J/$ψ$ suppression at $\sqrt{\bf s} =$ 200 GeV in the comovers interaction model

TL;DR

Capella and Ferreiro analyze J/ψ suppression in A+A collisions at RHIC within a comovers-interaction framework, calibrating the comovers cross-section σ_co = 0.65 mb from SPS data and including shadowing corrections via Gribov-Reggeon formalism. The model computes J/ψ survival as a product of comovers and nuclear-absorption factors, with the comovers density N^co obtained from the dual parton model and adjusted for shadowing; results show significantly stronger suppression at √s = 200 GeV than at SPS, with central AuAu suppression sensitive to σ_abs. They find that lighter and heavier systems have comparable suppression at the same N_part due to the density dynamics, and stress that σ_abs must be constrained by d+Au data. The study highlights the smooth, centrality-dependent onset of suppression in the comovers picture and discusses how forthcoming RHIC and d+Au measurements can differentiate this mechanism from deconfinement-based scenarios.

Abstract

The yield of $J/ψ$ per binary nucleon-nucleon collision in $AuAu$ and $CuCu$ collisions at $\sqrt{s} = 200$ GeV is computed in the framework of the dual parton model, supplemented with final state interaction (comovers interaction). For the latter we use the same value of the cross-section, $σ_{co} = 0.65$ mb, which describes the anomalous $J/ψ$ suppression observed at CERN-SPS energies. Several possibilities for the value of the absorptive cross-section are considered. Shadowing is introduced in both the comovers and the $J/ψ$ yields. A comparison with the results at CERN-SPS, including a prediction for $InIn$ collisions, is also presented.

Figures (3)

• Figure 1: Multiplicity of charged particles per participant pairs, versus $N_{part}$, computed from (\ref{['13e']}) are compared to experimental data from PHENIX 15r.
• Figure 2: $R_{AB}^{J/\psi}(b)$ for $AuAu$ collisions at $\sqrt{s}=200$ GeV (full curve), $CuCu$ collisions at $\sqrt{s}=200$ GeV (dashed curve), $PbPb$ at $p_{lab}=158$ GeV/c (dotted curve) and $InIn$ at $p_{lab}=158$ GeV/c (dashed-dotted curve). All the results have been obtained with $\sigma_{co} = 0.65$ mb and $\sigma_{abs} = 4.5$ mb. The normalization, the same for all four curves, is arbitrary. It corresponds to taking $dN_{pp}^{J/\psi}/dy = 1$ in eq. (\ref{['1e']}).
• Figure 3: $R_{AB}^{J/\psi}(b)$ for $AuAu$ collisions at $\sqrt{s}=200$ GeV multiplied by the dilepton branching ratio, normalized to the measured value in $pp$ collisions 16r. From up to down: result with $\sigma_{co} = 0.65$ mb and $\sigma_{abs} = 0$ mb (dashed curve), result with $\sigma_{co} = 0.65$ mb and $\sigma_{abs} = 1$ mb (dotted-dashed curve), result with $\sigma_{co} = 0.65$ mb and $\sigma_{abs} =3$ mb (dotted curve) and result with $\sigma_{co} = 0.65$ mb and $\sigma_{abs} =4.5$ mb (full curve).