The Future of Hadronic Physics in the US

1. The Future of Hadronic Physics in the US • Introduction • RHIC-spin • JLab at 12 GeV • Electron-Ion Collider • Other Issues • Summary QNP04 May 27, 2004 Bloomington Kees de Jager Jefferson Lab

2. What are the goals? • Understanding the structure of protons and neutrons in terms of quarks and gluons • Understanding the structure of light nuclei in terms of nucleons at low energy and of quarks and gluons at high energy • Linking the physics of nuclei to strong QCD • How do we reach those goals? • Measure form factors, structure functions and generalized parton distributions to determine how the quarks and gluons are distributed inside the nucleons • Probe nucleons and nuclei with photons and electrons to produce excited mesonic and baryonic states • High-energy proton-proton collisions provide a complimentary window into how quarks and gluons build up nucleons • Lattice QCD calculations are expected to provide the best theoretical means to compare experimental results with QCD What is Hadronic Physics? NSAC Report on Performance Measures (November 2003)

3. RHIC-spin: Non-pQCD Spin Structure from Hard Scattering • Does preferential spin orientation of gluons account for a major portion of the “nucleon spin puzzle”? • Either answer interesting! If not gluon spins, then Lorbital ! • Do sea antiquarks have a substantial and flavor-dependent helicity preference in a polarized nucleon? • Illuminates the relative roles of gluon splitting vs. pseudoscalar meson clouds in generating the “sea” • 3)Unravel the contributions to transverse spin asymmetries (an area of intense recent theoretical development) from: • a) quark transverse spin preferences in a transversely polarized proton (p) • “transversity”  quark property decoupled from gluons • b) quark transverse motion preferences in p • spin-kT correlation related to quark orbital angular momentum • c) explicit chiral symmetry breaking from mq terms in LQCD

4. The RHIC Spin Facilities  Absolute Polarimeter (H jet) Equip-ment to be installed after FY03 Strong AGS Snake • First polarized collider, exploits Siberian Snake technology   • Enables p + p pol’n measurements in s and pT regime where low-order pQCD is applicable • Provides access to nucleon spin structure info complementary to polarized DIS • Major experimental efforts at STAR, PHENIX and PP2PP • Virgin territory + new technology  signifi-cant challenges + steep learning curve

5. RHIC-spin Timeline • First p + p collisions in 1/02: 200 GeV, Pbeam ~ 15% (vert. spin only), L ~ 5 x 1029, L dt ~ 300 nb-1  see polarization survival, first transverse spin results • Second run 5/03: 200 GeV, Pbeam ~ 30% (vert. + longitudinal), L ~ 2 x 1030, L dt~ 800 nb-1 commission rotators, first ALL measurements • 2004-5: commissioning of new AGS snakes to improve Pbeam; absolute Pbeam calibration exp’t; first measurements of g via ALL for abundant probes(jets, 0’s with ~ 5 pb1); measure transverse single-spin asymmetry for not-quite-back-to-back dijets for kT sensitivity. • 2006-10: “Rare” processes to map Dg(x) fully: • Detect -jet coincidences in polarized proton collisions at s = 200 and 500 GeV • Measure two-spin asymmetry in production rates between equal vs. opposite helicities, as function of (jet), (), pT ( ) • Assuming two-body parton kinematics, can infer initial x values of gluon and quark • 2009-12: W Production-> Direct determination of Du/u and Dd/d: • Measure single-spin parity-violating asym. AL for p + p  W  + X with respect to helicity flip of each beam. • Requires 500 GeV, upgraded forward tracking, and as much P2L dt as we can get! - -

6. CEBAF @ 6 GeV, Present and Future • How are nucleons made from quarks and gluons? • Nucleon (electro-magnetic and -weak) form factors, separate u, d and s • Nucleon excitation spectrum, new resonances (pentaquark) • Spin structure functions in valence region • Generalized Parton Distributions, mainly DVCS • How does QCD work in the strong (confinement) region • Pion form factor • How does the NN force arise from the partonic structure of hadronic matter? • Medium modifications • Color transparancy • What is the Structure of Nuclear Matter? • High-resolution (~300 keV) hypernuclear spectroscopy (1p-shell) • Proton knock-out (2H, 3,4He, 16O, …) • At what scale does the partonic structure of nuclear matter become apparent? • Few-body form factors, deuteron photodisintegration • Standard Model Tests • Q-weak

7. CEBAF @ 12 GeV, WHY? • Gluonic Excitations and the Origin of Confinement • Developing a Unified Description of Hadron Structure • The Generalized Parton Distributions (GPDs) as Accessed via Deep(ly) Exclusive Reactions • Valence Quark Structure and Parton Distributions • Form Factors – Constraints on the GPDs • Other Topics in Hadron Structure • The Physics of Nuclei • The Short-Range Behavior of the N-N Interaction and Its QCD Basis • Identifying and Exploring the Transition from the Nucleon/Meson Description of Nuclei to the Underlying Quark/Gluon Description • Symmetry Tests in Nuclear Physics • Standard Model Tests

