Electron Ion Collider: Realization of ELIC Rolf Ent Jefferson Lab

1
Electron Ion ColliderRealization of ELICRolf
EntJefferson Lab
NSAC Subcommittee on Relativistic Heavy Ions BNL,
June 4 2004
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ELIC_at_JLab - Science
(x 0.01)
Glue 100
EIC is the ultimate gluon spin machine
ELIC
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ELIC_at_JLab - Science

• Science addressed by ELIC
• How do quarks and gluons provide the binding and
  spin of the nucleons?
• How do quarks and gluons evolve into hadrons?
• How does nuclear binding originate from quarks
  and gluons?

(x 0.01)
Glue 100
12 GeV
ELIC
_at_Q2 1
4
12 GeV Upgrade_at_JLab

• Clear scientific case by 12-GeV JLab Upgrade,
  addressing outstanding issues in Hadron Physics
• Unprecedented measurements to region in x (gt 0.1)
  where basic three-quark structure of nucleons
  dominates.
• Measurements of correlations between quarks,
  mainly through Deep-Virtual Compton Scattering
  (DVCS) and constraints by nucleon form factors,
  in pursuit of the Generalized Parton
  Distributions.
• Finishing the job on the transition from hadronic
  to quark-gluon degrees of freedom.
• Search for photoproduction of hybrids gluonic
  excitations of mesons with as goal to
  definitively and in detail map their spectrum and
  shed light on confinement.
• 12-GeV Upgrade recently received CD-0, with
  detailed work on a Conceptual Design Report now
  in progress.
• JLab community has began thinking about the needs
  of Hadron Physics in the post-12 GeV era.

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CEBAF Beyond 12 GeV

• JLab community has began thinking about the needs
  of Hadron Physics in the post-12 GeV era.
• At present, uncertain what range of Q2 really
  required to determine complete structure of the
  nucleon. Most likely Q2 10 GeV2?
• Upcoming years wealth of data from RHIC-Spin,
  COMPASS, HERMES, JHF, JLab, etc.
• DVCS (JLab-12!) and single-spin asymmetries
  possible at lower Q2
• Range of Q2 defines the required luminosity
• What energy and luminosity, collider or
  fixed-target facility (or both)?
• Electron-Light Ion Collider, center-of-mass
  energy of 20-65 GeV?
• 25 GeV Fixed-Target Facility?

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Basis of the ELIC Proposal
(Derbenev, Chattopadhyay, Merminga et al.)

• A Linac-Ring Collider Design (with additional
  Circulator Ring)
• Linac
• CEBAF is used for the (one-pass) acceleration of
  electrons
• Energy recovery is used for rf power savings and
  beam dump requirements
• Ring
• Figure-8 storage ring is used for the ions for
  flexible spin manipulations of all light-ion
  species of interest
• Circulator ring for the electrons may be used to
  ease high current polarized photoinjector
  requirements

Luminosity of up to 8x1034 cm-2 sec-1
(per interaction point, for a one-day lifetime)
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ELIC Layout
One accelerating one decelerating pass through
CEBAF
Ion Linac and pre
Ion Linac and pre
(A1-40)
Electron Cooling
-
-
booster
booster
IR
IR
IR
IR
Snake
Snake
Solenoid
Solenoid
3
-
7 GeV
electrons
30
-
150 GeV light ions
3
-
7 GeV
electrons
30
-
150 GeV (light) ions
Electron Injector
CEBAF with Energy Recovery
CEBAF with Energy Recovery
Beam Dump
Beam Dump
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ELIC Physics Specifications

• Flexible Center-of-mass energy between 20 and 65
  GeV
• Ee 3 GeV on Ei 30 GeV up to Ee 7 GeV on Ei
  150 GeV worked out in detail (gives Ecm up to
  65 GeV)
• CW Luminosity up to 8x1034 cm-2 sec-1 per
  Interaction Point
• Ion species of interest protons, deuterons, 3He,
  light-medium ions
• Proton and neutron
• Light-medium ions not necessarily polarized
• Up to Calcium
• Longitudinal polarization of both beams in the
  interaction region (Transverse polarization of
  ions Spin-flip of both beams)

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The same electron accelerator can also provide 25
GeV electrons for fixed target experiments for
physics

• Implement 5-pass recirculator, at 5 GeV/pass, as
  in present CEBAF

(straightforward upgrade, no accelerator RD
needed)

• Luminosity of 1038
• Complementary capabilities for broad class of
  experiments

• Exploring whether collider and fixed target
  modes can run simultaneously (can in alternating
  mode)

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ELIC_at_JLab Realization
Because ELIC is based on a completely new ring it
is possible to optimize for spin preservation
handling and for high luminosity
Parameters have been pushed into new
territory ß, lb, ring shape, crab crossing,
ELIC proposes some very elegant and innovative
features worth further investigation
(U. Wienands, EIC2004 Summary)
The physics needs that drove us to this design
are the importance of spin, a luminosity as high
as possible, and a broad and flexible energy
range for Hadron Physics
Data from RHIC/RHIC-Spin, COMPASS, HERMES, JHF,
JLab forthcoming to guide the requirements for
key physics
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Kinematics at an Electron Light Ion Collider
ELIC kinematics at Ecm 65 GeV, and beyond the
resonance region.

