Orateur
Description
Abstract:
The SMOG2 fixed-target system at LHCb provides a unique opportunity to study cold nuclear matter effects and nuclear structure in a complementary kinematic region with respect to collider measurements. This contribution presents the first measurement of the production of the $\Upsilon(nS, n=1,2,3)$ states in fixed-target collisions where the three states are separately reconstructed. The $\Upsilon(1S)$ production cross-section per nucleon and the excited-to-ground state production ratios ($\Upsilon(nS, n=2,3)/\Upsilon(1S)$) are measured in pAr and pp collisions at $\sqrt{s_{NN}}=113$ GeV using 2024 SMOG2 data. The analysis of both samples also permits the measurement of the $\Upsilon$ nuclear modification factor $R_{pA}$. The contribution also presents studies on the exclusive $\rho$ and $J/\psi$ photoproduction in PbAr fixed-target collisions at $\sqrt{s_{NN}}=70.9$ GeV. The measurement of the $\rho$ photoproduction cross-section as a function of the momentum transfer $|t|$ or as a function of the centre-of-mass rapidity $y^*$ provides a way to disentangle different nuclear shape models and to test ab-initio calculations of the nuclear structure.
| Working Group | WG3. Precision QCD and hard probes |
|---|---|
| Type of oral contribution | Experiment |