TMDs at Small-x: What We Have Learnt and What We Expect

30 Apr 2015, 09:45


WG2 Small-x, Diffraction and Vector Mesons WG2 Small-x, Diffraction and Vector Mesons


Feng Yuan (LBNL)


In this talk, we will discuss the theory developments on the next-to-leading order calculation for forward hadron production in pA collisions in the small-x factorization framework. In particular, we emphasize the matching between this calculation and the collinear factorization calculation at large transverse momentum. The small-x calculation can be viewed as a power series in $Q_s^2/k_T^2$, in which the collinear factorization result corresponds to the leading term. At high transverse momentum, the subleading correction terms are insignficant, whereas at low $p_T$, the power corrections become important and the small-x resummation is essential to describe the differential cross section. We show that the familiar collinear factorization calculation can smoothly match the results from small-x factorization at next-to-leading order in $\alpha_s$ when we use exact kinematics, as opposed to the approximate kinematics in previous work. With this matching, we can describe the experimental data from RHIC very well at high $p_T$.

Primary author

Presentation Materials