# 25ème Congrès Général de la SFP 2019

8-12 July 2019
Cité des Congrès
Europe/Paris timezone

## Measurement of an excess in the yield of $J/\psi$ at very low $p_T$ in Pb-Pb collisions at $\sqrt{s_{NN}} =5.02$ TeV with ALICE

Not scheduled
20m
Auditorium 450 (Cité des Congrès)

### Auditorium 450

#### Cité des Congrès

5, rue de Valmy, Nantes, France Site web : https://lacite-nantes.fr/
Poster

### Speaker

Ophélie Bugnon (Subatech)

### Description

In 2015, the ALICE collaboration reported the first excess in the yield of $J/\psi$ at very low transverse momentum ($p_T<0.3\ GeV/c$) in the forward rapidity region ($2.5 < y < 4$) in peripheral Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV at the CERN LHC. [1] The coherent photo-production is proposed as the potential underlying physics mechanism. This mechanism is the main responsible for low-$p_T$ $J/\psi$ production in ultra-peripheral collisions. However, the observation of a large effect also in more central collisions that are dominated by the hadronic interactions was quite surprising. If the photo-production is confirmed as the origin of the excess, this will open up fundamental questions on the nature of the coherence in collisions where the nuclei break up. Furthermore, the $J/\psi$ from the coherent photo-production might become an additional probe of the Quark and Gluon Plasma. This poster presents the analysis strategy for Pb-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV for which the data sample is expected to be about thirty times larger than at $\sqrt{s_{NN}} = 2.76$ TeV.

References
[1] ALICE Collaboration, J. Adam et al., “Measurement of an excess in the yield of $J/\psi$ at very low $p_T$ in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV", Phys.Rev.Lett.116(2016) 222301, arXiv:1509.08802 [nucl-ex].

Choix de session parallèle 1.3 Physique nucléaire: physique hadronique et QCD

### Primary author

Ophélie Bugnon (Subatech)

### Presentation Materials

There are no materials yet.