Observation of excess J/$\psi$ yield at very low transverse momenta in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV and U+U collisions at $\sqrt{s_{\mathrm{NN}}}=$ 193 GeV

Abstract

We report on the first measurements of J/$\psi$ production at very low transverse momentum ($p_T<$ 0.2 GeV/c) in hadronic Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV and U+U collisions at $\sqrt{s_{\mathrm{NN}}}=$ 193 GeV. Remarkably, the inferred nuclear modification factor of J/$\psi$ at mid-rapidity in Au+Au (U+U) collisions reaches about 24 (52) for $p_T<$ 0.05 GeV/c in the 60-80$\%$ collision centrality class. This noteworthy enhancement cannot be explained by hadronic production accompanied by cold and hot medium effects. In addition, the $dN/dt$ distribution of J/$\psi$ for the very low $p_T$ range is presented for the first time. The distribution is consistent with that expected from the Au nucleus and shows a hint of interference. Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semi-central collisions, perhaps due to the violent hadronic interactions. Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J/$\psi$ yield observed at extremely low $p_T$ originates from coherent photon-nucleus interactions. In particular, coherently produced J/$\psi$'s in violent hadronic collisions may provide a novel probe of the quark-gluon-plasma.

References in corpus (9)

• The order of the quantum chromodynamics transition predicted by the standard model of particle physics
• Glauber Modeling in High Energy Nuclear Collisions
• Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR
• EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions
• J/psi Production vs Centrality, Transverse Momentum, and Rapidity in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• J/psi Production in Quark-Gluon Plasma
• Charmonium in Medium: From Correlators to Experiment
• The STAR Vertex Position Detector
• Observation of Two-source Interference in the Photoproduction Reaction $AuAu\to AuAu{\rho }^0$

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• Mapping the Electromagnetic Fields of Heavy-Ion Collisions with the Breit-Wheeler Process
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• The $\cos 2\varphi$ azimuthal asymmetry in ${\rho }^0$ meson production in ultraperipheral heavy ion collisions
• Report on Progress in Physics: Observation of the Breit-Wheeler Process and Vacuum Birefringence in Heavy-Ion Collisions
• $J/\psi$ photo-production in Pb-Pb peripheral collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5 TeV
• Quarkonium propagation in the quark gluon plasma
• Prospects for quarkonium studies at the high-luminosity LHC
• Coulomb nuclear interference effect in dipion production in ultraperipheral heavy ion collisions
• Challenges to the Good-Walker paradigm in coherent and incoherent photoproduction
• Photoproduction of low-$p_{\mathrm{T}}$ J/$\psi$ from peripheral to central Pb$-$Pb collisions at 5.02 TeV
• Measurement of inclusive $J/\psi$ production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=54.4$ GeV at STAR