Physics Opportunities and Capabilities with MEIC

1. Physics Opportunities and Capabilities with MEIC R. D. McKeown Jefferson Lab College of William and Mary POETIC V Sept. 24, 2014

2. Outline • EIC Motivation • Some Physics Highlights • MEIC design and capabilities • Outlook

3. Why We Need EIC • HERA discovered a very large abundance of soft gluons inside the proton. However, the role of gluons in nucleon structure and dynamics is still unclear. • The origin of nucleon spin and the distributions of quarks and gluons in nuclei remain mysteries after decades of study. • We have new phenomenology to explore nucleon structure: Generalized Parton Distributions (GPDs) and Transverse Momentum Dependent (TMDs) distributions that provide powerful “imaging” of quarks and gluons and access to orbital angular momentum. These studies will require high luminosity and polarized beams. • Therefore we have a new QCD frontier: precisely image the sea quarks and gluons in nucleons and nuclei, to explore the new QCD frontier of strong color fields in nuclei, and to resolve outstanding issues in understanding nucleons and nuclei in terms of QCD. • A new facility, EIC, with a versatile range of kinematics, beam polarizations, and beam species, is required to explore these new aspects of QCDand nucleon and nuclear structure.

4. Science Questions • What is the transverse spatial and momentum structure of the gluons and sea quarks? Are there non-perturbative structures and can one image them? • How much do the gluons contribute to the nucleon spin? Is there significant orbital angular momentum? • How is the gluon distribution in nuclei different than in the nucleon? How does this relate to nuclear binding or short range nucleon-nucleon correlations? • Can one find evidence for saturation of the gluon density? • How do quarks and gluons propagate in nuclear matter and join together to form hadrons?

5. Present Knowledge • Dramatic rise in gluon distribution discovered at HERA in 1990’s. • Gluon splitting drives the dynamics at x<0.1 • Otherwise the low x region is essentially unexplored. • Generally expect saturation at lower x where high gluon density drives recombination – but where? + ?

6. New Paradigm for Nucleon Structure • JLab12 • 3D imaging of valence quarks • EIC • 3D imaging of sea and gluons • TMDs • – Confined motion in a nucleon • (semi-inclusive DIS) • GPDs • – Spatial imaging • (exclusive DIS)

7. The First Crude Images the GPD H in Im DVCS Projection for JLab12 GeV

8. EIC: The New QCD Frontier • High Luminosity •  1034 cm-2s-1 • Low x regime • x  0.0001 • High Polarization •  70% JLab 12 EIC Discovery Potential! EMC HERMES

9. Spatial Imaging of Gluon Density at EIC • Exclusive vector meson production: Q J/Ψ, Φ, … • Fourier transform of the t-dep Spatial imaging of glue density t-dep • Resolution ~ 1/Q or 1/MQ • Gluon imaging from simulation: _ Images of gluons from exclusive J/ψ production

10. Helicity PDFs at an EIC • A Polarized EIC: • Tremendous improvement on DG • Alsoimprovement in DS • Spin Flavor decomposition of the Light Quark Sea Q2 = 10 GeV2 current data w/ EIC data DG DS

11. Gluon Saturation at EIC Radiation Recombination Diffractive event

12. Electron Ion Collider: A QCD Laboratory Understanding the “99%”, the glue that binds us • Tomography of the nucleus • Gluon and sea quarks • Spin • Orbital angular momentum • QCD at high gluon density • Propagation of color in nuclei, formation of hadrons

13. EIC Properties • Access to low values of x~0.0001 (not available at JLab12), which requires collisions of high energy electrons with high energy nucleons and nuclei. • Highly polarized beams of nucleons and light ions (not available at HERA), and polarized electrons to access the spin and orbital motion of the partons. • High luminosity to enable 3D tomography of the distributions of partons (not available at HERA). • Collisions of electrons with atomic nuclei (not available at HERA), up to the heaviest available, to provide information on the effect of the nuclear medium on the parton distributions as well as the properties of partons traversing the nuclear medium.

