1 / 24

Physics with ELIC at JLab

Physics with ELIC at JLab. Introduction ELIC Concept Physics with ELIC Rolf Ent 05/23/2003. ELIC@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?

jessie
Télécharger la présentation

Physics with ELIC at JLab

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics with ELIC at JLab Introduction ELIC Concept Physics with ELIC Rolf Ent 05/23/2003

  2. ELIC@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 ELIC 12 GeV

  3. ELIC@JLab - Science • Clear scientific case by 12-GeV JLab Upgrade, addressing outstanding issues in Hadron Physics: • Unprecedented measurements to region in x (> 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. • 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 directly linked to required luminosity • What energy and luminosity, fixed-target facility or collider (or both)? • 25 GeV Fixed-Target Facility? • Electron-Light Ion Collider, center-of-mass energy of 20-65 GeV?

  4. Basis of the ELIC Proposal (Lia Merminga, Slava Derbenev, 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 1035 cm-2 sec-1 But .... still needs integration of detector with interaction region ....

  5. Ion Source RFQ DTL Snake CCL IR IR Snake Solenoid 5 GeVelectrons 50-100 GeV light ions Injector CEBAF with Energy Recovery Beam Dump ELIC Layout One accelerating & one decelerating pass through CEBAF

  6. 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 R&D needed) • Exploring whether collider and fixed target modes can run simultaneously (can in alternating mode)

  7. Luminosity Potential with ELIC x10,000 More info: Talk on ELIC Project by Lia Merminga

  8. ELIC@JLab - Kinematics ELIC kinematics at Ecm = 45 GeV, and beyond the resonance region. • Luminosity of up to 1035 cm-2 sec-1 • One day  5,000 events/pb • Supports precision experiments • DIS Limit for Q2 > 1 GeV2 implies (Bjorken) x down to 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 5 times 10-3 • Typical cross sections factor 100-1,000 smaller than inclusive scattering  still easily accessible

  9. The Structure of the Proton – F2 F2 Structure Function measured over impressive range of x and Q2. Q2 evolution also constrains glue! Still large uncertainty in glue, especially at Q2 < 20 GeV2

  10. The Structure of the Proton – FL Great Opportunity to (finally) determine FL with good precision (JLab-6 example here in the nucleon resonance region only) Complementarity of 25-GeV fixed-target and ELIC for this example!  Glue at low Q2 De > 0.3 > > 20 known

  11. 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 = 1.0+1.9 ,, • quark polarization Dq(x) first 5-flavor separation from HERMES (see later) • transversity dq(x) a new window on quark spin azimuthal asymmetries from HERMES and JLab-6 • gluon polarization DG(x) RHIC-spin and COMPASS will provide some answers! • orbital angular momentum L how to determine?  GPD’s -0.6 CEBAF II/ELIC Upgrade can solve this puzzle due to large range in x and Q2 and precision due to high luminosity

  12. 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 @ Q2 > 10 GeV2 •  disentangles flavor and • spin! • r and f Production give access to gluon GPD’s at small x (<0.2) 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?

  13. Generalized Parton Distributions • What could be the role of a 25 GeV Fixed Target facility? • Enhances phase space to Q2>10 GeV2 • Comfortable to do flavor separation of GPD’s • Also L/T separations to verify how hard process really is! Deep Virtual Meson Production sL dominant, and ~ Q-6?

  14. New Spin Structure Function: Transversity (in transverse basis) - dq(x) ~ • Nucleon’s 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) • COMPASS, RHIC-spin plans • Future: Flavor decomposition? Estimates for TESLA-N (Ecm = 22 GeV)

  15. How Do Quarks and Gluons form Hadrons? In semi-inclusive DIS a hadron h is detected in coincidence with the scattered lepton Study quark-gluon substructure of • nucleon target  parton distribution functions q(x,Q2) • hadron formation (or hadronization)  fragmentation functions D(z,Q2) Process both of interest in its own right and as a tool (see also next slides)

  16. Hadronization as a Tool First 5-flavor fit to Dq(x) (Ds(x) = Ds(x) assumed) Quark Polarization from Semi-Inclusive DIS _ - - • Goal: Flavor Separation of quark and antiquark helicity distributions • Technique: Flavor Tagging The flavor content of the final state hadrons is related to the flavor of the struck quark through the agency of the fragmentation functions Chiral-Quark Soliton Model Light sea quarks polarized but Data consistent with zero

  17. Hadronization (Or: The Long-Range Dynamics of Confinement) What do we know? What don’t we (exactly) know? The Lund String Model Phenomenological description in terms of color-string breaking and parton clustering Evolution of the fragmentation functions • Spin Transfer: Is the spin of the struck quark communicated to the hadronic final state? • Single-Spin Asymmetries: How important is intrinsic transverse momentum? • Space-Time Structure: How long does it take to form a hadron? Present and future studies (HERMES, JLab-6, JLab-12) use the nuclear radius as a yardstick to measure the time scale of hadron formation

  18. Nuclear Binding • Natural Energy Scale of QCD: O(100 MeV) • Nuclear Binding Scale O(10 MeV) • Does it result from a complicated detail of near cancellation of strongly attractive and repulsive terms in N-N force, or is there another explanation? How can one understand nuclear binding in terms of quarks and gluons? Complete spin-flavor structure of modifications to quarks and gluons in nuclear system may be best clue.

  19. Quarks in a Nucleus 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!) F2A/F2D “EMC Effect” 10-4 10-3 10-2 10-1 1 x Nuclear attenuation negligible for n > 50 GeV hadrons escape nuclear medium undisturbed Space-Time Structure of Photon

  20. Sea-Quarks and Gluons in a Nucleus Drell-Yan  No Nuclear Modifications to Sea-Quarks found at x ~ 0.1 Where is the Nuclear Binding? Constraints on possible nuclear modifications of glue come from 1) Q2 evolution of nuclear ratio of F2 in Sn/C (NMC) 2) Direct measurement of J/Psi production in nuclear targets F2 G • Compatible with EMC effect? • Precise measurements possible of • Nuclear ratio of Sn/C (25 GeV) • J/Psi production (ELIC) Flavor tagging can also (in principle) disentangle sea-quark contributions

  21. ELIC@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 1035 cm-2 sec-1, for electron-light ion collisions at a center-of-mass energy between 20 and 65 GeV • This design, using energy recovery on the JLab site, can be cost-effectively integrated with a 25 GeV fixed target program for physics

  22. ELIC Physics Specifications • Center-of-mass energy between 20 and 65 GeV (with energy asymmetry of ~10) • Ee ~ 3 GeV on Ei ~ 30 GeV up to Ee ~ 5 GeV on Ei ~ 100 GeV worked out in detail (gives Ecm up to 45 GeV) • Ee ~ 7 GeV on Ei ~ 150 GeV seems o.k., but details to be worked out (extends Ecm to 65 GeV) • CW Luminosity up to1035cm-2 sec-1 • Ion species of interest: protons, deuterons, 3He, light-medium ions • Proton and neutron • Light-medium ions not necessarily polarized • Longitudinal polarization of both beams in the interaction region(+Transverse polarization of ions +Spin-flip of both beams)

  23. R&D Topics • Several important R&D topics have been identified: • High charge per bunch and high average current polarized electron source • High energy electron cooling of protons/ions • High current and high energy demonstration of energy recovery • Integration of interaction region design with detector geometry

  24. Luminosity Potential with ELIC x100 x10,000 EIC

More Related