an electron-ion collider for jlab antje bruell lia merminga (kees de jager) jefferson lab

Thomas Jefferson National Accelerator Facility

ELIC, June 15, 2006, 1

An Electron-Ion Collider for JLabAn Electron-Ion Collider for JLab

Antje Bruell

Lia Merminga

(Kees de Jager)

Jefferson Lab

QCD-N’06

June 15, 2006


ELIC, June 15, 2006, 2

CHL-2CHL-2

Upgrade magnets Upgrade magnets and power and power suppliessupplies

Enhance equipment in Enhance equipment in existing hallsexisting halls

6 GeV CEBAF1112Add new hallAdd new hall

• JLab Upgrade only present construction project in DOE-NP

• First 12 GeV beam expected in ~2012

• However, plans for next upgrade already being developed now


ELIC, June 15, 2006, 3

Why Electron-Ion Collider?

• Polarized DIS and e-A physics: in past only in fixed-target mode• Collider geometry allows complete reconstruction of final state• Better angular resolution between beam and target fragments

• Lepton probe provides precision but requires high luminosity to be effective

• High Ecm large range of x, Q2 Qmax2= ECM

2•x

x range: valence, sea quarks, glueQ2 range: utilize evolution equations of QCD

• High polarization of lepton, nucleon achievable


ELIC, June 15, 2006, 4

com

pass

herm

es JLab (upgraded)

clas

Q2

Kinematic coverage of ELIC

EIC

• Luminosity of up to 8x1034 cm-2 sec-1 (one-day life time)

• One day 4,000 events/pb• Supports Precision

Experiments

Lower value of x scales as s-1

• DIS Limit for Q2 > 1 GeV2 implies x down to 2.5 times 10-4

• Significant results for 200 events/pb for inclusive scattering

• If Q2 > 10 GeV2 required for Deep Exclusive Processes can reach x down to 2.5 times 10-3

• Typical cross sections factor 100-1,000 smaller than inclusive scattering high luminosity essential


ELIC, June 15, 2006, 5

EIC Monte Carlo Group•Antje Bruell (JLab)•Abhay Deshpande (SBU)•Rolf Ent (JLab)•Ed Kinney (Colorado)•Naomi Makins (UIUC)•Christoph Montag (BNL)•Joe Seele (Colorado)•Ernst Sichtermann (LBL)•Bernd Surrow (MIT)

+ Several “one-timers”: Harut Avakian,

Dave Gaskell,

Andy Miller, …

GRSV

ELIC projection (~10 days)

Examples: g1p,Transversity, Bjorken SR

Can determine the Bjorken Sum Rule to better than 2% (presently 10%)

EIC Monte Carlo work by Antje Bruell + Mindy Kohler

EIC Monte Carlo work by Naomi Makins

Examples: g1p


ELIC, June 15, 2006, 6

Exclusive 0 production on transverse target

2 (Im(AB*))/ T

t/4m2) - ReUT

A ~ 2Hu + Hd

B ~ 2Eu + Ed0

K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001

Q2=5 GeV2

Eu, Ed needed forangular momentum sum rule. 0

B

A ~ Hu - Hd

B ~ Eu - Ed+

EIC

Higher Q2 of EIC may be crucial


ELIC, June 15, 2006, 7

Sivers function extraction from AUT (0) does not require information on fragmentation function. It is free of HT and diffractive contributions.

F1T=∑qeq2f1T

┴q

AUT (0) on proton and neutron will allow flavor decomposition w/o info on FF.

In large Nc limit:

f1Tu = -f1T

d

Efremov et al(large xB behavior of

f1T from GPD E)

CLAS12projected

CLAS12projected

From CLAS12 to ELIC: Sivers effect projections

EIC


ELIC, June 15, 2006, 8

Nonperturbative TMD Perturbative region

PT-dependence of beam SSA

sinLU(UL) ~FLU(UL)~ 1/Q (Twist-3)

In the perturbative limit 1/PT

behavior expected (F.Yuan SIR-2005)

Study for SSA transition from non-perturbative to perturbative regime.

ELIC will significantly increase the PT range.

