Measurement of Differences Between J/Psi and Psi' Suppression in p-A Collisions

TL;DR

The suppression of the yield per nucleon of J/psi and psi(') production for 800 GeV/ c protons incident on heavy nuclear targets, relative to lightnuclear targets, has been made with very broad coverage in x(F) and p(T).

Abstract

Measurements of the suppression of the yield per nucleon of J/Psi and Psi' production for 800 GeV/c protons incident on heavy relative to light nuclear targets have been made with very broad coverage in xF and pT. The observed suppression is smallest at xF values of 0.25 and below and increases at larger values of xF. It is also strongest at small pT. Substantial differences between the Psi' and J/Psi are observed for the first time in p-A collisions. The suppression for the Psi' is stronger than that for the J/Psi for xF near zero, but becomes comparable to that for the J/Psi for xF > 0.6.

Figures (4)

• Figure 1: Fit to the mass spectrum for the Be target in the $x_F$ range from 0.00 to 0.05. Components in the fit are the $J/\psi$, the $\psi'$, Drell-Yan (long-dashed), randoms (short-dashed), and open charm (dot-dash). The solid curve represents the total of all fitted lineshapes and the dotted curve represents the continuum which is the sum of the Drell-Yan, randoms and open charm.
• Figure 2: $\alpha$ versus $p_T$ for $J/\psi$ (solid circles) and $\psi'$ (open boxes) production by 800 GeV/c protons. Results are shown for the three data sets -- SXF, IXF and LXF (see text) -- which have $\langle x_F \rangle =$ 0.055, 0.308 and 0.480, respectively. Only statistical uncertainties are shown. An additional systematic uncertainty of 0.5% is not included. Also shown are the NA3 results at 200 GeV/c whose $x_F$ range can be seen in Fig. 4. The solid curves represent the parameterization discussed in the text.
• Figure 3: $\alpha$ for the $J/\psi$ versus $x_F$ for the three different data sets (top) and for the $J/\psi$ and $\psi'$ after the data sets are combined (bottom). Values are corrected for the $p_T$ acceptance, as discussed in the text. These corrections ($\Delta\alpha$) have a maximum value of 0.06 and are shown using the right-hand vertical scale in the top panel. The relative systematic uncertainty between $\alpha$ for the $J/\psi$ and $\psi'$ is estimated to be 0.003, while the absolute systematic uncertainty is 0.01 in $\alpha$; neither is included here. The solid curve represents the parameterization discussed in the text.
• Figure 4: $\alpha$ versus $x_F$ and versus $p^{LAB}_{J/\psi}$ for the $J/\psi$ from E866/NuSea (800 GeV/c) (solid circles) compared to E772 (open diamonds) and NA3 (200 GeV/c) (open squares) showing the scaling with $x_F$ (bottom) and lack of scaling with $p^{LAB}_{J/\psi}$ (top).