Cold nuclear matter effects on J/ψ production as constrained by deuteron-gold measurements at sNN=200 GeV

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We present a new analysis of $J/\ensuremath{\psi}$ production yields in deuteron-gold collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV using data taken from the PHENIX experiment in 2003 and previously published in S. S. Adler et al. [Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton $J/\ensuremath{\psi}$ data taken in 2005 are used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors (${R}_{d\mathrm{Au}}$). A suppression of $J/\ensuremath{\psi}$ in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial-state low-$x$ gluons in the gold nucleus. The measured nuclear modification factors are compared to theoretical calculations of nuclear shadowing to which a $J/\ensuremath{\psi}$ (or precursor) breakup cross section is added. Breakup cross sections of ${\ensuremath{\sigma}}_{\mathrm{breakup}}=2.{8}_{\ensuremath{-}1.4}^{+1.7}$ $(2.{2}_{\ensuremath{-}1.5}^{+1.6})$ mb are obtained by fitting these calculations to the data using two different models of nuclear shadowing. These breakup cross-section values are consistent within large uncertainties with the $4.2\ifmmode\pm\else\textpm\fi{}0.5$ mb determined at lower collision energies. Projecting this range of cold nuclear matter effects to copper-copper and gold-gold collisions reveals that the current constraints are not sufficient to firmly quantify the additional hot nuclear matter effect.

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