MEIC Overview: Physics, Project & Timeline Rolf Ent MEIC Accelerator Design Review September 15-16, 2010

The Structure of the Proton Naïve Quark Model:proton = uud (valence quarks) QCD:proton = uud + uu + dd + ss + … The proton sea has a non-trivial structure: u ≠ d The proton is far more than just its up + up + down (valence) quark structure

QCD and the Origin of Mass 99% of the proton’s mass/energy is due to the self-generating gluon field – Higgs mechanism has almost no role here. The similarity of mass between the proton and neutron arises from the fact that the gluon dynamics are the same – Quarks contribute almost nothing.

Gluons and QCD QCD is the fundamental theory that describes structure and interactions in nuclear matter. Without gluons there are no protons, no neutrons, and no atomic nuclei Gluons dominate the structure of the QCD vacuum Facts: –The essential features of QCD (e.g. asymptotic freedom, chiral symmetry breaking, and color confinement) are all driven by the gluons! –Unique aspect of QCD is the self interaction of the gluons –99% of mass of the visible universe arises from glue –Half of the nucleon momentum is carried by gluons

Study the Force Carriers of QCD Nuclear Physics – 12 GeV to EIC The role of Gluons and Sea Quarks

High-Level Science Overview 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.

Slide 7 The Science of an (M)EIC Nuclear Science Goal: 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 Three Major Science Questions for an EIC (from NSAC LRP07): 1)What is the internal landscape of the nucleons? 2)What is the role of gluons and gluon self-interactions in nucleons and nuclei? 3)What governs the transition of quarks and gluons into pions and nucleons? Or, Elevator-Talk EIC science goals: Map the spin and 3D quark-gluon structure of protons (show the nucleon structure picture of the day…) Discover the role of gluons in atomic nuclei (without gluons there are no protons, no neutrons, no atomic nuclei) Understand the creation of the quark-gluon matter around us (how does E = Mc 2 work to create pions and nucleons?) + Hunting for the unseen forces of the universe

Obtain detailed differential transverse quark and gluon images (derived directly from the t dependence with good t resolution!) - Gluon size from J/  and  electroproduction - Singlet quark size from deeply virtual compton scattering (DVCS) - Strange and non-strange (sea) quark size from  and K production Determine the spin-flavor decomposition of the light-quark sea Constrain the orbital motions of quarks & anti-quarks of different flavor - The difference between  +,  –, and K + asymmetries reveals these orbits. Map both the gluon momentum distributions of nuclei (F 2 & F L measurements) and the transverse spatial distributions of gluons on nuclei (coherent DVCS & J/  production). At high gluon density, the recombination of gluons should compete with gluon splitting, rendering gluon saturation. Can we reach such state of saturation? Map the physical mechanism of fragmentation of correlated quarks and gluons, and understand how we can calculate it quantitatively. Why a New-Generation EIC? longitudinal momentum transverse distribution orbital motion quark to hadron conversion Dynamical structure! Gluon saturation?

A High-Luminosity ELectron Ion Collider at JLab Requirements in our view: range in energies from s = few 100 to s = few 1000 & variable fully-polarized (>70%), longitudinal and transverse ion species up to A = 200 or so high luminosity: about e-nucleons cm -2 s -1 upgradable to higher energies NSAC 2007 Long-Range Plan: “An Electron-Ion Collider (EIC) with polarized beams has been embraced by the U.S. nuclear science community as embodying the vision for reaching the next QCD frontier. EIC would provide unique capabilities for the study of QCD well beyond those available at existing facilities worldwide and complementary to those planned for the next generation of accelerators in Europe and Asia.”

