Transcript An Electron-Ion Collider for JLab Antje Bruell Lia Merminga (Kees de Jager)

An Electron-Ion Collider for JLab
Antje Bruell
Lia Merminga
(Kees de Jager)
Jefferson Lab
QCD-N’06
June 15, 2006
Thomas Jefferson National Accelerator Facility
ELIC, June 15, 2006, 1
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Add new hall
12
116 GeV CEBAF
Upgrade magnets
and power
supplies
CHL-2
Enhance equipment in
existing halls
• 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
Thomas Jefferson National Accelerator Facility
ELIC, June 15, 2006, 2
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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= ECM2•x
x range: valence, sea quarks, glue
Q2 range: utilize evolution equations of QCD
• High polarization of lepton, nucleon achievable
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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
Q2
EIC
• 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
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p
p
Examples:
g
Examples: g11 ,Transversity, Bjorken SR
EIC Monte Carlo Group
•AntjeGRSV
Bruell (JLab)
•Abhay Deshpande (SBU)
•Rolf Ent (JLab)
ELIC projection
(~10 days)
•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,
… Makins
EIC Monte
Carlo
work by Naomi
Can determine the Bjorken Sum Rule to
better than 2% (presently 10%)
Thomas Jefferson National Accelerator Facility
EIC Monte Carlo work by Antje Bruell + Mindy Kohler
ELIC, June 15, 2006, 5
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Exclusive 0 production on transverse target
AUT = -
2D (Im(AB*))/p
|A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB*)2x2
0
A ~ 2Hu + Hd
B ~ 2Eu + Ed
+
A ~ Hu - Hd
B ~ Eu - Ed
Q2=5 GeV2
EIC
Eu, Ed needed for
angular momentum
sum rule.
0
Higher Q2 of EIC
may
be crucial
K. Goeke, M.V. Polyakov,
M. Vanderhaeghen, 2001
B
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ELIC, June 15, 2006, 6
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From CLAS12 to ELIC: Sivers effect projections
In large Nc limit:
f1Tu =
-f1T
F1T=∑qeq2f1T┴q
d
Efremov et al
(large xB behavior of
f1T from GPD E)
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.
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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
Nonperturbative TMD
Perturbative region
Study for SSA transition from non-perturbative to perturbative regime.
ELIC will significantlyThomas
increase
theNational
PT range.
Jefferson
Accelerator Facility
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ELIC, June 15, 2006, 8
From CLAS12 to ELIC: Transversity projections
Collins
AUT ~
EIC
10-3
Simultaneous measurement of, exclusive ,+,w with a transversely polarized target
The background from vector mesons very different for CLAS12 and EIC.
Thomas Jefferson National Accelerator Facility
ELIC, June 15, 2006, 9
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From CLAS12 to ELIC: Mulders TMD projections
KM
sUL
~
EIC
Simultaneous measurement of, exclusive ,+,w with a longitudinally
polarized target important to control the background.
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 10
ERL-based ELIC Design
IR
IR Solenoid
IR
3-7
3
-7 GeV electrons
Snake
3030 -150
150 GeV light ions
Electron Injector
CEBAF with Energy Recovery
Beam Dump
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ELIC, June 15, 2006, 11
Challenges of ERL-based ELIC
• 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
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 12
Ring-Ring Concept
Use present CEBAF as
injector to electron
storage ring
Add light-ion complex
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ELIC, June 15, 2006, 13
Polarized Electron Injection & Stacking
J
Injector
3000 pulses
4 ms*
1 mA
5 s
t
J
Storage ring
t
*4 ms is the radiation damping time at 7 GeV
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 14
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
C≈75-100 m
Ion Large Booster 20 GeV
(Electron Storage Ring)
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 15
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)
• …..
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 16
Achieving the Luminosity of ELIC
Ni Ne
L=
f
*2 b
4ps
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
(xi ~ 0.01 per IP; 0.025 is presently utilized in Tevatron)
• Interaction Region
 High bunch collision frequency (f = 1.5 GHz)
 Short ion bunches (sz ~ 5 mm)
 Very strong focus (* ~ 5 mm)
 Crab crossing
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ELIC, June 15, 2006, 17
Polarization of Electrons
spin
rotator
spin rotator
with 90º
solenoid snake
collision
point
collision
point
collision
point
collision
point
spin
rotator
spin
rotator
spin rotator
with 90º
solenoid snake
spin
rotator
• 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
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 18
Polarization for Positrons
spin
rotator
spin rotator
with 90º
solenoid snake
collision
point
collision
point
collision
point
collision
point
spin
rotator
spin
rotator
spin rotator
with 90º
solenoid snake
spin
rotator
•
•
•
•
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%
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 19
Polarization of Ions
Protons and 3He
Deuterons
collision
collision
point
point
collision
collision
point
point
Snake
collision
collision
point
point
collision
collision
point
point
d
P, He3
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.
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.
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 20
ELIC Interaction Region Concept
Crab
cavity
m
44m
Crab
cavity
spin
i
2m
focusing
triplet
spin tune
solenoid
e
cross
bend
focusing
doublet
detector
α
80 MV
cross
bend
focusing
triplet
focusing
doublet
Crab
spin tune cavity
solenoid
Crab
cavity
0.1 rad
0.1
rad
Focal Points
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ELIC, June 15, 2006, 21
i
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.
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 22
ELIC Parameters
Thomas Jefferson National Accelerator Facility
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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
Thomas Jefferson National Accelerator Facility
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