Saturation Physics: NLO Precision and Quasi Collectivity

University Of Connecticut, Storrs CT

Investigators

Abstract

The study of Quantum Chromodynamics (QCD), the theory describing the fundamental interactions between quarks and gluons, the most fundamental constituents of nuclei, represents an area of intense inquiry in nuclear physics. In particular, QCD is called upon to describe the behavior of matter under extreme conditions of temperature, pressure, and density, and precision calculations are needed to compare quantitatively experiments and theory. In this context, the PI and his collaborators will develop accurate calculational methods that will allow searches of exotic forms of matter predicted to occur in highly energetic proton-proton and lead-proton collisions currently studied at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Switzerland. This project includes also educational and outreach activities: the PI will organize a workshop for graduate students from universities in the North East. Mini-courses on aspects of high energy/heavy ion physics will be organized for faculty involved in this research. At very high energies the structure of strongly interacting particles (hadrons) is believed to undergo a qualitative transition. Instead of dilute objects containing several quarks and gluons, they should rather resemble a drop of saturated liquid densely filled with gluons. This must lead to very different characteristics of final states in high energy collisions. The theory that qualitatively describes this behavior is the perturbative saturation or Color Glass Condensate (CGC). At current LHC energies one expects this new phase to have been already attained. Indeed many observations point to some sort of collective, or quasi collective behavior in the final state of the proton-proton and proton-lead collisions, especially when the number of produced particles is larger than average. In this context, the PI and his collaborators will contribute the development of a program for systematic improvement of current calculational paradigms of saturation effects. This involves first, systematic resummation program in the high-energy evolution equation, the so-called JIMWLK equation in order to stabilize it at next-to-leading order (NLO). The resummed evolution then will be applied to a variety of hadronic observables consistently calculated at NLO. In addition, the PI will study in depth to what extent the structure of initial CGC state can lead to quasi collectivity in the state produced in p-p and p-A collisions.