Slide 10 Current Ideas for a Collider EnergiessDesign Luminosity to 11 x Close to Future Up to 11 x 250 (20? x 250) (20000?) Close to Staged Up to 5 x Close to to 20 x 325 (30 x 325) (39000) Close to to 3 x 15180Few x to 150 x Close to Design Goals for Colliders Under Consideration World-wide Present focus of interest (in the US) are the (M)EIC and Staged MeRHIC versions, with s up to ~3000 and 5000, respectively

Both laboratories (BNL & JLab) are working together to get advice on the best steps towards a US Electron-Ion Collider. Sam Aronson and Christoph Leemann/Hugh Montgomery have named an international EIC Advisory Committee: Joachim Bartels Allen Caldwell Albert De Roeck Walter Henning (chair) David Hertzog Xiangdong Ji Robert Klanner Alfred Mueller Katsunobu Oide Naohito Saito Uli Wienands *likely add few more accelerator experts 1 st meeting Feb. 16, 2009 at SURA headquarters, D.C. 2 nd meeting Nov. 2&3, 2009 at Jefferson Lab 3 rd meeting anticipated Fall 2010 (at BNL?) Concrete design for requested by this meeting Internal reviewed cost estimate requested by this meeting EIC Advisory Committee

Slide 12 EIC Project - Roadmap YearCEBAF UpgradeElectron-Ion Collider st CEBAF at Higher Energies Workshop 1996 (LRP)CEBAF Upgrade an Initiative ~2000Energy choice settled, “Golden Experiments” 1 st workshops on US Electron-Ion Collider 2002 (LRP)JLab 12-GeV Upgrade 4 th recommendation Electron-Ion Collider an Initiative 2007 (LRP)JLab 12-GeV Upgrade highest recommendation Electron-Ion Collider “half-recommendation” ~2010EIC “Golden Experiments”??? 2013? (LRP)JLab 12-GeV construction & operation, FRIB construction highest recommendation(s)? EIC a formal (numbered) recommendation? 2015JLab 12-GeV Upgrade construction complete EIC Mission Need, formal R&D ongoing? 2025?EIC construction complete?

Slide 13 EIC – JLab User Meetings Roadmap March 12 + Electron-Nucleon Exclusive Reactions March 14 + Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions April 07, 08, Nuclear Chromo-Dynamic Studies May 17 Electroweak Studies June 04 + MEIC Detector Workshop June 07,08, JLab Users Group Meeting (with session dedicated to a summary of users workshops, held in Spring 2010, that explored physics motivations of an Electron-Ion Collider, entitled “Beyond the 12 GeV Upgrade: an EIC at JLab?”) In parallel: MEIC/ELIC design worked out following highest EICAC (Nov meeting) recommendation related to accelerator Energy-Luminosity profile of EIC design will likely be optimized over time to adjust to novel accelerator science ideas & the nuclear science case  For now we assume a base luminosity, ~10 34 e-nucleons/cm 2 /s  Study what luminosity is required at what energies to optimize the science output, and fold in implications for the detector/acceptance

Slide 14 EIC Collaboration – Roadmap EIC (eRHIC/ELIC) webpage: Weekly meetings at both BNL and JLab Wiki pages at & EIC Collaboration has biannual meetings since 2006 Last EIC meeting: July 29-31, Catholic University, DC Long INT10-03 Institute for Nuclear Theory, centered around spin, QCD matter, imaging, electroweak Sept. 10 – Nov. 19, 2010 Periodic EIC Advisory Committee meetings (convened by BNL & JLab) After INT10-03 program (2011 – next Nuclear Science Long Range Plan) need to produce single, community-wide White Paper laying out full EIC science program in broad, compelling strokes and need to adjust EIC designs to be conform accepted energy-luminosity profile of highest nuclear science impact followed by an apples-to-apples bottom-up cost estimate comparison for competing designs, folding in risk factors and folding in input from ongoing Accelerator R&D, EICAC and community

Slide 15 Summary The last decade or so has seen tremendous progress in our understanding of the partonic sub-structure of nucleons and nuclei based upon: The US nuclear physics flagship facilities: RHIC and CEBAF The surprises found at HERA (H1, ZEUS, HERMES) The development of a theory framework allowing for a revolution in our understanding of the inside of hadrons … Generalized Parton Distributions, Transverse Momentum Dependent Parton Distributions, Lattice QCD This has led to new frontiers of nuclear science: - the possibility to truly explore the nucleon - a new QCD regime of strong color fields in nuclei - mapping the mechanism of nucleon and pion creation The EIC presents a unique opportunity to maintain US leadership in high energy nuclear physics and precision QCD physics