8. GluonicExcitationsandtheOriginofConfinement Theoretical studies of QCD suggest that confinement is due to the formation of “Flux tubes” arising from the self-interaction of the glue, leading to a linear potential (and therefore a constant force) From G. Bali linear potential Experimentally, we want to “pluck” the flux tube and see how it responds

9. Photons Preferred for Flux Tube Excitations Normal mesons:JPC = 0-+1+-2-+ First excited state of flux tube has J=1 combined with S=1 for quarks JPC = 0-+ 0+-1+- 1-+2-+ 2+- exotic (mass ~ 1.7 – 2.3 GeV) Double-blind Monte Carlo simulation: 2 % exotic signal clearly visible Photons couple to exotic mesons via g VM transition (same spin configuration)

10. Strategy for Exotic Meson Search • Use photons to produce meson final states • tagged photon beam with 8 – 9 GeV • linear polarization to constrain production mechanism • Use large acceptance detector • hermetic coverage for charged and neutral particles • typical hadronic final states:f1h KKh KKppp b1pwppppprpppp • high data-acquisition rate • Perform partial-wave analysis • identify quantum numbers as a function of mass • check consistency of results in different decay modes

11. GPDs: A Unified Description of Hadron Structure Transverse momentum of partons Quark angular momentum Quark spin distributions GPDs Form factors Pion distribution amplitudes Pion cloud Quark momentum distributions

12. DVCS SSA Measures phase and amplitude directly DVCS at 11 GeV can cleanly test correlations in nucleon structure (data shown – 2000 hours in CLAS++) DVCS and Bethe-Heitler are coherent  can measure amplitude AND phase

13. Measuring the GPDs • Key experimental capabilities include: • CW (100% duty factor) electron beams (permits fully exclusive reactions) • modern detectors (permit exclusive reactions at high luminosity) • adequate energy (~10 GeV to access the valence quark regime)  Measurements of GPDs through many reaction channels CLAS++ and calorimeter+MAD in Hall A DVCS on proton and neutron, DVMP, RCS, nucleon EMFF

14. Extending DIS to High xwithA1n 12 GeV will access the valence quark regime (x > 0.4), where constituent quark properties are not masked by the sea quarks

15. Transition from ‘Strong’ to pQCD Pion Elastic Form Factor Electroproduction -/+ Ratio in 4He • Simplest valence quark structure • pQCD is expected to manifest at low momentum transfer • pQCD and non-pQCD calculations exist • The asymptotic pion form factor:

16. JLab tests of the Standard Model • Measurements of sin2(qW) below MZ provide strict tests of the SM • Measurements in different systems provide complementary information • Møller Parity Violation can be measured at JLab even more accurately than in E158 • DIS-Parity violation measurement is easily carried out at JLab hep-ph/0205183 RPV Weak Mixing Angle MS-bar scheme Jens Erler No SUSY dark matter

17. CEBAF @ Higher EnergiesHow? • Design choices for CEBAF’s construction make tripling the original energy to 12 GeV remarkably cost effective • The extraordinary performance of the original SRF cavities has already brought us to 6 GeV, and further advances in SRF make 12 GeV straightforward • Much of the existing experimental equipment can be upgraded for use at higher energies, minimizing equipment costs

18. Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls Add new hall 12 11 6 GeV CEBAF

19. Hall A: MAD and the HRS Medium Acceptance Detector (MAD) at high luminosity and large acceptance MAD Design Properties Momentum Range 0.4 - 8.6 GeV/c Momentum Acceptance ± 15% Momentum Resolution 0.1% Scattering Angle Range 5° - 150° Angular Acceptance 5 - 28 msr Angular Resolution horizontal 1 mrad vertical 1 mrad Target Length Acceptance 50 cm Vertex Resolution 0.5 cm e/h discrimination 50000:1 (98%) π/K discrimination 1000:1 (95%) Maximum DAQ Rate 20 kHz

20. Hall B: CLAS++ CLAS upgraded to higher (1035) luminosity and coverage • Angular coverage • Forward 5° - 37° • Central 40° - 135° • Track resolution • momentum 0.001p • dq ` 1 mrad • df 1 mrad

21. Hall C: HMS and SHMS Central Momentum 2.5 - 11 GeV/c Momentum Acceptance -15 - +25% Momentum Resolution 0.2% Scattering Angle Range 5.5° - 25° Angular Acceptance 2 - 4 msr horizontal ± 18 mrad vertical ± 50 mrad Angular Resolution horizontal 2 mrad vertical 1 mrad Target Length Acceptance 50 cm Vertex Resolution 0.2 cm e/h discrimination 1000:1 (98%) π/K discrimination 100:1 (95%) Super High Momentum Spectrometer (SHMS) at high luminosity and forward angles

