ar X iv : h ep - p h / 04 10 01 9 v 1 1 O ct 2 00 4 Manifestation of the Color Glass Condensate in particle production at RHIC ∗

PACS numbers: 13.85.Hd,13.60.Hb,13.85.Ni,24.85 In this paper we discuss the experimental signatures of the new form of nuclear matter – the Color Glass Condensate (CGC) in particle production at RHIC. Let us first see how the notion of the CGC arises in pA collisions at high energy. Consider a process of inclusive particle production in pA collisions in a nucleus rest frame. At high energies the typical values of the Bjorken x are small. It is well-known that at small x hard processes develop over large ‘coherence length’ lc. In particular, a gluon production is coherent over lc ≃ 1/(Mx), where M is the proton’s mass. For instance, at midrapidity at RHIC the coherence length of 2 GeV gluon is lc ≃ 20 fm (at √ s = 200 GeV). It is much bigger than the size of the target ≃ 6.5 fm. This allows formal separation of the gluon production process into two parts: slow gluon emission described by the proton’s light cone wave function, and almost instantaneous interaction with the target at given impact parameter b described by the amplitude NG(r, b, x), where r is the variable Fourier-conjugated to the gluon’s transverse momentum k. In the one gluon exchange approximation, assuming that scattering on different nucleons is independent, one arrives at the formula [1, 2, 3]