Nuclear Modification Factors for Hadrons At Forward and Backward Rapidities in Deuteron-Gold Collisions at sqrt(s_NN) = 200 GeV

Abstract

We report on charged hadron production in deuteron-gold reactions at sqrt(s_NN) = 200 GeV. Our measurements in the deuteron-direction cover 1.4 < eta < 2.2, referred to as forward rapidity, and in the gold-direction -2.0 < eta < -1.4, referred to as backward rapidity, and a transverse momentum range p_T = 0.5-4.0 GeV/c. We compare the relative yields for different deuteron-gold collision centrality classes. We observe a suppression relative to binary collision scaling at forward rapidity, sensitive to low momentum fraction (x) partons in the gold nucleus, and an enhancement at backward rapidity, sensitive to high momentum fraction partons in the gold nucleus.

Figures (4)

• Figure 1: (color online). (left) The total momentum $p_{tot}$ measured in the MuTr without energy loss correction of all charged tracks penetrating to MuID layers 2 (grey) and 3 (black). (right) Collision vertex distribution for events with muons at forward rapidity, corrected for the minimum bias collision vertex distribution.
• Figure 2: (color online). $R_{cp}$ as a function of $p_T$ at forward rapidity (squares) and backward rapidity (circles) for different centrality classes.
• Figure 3: (color online). $R_{cp}$ as a function of $\eta$ for $1.5 < p_T < 4.0$ GeV/$c$ for different centrality classes.
• Figure 4: (color online). PHENIX $R_{cp}$ as a function of $p_{T}$ at forward rapidities shown as the average of the two methods. Note that the BRAHMS results are for negative hadrons at $\eta=2.2,3.2$ and their centrality ranges ($0-20\%/60-80\%$ and $30-50\%/60-80\%$) are somewhat different from ours.