1

Fermilab: Joint Experimental-Theoretical SeminarJanuary 11, 2013

Probing the Quark Sea and Gluons: the Electron-Ion Collider Project

Rolf Ent (JLab)

2007 Long-Range PlanEIC: “half” recommendation

2010 JLab User Workshops

INT10-3 program>500 page report

EIC white paper – to be published

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Probing the Quark Sea and Gluons: the Electron-Ion Collider Project

• Electron-Ion Colliders Worldwide

• Electron-Ion Collider Nuclear Science

• Electron-Ion Collider Accelerator Design

• Integrated Detector and Interaction Region

• Electron-Ion Collider Status and Plans

EIC is the generic name for the Nuclear Science-driven Electron-Ion Collider, presently considered in the US

3

Electron Ion Colliders on the World Map

RHIC eRHIC

LHC LHeCCEBAF MEIC

HERA

FAIR ENC

HIAFEIC@China

4

Possible FuturePast

High-Energy Physics Nuclear Physics

Electron Ion Colliders

HERA@DESY LHeC@CERN eRHIC@BNL MEIC@JLab HIAF@CAS ENC@GSI

ECM (GeV) 320 800-1300 45-175 12-140 12 65 14

proton xmin 1 x 10-5 5 x 10-7 3 x 10-5 5 x 10-5 7 x10-3 3x10-4 5 x 10-3

ion p p to Pb p to U p to Pb ? p to ~40Ca

polarization - - p, 3He p, d, 3He (6Li) p, 3He? p,d

L [cm-2 s-1] 2 x 1031 1033 1033-34 1034-35 1032-33 1035 1032

IP 2 1 2+ 2+ ? 1

Year 1992-2007 2022 (?) 2022 (?) Post-12 GeV 2019 2030 upgrade to FAIR

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EIC vs LHeCLHeC: L = 1.1x1033 cm-2s-1

Ecm = 1.4 TeV

EIC: L = 1033-1034 cm-2s-1

Ecm = 20-70+ GeV • Add 70-100 GeV electron ring to interact with LHC ion beam• Use LHC-B interaction region• High luminosity mainly due to large g’s (= E/m) of beams

• Variable energy range• Polarized and heavy ion beams• High luminosity in energy region of interest for nuclear science

Nuclear science goals:• Map the spin and spatial structure of quarks and gluons in nucleons• Discover the collective effects of gluons in atomic nuclei• Understand the emergence of hadronic matter from color charge

High-Energy/Nuclear physics goals:• Parton dynamics at the TeV scale - high-Q2 electron-quark scattering

(constrain the size of the quark) - physics beyond the Standard Model - physics of high parton densities (low x)

“world’s first polarized e-p collider and world’s first e-A collider”

high-energy e-p collider to follow on DESY, plus plans for e-A collider

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eRHIC: take advantage of higher proton/ion energies

Stage I eRHIC @ BNL MEIC / ELIC @ JLab

√s = 15 – 66 GeV

Ee = 3 – 11 GeV

Ep = 20 – 100 GeV

EPb

= up to 40 GeV/A

√s = 25 – 100 GeV

Ee = 3 – 10 GeV

Ep = 50 – 250 GeV

EPb

= up to 100 GeV/A

(MEIC)

MEIC: take advantage of lower proton/ion energies for detector/IR design

Stage I

A High-Luminosity US-Based Electron Ion Collider

“world’s first polarized e-p collider and world’s first e-A collider” Stage 1 MEIC: dedicated ~1 km ring

optimized for 30-100 GeV protons

MEICELIC

(Hall A & C)

CLAS12

eRHIC2

eRHIC1

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• An EIC aims to study the sea quarks and gluon-dominated matter.

EIC12 GeV

• With 12 GeV we study mostly the valence quark component

MEIC

Into the “sea”: the EIC

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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

Nuclear physicists are trying to answer how basic properties like mass, shape, and spin come about from the flood of gluons, quark/anti-quark pairs, and a few ever-present quarks.

& gluons are abundant

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QCD and the Origin of Mass

99% of the proton’s mass/energy is due to the self-generating gluon field

– Higgs mechanism has 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.

M(up) + M(up) + M(down) ~ 10 MeV << M(proton)

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The Physics Program of an EICI) Map the spin and spatial structure of quarks and gluons in nucleons

Sea quark and gluon polarizationTransverse spatial distributionsOrbital motion of quarks/gluonsParton correlations: beyond one-body densities

(show the nucleon structure picture of the day…)

II) Discover the collective effects of gluons in atomic nucleiColor transparency: Small-size configurationsNuclear gluons: EMC effect, shadowingStrong color fields: Unitarity limit, saturationFluctuations: Diffraction

(without gluons there are no protons, no neutrons, no atomic nuclei)

III) Understand the emergence of hadronic matter from color chargeMaterialization of color: Fragmentation, hadron breakup, color correlationsParton propagation in matter: Radiation, energy loss

(how does M = E/c2 work to create pions and nucleons?)

