High Energy Proton-nucleus Collisons In The Color Glass Condensate Formalism

Long before the Large Hadron Collider(LHC)was built,the idea for color glass condensate(CGC)had already been proposed to help to understand heavy ion collisions at Relativistic Heavy Ion Collider(RHIC).Then in 2012,collisions between particles inside the LHC created what looks like a new form of matter,a state of saturated gluons,which indicated the existence of CGC.Multipoles or multipoint functions within the CGC framework play improtant roles in high energy proton-nucleus collisions.We will evaluate the octupole in the large N,limit in the McLerran-Venugopalan model,and derive a general expression of the 2n-point correlator.We also use n=3 case as an example to show how the general formula gives the correct expression for the sextupole.Finally,we will discuss the case that several coordinates coincide in the multipole amplitude.Using the dilute-dense factorization in the Color Glass Condensate framework,we will investigate the azimuthal angular correlation between a heavy quarkonium and a charged light hadron in proton-nucleus collisions.We extract the second harmonic V2,with the light hadron as the reference,commonly known as the elliptic flow.This particular azimuthal angular correlation between a heavy meson and a light hadron has first been measured at the LHC recently.The experimental results indicate that the elliptic flows for heavy-flavor mesons(J/^and D0)are almost as large as those for light hadrons.Our calculation demonstrates that this result can be naturally interpreted as an initial state effect due to the interaction between the incoming partons from the proton and the dense gluons inside the target nucleus.With the fact that the heavy quarkonium v2 exhibits a weak mass dependence according to our calculation,we predict that the heavy quarkonium T should have a similar elliptic flow as compared to that of the J/?,,which can be tested in future measurements.