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Peering into Hadronic Matter: The Electron-Ion Collider

Peering into Hadronic Matter: The Electron-Ion Collider. University of Massachusetts Amherst. Christine A. Aidala. Winter Workshop on Nuclear Dynamics. April 12, 2008. The EIC: Communities Coming Together.

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Peering into Hadronic Matter: The Electron-Ion Collider

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  1. Peering into Hadronic Matter:The Electron-Ion Collider University of Massachusetts Amherst Christine A. Aidala Winter Workshop on Nuclear Dynamics April 12, 2008

  2. The EIC: Communities Coming Together • At RHIC, heavy ions and nucleon spin structure already meet, but in some sense by “chance” • Genuinely different physics • Communities come from different backgrounds • Bound by an accelerator that has capabilities relevant to both • The proposed EIC a facility where HI and nucleon structure communities truly come together, peering into various forms of hadronic matter to uncover the secrets the QCD Lagrangian doesn’t reveal . . . C. Aidala, WWND, April 12, 2008

  3. QCD: Confounded Confinement! • Salient features of QCD not evident from Lagrangian! • Asymptotic Freedom & Color Confinement • Due largely to non-perturbative structure of QCD vacuum • Gluons: mediator of the strong interactions • Determine essential features of strong interactions • Dominate structure of QCD vacuum (fluctuations in gluon fields) • Responsible for > 98% of the visible mass in universe(!) • QCD requires fundamental investigation via experiment C. Aidala, WWND, April 12, 2008

  4. Goals & Key Questions • Explore the new QCD frontier: strong color fields in nuclei • How do the gluons contribute to the structure of the nucleus? • What are the properties of high-density gluon matter? • How do fast quarks or gluons interact as they traverse nuclear matter? • Precisely image the sea quarks and gluons in the nucleon • How do the gluons and sea quarks contribute to the spin structure of the nucleon? • What is the spatial distribution of the gluons and sea quarks in the nucleon? • How do hadronic final states form in QCD? How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? C. Aidala, WWND, April 12, 2008

  5. Deep-Inelastic Scattering: A Tool of the Trade in Probing the Partons within Nucleons/Nuclei • Probe nucleon with an electron or muon beam • Interacts electromagnetically with (charged) quarks and antiquarks • “Clean” process theoretically—quantum electrodynamics well understood and easy to calculate! C. Aidala, WWND, April 12, 2008

  6. Deep Inelastic Scattering: Measure of resolution power: ~1/wavelength2 Measure of momentum fraction of struck quark Measure of inelasticity “Perfect” Tomography DIS Kinematic Variables “Bjorken x” Inclusive DIS: Measure only energy and scattering angle of outgoing e Semi-inclusive DIS: Measure outgoing e & some final-state hadrons Exclusive DIS: Measure entire final state C. Aidala, WWND, April 12, 2008

  7. Goals & Key Questions • Explore the new QCD frontier: strong color fields in nuclei • How do the gluons contribute to the structure of the nucleus? • What are the properties of high-density gluon matter? • How do fast quarks or gluons interact as they traverse nuclear matter? • Precisely image the sea quarks and gluons in the nucleon • How do the gluons and sea quarks contribute to the spin structure of the nucleon? • What is the spatial distribution of the gluons and sea quarks in the nucleon? • How do hadronic final states form in QCD? Investigate using the tools of deep-inelastic scattering at high energies: An Electron-Ion Collider C. Aidala, WWND, April 12, 2008

  8. Goals & Key Questions • Explore the new QCD frontier: strong color fields in nuclei • How do the gluons contribute to the structure of the nucleus? • What are the properties of high-density gluon matter? • How do fast quarks or gluons interact as they traverse nuclear matter? • Precisely image the sea quarks and gluons in the nucleon • How do the gluons and sea quarks contribute to the spin structure of the nucleon? • What is the spatial distribution of the gluons and sea quarks in the nucleon? • How do hadronic final states form in QCD? C. Aidala, WWND, April 12, 2008

  9. Gluons dominate low-x wave function What Do We Know About Glue in Matter? Access the gluons in DIS via scaling violations: dF2/dlnQ2 and linear DGLAP evolution in Q2  G(x,Q2) ! C. Aidala, WWND, April 12, 2008

  10. Other Handles on the Gluon Gluon distribution G(x,Q2) • Shown here: • Scaling violation in F2: dF2/dlnQ2 • FL ~ as G(x,Q2) • Other Methods: • 2+1 jet rates (needs jet algorithm and modeling of hadronization for inelastic hadron final states) • inelastic vector meson production (e.g. J/) • diffractive vector meson production ~ [G(x,Q2)]2 C. Aidala, WWND, April 12, 2008