Needs high luminosity and range of energies

+ some developing ideas for fundamental symmetry tests

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5 x 250 starts here

5 x 100 starts here

current data

w/ EIC data

Q2 = 10 GeV2Helicity PDFs at an EIC

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Sea Quark Polarization• Spin-Flavor Decomposition of the Light Quark Sea

| p = + + + …>u

u

d

u

u

u

u

d

u

u

dd

d Many models predict

Du > 0, Dd < 0

Needs intermediate √s ~ 30 (and good luminosity)}

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Wpu(x,k

T,r) Wigner distributions

d2kT

PDFs f1

u(x), .. h1u(x)

d3r

TMD PDFs f1

u(x,kT), .. h1u(x,kT)

3D imaging

6D Dist.

Form FactorsGE(Q2), GM(Q2)

d2rT

dx &Fourier Transformation

1D

Unified View of Nucleon Structure

GPDs/IPDs

d2kT drz

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TMDs2+1 D picture in momentum space

GPDs2+1 D picture in impact-parameter space

Towards Imaging - Two Approaches

• intrinsic transverse motion

• spin-orbit correlations = indicator of OAM

• non-trivial factorization

• accessible in SIDIS, DY

• collinear but long. momentum transfer

• indicator of OAM; access to Ji’s total Jq,g

• existing factorization proofs

• DVCS, deep exclusive meson production

Quark Sivers function fit to SIDIS (Anselmino et al. 2009)

k y

kx

-0.5

0.5

0.0

-0.5 0.0 0.5

(Lattice Calculation of the IP density of up quark, QCDSF/UKQCD Coll., 2006)

bx [fm]

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Transverse Quark & Gluon ImagingDeep exclusive measurements in ep/eA with an EIC:

diffractive: transverse gluon imaging J/y, f, ro, g (DVCS) non-diffractive: quark spin/flavor structure p, K, r+, …

Describe correlation of longitudinal momentum and transverse position of quarks/gluons

Transverse quark/gluon imaging of nucleon(“tomography”)

Are gluons uniformly distributed in nuclear matter or are there small clumps of glue?Are gluons & various quark flavors similarly distributed? (some hints to the contrary)

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Detailed differential images from nucleon’s partonic structure

EIC: Gluon size from J/Y and f electroproduction (Q2 > 10 GeV2)

[Transverse distribution derived directly from t dependence]

t

Hints from HERA:Area (q + q) > Area (g)

Dynamical models predict difference: pion cloud, constituent quark picture

-

t

EIC: singlet quark size from deeply virtual compton scattering

EIC: strange and non-strange (sea) quark size from p and K production

• Q2 > 10 GeV2 for factorization • Statistics hungry at high Q2!

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Example: Transverse Spatial Distribution of Gluons from J/Y

DVCS transverse spatial projections in progress

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Image the Transverse Momentum of the Quarks

The difference between the p+, p–, and K+ asymmetries reveals that quarks and anti-quarks of different flavor are orbiting in different ways within the proton.

Swing to the left, swing to the right: A surprise of transverse-spin experiments

dsh ~ Seq2q(x) dsf Df

h(z)

Sivers distribution

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Image the Transverse Momentum of the Quarks

Only a small subset of the (x,Q2) landscape has been mapped here:

terra incognitaGray band: present

“knowledge”Purple band: EIC (2s)

u u

An EIC with good luminosity & high

transverse polarization is the optimal tool to to

study this!

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Gluons in Nuclei

NOTHING!!!

What do we know about gluons in a nucleus?

Ratio of gluons in lead to deuterium

• EIC: access gluons through FL (needs variable energy) and dF2/dln(Q2)

• Knowledge of gluon PDF essential for quantitative studies of onset of saturation

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Tomography: Hard Diffraction

A 7 TeV equivalent electron bombarding the proton … but nothing happens to the proton in 15% of cases

Diffractive event

No activity in proton direction

Predictions for eA for such hard diffractive events range up to: ~30-40%... given saturation models

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Hadronization – parton propagation in matter

EIC: Understand the conversion of color charge to hadrons through fragmentation and breakup

Le

e’g*

p+

pT

DpT2 = pT

2(A) – pT2(2H)

“pT Broadening”

Dp T

2

Comprehensive studies possible:• wide range of energy v = 10-1000 GeV move hadronization inside/outside nucleus, distinguish energy loss and attenuation• wide range of Q2: QCD evolution of fragmentation functions and medium effects• Hadronization of charm, bottom Clean probes with definite QCD predictions• High luminosity Multi-dimensional binning and correlations• √s > 30: jets and their substructure in eA

Accardi, Dupre

Can we learn more from correlating with the target fragmentation region?

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C. Weiss

s

• For large or small y, uncertainties in kinematic variables become large

Range in y

Range in s

Range of kinematics

• Detecting the electron ymax

/ ymin

~ 10• Also detecting hadrons y

max / y

min ~ 100

– Requires hermetic detector (no holes)

• Accelerator considerations limit smin

– Depends on smax

(dynamic range)

• At fixed s, changing the ratio Ee / E

ion

can for some reactions improve resolution, particle identification (PID), and acceptance

C. WeissC. Weiss

valence quarks/gluons

non-pert. sea quarks/gluons

radiative gluons/sea

s

To cover the physics we need…

Vacuum fluct.

pQCD radiation

x = Q2/ys

Range of nuclei

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A High-Luminosity US-Based Electron Ion Collider

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.”