Slide 16 Backup

Slide 17 assumptions (x,Q 2 ) phase space directly correlated with s (=4E e E p ) Q 2 = 1 lowest x scales like s Q 2 = 10 lowest x scales as 10s -1 General science assumptions: (“Medium-Energy”) option driven by: access to sea quarks (x > 0.01 (0.001?) or so) deep exclusive scattering at Q 2 > 10 (?) any QCD machine needs range in Q 2  s = few seems right ballpark  s = few 1000 allows access to gluons, shadowing Requirements for deep exclusive and high-Q 2 semi-inclusive reactions also drives request for (lower &) more symmetric beam energies. Requirements for very-forward angle detection folded in IR design x = Q 2 /ys

Why a Novel High-Luminosity EIC? Several pluses of (M)EIC/ELIC conceptual design - Four Interaction Regions available ( only two can run simultaneously ) - novel design ideas promise high luminosity (& full acceptance) - more symmetric beam energies ( “central” angles facilitates detection ) - figure-8 design optimized for spin ( allows for polarized deuteron beams ) High luminosity in our view a must - Semi-inclusive and deep exclusive processes depend on many kinematic variables beyond x, Q 2, and y: e.g. t and  for DES z, p T and  for SIDIS - More exclusive cross sections drop rapidly with Q 2, t and/or p T - True progress only possible by multi-dimensional experiments - Multiple running conditions required: Longitudinal and transversely polarized beam, Various ion species: 1 H, 2 H, 3 He, heavy A Low E cm and high E cm runs Full science program needs “n times 100 days of good luminosity”

Slide 19  Luminosity [cm -2 s -1 ]  s [GeV 2 ] COMPASS JLAB6&12 HERMES MEIC ELIC DIFF DIS SIDIS EW DES JETS Science versus Luminosity Matrix Legend: DIS deep inelastic scattering SIDISsemi-inclusive DIS DESdeep exclusive (pseudoscalar and vector mesons) DIFFdiffractive scattering JETSjet production EWelectroweak processes No scientific judgment applied: luminosity is taken from what EIC simulations assumed Illustration only

Slide 20 Rough Ideas of Energies (don’t take these too strict) Energy combination (E e & E p ) Physics discussed in workshops 3 on 12 to 3 on 20 (s ~ ) Longitudinal/Transverse separations for meson electro- production, form factor measurements 5 on 20 (s ~ 400) Low-Q 2 part of semi-inclusive deep-inelastic scattering physics 5 on 30 to 5 on 60 (s ~ 600 – 1200) Deep exclusive scattering experiments aimed at nucleon/nucleus imaging 5 on 60 to 10 on 60 (s ~ ) Shadowing region of electron-nucleus scattering High-Q 2 part of semi-inclusive deep-inelastic scattering physics. Start of jet physics. 10 on (s ~ ) Push to smaller x (~10 -3, with reasonable lever-arm in Q 2 ) for e-D and e- 3 He cases (Luminosity x s) high e.g., L ~ 10 34, s ~ 3000 Electroweak searches Highest energies (but low luminosities) Push for small x, saturation

Slide 21 MEIC Design Efforts - Status Near-term design concentrates on parameters that are within state-of-the-art (exception: small bunch length & small vertical  * for proton/ion beams) Detector/IR design has concentrated on maximizing acceptance for deep exclusive processes and processes associated with very-forward going particles  detect remnants of both struck & spectator quarks Optimal energy/luminosity profile still a work in progress Many parameters related to the MEIC detector/IR design seem well matched now (lattices, ion crossing angle, magnet apertures, gradients & peak fields, range of proton energies, detector requirements), such that we do not end up with large “blind spots”.

Slide 22 Reaching Saturation: EIC Options Energies (GeV x GeV) s (GeV 2 ) s EIC /s HERA boost in gluon density over HERA “virtual” x reach boost over HERA at Q 2 = const 11 x / x / x / x / G ~ A 1/3 x s 0.3 (A = 208) Energies for heavy-ion beams At high gluon density, gluon recombination should compete with gluon splitting  density saturation. Color glass condensate