  11. Limitations of Linear Evolution in QCD Established models: • Linear DGLAP evolution in Q2 • Linear BFKL evolution in x Linear evolution in Q2 has a built-in high-energy “catastrophe” • xG rapid rise for decreasing x and violation of unitary bound •  must saturate • What’s the underlying dynamics?  Need new approach C. Aidala, WWND, April 12, 2008

  12. proton N partons any 2 partons can recombine into one proton N partons new partons emitted as energy increases could be emitted off any of the N partons Non-Linear QCD - Saturation • Linear BFKL evolution in x • Explosion of color field as x0?? • New: BK/JIMWLK based models • introduce non-linear effects saturation • characterized by a scale Qs(x,A) • arises naturally in the Color Glass Condensate (CGC) framework Regimes of QCD Wave Function C. Aidala, WWND, April 12, 2008

  13. e+A: Studying Non-Linear Effects Scattering of electrons off nuclei: • Probes interact over distances L ~ (2mN x)-1 • For L > 2 RA ~ 2A1/3 probe cannot distinguish between nucleons in front or back of nucleus • Probe interacts coherently with all nucleons Nuclear “Oomph” Factor Pocket Formula: Enhancement of QS with A  non-linear QCD regime reached at significantly lower energy in heavy nuclei than in proton C. Aidala, WWND, April 12, 2008

  14. Nuclear “Oomph” Factor More sophisticated analyses Oomph exceeds that of pocket formula (e.g. Armesto et al., PRL 94:022002, Kowalski, Teaney, PRD 68:114005) C. Aidala, WWND, April 12, 2008

  15. Universality & Geometric Scaling Crucial consequence of non-linear evolution towards saturation: • Physics invariant along trajectories parallel to saturation regime (lines of constant gluon occupancy) • Scale with Q2/Q2s(x) instead of x and Q2 separately Geometric Scaling • Consequence of saturation x < 0.01 C. Aidala, WWND, April 12, 2008

  16. Qs : A Scale that Binds Them All Geometric scaling Nuclear shadowing proton x 5 nuclei Freund et al., hep-ph/0210139 Is the wave function of hadrons and nuclei universal at low x? C. Aidala, WWND, April 12, 2008

  17. Well mapped in ℓ+p Not in ℓ+A! Mostly small A Low statistics Much to be learned from an Electron-Ion Collider! e+A Landscape and a New Electron-Ion Collider Terra incognita:small-x, Q  Qs high-x, large Q2 C. Aidala, WWND, April 12, 2008

  18. F2 : Sea Quarks Generated by Glue at Low x F2 will be one of the first measurements at EIC nDS, EKS, FGS: pQCD-based models with different amounts of shadowing • Syst. studies of F2(A,x,Q2): • GA(x,Q2) with precision • distinguish among • models C. Aidala, WWND, April 12, 2008

  19. FL at EIC: Measuring the Glue Directly Access by making measurements at fixed x, Q2 for different y y= Q2/xs Scan in ! GA(x,Q2) with great precision C. Aidala, WWND, April 12, 2008

  20. RHIC LHC Connection to RHIC & LHC Physics Matter at RHIC • Thermalizes fast (t0 ~ 0.6 fm/c) • We don’t know why and how • Initial conditions?  G(x, Q2) Role of saturation? • RHIC → forward region • LHC → midrapidity • bulk (low-pT matter) & semi-hard jets Jet Quenching: • Need Reference: E-loss in cold matter • No HERMES data for • charm energy loss • in LHC energy range EIC provides essential new input: • Precise handle on x, Q2 • Means to study exclusive effects C. Aidala, WWND, April 12, 2008

  21. Goals & Key Questions • Explore the new QCD frontier: strong color fields in nuclei • How do the gluons contribute to the structure of the nucleus? • What are the properties of high-density gluon matter? • How do fast quarks or gluons interact as they traverse nuclear matter? • Precisely image the sea quarks and gluons in the nucleon • How do the gluons and sea quarks contribute to the spin structure of the nucleon? • What is the spatial distribution of the gluons and sea quarks in the nucleon? • How do hadronic final states form in QCD? C. Aidala, WWND, April 12, 2008

  22. 50% of Momentum Carried by Gluons … But Still Gluon Puzzles S g xS > xg ??? S If sea quarks come from gluon splitting, how can the gluon and sea distributions diverge as they appear to at low Q2?? EIC luminosity 100x > HERA  Precision measurements! A low Q2 puzzle … C. Aidala, WWND, April 12, 2008

