Electron Ion Collider: The Next QCD Frontier - Understanding the glue that binds us all

Abstract

This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on "Gluons and quark sea at high energies" at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users' communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the U.S., established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier. Editors' Note for the Second EditionThe first edition of this White Paper was released in 2012. In the current (second) edition, the science case for the EIC is further sharpened in view of the recent data from BNL, CERN and JLab experiments and the lessons learnt from them. Additional improvements were made by taking into account suggestions from the larger nuclear physics community including those made at the EIC Users Group meeting at Stony Brook University in July 2014, and the QCD Town Meeting at Temple University in September 2014.

Color charge correlations in the proton at NLO: beyond geometry based intuition

“…This initial condition depends not only on the impact parameter and the dipole vectors but also on their relative angle, and on the light-cone momentum fraction x in the target. In the future, proton "imaging" in the regime of moderate x performed at the EIC [1][2][3][4], or at other future nuclear DIS facilities, will further constrain the proton light cone wave function, and the dipole scattering amplitude which we relate to it.…”

“…Revealing the proton and nuclear structure at high energies, or equivalently at small momentum fraction x, is one of the major tasks of the planned future nuclear deep inelastic scattering (DIS) facilities such as the Electron-Ion Collider (EIC) [1][2][3][4] in the US, LHeC/FCC-he [5] at CERN and EicC in China [6]. Thanks to the high energies and luminosities available at these future facilities, it will be possible to perform multi dimensional "proton imaging" and accurately determine the hadron structure not only as a function of momentum fraction x, but also including the geometric profile and intrinsic transverse momenta.…”

J/ψ polarization in semi-inclusive DIS at low and high transverse momentum

“…A satisfactory theoretical description will be achieved only if all these observables can be simultaneously described within a unique framework. Their experimental determination could be reached at the future Electron-Ion Collider (EIC) [15][16][17], which will be built in the United States.…”

Three-loop off-forward evolution kernel for axial-vector operators in Larin's scheme

“…The QCD description of hard exclusive reactions in the framework of collinear factorization involves matrix elements of leading-twist operators between hadron states with different momenta -generalized parton distributions (GPDs) or light-cone distribution amplitudes (LCDAs). Such processes are attracting increasing attention because they provide complementary information on the hadron structure as compared to inclusive reactions, and because of the very high quality of experimental data from the JLab 12 GeV upgrade [1], Su-perKEKB [2], and, in the future, from the EIC [3]. The main motivation for this study is provided by the applications to deeply-virtual Compton scattering (DVCS), but the results are also relevant for reactions of the type γγ * → π etc.…”