MEIC Overview: Physics, Project & Timeline

Rolf Ent

MEIC Accelerator Design ReviewSeptember 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

EIC@JLab 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 (Q2) dependence.

Slide 7

The Science of an (M)EICNuclear 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 QCDThree 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 = Mc2 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/Y and f electroproduction- Singlet quark size from deeply virtual compton scattering (DVCS)- Strange and non-strange (sea) quark size from p 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 p+, p–, and K+ asymmetries reveals these orbits.• Map both the gluon momentum distributions of nuclei (F2 & FL

measurements) and the transverse spatial distributions of gluons on nuclei (coherent DVCS & J/Y 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 1034 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

Energies s Design Luminosity

(M)EIC@JLab Up to 11 x 60+ 240-3000 Close to 1034

Future ELIC@JLab

Up to 11 x 250 (20? x 250)

11000 (20000?)

Close to 1035

Staged MeRHIC@BNL

Up to 5 x 250 600-5000 Close to 1034

eRHIC@BNL Up to 20 x 325 (30 x 325)

26000 (39000)

Close to 1034

ENC@GSI Up to 3 x 15 180 Few x 1032

LHeC@CERN Up to 150 x 7000 4200000 Close to 1033

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 CaldwellAlbert De Roeck Walter Henning (chair)David Hertzog Xiangdong JiRobert Klanner Alfred MuellerKatsunobu Oide Naohito SaitoUli Wienands *likely add few more accelerator experts

• 1st meeting Feb. 16, 2009 at SURA headquarters, D.C.• 2nd meeting Nov. 2&3, 2009 at Jefferson Lab• 3rd meeting anticipated Fall 2010 (at BNL?)

Concrete design for EIC@Jlab requested by this meeting

Internal reviewed cost estimate requested by this meeting

EIC Advisory Committee

Slide 12

EIC Project - RoadmapYear CEBAF Upgrade Electron-Ion Collider

1994 1st CEBAF at Higher Energies Workshop

1996 (LRP) CEBAF Upgrade an Initiative

~2000 Energy choice settled, “Golden Experiments”

1st workshops on US Electron-Ion Collider

2002 (LRP) JLab 12-GeV Upgrade 4th recommendation

Electron-Ion Collider an Initiative

2007 (LRP) JLab 12-GeV Upgrade highest recommendation

Electron-Ion Collider “half-recommendation”

~2010 EIC “Golden Experiments”???

2013? (LRP) JLab 12-GeV construction & operation, FRIB construction highest recommendation(s)?

EIC a formal (numbered) recommendation?

2015 JLab 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 + 13 @Rutgers: Electron-Nucleon Exclusive Reactions• March 14 + 15 @Duke: Partonic Transverse Momentum in Hadrons:

Quark Spin-Orbit Correlations and Quark-Gluon Interactions• April 07, 08, 09 @ANL: Nuclear Chromo-Dynamic Studies• May 17 +18 @W&M: Electroweak Studies• June 04 + 05 @JLab: MEIC Detector Workshop• June 07,08,09 2010 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. 2009 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, ~1034 e-nucleons/cm2/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: http://web.mit.edu/eicc/• Weekly meetings at both BNL and JLab

• Wiki pages at http://eic.jlab.org/ & https://wiki.bnl.gov/eic• EIC Collaboration has biannual meetings since 2006

• Last EIC meeting: July 29-31, 2010 @ Catholic University, DC• Long INT10-03 program @ 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

SummaryThe 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

EIC@JLab assumptions(x,Q2) phase space directly correlated with s (=4EeEp) :

@ Q2 = 1 lowest x scales like s-1

@ Q2 = 10 lowest x scales as 10s-1

General science assumptions:(“Medium-Energy”) EIC@JLab option driven by:

access to sea quarks (x > 0.01 (0.001?) or so)deep exclusive scattering at Q2 > 10 (?)any QCD machine needs range in Q2

s = few 100 - 1000 seems right ballpark s = few 1000 allows access to gluons, shadowing

Requirements for deep exclusive and high-Q2 semi-inclusive reactions also drives request for (lower &) more symmetric beam energies.Requirements for very-forward angle detection folded in IR design

x = Q2/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, Q2, and y:

• e.g. t and f for DES• z, pT and f for SIDIS

- More exclusive cross sections drop rapidly with Q2, t and/or pT

- True progress only possible by multi-dimensional experiments- Multiple running conditions required:

• Longitudinal and transversely polarized beam,• Various ion species: 1H, 2H, 3He, heavy A• Low Ecm and high Ecm runs

Full science program needs “n times 100 days of good luminosity”

Slide 19

Lu

min

osity

[cm

-2 s

-1]

s [GeV2]

1035

1034

1033

1032

10 100 1000 10000 100000

COMPASS

JLAB6&12HERMESENC@GSI

MEICELIC

DIFF

DIS

SIDIS

EW

DES

JETS

Science versus Luminosity Matrix

Legend:DIS deep inelastic scatteringSIDIS semi-inclusive DISDES deep exclusive

(pseudoscalar and vector mesons)

DIFF diffractive scatteringJETS jet productionEW electroweak 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 (Ee & Ep)

Physics discussed in workshops

3 on 12 to 3 on 20(s ~ 150 - 300)

Longitudinal/Transverse separations for meson electro-production, form factor measurements

5 on 20(s ~ 400)

Low-Q2 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 ~ 1200 - 2400)

Shadowing region of electron-nucleus scatteringHigh-Q2 part of semi-inclusive deep-inelastic scattering physics. Start of jet physics.

10 on 80-100(s ~ 3200-4000)

Push to smaller x (~10-3, with reasonable lever-arm in Q2) for e-D and e-3He cases

(Luminosity x s) highe.g., L ~ 1034, 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 b* 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 OptionsEnergies

(GeV x GeV)s

(GeV2)sEIC/sHERA boost in

gluon density over HERA

“virtual” x reachboost over HERA at Q2 = const

11 x 38 1700 1/60 1.73 6 5 x 100 2000 1/50 1.83 820 x 100 8000 1/12 2.81 3130 x 130 15600 1/6 3.46 63

G ~ A1/3 x s0.3 (A = 208)

Energies for heavy-ion

beams

At high gluon density, gluon recombination should compete with gluon splitting density saturation.

Color glass condensate