  23. Spin Structure of the Nucleon Quark spin contribution to the proton spin: “Spin Crisis” The rest from gluons and orbital angular momentum. • Gluon spin contribution, DG, still poorly constrained • Only recent ideas on probing orbital angular momentum! C. Aidala, WWND, April 12, 2008

  24. Region of existing g1p data World Data on F2p World Data on g1p Not enough range in x, Q2 to access DG via scaling violations An EIC makes it possible! C. Aidala, WWND, April 12, 2008

  25. Spin-Orbit Effects and Transverse Spin p+  L R Also access orbital angular momentum and spatial distribution of partons within nucleon via measurements of Generalized Parton Distributions (GPD’s) - Exclusive measurements - Possible due to high luminosities, large detector coverage Now confirmed at much higher energies at RHIC Fermilab E704: p p pX at 400 GeV STAR Must be due to spin-orbit effects in the proton itself and/or in the fragmentation process Observed Large Single-Spin Asymmetry C. Aidala, WWND, April 12, 2008

  26. EIC Status: White Papers 2007 • The Electron Ion Collider White Paper • The GPD/DVCS White Paper • Position Paper: e+A Physics at an Electron Ion Collider • The eRHIC machine: Accelerator Position Paper • ELIC ZDR Draft • Available at: • NSAC LRP2007 home page • Rutgers Town Meeting page • http://www.bnl.gov/eic C. Aidala, WWND, April 12, 2008

  27. The EIC Working Group 17C. Aidala, 28E. Aschenauer, 10J. Annand, 1J. Arrington, 26R. Averbeck, 3M. Baker, 26K. Boyle, 28W. Brooks, 28A. Bruell, 19A. Caldwell, 28J.P. Chen, 2R. Choudhury, 10E. Christy, 8B. Cole, 4D. De Florian, 3R. Debbe, 26,24-1A. Deshpande*, 18K. Dow, 26A. Drees, 3J. Dunlop, 2D. Dutta, 7F. Ellinghaus, 28R. Ent, 18R. Fatemi, 18W. Franklin, 28D. Gaskell, 16G. Garvey, 12,24-1M. Grosse-Perdekamp, 1K. Hafidi, 18D. Hasell, 26T. Hemmick, 1R. Holt, 8E. Hughes, 22C. Hyde-Wright, 5G. Igo, 14K. Imai, 10D. Ireland, 26B. Jacak, 15P. Jacobs, 28M. Jones, 10R. Kaiser, 17D. Kawall, 11C. Keppel, 7E. Kinney, 18M. Kohl, 9H. Kowalski, 17K. Kumar, 2V. Kumar, 21G. Kyle, 13J. Lajoie, 16M. Leitch, 27A. Levy, 27J. Lichtenstadt, 10K. Livingstone, 20W. Lorenzon, 145. Matis, 12N. Makins, 6G. Mallot, 18M. Miller, 18R. Milner*, 2A. Mohanty, 3D. Morrison, 26Y. Ning, 15G. Odyniec, 13C. Ogilvie, 2L. Pant, 26V. Pantuyev, 21S. Pate, 26P. Paul, 12J.-C. Peng, 18R. Redwine, 1P. Reimer, 15H.-G. Ritter, 10G. Rosner, 25A. Sandacz, 7J. Seele, 12R. Seidl, 10B. Seitz, 2P. Shukla, 15E. Sichtermann, 18F. Simon, 3P. Sorensen, 3P. Steinberg, 24M. Stratmann, 22M. Strikman, 18B. Surrow, 18E. Tsentalovich, 11V. Tvaskis, 3T. Ullrich, 3R. Venugopalan, 3W. Vogelsang, 28C. Weiss, 15H. Wieman,15N. Xu,3Z. Xu, 8W. Zajc. 1Argonne National Laboratory, Argonne, IL; 2Bhabha Atomic Research Centre, Mumbai, India; 3Brookhaven National Laboratory, Upton, NY; 4University of Buenos Aires, Argentina; 5University of California, Los Angeles, CA; 6CERN, Geneva, Switzerland; 7University of Colorado, Boulder,CO; 8Columbia University, New York, NY; 9DESY, Hamburg, Germany; 10University of Glasgow, Scotland, United Kingdom; 11Hampton University, Hampton, VA; 12University of Illinois, Urbana-Champaign, IL; 13Iowa State University, Ames, IA; 14University of Kyoto, Japan; 15Lawrence Berkeley National Laboratory, Berkeley, CA; 16Los Alamos National Laboratory, Los Alamos, NM; 17University of Massachusetts, Amherst, MA; 18MIT, Cambridge, MA; 19Max Planck Institüt für Physik, Munich, Germany; 20University of Michigan Ann Arbor, MI; 21New Mexico State University, Las Cruces, NM; 22Old Dominion University, Norfolk, VA; 23Penn State University, PA; 24RIKEN, Wako, Japan; 24-1RIKEN-BNL Research Center, BNL, Upton, NY; 25Soltan Institute for Nuclear Studies, Warsaw, Poland; 26SUNY, Stony Brook, NY; 27Tel Aviv University, Israel; 28Thomas Jefferson National Accelerator Facility, Newport News, VA ~100 Scientists, 30 Institutions, 9 countries C. Aidala, WWND, April 12, 2008 *Contact People