• Luminosity of up to 8x1034 cm-2 sec-1
• One day ? 4,000 events/pb
• Supports Precision Experiments
• Lower value of x scales as s-1
• DIS Limit for Q2 gt 1 GeV2 implies x down to 2.5
  times 10-4
• Significant results for 200 events/pb for
  inclusive scattering
• If Q2 gt 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
• For Q2 gt 200 GeV2, typical cut required for
  Electroweak Processes, can reach x down to 4
  times 10-2

Q2 (GeV2)
eRHIC
ELIC (W2 gt 4)
W2lt4
x
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The Spin Structure of the Proton
½ ½ DS DG Lq Lg

• From NLO-QCD analysis of DIS measurements (SMC
  analysis)
• DS 0.38 (in AB scheme)
• DG 1.01.9 ,,
• quark polarization Dq(x)
• ?first 5-flavor separation from HERMES
• transversity dq(x)
• ?a new window on quark spin
• ?azimuthal asymmetries from HERMES and
  JLab-6
• ?future flavor decomposition
• gluon polarization DG(x)
• ?RHIC-spin and COMPASS will provide some
  answers!
• orbital angular momentum L
• ?how to determine? ? GPDs

-0.6
ELIC_at_JLab can solve this puzzle due to large
range in x and Q2 and precision due to high
luminosity
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Examples g1p
GRSV
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Examples g1p
GRSV
ELIC projection (1 day)
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Examples g1p, Transversity
GRSV
ELIC projection (1 day)
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Examples g1p, Transversity
GRSV
ELIC projection (1 day)
DG/G from open charm RHIC-SPIN precision
down to x 0.001
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Orbital Angular Momentum
Analysis of hard exclusive processes leads to a
new class of generalized parton distributions
Four new distributions
helicity conserving ? H(x,x,t),
E(x,x,t) helicity-flip
? H(x,x,t),
E(x,x,t)

• skewedness parameter x
• mismatch between quark momenta
• ?sensitive to partonic correlations

• New Roads
• Deeply Virtual Meson
• Production _at_ Q2 gt 10 GeV2
• ? disentangles flavor and
• spin!
• r and f Production give access
• to gluon GPDs at small x (lt0.2)

3-dimensional GPDs give spatial distribution of
partons and spin

• Angular Momentum Jq ½ DS Lq !

Can we achieve same level of understanding as
with F2?
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Tomography of the Nucleon
Generalized Parton Distributions
Ji

• A framework to extract 3-D spatial information of
  quarks in a nucleon at rest
• Generate Wigner (quantum phase-space)
  distributions
• Obtain proton images at fixed x
• Direct connection to GPDs through Fourier
  Transforms

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Proton Images at Fixed x
Up-quark densities
x 0.01 x 0.4
x 0.7
z
y
x
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Quarks in a Nucleus
EMC Effect
F2A/F2D
Can pick apart the spin-flavor structure of EMC
effect by technique of flavor tagging, in the
region where effects of the space-time structure
of hadrons do not interfere (large n!)
ELIC
10-4 10-3 10-2 10-1
1

x
Nuclear attenuation negligible for n gt 50 GeV
?hadrons escape nuclear medium undisturbed
Space-Time Structure of Photon
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ELIC_at_JLab RD Topics

• Electron-Light Ion Collider (ELIC)
• RD needed on
• High Charge per Bunch and High Average Current
  Polarized Electron Source
• High Energy Electron Cooling of Protons/Ions
• Practical only if based on SRF-ERL technology.
  Rigorous e-cooling RD program established at BNL
• High Current and High Energy demonstration of
  Energy Recovery
• Integration of Interaction Region design with
  Detector Geometry
• NSAC LRP ... strong consensus among nuclear
  scientists to pursue RD over the next three
  years to address a number of EIC design issues
• 25-GeV Fixed-Target Facility
• Use existing CEBAF footprint
• Upgrade Cryo modules to 12-GeV design (7-cell
  design, 18 MV/m)
• Change ARC magnets, Switchyard, Hall Equipment
• Significant RD Issues to Resolve But Work in
  Progress!!

