Quark correlations in the color glass condensate: Pauli blocking and the ridge

We consider, for the first time, correlations between quarks produced in p-A collisions in the framework of the color glass condensate. We find a quark-quark ridge that shows a dip at $\mathrm{\Delta }\eta \sim 2$ relative to the gluon-gluon ridge. The origin of this dip is the short-range (in rapidity) Pauli blocking experienced by quarks in the wave function of the incoming projectile. We observe that these correlations, present in the initial state, survive the scattering process. We suggest that this effect may be observable in open charm–open charm correlations at the Large Hadron Collider.

Figure 1

The uncorrelated contribution originating from $({\mathrm{\Phi }}_2{)}^2$. We work at large $N_c$ where gluons are represented as double lines, and the short vertical lines correspond to an observed particle. Arrows indicated the color flux, while momenta flow from left to right.

Figure 2

The first correlated contribution of order $N_c^2$ originating from $({\mathrm{\Phi }}_2{)}^2$.

Figure 3

The second correlated contribution of order $N_c^2$ originating from $({\mathrm{\Phi }}_2{)}^2$.

Figure 4

The basic graph contributing to the correlated quark production in the CGC.

Figure 5

The leading order in $N_c$ source contraction that corresponds to the contribution ${\mathrm{\Phi }}_4^A$.

Figure 6

The leading order in $N_c$ source contraction that corresponds to the contribution ${\mathrm{\Phi }}_4^B$.

Figure 7

The subleading in $N_c$ source contraction not considered in this paper.

Figure 8

The graph for the $({\mathrm{\Phi }}_2{)}^2$ contribution in coordinate space.

Figure 9

The graph for the ${\mathrm{\Phi }}_4$ contribution in coordinate space.