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An Electron-Ion Collider for JLab

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Thomas Jefferson National Accelerator Facility. Page 1. ELIC, June 15, 2006, 1 ... Integration with the existing 12 GeV CEBAF accelerator is challenging. ... – PowerPoint PPT presentation

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Title: An Electron-Ion Collider for JLab


1
  • An Electron-Ion Collider for JLab
  • Antje Bruell
  • Lia Merminga
  • (Kees de Jager)
  • Jefferson Lab
  • QCD-N06
  • June 15, 2006

2
Add new hall
12
6 GeV CEBAF
11
  • 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

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 ECM2x
  • x range valence, sea quarks, glue
  • Q2 range utilize evolution equations of QCD
  • High polarization of lepton, nucleon achievable

4
Kinematic coverage of ELIC
  • 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 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

EIC
5
Examples g1p
Examples g1p,Transversity, Bjorken SR
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)
EIC Monte Carlo work by Naomi Makins
Can determine the Bjorken Sum Rule to better than
2 (presently 10)
EIC Monte Carlo work by Antje Bruell Mindy
Kohler
6
Exclusive ?0 production on transverse target
2D (Im(AB))/p
T
AUT -
A2(1-x2) - B2(x2t/4m2) - Re(AB)2x2
A 2Hu Hd
r0
B 2Eu Ed
A Hu - Hd B Eu - Ed
r
Eu, Ed needed for angular momentum sum rule.
r0
EIC
Higher Q2 of EIC may be crucial
K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001
B
7
From CLAS12 to ELIC Sivers effect projections
Efremov et al (large xB behavior of f1T from GPD
E)
In large Nc limit
F1T?qeq2f1T-q
f1Tu -f1Td
CLAS12 projected
EIC
CLAS12 projected
Sivers function extraction from AUT (p0) does not
require information on fragmentation function. It
is free of HT and diffractive contributions.
AUT (p0) on proton and neutron will allow flavor
decomposition w/o info on FF.
8
PT-dependence of beam SSA
ssinfLU(UL) FLU(UL) 1/Q (Twist-3)
In the perturbative limit 1/PT behavior expected
(F.Yuan SIR-2005)
EIC
2.0
Perturbative region
Nonperturbative TMD
Study for SSA transition from non-perturbative to
perturbative regime. ELIC will significantly
increase the PT range.
9
From CLAS12 to ELIC Transversity projections
EIC
10-3
Simultaneous measurement of, exclusive r,r,w
with a transversely polarized target
The background from vector mesons very different
for CLAS12 and EIC.
10
From CLAS12 to ELIC Mulders TMD projections
EIC
Simultaneous measurement of, exclusive r,r,w
with a longitudinally polarized target important
to control the background.
11
ERL-based ELIC Design
12
Challenges of ERL-based ELIC
  • Polarized electron current of 10s 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

13
Ring-Ring Concept
  • Use present CEBAF as injector to electron storage
    ring
  • Add light-ion complex

14
Polarized Electron Injection Stacking
4 ms is the radiation damping time at 7 GeV
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

Ion Collider Ring
spin
Linac 200 MeV
Pre-Booster 3 GeV/c C75-100 m
Ion Large Booster 20 GeV (Electron Storage Ring)
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
  • ei colliding beams (longitudinally polarized)
  • ee- colliding beams (longitudinally polarized up
    to 7x7 GeV)
  • ..

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

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

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 -gt equilibrium
    polarization 90

20
Polarization of Ions
  • Protons and 3He Two snakes are required to
    ensure longitudinal polarization at 4 IPs
    simultaneously.
  • Two IPs (along straight section) with
    simultaneous longitudinal polarization with no
    snakes.

Deuterons Two IPs with simultaneous
longitudinal polarization with no snakes.
Solenoid (or snake for protons) to stabilize
spin near longitudinal direction for all species.
21
ELIC Interaction Region Concept
Focal Points
22
Crab Crossing
Short bunches make Crab Crossing feasible. SRF
deflectors at 1.5 GHz can be used to create a
proper bunch tilt.
SRF dipole
F
Final lens
F
Parasitic collisions are avoided without loss of
luminosity.
23
ELIC Parameters
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
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