Base EIC Requirements per Executive Summary of Institute for Nuclear Theory Report:• range in energies from √s ~ 20 to √s ~ 70 & variable• fully-polarized (>70%), longitudinal and transverse• ion species from deuterium to A = 200 or so• high luminosity: about 1034 e-nucleons cm-2 s-1

• multiple interaction regions• upgradable to higher energies (√s ~ 150 GeV)

“world’s first polarized

e-p collider and world’s

first e-A collid

er”

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How MEIC meets the Design Specs

Base EIC Requirements per Executive Summary INT Report:• center of mass energies from √s ~ 20 to √s ~ 70 GeV & variable

- electron energies above 3 GeV to allow efficient electron trigger- proton energy adjustable to optimize particle identification

• highly polarized (>70%) electron and nucleon beams- longitudinally polarized electron and nucleon beams- transversely polarized nucleon beams

• ion species from deuterium to A = 200 or so• high luminosity ~1034 e-nucleons cm-2 s-1

- optimal luminosity in √s ~ 30-50 region- luminosity ≥1033 e-nucleons cm-2 s-1 in √s ~ 20-70 region

• multiple interaction regions• integrated detector/interaction region

- non-zero crossing angle of colliding beams- crossing in ion beam to prevent synchrotron background

- ion beam final focus quads at ~7 m to allow for full acceptance detector space- bore of ion beam final focus quads sufficient to let particles pass through

up to t ~ 2 GeV2 (t ~ Ep2Q2)

• upgradeable to center of mass energy of about √150 GeV

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MEIC (= stage-I EIC @ JLab) Design• Collider is based on a figure eight concept

– Avoids crossing polarization resonances• Improves polarization for all species• Makes polarized deuterons possible

– Advantage of having a new ion ring

• Highest luminosity comes with final focus quadrupoles close together – Interferes with detection of (spectator) particles at small angles– MEIC is designed around a full-acceptance

detector with ±7 meters free space around

the interaction point and a high-luminosity

detector with ±4.5 meters free space

• The present MEIC design takes a conservative technical approach by limiting

several key design parameters within state-of-the-art. It relies on regular

electron cooling to obtain the ion beam properties.

• The present JLab EIC design focuses on a

CM energy range from 12 up to 65 GeV

Emphasis on integrated detector/interaction region

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EIC@JLab (MEIC) Technical Design Strategy

Limit as many design parameters as we can to within or close to the present state-of-art in order to minimize technical uncertainty and R&D tasks

– Stored electron current should not be larger than 3 A– Stored proton/ion current should be less than 1 A (better below 0.5 A)– Maximum synchrotron radiation power density is 20 kW/m

– Maximum peak field of warm electron magnet is 1.7 T– Maximum peak field of ion superconducting dipole magnet is 6 T

– Maximum betatron value at FF quad is 2.5 km

• New beta-star, appropriate to the detector requirements

2.5 km βmax + 7 m βy*= 2 cm Full acceptance

2.5 km βmax + 4.5 m βy*=0.8 cm Large acceptance

• This design will form a base for future optimization guided by – Evolution of the science program – Technology innovation and R&D advances

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Medium Energy EIC@JLab

JLab Concept

Initial configuration (LEIC & MEIC):• 3-11 GeV on 10-25 & 20-100 GeV ep/eA collider• fully-polarized, longitudinal and transverse• luminosity: up to ~2 x 1034 e-nucleons cm-2 s-1

Upgradable to higher energies (EIC)• 3-11 GeV on up to 250 GeV ep/eA collider• luminosity: up to few x 1034 e-nucleons cm-2 s-1

Electron collider ring

(3 to 11 GeV)

Cold ion collider ring

(up to 100 GeV)

Warm ion collider ring (up to 25 GeV)

“Like Mike”

“Ike”

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MEIC Design Report

• Posted: arXiv:1209.0757

• Stable concept for 3 yearsDesign Feature: High & Flexible PolarizationFully integrated detector/interaction region

“… was impressed by the outstanding quality of the present MEIC design”“The report is an excellent integrated discussion of all aspects of the MEIC concept.” (JSA Science Council 08//29/12)

• EPJA article by JLab theory on EIC science case• EIC white paper near-final (w. BNL & JLab users)

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Design Features: High Polarization

All ion rings (two boosters, collider) have a figure-8 shape • Spin precessions 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 medium energy polarized deuterons

This design feature promises a high polarization for all light ion beams

(The electron ring has a similar shape since it shares a tunnel with the ion ring, section 4.7)

Use Siberian Snakes/solenoids to arrange polarization at IPs

IIP

IP

longitudinal axis

IIP

IP

Vertical axis

IP

IIP

Solenoid

IP

IIP

Insertion

Longitudinal polarization at both IPs

Transverse polarization at both IPs

Longitudinal polarization at one IP

Transverse polarization at one IP

Proton or Helium-3 beams Deuteron beam

Slide 30

31

Design Features: High Luminosity

• Based on high bunch repetition rate CW colliding beams• Very high bunch repetition rate Very small bunch charge

• Very short bunch length (sz ~ b*) Very small β*

• Crab crossing Small transverse emittance

• A proven concept: KEK-B @ 2x1034 /cm2/s

• JLab aims to replicate this in colliders w/ hadron beams• The electron beam from CEBAF possesses a high bunch repetition rate • Ion beams from a new ion complex to match the electron beam

