Energy dependence of coherent photonuclear production of J/$\psi$ mesons in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$=5.02 TeV

Abstract

The cross section for coherent photonuclear production of J/$\psi$ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. Cross sections are presented in five different J/$\psi$ rapidity ranges within $|y|<4$, with the J/$\psi$ reconstructed via its dilepton decay channels. In some events the J/$\psi$ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range $17<W_{\gamma \mathrm{Pb},\mathrm{n}}<920$ GeV, where $W_{\gamma \mathrm{Pb},\mathrm{n}}$ is the centre-of-mass energy per nucleon of the $\gamma \mathrm{Pb}$ system. This range corresponds to a Bjorken-$x$ interval spanning about three orders of magnitude: $1.1\times 10^{-5}<x<3.3\times 10^{-2}$. In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies.

34 pages, 5 captioned figures, 5 tables, authors from page 29, published version, figures at http://alice-publications.web.cern.ch/node/9351

References in corpus (8)

• EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions
• The Physics of Ultraperipheral Collisions at the LHC
• Mining for Gluon Saturation at Colliders
• J/Psi production in ultraperipheral Pb+Pb and p+Pb collisions at energies available at the CERN Large Hadron Collider
• Imaging the nucleus with high-energy photons
• Energy dependence of dissociative $J/\psi$ photoproduction as a signature of gluon saturation at the LHC
• Theoretical uncertainties in exclusive electroproduction S-wave heavy quarkonia
• Spin rotation effects in diffractive electroproduction of heavy quarkonia

Cited by in corpus (14)

• Energy dependent nuclear suppression from gluon saturation in exclusive vector meson production
• Observation of strong nuclear suppression in exclusive $J/\psi$ photoproduction in Au$+$Au ultra-peripheral collisions at RHIC
• Finite-size effects on small-$x$ evolution and saturation in proton and nuclear targets
• Exclusive $J/\psi$, $\psi (2s)$, and $e^{+}{e}^{-}$ pair production in Au$+$Au ultra-peripheral collisions at RHIC
• Global Bayesian Analysis of $\mathrm{J}/\psi$ Photoproduction on Proton and Lead Targets
• Novel Cross Section Ratios as Possible Signals of Saturation in UPCs
• Measurement of exclusive $J/\psi$ and $\psi (2S)$ production at $\sqrt{s}=13$ TeV
• Exclusive quarkonium photoproduction: predictions with the Balitsky-Kovchegov equation including the full impact-parameter dependence
• Probing gluon fluctuations in nuclei with the first energy-dependent measurement of incoherent J/$\psi$ photoproduction in ultraperipheral PbPb collisions
• The energy dependence of exclusive heavy vector meson photoproduction cross-sections and NLO BFKL evolution
• Physics with high-luminosity proton-nucleus collisions at the LHC
• Observation of coherent $\varphi$(1020) meson photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_{\text{NN}}}$ = 5.36 TeV
• Diffractive vector meson photo-production in oxygen-oxygen and neon-neon ultraperipheral collisions at energies available at the CERN Large Hadron Collider
• Probing nuclear structure with the Balitsky-Kovchegov equation in full impact-parameter dependence