf{References:}$
[1] Sudhansu S. Biswal, Sushree S. Mishra and K. Sridhar, Phys. Lett. B $\bf{832}$, 137221 (2022) [arXiv:2201.09393 [hep-ph]].
[2] Sudhansu S. Biswal, Sushree S. Mishra and K. Sridhar, [arXiv:2206.15252 [hep-ph]]; Communicated to journal.
| Session | Heavy Ions and QCD |
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