14. EIC Requirements From the 2013 EIC White Paper:

15. Medium Energy EIC@JLab • JLab Concept • Initial configuration (MEIC): • 3-12 GeV on 20-100 GeVep/eAcollider • Fully-polarized, longitudinal and transverse • Luminosity: • up to few x 1034 e-nucleons cm-2s-1 • Upgradable to higher energies • 250 GeVprotons + 20 GeV electrons

16. MEIC Design Goals • Energy • Full coverage of √s from 15 to 70 GeV • Electrons 3-12 GeV, protons 20-100 GeV, ions 12-40 GeV/u • Ion species • Polarized light ions: p, d, 3He, and possibly Li • Un-polarized light to heavy ions up to A above 200 (Au, Pb) • At least 2 detectors • Full acceptance is critical for the primary detector • Luminosity • Above 1033 cm-2s-1 per IP in a broad CM energy range • Maximum luminosity >1034optimized to be around √s=45 GeV • Polarization • At IP: longitudinal for both beams, transverse for ions only • All polarizations >70% • Upgrade to higher energies and luminosity possible • 20 GeV electron, 250 GeV proton, and 100 GeV/uion • Design goals consistent with the White Paper requirements

17. Design Features: High Polarization All ion rings (two boosters, collider) have a figure-8 shape • Spin precession in the left &right parts of the ring are exactly cancelled • Net spin precession (spin tune) is zero, thus energy independent • Ensures spin preservation and ease of spin manipulation • Avoids energy-dependent spin sensitivity for ion all species • The only practical way to accommodate polarized deuterons which allows for “clean” neutron measurements This design feature permits a high polarization for all light ion beams (The electron ring has a similar shape since it shares a tunnel with the ion ring) Use Siberian Snakes/solenoids to arrange polarization at IPs longitudinal axis Solenoid Vertical axis Proton or Helium-3 beams Deuteron beam Insertion Longitudinal polarization at one IP Transverse polarization at one IP Longitudinal polarization at both IPs Transverse polarization at both IPs

18. Multi-Staged e-Cooling Scheme large booster (25 GeV) medium energy collider ring pre-booster (3 GeV) (accumulation) DC cooling High Energy cooling ion sources SRF Linac Existing technology

19. Luminosity at different cooling stages Based on existing technologies 56 Add “weak” electron cooling & stochastic cooling (heavy ions) during collision Full capacity electron cooling (ERL-circulator cooler) Luminosity (1033 1/cm2/s) ~3.3 Low energy DC cooling only at pre-booster injection Add 3 GeV DC cooling at pre-booster ~1.1 ~0.41

20. Nominal Design Parameters

21. The MEIC full-acceptance detector Design goals: 1. Detection/identification of complete final state 2. Spectator pT resolution << Fermi momentum 3. Low-Q2 electron tagger for photoproduction (from GEANT4, top view) IP FP far forward hadron detection n, g low-Q2 electron detection e ion quads large-aperture electron quads ~60 mrad bend small-diameter electron quads 50 mrad beam (crab) crossing angle p Fixed trackers Thin exit windows Roman pots central detector with endcaps dual-solenoid in common cryostat 4 m inner coil RICH + TORCH? 1 m barrel DIRC + TOF Ion quadrupoles 1 m Endcap e/π threshold Cherenkov 2 Tm dipole EM calorimeter Tracking Electron quadrupoles EM calorimeter EM calorimeter Trackers and “donut” calorimeter

22. MEIC/EIC e-A luminosity EIC MEIC

23. MEIC/EIC e- P Luminosity EIC MEIC A. Accardi

24. QCD Town Meeting Result “A high luminosity, high-energy polarized Electron Ion Collider (EIC) is the highest priority of the U.S. NP QCD community for future new construction.” • Approved by joint session of Hadronic Physics and Phases of QCD • An essential first step towards an NSAC Long Range Plan recommendation

25. Summary & Outlook • Science case is much advanced  white paper • Common set of facility requirements – 2 viable facility designs are emerging • Support of Hot and Cold QCD communities is evident – recommendations from QCD Town Meeting • Must articulate the science case for NP community and also broader audience • US leadership in nuclear science • US leadership in accelerator science and technology • NSAC LRP Recommendation  CD-0