Cold Nuclear Matter Effects on J/Psi as Constrained by Deuteron-Gold Measurements at sqrt(s_NN) = 200 GeV

TL;DR

This study addresses how cold nuclear matter influences J/psi production in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV to inform interpretations of Au+Au and Cu+Cu data. Using a refined analysis with a large, consistent p+p baseline, the authors extract updated $R_{dAu}$ across rapidity and centrality and fit shadowing models with a breakup cross section, finding $\sigma_{breakup} = 2.8^{+1.7}_{-1.4}$ mb (EKS) or $2.2^{+1.6}_{-1.5}$ mb (NDSG). These CNM constraints align with SPS results within uncertainties but are too imprecise to quantify hot-m Nuclear Matter effects in heavy-ion collisions, particularly at forward rapidity. The work underscores the need for higher-statistics data to disentangle CNM from hot matter contributions and to improve predictive power for $J/\psi$ production in heavy-ion systems.

Abstract

We present a new analysis of J/psi production yields in deuteron-gold collisions at sqrt(s_NN) = 200 GeV using data taken by 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/psi data taken in 2005 is used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors R_dAu. A suppression of J/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/psi (or precursor) break-up cross-section is added. Breakup cross sections of sigma_breakup = 2.8^[+1.7_-1.4] (2.2^[+1.6_-1.5]) 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 +/- 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.

Figures (13)

• Figure 1: (color online) Invariant mass spectra in minimum bias $d+{\rm Au}$ reactions for $J/\psi \longrightarrow e^{+}e^{-}$ at $|y|<0.35$, with the functional forms used to extract the number of reconstructed $J/\psi$ mesons.
• Figure 2: (color online) Invariant mass spectra in minimum bias $d+{\rm Au}$ reactions for (left) $J/\psi \longrightarrow \mu^{+}\mu^{-}$ at $-2.2<y<-1.2$ and (right) $J/\psi \longrightarrow \mu^{+}\mu^{-}$ at $1.2<y<2.2$, with the functional forms used to extract the number of reconstructed $J/\psi$ mesons.
• Figure 3: (color on-line) $J/\psi$ invariant yield versus ${p_{\rm T}}$ in $d+{\rm Au}$ collisions and $p+p$ collisions. The three panels are for rapidity selections $-2.2 < y < -1.2$, $|y|<0.35$, and $1.2 < y < 2.2$ from top to bottom. See text for description of the uncertainties and details of the functional fits.
• Figure 4: (color online) $J/\psi$ invariant yield as a function of rapidity for $d+{\rm Au}$ collisions. Shown are the new analysis results from this paper, in addition to the originally published results Adler:2005ph using the same data. The global systematic uncertainty quoted is for the new analysis.
• Figure 5: (color online) $J/\psi$ invariant yield as a function of rapidity for $p+p$ collisions. Shown are the high statistics results from 2005 $p+p$ PHENIX data taking period Adare:2006kf, and the originally published results Adler:2005ph using the 2003 $p+p$ data set. The global systematic uncertainty quoted is for the new analysis.