2.0

EIC


ELIC, June 15, 2006, 9

From CLAS12 to ELIC: Transversity projections

AUT ~Collins

Simultaneous measurement of, exclusive with a transversely polarized target

The background from vector mesons very different for CLAS12 and EIC.

EIC

10-3


ELIC, June 15, 2006, 10

From CLAS12 to ELIC: Mulders TMD projections

Simultaneous measurement of, exclusive with a longitudinally polarized target important to control the background.

UL ~KM

EIC


ELIC, June 15, 2006, 11

Ion Linac and pre-booster

IR IR

Beam Dump

Snake

CEBAF with Energy Recovery

3-7 GeV electrons 30- 150 GeV light ions

Solenoid


IR IR

Beam Dump

Snake


3-7 GeV electrons 30- 150 GeV light ions

Solenoid


IR IR

Beam Dump

Snake


3 -7 GeV electrons 30 -150 GeV light ions

Solenoid

Electron Injector

Electron Cooling

ERL-based ELIC DesignERL-based ELIC Design


ELIC, June 15, 2006, 12

• Polarized electron current of 10’s of mA is required for ERL-based ELIC with circulator ring. Present state of art ~0.3 mA.

• A fast kicker with sub-nanosecond rise/fall time is required to fill the circulator ring. Present state of art is ~10 ns.

• Substantial upgrades of CEBAF and the CHL (beyond the 12 GeV Upgrade) are required. Integration with the existing 12 GeV CEBAF accelerator is challenging.

• Exclusion of physics experiments with positron beam.

• Electron cooling of the high-energy ion beam is required.

• All these challenges led to the design of a new Ring-Ring Concept

Challenges of ERL-based ELICChallenges of ERL-based ELIC


ELIC, June 15, 2006, 13

Ring-Ring Concept

Use present CEBAF as injector to electron storage ringAdd light-ion complex


ELIC, June 15, 2006, 14

Polarized Electron Injection & Stacking

J Storage ring

t

J

t

3000 pulses5 s

Injector

4 ms*1 mA

*4 ms is the radiation damping time at 7 GeV


ELIC, June 15, 2006, 15

Ion Complex

“Figure-8” boosters and storage rings• Zero spin tune avoids intrinsic spin resonances• No spin rotators required around the IR• Ensure simultaneous longitudinal polarization for

deuterons at 2 IPs, at all energies

Linac 200 MeV

Ion Collider Ring

Pre-Booster3 GeV/c

C≈75-100 mIon Large Booster 20 GeV(Electron Storage Ring)

spin


ELIC, June 15, 2006, 16

Positrons!

Generation of positrons: (based on CESR experience)• Electron beam at 200 MeV yields unpolarized positron accumulation

of ~100 mA/min• ½ hr to accumulate 3 A of positron current• Polarization time 2 hrs at 7 GeV (Sokolov-Ternov polarization)• Equilibrium polarization ~90%

Possible applications:• e+i colliding beams (longitudinally polarized)• e+e- colliding beams (longitudinally polarized up to 7x7 GeV)• …..


ELIC, June 15, 2006, 17

Achieving the Luminosity of ELIC

For 150 GeV protons on 7 GeV electrons, L~ 8 x 1034 cm-2 s-1 is compatible with realistic Interaction Region design.

Beam Physics Issues

• High energy electron cooling

• Beam – beam interaction between electron and ion beams

(i ~ 0.01 per IP; 0.025 is presently utilized in Tevatron)

• Interaction Region

High bunch collision frequency (f = 1.5 GHz)

Short ion bunches (z ~ 5 mm)

Very strong focus (* ~ 5 mm)