KEK-B MEIC

Repetition rate MHz 509 748.5

Particles per bunch (e-/e+) or (p/e-) 1010 3.3 / 1.4 0.42 / 2.5

Beam current A 1.2 / 1.8 0.5 / 3

Bunch length cm 0.6 1 / 0.75

Horizontal & vertical β* cm 56 / 0.56 10/2 to 4/0.8

Beam energy (e-/e+) or (p/e-) GeV 8 / 3.5 60 / 5

Luminosity per IP, 1034 cm-2s-1 2 0.56 ~ 1.4

• •

•

Slide 31

32

A New Ion Complex at JLab

Length (m)

Max. energy (GeV/n)

Electron Cooling Process

Proton Lead

SRF linac ~100 0.285 0.1 Stripping

Pre-booster ~300 3 1.2 DC accumulation

Large booster ~1350 25 10 Stacking

collider ring~1350 100 40 ERL

De-bunching/re-bunching

ion sources

SRF Linacpre-booster

(accumulator ring)large booster medium energy

collider ring

to high energy collider ring

coolingcooling

Slide 32

Ion Linac (by ANL)MEBT

QWR

QWR HWR

DSR

Ion Sources

IHRFQ

Stripper

SuperconductingNormal conducting

ARC 1

Injection Insertion section

ARC 2

ARC 3

RF Cavities

Electron Cooling

Solenoids

Extraction to

large booster

Collimation

Beam from LINAC

Pre-booster (by NIU)

33

MEIC Layout

• Vertical stacking for identical ring circumferences• Horizontal crab crossing at IPs due to flat colliding beams• Ion beams execute vertical excursion to the plane of the

electron orbit for enabling a horizontal crossing

• Ring circumference: 1340 m• Maximum ring separation: 4 m• Figure-8 crossing angle: 60 deg.

Interaction point locations:

• Downstream ends of the electron straight sections to reduce synchrotron radiation background

• Upstream ends of the ion straight sections to reduce residual gas scattering background

Electron Collider

Ion Collider

Large Ion Booster

Interaction Regions

PreboosterIon

source

Three Figure-8rings stacked

vertically

Ion transfer beam line

Medium energy IP withhorizontal crab

crossing

Electron ring

Injector

12 GeV CEBAF

SRF linac

Warm large booster

(up to 25 GeV/c)

Cold 97 GeV/c proton collider

ring

Electron path

Ion path

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Crab Crossing• High bunch repetition rate requires crab crossing of colliding beams to avoid parasitic beam-

beam collisions• Present baseline: 50 mrad crab crossing angle

Crab Cavity

Energy (GeV/c)

Kicking Voltage (MV)

R&D

electron 5 1.35 State-of-art

proton 60 8 Factor of six

Crab cavity State-of-the-art: KEKB Squashed cell@TM110 Mode Vkick=1.4 MV, Esp= 21 MV/m 750 MHz SRF crab cavity design ongoing

35

Crab Crossing• Restore effective head-on bunch collisions with 50 mrad crossing angle Preserve luminosity• Dispersive crabbing (regular accelerating / bunching cavities in dispersive region) vs.

Deflection crabbing (novel TEM-type SRF cavity at ODU/JLab, very promising!)

Incoming At IP Outgoing

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Electron Cooling

• Essential to achieve high luminosity for MEIC

• Traditional electron cooling, not Coherent Electron Cooling

• MEIC cooling schemePre-booster: Cooling for assisting accumulation of positive ion beams

(Using a low energy DC electron beam, existing technology)

Collider ring: Initial cooling after injection Final cooling after boost & re-bunching, for reaching design values Continuous cooling during collision for suppressing IBS

(Using new technologies)

• Challenges in cooling at MEIC collider ring – High ion energy

(State-of-the-art: Fermilab recycler, 8 GeV anti-proton, DC e-beam)

– High current, high bunch repetition rate CW cooling electron beam

Slide 36

37

Staged Electron Cooling In Collider Ring

Initial Cooling after boost & bunching

Colliding Mode

Energy GeV/MeV 20 / 8.15 60 / 32.67 60 / 32.67

Beam current A 0.5 / 3 0.5 / 3 0.5 / 3

Particles/Bunch 1010 0.42 / 3.75 0.42 / 3.75 0.42 / 3.75

Ion and electron bunch length cm (coasted) 1 / 2~3 1 / 2~3

Momentum spread 10-4 10 / 2 5 / 2 3 / 2

Horiz. and vert. emitt, norm. µm 4 / 4 0.35 / 0.07

Laslett’s tune shift (proton) 0.002 0.006 0.07

Cooling length /circumference m/m 15 / 1000 15 / 1000 15 / 1000

• Initial cooling: after injection for reduction of longitudinal emittance < acceleration

• Final cooling: after boost & rebunching, for reaching design values of beam parameters

• Continuous cooling: during collision for suppressing IBS & preserving luminosity lifetime

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ERL Circulator Electron Cooler

ion bunch

electron bunch

circulator ring

Cooling section

solenoid

Fast kickerFast kicker

SRF Linac dumpinjector

e-bunches circulates 10 -100 times reduction of current from an ERL by a same factor