  28. ElectronCooling e-cooling (RHIC II) Snake IR IR PHENIX Snake Main ERL (2 GeV per pass) STAR Four e-beam passes Electron Ion Collider Concepts • ELIC (JLAB): Add hadron beam facility to CEBAF • eRHIC (BNL): Add Energy Recovery Linac to RHIC eRHIC (Linac-Ring) ELIC C. Aidala, WWND, April 12, 2008

  29. Detector Design p/A Si tracking stations EM calorimeter Main detector: Top view Main detector: Emphasize high-luminosity, full physics program (Pasukonis, Surrow, physics/0608290) Hadronic calorimeter e Additional detector: Emphasize low-x, low-Q2 diffractive physics (Abt, Caldwell, Liu, Sutiak, hep-ex/0407053) Learn from experience at HERA! C. Aidala, WWND, April 12, 2008

  30. EIC Timeline & Status • NSAC Long Range Plan 2007 • Recommendation: $6M/year for 5 years for machine and detector R&D • Goal for Next Long Range Plan 2012 • High-level recommendation for construction • EIC Roadmap (Technology Driven) • Finalize Detector Requirements from Physics 2008 • Revised/Initial Cost Estimates for eRHIC/ELIC 2008 • Investigate Potential Cost Reductions 2009 • Establish process for EIC design decision 2010 • Conceptual detector designs 2010 • R&D to guide EIC design decision 2011 • EIC design decision 2011 • “MOU’s” with foreign countries? 2012 C. Aidala, WWND, April 12, 2008

  31. Summary An Electron-Ion Collider would offer unprecedented opportunities to explore the next QCD frontier • What is the role of gluons and gluon self-interactions in nucleons and nuclei? • Explore non-linear QCD • Existence of universal saturation regime? • What is the internal spin, flavor, and space-time structure of the nucleon? New collaborators and ideas welcome! C. Aidala, WWND, April 12, 2008

  32. C. Aidala, WWND, April 12, 2008

  33. Extra Slides C. Aidala, WWND, April 12, 2008

  34. e-cooling (RHIC II) PHENIX Main ERL (2 GeV per pass) STAR Four e-beam passes eRHIC at BNL 24-250 GeV protons 30-100 GeV/n ions 3-10 (20) GeV electrons Add energy-recovery linac to RHIC • Peak luminosity 2.6 x 1033 cm-2s-1 in electron-hadron collisions • Electron beam polarization not affected by energy • +- 5 meter “element-free” straight section for detectors • Ion beams up to U • Ability to take full advantage of electron cooling of the hadron beams • Can run hadron-hadron collisions in RHIC simultaneously C. Aidala, WWND, April 12, 2008

  35. ELIC at JLab ElectronCooling Snake 30-225 GeV protons 30-100 GeV/n ions IR Add hadron beam facility to CEBAF IR Snake 3-9 GeV electrons • Visionary green-field design: • Peak luminosity up to ~8 x 1034 cm-2s-1 through short ion bunches • “Figure-8” lepton and ion rings • +- 3m “element-free” straight sections • Ion beams up to Au • Superconducting RF ion linac concept for all ions • 12 GeV CEBAF accelerator serves as injector to electron ring C. Aidala, WWND, April 12, 2008

  36. eRHIC vs. ELIC • eRHIC could potentially go up to higher electron energy of 20 GeV, compared to 9 for ELIC. • eRHIC can run hadron-hadron collisions simultaneously • Successful R&D for ELIC could lead to luminosities ~10-50 times higher than eRHIC • ELIC costs higher • ELIC timeline longer C. Aidala, WWND, April 12, 2008