Crab crossing

*24i e

b

N NL f

=


ELIC, June 15, 2006, 18

Polarization of Electrons

• Spin injected vertical in arcs (using Wien filter) • Self-polarization in arcs to support injected polarization • Spin rotators matched with the cross bends of IPs

spin rotator

spin rotator

spin rotator

spin rotator

collision point

spin rotator with 90º

solenoid snake

collision point

collision point

collision point


solenoid snake


ELIC, June 15, 2006, 19

Polarization for Positrons

• Sokolov-Ternov polarization for positrons• Vertical spin in arcs • 4 IPs with longitudinal spin• Polarization time is 2 hrs at 7 GeV – varies as E-5 (can be accelerated

by introduction of wigglers).• Quantum depolarization in IP bends -> equilibrium polarization ≈ 90%

spin rotator

spin rotator

spin rotator

spin rotator

collision point


solenoid snake

collision point

collision point

collision point


solenoid snake


ELIC, June 15, 2006, 20

Polarization of Ions

Protons and 3He: Two snakes are required to ensure longitudinal polarization at 4 IP’s simultaneously.Two IP’s (along straight section) with simultaneous longitudinal polarization with no snakes.

collision point

collision point

collision point

collision point

Snake

P, He3

Protons and 3He

Deuterons: Two IP’s with simultaneous longitudinal polarization with no snakes. Solenoid (or snake for protons) to stabilize spin near longitudinal direction for all species.

collision point

collision point

collision point

collision point

Solenoid

d

Deuterons


ELIC, June 15, 2006, 21

ELIC Interaction Region Concept

Focal Points

2 m

spin detectorCrab cavity

Crab cavity

focusing triplet

focusing triplet

80 MV

focusing doublet

focusing doublet

Crab cavity

Crab cavity

spin tune solenoid

spin tune solenoid

cross bend

cross bend

α

0.1 rad

4 m

i

e

i

4 m

0.1 rad


ELIC, June 15, 2006, 22

Short bunches make Crab Crossing feasible.

SRF deflectors at 1.5 GHz can be used to create a proper bunch tilt.

SRF dipole

Final lens FF

Crab CrossingCrab Crossing

Parasitic collisions are avoided without loss of luminosity.


ELIC, June 15, 2006, 23

ELIC ParametersParameter Unit ERL Ring-Ring Beam ener gy GeV 150/ 7 150/ 7 100/ 5 30/ 3

Bunch collisi on r ate GHz 1.5

Number of

par ticles / bunch

1010 0.4/ 1.0 0.4/ 1.0 0.4/ 1.1 0.12/1 .7

Beam curr ent A 1/ 2.4 1/ 2.4 1/ 2.7 0.3/4 .1

Cooling beam energ y MeV 75 75 50 15

Cooling beam curre nt A 2 2 2 .6

Ener gy spr ead, rms 10-4 3/ 3

Bunch length, rms mm 5/ 5

Beta -sta r mm 5/ 5

Hor izontal emit tance

(nor m)

m 1/ 86 1/ 86 0.7/7 0 0.2/4 3

Ver tical emitt ance (nor m) m 0.04/ 3.4 0.04/ 3.4 0.06/ 6 0.2/4 3

Beam-beam t une shif t

(vert ical) per IP

0.01/ 0.086 0.01/ 0.086 0.01/0. 073 0.01/0. 007

Laslet t t une shif t (p -

beam)

0.015 0.015 0.03 0.06

Luminosity pe r IP , 1034 cm-2 s-1 7.7 7.7 5.6 0.8

Number of inte r act ion

point s

4

Cor e & luminosit y IBS

life t ime

h 24 24 24 >4


ELIC, June 15, 2006, 24

Summary

Design studies at JLab have led to an approach that promises

luminosities up to nearly 1035 cm-2 s-1, for electron-light ion collisions at

a center-of-mass energy between 20 and 65 GeV.

A fundamentally new approach has led to a design that can be realized

on the JLab site using CEBAF as a full-energy injector into an electron

storage ring and that can be integrated with the 12 GeV fixed-target

physics program.

Understanding the structure of the nucleon requires measurements of

the Generalised Parton Distributions over the full x range and

at high Q2 necessary for a full flavor decomposition

Measurements of both DVCS and exclusive meson production at EIC

will allow the determination of the quark and gluon orbital momenta

Extend single-spin asymmetry measurements in semi-inclusive

scattering to much lower x-values and over large pT-range

an electron-ion collider for jlab antje bruell lia merminga (kees de jager) jefferson lab

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