Design Choices• Energy Recovery Linac (ERL) • Compact circulator ring

to meet design challenges• Large RF power (up to 81 MW) • Long gun lifetime (average current 1.5 A)

Required technologies• High bunch charge magnetized gun• High current ERL (55 MeV, 15 to150 mA)• Ultra fast kicker

energy recovery

30 m

Solenoid (20 m)

SRF

injector

dumper

Optimization• eliminating a long return path could double the cooling rate Proposal: A technology demonstration

using JLab FEL facility

Slide 38

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MEIC Collider Ring Footprint

m

Quarter arc 140

Universal spin rotator

50

IR insertion 125

Figure-8 straight 140 x 2

RF short straight 25

Circumference ~ 1300

Ring design is a balance between • Synchrotron radiation prefers a large ring (arc) length• Ion space charge prefers a small ring circumference

Multiple IPs require long straight sections

Straights also hold required service components (cooling, injection and ejection, etc.)

3 rd IR (125 m)

UniversalSpin Rotator

(8.8°/4.4°, 50 m)

1/4 Electron Arc

(106.8°, 140 m)

Figure-8 Crossing Angle: 2x30°

Experimental Hall (radius 15 m)

RF (25 m)

Universal

Spin Rotator

(8.8°/4.4°, 5

0 m)

Universal

Spin Rotator

(8.8°/4.4°, 5

0 m)

UniversalSpin Rotator

(8.8°/4.4°, 50 m)

IR (125 m) IR (125 m)

Injection from CEBAF

Compton Polarimeter

(28 m)

1/4 Electron Arc

(106.8°, 140 m)

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MEIC 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

(“Medium-Energy”) MEIC@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

C. Weiss

s

C. Weiss

s

• Detecting only the electron ymax

/ ymin

~ 10

• Also detecting all hadrons ymax

/ ymin

~ 100

41

Where do particles go - generalp or A e

Several processes in e-p:1) “DIS” (electron-quark scattering) e + p e’ + X2) “Semi-Inclusive DIS (SIDIS)” e + p e’ + meson + X3) “Deep Exclusive Scattering (DES)” e + p e’ + photon/meson + baryon4) Diffractive Scattering e + p e’ + p + X5) Target fragmentation e + p e’ + many mesons + baryons

Even more processes in e-A:6) “DIS” e + A e’ + X7) “SIDIS” e + A e’ + meson + X8) “Coherent DES” e + A e’ + photon/meson + nucleus9) Diffractive Scattering e + A e’ + A + X10)Target fragmentation e + A e’ + many mesons + baryons11)Evaporation processes e + A e’ + A’ + neutrons

In general, e-p and even more e-A colliders have a large fraction of their science related to the detection of what happens to the ion beams. The struck quark remnants can be guided to go to the central detector region with Q2 cuts, but the spectator quark or struck nucleus remnants will go in the forward (ion) direction.

Token example: 1H(e,e’π+)n

42

Transverse spatial imaging – recoil baryons

DVCS on the proton

J.H. Lee

~ √t/Ep

5x30 GeV5x250 GeV

ep → e'π +n

8 mrad @ t = -1

40 mrad @ t = -1 GeV2

T. Horn

• Colliders allow straightforward detection of recoil baryons, making it possible to map the t-distribution down to very low values of –t

– eRHIC (partially) solves this by squeezing the high-energy recoil baryons through a high-gradient interaction region focusing magnet and the use of Roman Pots

• At very high proton energies, recoil baryons are all scattered at small angles– Moderate proton energies give the best resolution

– High luminosity at intermediate proton energies and excellent small-angle detection make the MEIC a perfect tool for imaging of the proton

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Detector/IR in pocket formulas

• bmax ~ 2 km = l2/b* (l = distance IP to 1st quad)

• IP divergence angle ~ 1/sqrt(b*)

• Luminosity ~ 1/b*

Example: l = 7 m, b* = 20 mm bmax = 2.5 km

Example: l = 7 m, b* = 20 mm angle ~ 0.3 mrExample: 12 s beam-stay-clear area

12 x 0.3 mr = 3.6 mr ~ 0.2o

Making b* too small complicates small-angle (~0.5o) detection before ion Final Focusing Quads, and would require too high a peak field for these quads given the large apertures (up to ~0.5o). b* = 1-2 cm and Ep = 20-100 GeV ballpark right!

• FFQ gradient ~ Ep,max /sqrt(b*) (for fixed bmax, magnet length)

Example: 6.8 kG/cm for Q3 @ 12 m @ 60 GeV 7 T field for 10 cm (~0.5o) aperture

44

MEIC: Full acceptance detector – strategy

ultra forwardhadron detectionlow-Q2

electron detection large apertureelectron quads

small diameterelectron quads

central detector with endcaps

ion quads

50 mrad beam(crab) crossing angle

n

ep

p

small anglehadron detection

60 mrad bend

solenoid

electron FFQs50 mrad

0 mrad

ion dipole w/ detectors

ions

electrons

IP

ion FFQs

2+3 m 2 m 2 m

detectors

Central detector

7 meters

Three-stage detection

In general, e-p and even more e-A colliders have a large fraction of their science related to the detection of what happens to the ion beams… spectator quark or struck nucleus remnants will go in the forward (ion) direction this drives the integrated detector/interaction region design: NO HOLES!

