Towards an Electron Ion Collider R. D. McKeown Jefferson Lab INT Workshop November 19, 2010

2 Looking back over the last year The INT workshop Golden Experiments or Topics? The Road Ahead Outline Thanks to Rolf Ent, Christian Weiss, Z.-E. Meziani, and many others.

3 Beyond the 12 GeV Jlab Upgrade 3 12 GeV Hadrons in QCD are relativistic many-body systems, with a fluctuating number of elementary quark/gluon constituents and a very rich structure of the wave function. With 12 GeV we study mostly the valence quark component, which can be described with methods of nuclear physics (fixed number of particles). With an (M)EIC we enter the region where the many-body nature of hadrons, coupling to vacuum excitations, etc., become manifest and the theoretical methods are those of quantum field theory. An EIC aims to study the sea quarks, gluons, and scale (Q 2 ) dependence. mEIC EIC

4 The Wakeup Call(s) EICAC Report (Nov. 2009): - develop “unimpeachable” science case - Jlab concept less mature “the highest R&D priority for JLab should be the design, even if that activity is not strictly considered R&D, and resources need to be made available to do the work” Jlab user group, encouraged by Jlab director, organized workshops to further develop science case Encouraged by lab director, Jlab initiates effort to develop a “credible” and “cost-able” MEIC design

5 5 JLAB EIC Workshops  S tudy group on Hadronic Physics Nucleon spin and quark-gluon correlations: Transverse spin, quark and gluon orbital motion, semi-inclusive processes (Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark Gluons Interactions: workshop at Duke U., March 12-13, 2010 ) H. Gao et al. 3D mapping of the glue and sea quarks in the nucleon (Electron-Nucleon Exclusive Reactions: workshop at Rutgers U., March 14-15, 2010) R. Gilman et al.  Study group on Nuclear Physics 3D tomography of nuclei, quark/gluon propagation and the gluon/sea quark EMC effect (EIC Nuclear Chromodynamics: workshop at Argonne National Lab, April 7-9, 2010) K. Hafidi, et al.  Study group on Electroweak Physics Electroweak structure of the nucleon and tests of the Standard Model (workshop at the College of W&M, May 17-18, 2010) K. Kumar, D. Armstrong et al.  Study group on interaction region and detectors EIC Detectors/Instrumentation (workshop at JLab, June 04-05, 2010) C. Hyde et al.

6 Jlab User Workshops Excellent development of physics possibilities 4/5 will generate written papers to summarize the workshops – goal is early General emergent theme: Experimental study of multidimensional distribution functions that map out the quark/gluon properties of the nucleon, including: - (quark) flavor - spin and orbital angular momentum - longitudinal momentum - transverse momentum and position

7 SIDIS SSA at EIC GeV 3+20 GeV Huang, Qian, et al Duke workshop

8 A Personal View There has been much progress on the physics case in the last year There has been good convergence on the machine design specifications to include the broader physics program. Jlab user workshops benefited from 12 GeV physics development. However, some topics could use more work to extend the physics case from the valence region into the sea for EIC.

9 Medium Energy Three compact rings: 3 to 11 GeV electron Up to 12 GeV/c proton (warm) Up to 60 GeV/c proton (cold)

10 weekdatestopics 113–17 Sept Workshop on "Perturbative and Non-Perturbative Aspects of QCD at Collider Energies" 220–24 Sept open conceptual issues: factorization and universality, spin and flavor structure, distributions and correlations 3–527 Sept –15 Oct small x, saturation, diffraction, nuclear effects; connections to p+A and A+A physics; fragmentation/hadronization in vacuum and in medium 6–718–29 Oct parton densities (unpolarized and polarized), fragmentation functions, electroweak physics 8–91–12 Nov longitudinal and transverse nucleon structure; spin and orbital effects (GPDs, TMDs, and all that) 1015–19 Nov Workshop on "The Science Case for an EIC" 2010 INT Workshop Organizers: Daniel Boer KVI, University of Groningen Markus Diehl DESY Richard Milner MIT Raju Venugopalan Brookhaven National Laboratory Werner Vogelsang University of Tübingen

11 INT Workshop Nine weeks of intensive discussions Excellent organization, communication - talks online - weekly summaries We continue to see the physics case develop. Many good ideas are emerging. Written summaries to be prepared “Golden” experiments?

12 A Personal View Perhaps it is not realistic to agree upon “Golden Experiments” As an alternative, “Golden Topics” can be a useful and unifying theme (ref. FRIB) It is essential to keep the community united behind physics topics that motivate the facility we are proposing At Jlab we have started to think about “Golden Topics” as a possible way to both sell the physics and maintain coherence in the community

13 The Science of an EIC Nuclear Science Goals: How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? Overarching EIC Goal: Explore and Understand QCD Discover the collective effects of gluons in nuclei Map the spin and spatial structure of quark and gluons in nucleons Understand the emergence of hadronic matter from quarks and gluons EW Topic? (Discussion with R. Ent, C. Weiss, and others at Jlab)

14 Golden Topic #1 Discover collective effects of Gluons in Nuclei Explore the nuclear gluon density and coherence in shadowing through e + A  e‘ + X and e + A  e' + cc + X Discover novel signatures of dynamics of strong color fields in nuclei at high energies in e + A  e‘ + X (or A) and e + A  e' + hadrons + X Measure gluon/quark radii of nuclei through coherent scattering  * + A  J/  + A

15 Image the 3D spatial distributions of gluons and sea quarks through exclusive J/ ,  (DVCS) and meson production Measure  G, and the polarization of the sea quarks through SIDIS, g 1, and open charm production Establish the orbital motion of quarks and gluons through transverse momentum dependent observables in SIDIS and jet production Discover QCD-induced quark-gluon correlations in the nucleon through SIDIS and target fragmentation? Golden Topic #2 Map the spin and spatial quark-gluon structure of nucleons

16 Golden Topic #3 Explore the interaction of color charges with matter (energy loss, flavor dependence, color transparency) through hadronization in nuclei in e + A  e' + hadrons + X Understand the conversion of quarks and gluons to hadrons through fragmentation of correlated quarks and gluons and breakup in e + p  e' + hadron + hadron + X Understand the emergence of hadronic matter from quarks and gluons

17 EIC Realization Imagined Activity Name Gev Upgrade FRIB EIC Physics Case NSAC LRP EIC CD0 EIC Machine Design/R&D EIC CD1/Downsel EIC CD2/CD3 EIC Construction Note: 12 GeV LRP recommendation in 2002 – CD3 in 2008

18 Looking Forward We have made excellent progress in developing and refining the physics case for EIC over the last 2 years. We need to document the Jlab workshops and the INT workshop Machine designs and accelerator R&D need to continue A community white paper to synthesize this information is a logical next step (  Steve V.)

19 A Final Word We are on a good path to put the EIC forward at the next NSAC Long Range Plan We still need additional work, building on the discussions at the INT program, to produce a much more compelling physics justification We need to sharpen the arguments for a more general audience How could we expand the community of interested physicists? We need to continue to work together to advance the physics case for this exciting new facility