  37. The EIC and the LHeC EIC: L > 1x1033 cm-2s-1 Ecm = 20-100+ GeV LHeC: L = 1.1x1033 cm-2s-1 Ecm = 1.4 TeV • Variable energy range • Polarized and heavy ion beams • High luminosity in energy region • of interest for nuclear science • Add 70-100 GeV electron ring to • interact with LHC ion beam • Use LHC-B interaction region • High luminosity mainly due to • large g’s (= E/m) of beams • Nuclear science goals: • Explore the new QCD frontier: • strong color fields in nuclei • Precisely image the sea-quarks • and gluons to determine • the spin, flavor and spatial • structure of the nucleon. • High-Energy physics goals: • Parton dynamics at the TeV scale • - physics beyond the • Standard Model • - physics of high parton • densities (low x) • Important cross fertilization of ideas: • Significant European interest in an EIC • EIC collaborators on LHeC Science Advisory Committee • (with Research Directors of CERN, FNAL, DESY) C. Aidala, WWND, April 12, 2008

  38. A Truly Universal Regime? Small x QCD evolution predicts: • QSapproaches universal behavior for all hadrons and nuclei  Not only functional form f(Qs) universal but even Qsbecomes the same ? • Radical View: • Nuclei and all hadrons have a component of their wave function with the same behavior • This is a conjecture! Needs to be tested A.H. Mueller, hep-ph/0301109 C. Aidala, WWND, April 12, 2008

  39. Nuclear Modification of Structure Functions C. Aidala, WWND, April 12, 2008

  40. = x/xIP Diffractive Structure Function F2D at EIC xIP= momentum fraction of the pomeron w.r.t the hadron - Distinguish between linear evolution and saturation models - Insight into the nature of pomeron - Search for exotic objects (Odderon) Curves: Kugeratski, Goncalves, Navarra, EPJ C46, 413 C. Aidala, WWND, April 12, 2008

  41. Connection to p+A Physics F. Schilling, hex-ex/0209001 • e+A and p+A provide excellent information on properties of gluons in the nuclear wave functions • Both are complementary and offer the opportunity to perform stringent checks of factorization/universality • Issue: • p+A lacks the direct access to x, Q2 Breakdown of factorization (e+p HERA versus p+p TeVatron) seen for diffractive final states. C. Aidala, WWND, April 12, 2008

  42. Longitudinal Structure Function FL • Experimentally can be determined • directly IF VARIABLE ENERGIES! • Highly sensitive to effects of gluon + EIC alone + 12-GeV data C. Aidala, WWND, April 12, 2008 (includes systematic uncertainties)

  43. Gluon Contribution to the Proton Spin 150 GeV x 7 GeV, 5 fb-1 at small x Superb sensitivity to Dg at small x! C. Aidala, WWND, April 12, 2008

  44.  DG Via Open Charm and Dijet Production HERMES, COMPASS, SMC C. Aidala, WWND, April 12, 2008

  45. Dg Dijets DG Via Open Charm and Dijets at EIC Dg/g Projected data on Dg/g with an EIC, via g + p  D0 + X K- + p+ Advantage: measurements directly at single Q2 ~ 10 GeV2 scale! RHIC-Spin • Uncertainties in xDg smaller than 0.01 • Measure 90% of DG (@ Q2 = 10 GeV2) C. Aidala, WWND, April 12, 2008

  46. Precisely Image the Sea Quark Polarization Spin-Flavor Decomposition of the Light Quark Sea u u u > u d Many models predict Du > 0, Dd < 0 | p = + + + … u u u u d d d d RHIC-Spin region C. Aidala, WWND, April 12, 2008

  47. x = 0.01 x = 0.40 x = 0.70 m m d3r d2kT p p x GPD B TMD GPDu(x,x,t) Hu, Eu, Hu, Eu Wigner function: Probability to find a u(x) quark with a certain polarization at position r and with momentum k ~ ~ TMDu(x,kT) f1,g1,f1T ,g1T h1, h1T ,h1L ,h1 Fourier transform in momentum transfer dx x = 0, t = 0 d2kT u(x) Du, du F1u(t) F2u,GAu,GPu f1(x) g1, h1 Parton Distributions Form Factors gives transverse position of quark (parton) with longitud. mom. fraction x Towards a 3D spin-flavor landscape Wu(x,k,r) Link to Orbital Momentum Link to Orbital Momentum C. Aidala, WWND, April 12, 2008

  48. Detector Design Main detector: Learn from ZEUS + H1 at HERA But: - low-field region around central tracker - better particle identification - forward-angle detectors - auxiliary detectors for exclusive events - auxiliary detectors for normalization C. Aidala, WWND, April 12, 2008

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