(P. Nadel-Turonski, V. Morozov, T. Horn, C. Hyde)

45

solenoid

electron FFQs50 mrad

0 mrad

ion dipole w/ detectors

ions

electrons

IP

ion FFQs

2+3 m 2 m 2 m

Detect particles with angles below 0.5o beyond ion FFQs and in arcs.Need 4 m machine element free region

detectors

Central detector

Detect particles with angles down to 0.5o before ion FFQs.Need 1-2 Tm dipole

EM

Ca

lorim

ete

r

Ha

dro

n C

alo

rime

ter

Mu

on

De

tect

or

EM

Ca

lorim

ete

r

Solenoid yoke + Muon Detector

TOF

HT

CC

RIC

H

RICH or DIRC/LTCC

Tracking

2m 3m 2m

4-5m

Solenoid yoke + Hadronic Calorimeter

Very-forward detectorLarge dipole bend @ 20 meter from IP (to correct 50 mr ion horizontal crossing angle) allows for very-small angle detection (<0.3o).Need 20 m machine element free region

MEIC: Full Acceptance Detector

7 meters

Three-stage detection

All incorporated in MEIC design

(P. Nadel-Turonski, V. Morozov, T. Horn, C. Hyde)

4646

e

p

n20 Tm dipole

2 Tm dipole

solenoid

• 100 GeV maximum ion energy allows using large-aperture magnets with achievable field strengths

• Momentum resolution < 3x10-4

– limited by intrinsic beam momentum spread

• Excellent acceptance for all ion fragments

• Neutron detection in a 25 mrad cone down to zero degrees

• Recoil baryon acceptance:– up to 99.5% of beam energy for all angles

– down to 2-3 mrad for all momenta

npe

MEIC Detector & Interaction RegionGEANT4 model of extended IR exists

Full acceptance

47

Extended Detector & Interaction Region

Truly fully integrated detector & interaction region, also for eA

48

Design Feature: Full-Acceptance Detector

6 T max

9 T max

12 T max

Forward acceptance horizontal plane

Forward acceptance vertical plane

Full acceptance detector• Demonstrated excellent acceptance & resolution• Completed the detector-optimized IR optics

• Fully integrated detector and interaction region

• Working on hardware engineering design

Addressing accelerator challenges• Demonstrated chromaticity compensation (section 7.5)

49

Reviews and Activities

Slide 49

• 2nd EIC International Advisory Committee Review (Nov. 2-3, 2009) (Accelerator members: R. Gerig, U. Wienands)

• Physics-Machine Joint Meeting (for a design goal) (Feb. 11&12, 2010)

• MEIC Machine Design Week (March 4-8, 2010) (Detector/IR consultant: M. Sullivan of SLAC )

• MEIC Internal Machine Design Review (Sept. 15-16, 2010) (Reviewers: A. Chao and G. Hoffstaetter)

• RF & Beam Synchronization Mini-Workshop (Oct. 29, 2010)

• MEIC Ion Complex Design Workshop (Jan. 27-28, 2011)

• 3rd ElC International Advisory Committee Review (April 9, 2011) (Accelerator members: R. Gerig, S. Nagaitsev, V. Shiltsev)

• MEIC Detector and IR Design Mini-Workshop (Oct. 31, 2011)

• ERL Circulator Cooler Test Facility Retreat (Jan. 31, 2012)

50

EIC Progress• Close and frequent collaboration between accelerator and nuclear physicists regarding the machine, interaction region and detector requirements has taken place.

“We are proud to announce that we have achieved a fully integrated detector and interaction region”

• Several JLab user proposals for generic detector R&D call

• Draft MEIC Intermediate Design Report completed Aug. 2012

• Concept for regular electron cooling further worked out- Many aspects of cooling can be tested at JLab/FEL- Mainly use “brute force” lenient at lower energies

• Cost Estimate developed, estimate being iterated(3 main cost drivers: Ion Linac, SC Magnets & SRF Cooling, Civil construction)

• Steering committee with many JLab users working on EIC white paper accessible to general nuclear science community

• Integrate LEIC (up to 25 GeV/c protons) into design

51

MEIC

warm e-ring

warm p-ring

cold p-ring

warm e-ring

cold p-ring

EIC

(LEIC)25 GeV 100 GeV 250 GeV

MEIC = MEIC + LEIC has large advantages:1) Design flexibility2) Ease of commissioning3) Separate warm ion ring

from cold ion ring4) Reduce risk

Integrate LEIC into MEIC planning

cooling

52

LEIC as An Intermediate Technology StepLEIC minimizes technology challenges, and provides a test bed for MEIC• Electron cooling

– Requires lower electron energies (13.6 MeV vs. 4.3 MeV Fermilab cooler) and a lower (~0.5 A) current electron cooling beam

• Ion linac/pre-booster– An accumulation of a lower current ion beam in the pre-booster

• Beam synchronization – Variation of number of bunches in the LEIC ion collider ring provides a large set of

synchronization energies for experiments – Variation of the warm LEIC ion ring path-length for covering other energies is technically

feasible, RF frequency variation can be avoided • Crab cavity

– The integrated kicking voltage is reduced by a factor of 4, now about 3 times of KEK-B

• Chromaticity– Start with only one IR, the chromaticity is reduced by half.

