Session KE: Mini-Symposium on the Physics Program at EIC

Electron Ion Collider - Capabilities and Physics Highlights

Quantum Chromodynamics has established itself as a successful theory of strong interactions, yet the details of the underlying mechanism of the theory have not been fully characterized. Despite gluons being the mediator of the strong force and mostly responsible for the visible mass of the universe, their dynamics are far from being completely understood. The proposed Electron-Ion Collider (EIC) is a new high-energy and high-luminosity electron-ion machine with a versatile range of kinematics and beam polarizations, as well as beam species. The design offers unprecedented access to explore the nature of QCD matter and strong color fields. The physics goals for the machine have been set by identifying critical questions in QCD that remain unanswered despite the significant experimental and theoretical progress made over the past decade.\footnote{A. Accardi {\it et al.}, Electron Ion Collider: The Next QCD Frontier - {\it Understanding the glue that binds us all} (EIC White Paper), BNL-98815-2012-JA; JLAB-PHY-12-1652; arXiv:1212.1701 (2012).} The key questions are: How are the sea quarks and gluons and their spins, distributed in space and momentum inside the nucleon? Where does the saturation of gluon densities set in? How does the nuclear environment affect the distribution of quarks and gluons and their interactions in nuclei? In this talk, a summary of those scientific goals with a brief description of the key measurements and accelerator and detector required to achieve them is presented.   

Studying Nucleon Helicity Distributions at an EIC

Measuring the quark and gluon helicity distributions is a key goal in understanding nucleon spin structure. An Electron Ion Collider (EIC) will provide the definitive measurement of these distributions. Gluon polarisation can be studied at low partonic momentum fraction, x, ($\sim 10^{-4}$), where it is unconstrained by existing data. Meanwhile, measuring identified final-state hadrons will allow precise flavour decomposition of the sea quark helicity. The high luminosity and wide kinematic reach of an EIC mean measurements shall be made at currently unmeasured regimes of low x and high Q$^{2}$, and with unprecedented precision. The impact of EIC data on our understanding of nucleon helicity will be presented.   

DVCS at an EIC

The feasibility for a precise determination of the Generalized Parton Distribution (GPDs) functions at an Electron Ion Collider (EIC) has been explored. The high luminosity of the machine, together with the large resolution and rapidity acceptance of a newly designed dedicated detector, may open an opportunity for very high precision measurements of GPDs. I report on the access of GPDs from measuring deeply virtual Compton scattering (DVCS) and how such measurements provide insight into both, the transverse distribution of sea quarks and gluons as well as the proton spin decomposition.   

Parton and hadron propagation in the nuclear medium

Semi-inclusive hadron and jet production in DIS on nuclear targets can be used to investigate the propagation of quarks and hadrons in cold nuclear matter with a dual aim. First, the target nucleus can be used as a femtometer scale detector of parton energy loss dynamics and hadronization time scales, able to benchmark most existing model calculation of that effect. Second, the propagating parton can be used as a colored probe of gluonic ``matter,'' sensitive to gluon saturation as well as other small-$x$ effects. This talk will review the experimental possibilities offered by the EIC, which appears to be an ideal machine for this kind of studies.   

$J/\Psi$ production at EIC

We present a theoretical study of $J/\Psi$ photo- and electroproduction from deuterium accompanied by deuteron break-up. We demonstrate that this reaction, which can be efficiently studied at EIC kinematics, can be used to study various aspects of $J/\Psi$ dynamics, including the total $J/\Psi$-$N$ cross section for a wide range of center-of-mass energies, as well as the mechanism of $J/\Psi$ production from a coherent $2N$ state. The latter is sensitive to the hidden color component of the deuteron.   

Physics with polarized light ions at an EIC

Physics with polarized light nuclei such as He-3, and at JLab also vector- and tensor polarized deuterium, form an important part of the EIC program. Polarization, and a capability of high-resolution detection of all the outgoing target fragments in coincidence with the scattered electron and any particles produced in the current jet, allows the EIC to tackle physics at the crossroads between deep-inelastic scattering (QCD factorization, partonic structure) and low-energy nuclear structure (nuclear wave functions from many-body theory, spectral functions). A program with light nuclei at an EIC would include: 1) Neutron's partonic structure, essential for quark-flavor decomposition of the nucleon spin and the extraction of flavor non-singlet sea quark distributions. 2) The bound nucleon in QCD - the modifications of the single nucleon's structure due to nuclear binding and the quark/gluon origin of the nuclear force. 3) Collective quark/gluon fields. Coherent scattering, in which the nucleus remains intact, probes the quark/gluon field of the entire nucleus. Similar information comes from diffractive scattering on deuterium, where the tensor polarized structure function of is zero in single-nucleon scattering and precisely identifies the QCD double-scattering contribution.   

Studies of the e$+$A physics at an EIC

It is the ultimate long term quest of nuclear physics to understand the emergence of nuclear structure and dynamics in terms of quarks and gluons, the basic constituents in Quantum Chromo-Dynamics (QCD). Although past experiments were successful in determining the quark behavior in the nucleon and light nuclei, the gluons that determine the essential features of the strong interactions, remain largely unexplored. Of great interest is especially the high parton density (small x) regime where gluon self-interaction is expected to dominate and lead to parton saturation. The proposed high luminosity, high energy Electron-Ion Collider (EIC) can probe a variety of nuclei species within a wide kinematic reach. On such a machine, we will be capable of unveiling the collective behavior of densely packed gluons in a strong color field, exploring the internal 3-dimensional landscape of a nucleus, as well as studying the fast-moving color charge in a nuclear medium. In this talk, we are going to discuss the compelling physics cases in the e$+$A program at an EIC and Monte Carlo studies of the measurements.