ψ(2S) Production in p-Pb and Pb-Pb Collisions with the ALICE Experiment

The inclusive production of the charmonium state ψ ( 2 S ) was studied in p-Pb and Pb-Pb collisions at s NN = 8.16 TeV and 5.02 TeV respectively, using the ALICE detector at the CERN LHC. The ψ ( 2 S ) is less bound than the J / ψ and it represents an interesting probe for the study of cold nuclear matter effects in p-Pb collisions, while in the Pb-Pb system its formation can be strongly influenced by QGP production. The measurements are performed in different center-of-mass rapidity ranges, 2.03 < y cms < 3.53 and −4.46 < y cms < −2.96 for p-Pb collisions and 2.5 < y cms < 4.0 for Pb-Pb collisions, down to zero transverse momentum, through the ψ ( 2 S ) → μ + μ - decay channel. The results are compared to those obtained for the J / ψ and with theoretical predictions.

Comment on the X(3915) nonstandard hadron candidate

I review the experimental evidence for the X(3915), the candidate nonstandard meson associated with ωJ/ψ resonance-like peaks in B → KωJ/ψ and γγ → ωJ/ψ near M(ωJ/ψ) = 3920 MeV, and address the conjecture that it can be identified as the χ′c2, the radial excitation of the χc2 charmonium state. Since the partial decay width for B → KX(3915) is at least an order-of-magnitude higher than that for B → Kχc2, its assignment as the χ’c2 is dubious.

Recent LHCb results on charm and charmonium spectroscopy

The recent results on charm and charmonium spectroscopy obtained by the LHCb collaboration are reviewed. In particular, observation of new charmonium state in the decay modes X(3842) → D0D−0 and X(3842) → D+D−, evidence for ηc(1S)π− resonance in B0 → ηc(1S)K+π− decay and observation of three narrow P+c pentaquark candidates decaying to J/ψp are obtained. Also, lifetimes of Ξ+c, Λ+c, Ξ0c and Ω0c baryons are measured with high precision.

Recent heavy-flavour results from ATLAS

The ATLAS heavy-ion program utilizes heavy-flavour hadrons to probe the hot, dense matter formed at the LHC. Quarkonium measurements have been performed in pp, p+Pb and Pb+Pb systems to study medium effects. The Pb+Pb results show a strong suppression of charmonium productions in more central events. Proton-lead interactions show little modification of the 1S charmonium state, but seem to indicate a centrality dependence of the 2S state. Upsilons have been studied in p+Pb and are found to show decreasing behaviour in more central collisions. Inclusive muons with pT above 4 GeV have been studied to provide insight on open-flavour production, and are found to be strongly suppressed in Pb+Pb collisions with a substantial and significant elliptic flow signal. Muon-hadron correlations have also been studied in the 2016 [see formula in PDF] = 8.16 TeV p+Pb data. There are clear indications of a near-side ridge, suggesting that similar mechanisms may be relevant for both the small and large systems.