• IR magnets– The maximum fields are reduced by a factor of 4.

• Ion polarization– Magnetic field of some spin rotators are reduced by a factor of 4.

53

MEIC 2013 Plans/Goals

• By Spring 2013:• Finalize First Optimization:

- Copy main IR into 2nd IR and do dynamical aperture studies- Shorten electron spin rotator & reshuffle to allow LEIC to 25+ GeV

• Fold in Detector solenoid in accelerator design- optics requirements and initial return field optimization- ion beam deflection & optics compensation- polarization impact

• By Summer 2013:• Completing:

- Electron cooling channels in both warm and cold ion collider rings- Vertical chicane for separating two cooling beams- Ion vertical chicanes to electron ring plane

• Ramp up detector studies: resolution, fast MC• First concepts/checks of all magnets• Cartoon drawings of full MEIC

• Workshop adjacent to APS/DNP meeting October 2013• By end of 2013:

• Polarization tracking study with misalignments, etc.• Initial results of resolution & fast MC studies• Supplement to MEIC design report to outline the completed integration of machine

design and science capabilities utilizing protons/ions from the warm magnet ring

54

Dechirper Rechirper

MEIC Planned Accelerator R&D• Electron Cooling

– Proof of staged beam cooling concept– Design of an ERL Circulator cooler– Cooler test facility proposal

• Interaction Region Design– Detector/IR integration, small angle

(down to 0°) particle detection– Nonlinear beam dynamics, chromatic

compensation and dynamic aperture– Implementation of crab crossing

• Polarization– Electron spin matching– Proof of figure-8 ring concept– Realization of fast spin flip

• Beam-beam effect• Electron cloud effect in ion ring

Solenoid (15 m

)

SRF

injector

dumper

MEIC Electron cooler

e-Cooler Test Facility

Interaction Region w/ Forward tagging

55

EIC Realization Imagined

Activity Name 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

12 Gev Upgrade

FRIB

EIC Physics Case

NSAC LRP

EIC CD0

EIC Machine Design/R&D

EIC CD1/Downsel

EIC CD2/CD3

EIC Construction

Assumes endorsement for an EIC at the next NSAC Long Range Plan (2013/14?)

56

New MEIC/EIC Layout

57

Summary

• Collider environment provides tremendous advantages – Kinematic coverage (high center-of-mass energy)

– Polarization measurements with excellent Figure-of-Merit

– Detection of spectators, recoil baryons, and target fragmentation

• EIC is a maturing project– MEIC design report on arXiv, and elegant plans to integrate LEIC-MEIC:

Everybody wants to be “Like Mike”

– Accelerator R&D funds allocated, and joint detector R&D projects have started

• EIC is the ultimate tool to study sea quarks and gluons– Sea quarks and gluons play a prominent role in nucleon structure

– EIC is required to completely understand nucleon structure and the role of gluons in nuclei

• We have a unique opportunity to make a breakthrough in nucleon structure and QCD dynamics:

- explore and image the nucleon- discover the role of gluons in structure and dynamics- understand the emergence of hadrons from color charge

58

59

longitudinal momentum

transverse distribution

orbital motion

quark to hadron

conversion

Dynamical structure! Gluon saturation?

• 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 the 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?• Explore the interaction of color charges with matter and understand the conversion of quarks and gluons to hadrons through fragmentation and breakup.

Why a New-Generation EIC? Why not HERA?

60

A CB

D Continuous Electron Beam• Energy 0.4 ─ 6.0 GeV• 200 mA, polarization 85%• 3 x 499 MHz operation• Simultaneous delivery 3 halls

JLab accelerator CEBAF

• 416 PhDs completed• On average 22 US PhDs per year, close to 30% of US PhDs in nuclear physics• On average 50 undergrads per year involved in research at Jefferson Lab• 1385 users in FY12, anticipated to grow to ~1500+ users with 12-GeV operations• International: non-US nuclear physics users = 1/3 of total, from 33 countries

61

12 GeV Upgrade Project: $310M, ~80% obligated

Scope of the project includes: • Doubling the accelerator beam energy• New experimental Hall and beamline• Upgrades to existing Experimental Halls

Maintain capability to deliver lower pass beam energies: 2.2, 4.4, 6.6….

New Hall

Add arc

Enhanced capabilitiesin existing Halls

Add 5 cryomodules

Add 5 cryomodules

20 cryomodules

20 cryomodules

Upgrade arc magnets and supplies

CHL upgrade

Upgrade is designed to build on existing facility: vast majority of accelerator and experimental equipment have continued use

The completion of the 12 GeV Upgrade of CEBAF was ranked the highest priority in the 2007 NSAC Long Range Plan.

62

21st Century Science Questions

• What is the role of gluonic excitations in the spectroscopy of light mesons?

• Where is the missing spin in the nucleon?What is the role of orbital angular momentum?

• Can we reveal a novel landscape of nucleon substructure through measurements of new multidimensional distribution functions?

• What is the relation of short-range nuclear structure and parton dynamics?

• Can we discover evidence for physicsbeyond the standard modelof particle physics?

Excited Glue

63

The road to orbital motion

Final transverse momentum of the detected pion Pt arises from convolution of the struck quark transverse momentum kt with the transverse momentum generated during the fragmentation pt.

