Phenomenology of high gluon density QCD and heavy-ion physics at ISMD 2011: x smaller than ever !

TL;DR

This paper summarizes recent theoretical developments in small-x QCD phenomenology relevant to high-energy hadron and heavy-ion collisions, highlighting challenges posed by LHC results such as the ridge effect and initial state fluctuations.

Contribution

It reviews the state of small-x QCD evolution theory and discusses its application to recent experimental phenomena observed at the LHC.

Findings

Understanding of the long-range ridge in high-multiplicity p+p collisions

Insights into transverse momentum distributions at semi-hard pT

Discussion on the origin and scale of initial state density fluctuations

Abstract

I provide a brief summary of the theory presentations at ISMD 2011 related to the phenomenology of small-x QCD evolution and its application to particle production and fluctuations in high-energy hadron and heavy-ion collisions. I also mention some challenges for quantitative phenomenology which emerged from the LHC, such as understanding the long-range "ridge" in high-multiplicity p+p collisions, the transverse momentum distributions in p+p at semi-hard pT, and the origin and scale of density fluctuations in the initial state of heavy-ion collisions.