Azimuthal correlations of forward di-pions in D+Au collisions suppressed by saturation

The STAR collaboration has recently measured the azimuthal correlation function of forward di-pions. The data show a disappearance of the away-side peak in central D+Au collisions, compared to p+p collisions. We argue that this effect, absent at midrapidity, is a consequence of the small-x evolution into the saturation regime of the Gold nucleus wave function, and we show that the data can be quantitatively described in the Color Glass Condensate framework. This confirmation that forward mono-jets are produced in central D+Au collision is a concrete evidence for parton saturation. (authors)