Pt = pt + z kt + O(kt

2/Q2)

SIDIS – kT Dependence

p

M

xTMD

TMDu(x,kT)

f1,g1,f1T ,g1T

h1, h1T ,h1L ,h1

Linked to framework of Transverse Momentum Dependent Parton Distributions

64

Wu(x,k,r)Towards a “3D” spin-

flavor landscape (Wigner Function)

t

EIC: Transverse spatial distribution derived directly from t dependence:

• Gluon size from J/Y and f• Singlet quark size from g• Strange and non-strange (sea)

quark size from p and K production

Hints from HERA: Area (q + q) > Area (g)

(x,r)(x,k)

p

m

xTMD

EIC: Transverse momentum distribution derived directly from semi-inclusive measurements, plus large gain in our knowledge of transverse momentum effects as function of x.

Exact kT distribution presently unknown – EIC can do this well

-

65

Parameters for Full Acceptance Interaction Point

Proton Electron

Beam energy GeV 60 5

Collision frequency MHz 750 750

Particles per bunch 1010 0.416 2.5

Beam Current A 0.5 3

Polarization % > 70 ~ 80

Energy spread 10-4 ~ 3 7.1

RMS bunch length mm 10 7.5

Horizontal emittance, normalized µm rad 0.35 54

Vertical emittance, normalized µm rad 0.07 11

Horizontal β* cm 10 10

Vertical β* cm 2 2

Vertical beam-beam tune shift 0.014 0.03

Laslett tune shift 0.06 Very small

Distance from IP to 1st FF quad m 7 3.5

Luminosity per IP, 1033 cm-2s-1 5.6

66

Parameters for High Luminosity Interaction Point

Proton Electron

Beam energy GeV 60 5

Collision frequency MHz 750 750

Particles per bunch 1010 0.416 2.5

Beam Current A 0.5 3

Polarization % > 70 ~ 80

Energy spread 10-4 ~ 3 7.1

RMS bunch length mm 10 7.5

Horizontal emittance, normalized µm rad 0.35 54

Vertical emittance, normalized µm rad 0.07 11

Horizontal β* cm 4 4

Vertical β* cm 0.8 0.8

Vertical beam-beam tune shift 0.014 0.03

Laslett tune shift 0.06 Very small

Distance from IP to 1st FF quad m 4.5 3.5

Luminosity per IP, 1033 cm-2s-1 14.2

67

Chromaticity and Dynamic Aperture• Compensation of chromaticity with 2 sextupole families only using symmetry

• Non-linear dynamic aperture optimization under way

p/p = 0.310-3 at 60 GeV/c

5 p/p

Ions

p/p = 0.710-3 at 5 GeV/c

5 p/p

Electrons

Normalized Dynamic Aperture

𝑥 /𝜎 𝑥

𝑦/𝜎

𝑦

w/o Octupole

with Octupole

𝑥/𝜎

𝑥

𝛿 /𝜎 𝛿

68

-10000

-8000

-6000

-4000

-2000

0

2000

4000

6000

8000

10000

-20000 -15000 -10000 -5000 0 5000 10000 15000 20000x [cm]

z [cm]

Figure-8 Collider Ring - Footprint

Use Crab Crossing for Very-Forward Detection too!

Present thinking: ion beam has 50 mr horizontal crossing angleRenders good advantages for very-forward particle detection

~60 mr bend would need 12 Tm dipole @ ~20 m from IP

(Reminder: MEIC/ELIC scheme uses 50 mr crab crossing)

69

Pion momentum = 5 GeV/c, 4T ideal solenoid field, 1.25 m tracking region

Detector/IR – Magnetic Fields

Add <2 Tm transverse field component in forward-ion direction to get dp/p roughly constant vs. angle

• Goal: resolution dp/p (for pions) better than 1% for p < 10 GeV/c• obtain effective 0.5 Tm field by having 50 mr crossing angle (for 5 m long central solenoid)• probably suffices to add 1-2 Tm dipole field for small-angles (<10o?) only to get dp/p < 1% for pions of up to 10 GeV/c.

Here we added dipole for angles smaller than 25o

70

• From arc where electrons exit and magnets on straight section

Synchrotron radiation

Random hadronic background

• Dominated by interaction of beam ions with residual gas in beam pipe between arc and IP

• Comparison of MEIC (at s = 4,000) and HERA (at s = 100,000)− Distance from ion exit arc to detector: 50 m / 120 m = 0.4

− Average hadron multiplicity: (4000 / 100000)1/4 = 0.4

− p-p cross section (fixed target): σ(90 GeV) / σ(920 GeV) = 0.7

− At the same ion current and vacuum, MEIC background should be about 10% of HERAo Can run higher ion currents (0.1 A at HERA)o Good vacuum is easier to maintain in a shorter section of the ring

• Backgrounds do not seem to be a major problem for the MEIC− Placing high-luminosity detectors closer to ion exit arc helps with both background types

− Beyond arcs proton/ion beams get manipulated (crab crossing angle), electron beam stays straight to go through detector minimizes synchroton radiation

− Signal-to-background will be considerably better at the MEIC than HERAo MEIC luminosity is more than 100 times higher (depending on kinematics)

Backgrounds and detector placement