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

An Electron-Ion Collider for JLab Antje Bruell Lia Merminga (Kees de Jager) Jefferson Lab QCD-N ’ 06 June 15, 2006. Upgrade magnets and power supplies. CHL-2. Enhance equipment in existing halls. Add new hall. 12. 11. 6 GeV CEBAF.

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

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  1. An Electron-Ion Collider for JLab Antje Bruell Lia Merminga (Kees de Jager) Jefferson Lab QCD-N’06 June 15, 2006

  2. Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls Add new hall 12 11 6 GeV CEBAF • 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, Q2Qmax2= ECM2•x x range: valence, sea quarks, glue Q2 range: utilize evolution equations of QCD • High polarization of lepton, nucleon achievable

  4. Kinematic coverage of ELIC Q2 JLab (upgraded) compass hermes clas • 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/pbfor inclusive scattering • IfQ2 > 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. Q2=5 GeV2 Exclusive 0 production on transverse target 2D (Im(AB*))/p T AUT = - |A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB*)2x2 A~ 2Hu + Hd r0 B~ 2Eu + Ed A~ Hu - Hd B ~ Eu - Ed r+ Eu, Edneeded 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 Collins AUT ~ 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 sUL ~ KM EIC Simultaneous measurement of, exclusive r,r+,w with a longitudinally polarized target important to control the background.

  11. Ion Linac and pre Ion Linac and pre Ion Linac and pre Electron Cooling - - - booster booster booster IR IR IR IR IR IR Snake Snake Snake Solenoid Solenoid Solenoid 3 3 3 - - - 7 GeV 7 GeV 7 GeV electrons electrons electrons 30 30 30 - - - 150 GeV light ions 150 GeV light ions 150 GeV light ions Electron Injector CEBAF with Energy Recovery CEBAF with Energy Recovery CEBAF with Energy Recovery Beam Dump Beam Dump Beam Dump ERL-based ELIC Design

  12. 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 ~10ns. • 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 J Injector 3000 pulses 5 s 4 ms* 1 mA t J Storage ring t *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 C≈75-100 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 time2 hrsat 7 GeV (Sokolov-Ternov polarization) • Equilibrium polarization ~90% Possibleapplications: • e+icolliding beams (longitudinally polarized) • e+e- 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 rotator spin rotator spin rotator with 90º solenoid snake collision point collision point collision point collision point spin rotator with 90º solenoid snake spin rotator 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

  19. Polarization for Positrons spin rotator spin rotator spin rotator with 90º solenoid snake collision point collision point collision point collision point spin rotator with 90º solenoid snake spin rotator 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%

  20. Polarization of Ions Protons and 3He Deuterons Solenoid collision point collision point collision point collision point Snake collision point collision point collision point collision point P, He3 d 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.

  21. ELIC Interaction Region Concept spin tune solenoid Crab cavity e cross bend focusing doublet 4 m Crab cavity focusing triplet spin detector 4 m α i i 80 MV focusing triplet Crab cavity 2 m cross bend focusing doublet 0.1 rad Crab cavity spin tune solenoid 0.1 rad 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 nearly1035 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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