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ELIC_at_JLab RD Strategy

• Multi-pronged RD strategy
• Conceptual development
• Circulator Ring concept promises to ease high
  current polarized photoinjector and ERL
  requirements significantly
• Additional concepts, e.g. crab crossing, for
  luminosity improvements are being explored
• Analysis/Simulations
• Electron cooling and short bunches
• Beam-beam physics
• Circulator ring dynamics
• ERL physics
• IR design
• Experiments
• High current, high polarization source
  development at JLab
• High current ERL issues investigated at JLab FEL.
  E.g. multibunch Beam Breakup instabilities
• High energy (1 GeV) demonstration of energy
  recovery at CEBAF

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Towards Higher Electron Beam Current
JLab FEL program with unpolarized beam
ELIC with circulator ring
_at_highest luminosity
Lifetime Estimate _at_ 25 mA
CEBAF enjoys excellent gun lifetime 200 C
charge lifetime (until QE reaches 1/e of
initial value) 100,000 C/cm2 charge density
lifetime (we use a 0.5 mm dia. spot) If
Charge-Lifetime assumption valid With 1 cm
dia. spot size lifetime of 36 weeks at 25 mA!
Ave. Beam Current (mA)
Year
Need to test the scalability of charge lifetime
with laser spot diameter ? Measure charge
lifetime versus laser spot diameter in lab.
(Poelker, Grames)
First low polarization, then high polarization at
CEBAF
First polarized beam from GaAs photogun
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ERL Technology demonstrated at CEBAF _at_ 1 GeV
Special installation of a ?RF/2 path length
delay chicane, dump and beamline diagnostics.
500 MeV
50 MeV
1 GeV Accelerating beam
55 MeV Decelerating beam
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RF Response to Energy Recovery

• Gradient modulator drive signals with and without
  energy recovery in response to 250 ?sec beam
  pulse entering the RF cavity (SL20 Cavity 8)

250 ms
without ER
with ER
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ELIC_at_JLab Conclusions

• An excellent scientific case is developing for a
  high luminosity, polarized electron-light ion
  collider will address fundamental issues in
  Hadron Physics
• The (spin-flavor) quark-gluon structure of the
  proton and neutron
• How do quarks and gluons form hadrons?
• The quark-gluon origin of nuclear binding
• JLab design studies have led to an approach that
  promises luminosities as high as 8x1034 cm-2
  sec-1 (one day lifetime), for electron-light ion
  collisions at a center-of-mass energy between 20
  and 65 GeV
• RD Studies to illuminate details of the design
  are underway/planned
• This design, using energy recovery on the JLab
  site, can be integrated with a 25 GeV fixed
  target program for physics

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Luminosity Potential with eRHIC/ELIC
eRHIC 10 GeV Electrons on 250 GeV Protons (up to
Pb) _at_SPIN2004 mention of 20 GeV Electrons in
Linac-Ring Option ELIC 7 GeV Electrons on
150 GeV Protons (up to Ca)
25 GeV
ELIC
ELIC Luminosity
eRHIC Luminosity 1 x 1033 cm-2sec-1 (Linac-Ring
option 1 x 1034 cm-2sec-1)
eRHIC LINAC-RING?
100
8x1034 cm-2sec-1 (per interaction point,
one day lifetime)
eRHIC
EIC
x8,000
Precision Frontier
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ELIC on JLab Site
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Kinematics for Rosenbluth Separations ? FL
Still large uncertainty in glue, especially at Q2
lt 20 GeV2
Here De gt 0.3 ? DFL as small as 0.01!
FL constrains glue at low Q2
ELIC
W2 gt 4 GeV2
W2 gt 1.2 GeV2
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Lowest Order
known
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What follows are some slides that we passed on
to Richard Milner describing the present status
of the Interaction Region design and some physics
simulations
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• Science addressed by ELIC
• How do quarks and gluons provide the binding and
  spin of the nucleons?
• What is the quark-gluon structure of mesons?
• How do quarks and gluons evolve into hadrons?
• How does energy convert to mass?
• How does nuclear binding originate from quarks
  and gluons?
• How do gluons behave in nuclei?

