Speaker
Description
A large excess in the yield of $\mathrm{J/\psi}$ at very low transverse momentum (${p}_\mathrm{T}<\mathrm{300\ MeV/}c$) and forward rapidity (2.5< $y$ <4.0) was recently reported by ALICE using the LHC Run-1 data, in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV. This is suggestive of coherent $\mathrm{J/\psi}$ photo-production, similar to measurements in ultra-peripheral collisions (UPC), where the nuclei only interact electromagnetically.
During the LHC Run-2, the measurement of the very low ${p}_\mathrm{T}$ $\mathrm{J/\psi}$ at mid-rapidity (-0.9< $y$ <0.9) in the di-electron decay channel was possible thanks to the large sample of recorded Pb-Pb collisions. The central barrel detectors provide a good momentum resolution, and make the measurement sensitive to the key characteristics of $\mathrm{J/\psi}$ coherent photo-production, like the corresponding transverse momentum spectrum.
In this poster, we will present the ${p}_\mathrm{T}$-integrated and ${p}_\mathrm{T}$-dependent coherent $\mathrm{J/\psi}$ photo-production cross-section at mid rapidity in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV. Our data will be discussed in comparison to the UPC measurements and model calculations. The expectations for this measurements with LHC Run-3 and Run-4 data will be discussed.
| Content type | Experiment |
|---|---|
| Collaboration | ALICE |
| Centralised submission by Collaboration | Presenter name already specified |