• Luminosity of up to 8x1034 cm-2 sec-1
• One day ? 4,000 events/pb
• Supports Precision Experiments
• Lower value of x scales as s-1
• DIS Limit for Q2 gt 1 GeV2 implies x down to 2.5
  times 10-4
• Significant results for 200 events/pb for
  inclusive scattering
• If Q2 gt 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
• For Q2 gt 200 GeV2, typical cut required for
  Electroweak Processes, can reach x down to 4
  times 10-2

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Nuclear Physics Requirements

• The features of the facility necessary to address
  these issues
• Center-of-mass energy between 20 GeV and 65 GeV
• with energy asymmetry of 10, which yields
• Ee 3 GeV on Ei 30 GeV up to Ee 7 GeV on
  Ei 150 GeV
• CW Luminosity from 1033 to 1035 cm-2 sec-1
• Longitudinal polarization of both beams in the
  interaction region ? 50 80 required for the
  study of generalized parton distributions and
  transversity
• Transverse polarization of ions extremely
  desirable
• Spin-flip of both beams extremely desirable

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ELIC Layout
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One-Event Display from EIC Monte Carlo
150 GeV proton
7 GeV electron
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Simple First Exercise The Large x Region
Keep Same Q2 Cut gt 200 GeV2
0.04 lt x lt 0.60 gt10M events/bin with similar x
bins even 2M events for 0.60ltxlt0.90 (!)
Assumption 10 weeks of running at a luminosity
of 1035. Conclusion luminosity of 1033 is great,
luminosity of 1035 is tremendous improvement for
large x data/modeling.
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Examples g1p,Transversity, Bjorken SR
GRSV
ELIC projection (10 days)
EIC Monte Carlo work by Naomi Makins
Can determine the fundamental Bjorken Sum Rule to
precision of better than 2? (presently 10)
EIC Monte Carlo work by Antje Bruell Mindy
Kohler
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New Spin Structure Function Transversity
(in transverse basis)
-
dq(x)

• Nucleons transverse spin content ? tensor
  charge
• No transversity of Gluons in Nucleon ?
  all-valence object
• Chiral Odd ? only measurable in semi-inclusive
  DIS
• first glimpses exist in data (HERMES, JLab-6)
• Later work more complicated
• COMPASS 1st results 0 _at_ low x
• Future Flavor decomposition

EIC Monte Carlo work by Naomi Makins
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Examples g1p,Transversity, DG, Bjorken SR
GRSV
ELIC projection (10 days)
DG/G from open charm RHIC-SPIN precision
down to x 0.001
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Parity Violation
Beyond the Standard Model
Leptoquarks
RPV SUSY Extensions
E6 Z Based Extensions
Due to finite Y
1035 /cm2/s Sub 0.5 polarimetry
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ELIC Interaction Region Concept
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ELIC IR Initial Design Alex Bogacz (JLab) Slava
Derbenev (JLab) Lia Merminga (JLab) Christoph
Montag (BNL)
JLab Zero-order design Sept. 20-24, 2004 Work
with Christoph Montag initial design with small
beta changed to value close to those from beam
experience Present design nice solution of
interleaved final focus quads for ion and
electron lattice, with unchanged high
luminosity Close to realistic IR design.
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ELIC Interaction Region Design
IR for hadrons at E 150 GeV
bx 25 mm by 5 mm
max quad gradient 250 Tesla/m
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ELIC Interaction Region Design
IR for electrons at E 7 GeV
bx 25 mm by 5 mm
44
ELIC IR Magnet Concept Paul Brindza (JLab)
First final focus quad for ion lattice is 1.2
meter long, starts at 2 meter distance from IR,
and needs 6.2T peak field to achieve required
gradient. Only 4.9T peak field seems achievable,
for small-size SC magnet with 1 cm bore and 14
cm outer radius (out of synchrotron flare).
Cryostable magnet Solutions being investigated,
simple solutions are a slight reshuffling of
final focus magnets to allow for 1.5 meter long
quad in ion lattice, or to relax beta.
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• General Strategy Prepare White Paper with
  significantly refined physics case for an
  electron ion collider, including realistic
  accelerator and IR detector designs for next NSAC
  LRP.
• EIC Monte Carlo Group formed to study EIC
  physics/detector
• Meetings at Boulder (August 03)
• JLab (October 03)
• BNL (January 04)
• Boulder (November 04)
• Goal what energy and luminosity is really
  required to access the
• key physics issues, what are the
  implications in terms of
• resolution and particle
  identification for a detector
• Coherent Effort to design Interaction Region
  integrating High-Luminosity Accelerator Concepts
  and Detector Design
• ELIC Status Initial IR design developed, and
  Detector design ongoing
• Early findings 0.5 Tesla solenoid field
  extending the small
• electron-ion interaction region
  seems sufficient, with a
• larger field more radially outwards
  (not affecting beam).
• A toroidal field also under investigation.