22. Hall D: The GlueX Detector Photon Flux 108g/s Charged Particles coverage 1° - 170° momentum reso 1 - 2% position reso 150 µm vertex reso 500 µm Photons energy measured 1° - 120° Pb glass reso 2 + 5%/√E barrel reso 4.4%/√E Trigger level 1 rate 20 kHz Coherent bremsstrahlung

23. Status of 12 GeV Upgrade • JLab upgrade is relatively modest project (175 - 250 M$) • CD-0 was approved on April 1, 2004 • JLab is looking for 25+ M$ non-DOE fundingWithin a year JLab will present a CDR for review to CD-1 • The goal is to complete the upgrade early in the next decade

24. Why Electron-Ion Collider? • Polarized DIS and e-A physics: in past only in fixed target mode • Collider geometry--> distinct advantages (HERA Experience) • Better angular resolution between beam and target fragments • Better separation of electromagnetic probe • Recognition of rapidity gap events (recent diffractive physics) • Better measurement of nuclear fragments • Higher Center of Mass energies reachable • Tricky issues:integration of interaction region and detector

25. Deep Inelastic Scattering [1] • Observe scattered electron [1] inclusive measurement • Observe [1] + current jet [2] semi-inclusive measurement • Observe [1] + [2] + remnant jet [3] exclusive measurement • Luminosity requirements goes up as we go from [1] --> [2] --> [3] • Exclusive measurements also puts demanding requirement on integration of detectors and interaction region [2] [3]

26. Scientific Frontiers Open to EICs • Nucleon structure, role of quarks and gluons in the nucleons • Unpolarized quark and gluon distributions, confinement in nucleons • Polarized quark and gluon distributions • Correlations between partons • Exclusive processes--> Generalized Parton Distributions • Understanding confinement with low x/lowQ2 measurements • Meson Structure: • Goldstone bosons and play a fundamental role in QCD • Nuclear Structure, role of partons in nuclei • Confinement in nuclei through comparison e-p/e-A scattering • Hadronization in nucleons and nuclei & effect of nuclear media • How do knocked off partons evolve in to colorless hadrons • Partonic matter under extreme conditions • For various A, compare e-p/e-A

27. Unpolarized e-p at EIC • Although large kinematic region already covered at HERA, additional studies with high luminosities desirable • Unique features: high luminosity, variable CM energy, He beams, and improved detectors and interaction regions • Precision Measurements: • With d, He beams: neutron structure • The evolution of the strong coupling constant • Photo-production physics at high energies • Gluon distribution • FL structure function • Slope of F2 structure function to explore confinement • Diffractive physics • Semi-inclusive and exclusive reactions • Nuclear fragmentation region [1] [1] [1] [1] [1] [1] [1] [1,2] [2,3]

28. Polarized DIS at EIC [1] [1] [1] [1] [1,2] [1] [1,2] [3] [1] [1] [2,3] • Spin structure functions g1 (p,n) at low x, high precision • g1(p-n): Bjorken Spin sum rule to better than 1% accuracy • Polarized gluon distribution function DG(x,Q2) • at least three different experimental methods • Precision measurement of aS(Q2) from g1 scaling violations • Polarized s.f. of the photon from photo-production • Electroweak s. f. g5 via W+/- production • Flavor separation of PDFs through semi-inclusive DIS • Deeply Virtual Compton Scattering (DVCS) • Generalized Parton Distributions (GPDs) • Transversity • Drell-Hern-Gerasimov spin sum rule test at high n • Target/Current fragmentation studies • … etc….

29. Proton Spin Structure at Low x Fixed target experiments 1989 – 1999 Data eRHIC 250 x 10 GeV Luminosity = ~85 inv. pb/day 10 days of EIC run Assume: 70% Machine Eff. 70% Detector Eff. Studies included statistical error & detector smearing to confirm that asymmetries are measurable. No present or future approved experiment will be able to make this measurement

30. Spin Structure of Neutron at Low x • With polarized 3He • ~ 2 weeks of data at EIC • Compared with SMC(past) & possible HERA data • If combined with g1 of proton results in Bjorken sum rule test to better than 1-2% within a couple of months of running eRHIC 1 inv.fb

31. Photon Gluon Fusion • “Direct” determination of DG • Di-Jet events: (2+1)-jet events • High pT hadrons • High √s at EIC • no theoretical ambiguities regarding interpretation of data • Both methods tried at HERA in un-polarized gluon determination & both are successful! • NLO calculations exist • H1 and ZEUS results • Consistent with scaling violation F2 results on G Signal: PGF Background QCD Compton

32. Di-Jet at EIC vs. World Data for DG/G eRHIC Di-Jet DATA 2fb-1 Good precision Clean measurement in x range 0.01 < x < 0.3 Constrains shape of DG(x) Polarization in HERA much more difficult than RHIC ELIC DG from scaling violations > xmin~ 10-4 at eRHIC > xmin~ 3.10-4 at ELIC

33. DVCS/Vector Meson Production • Hard Exclusive DIS process • g(default) but also vector mesons possible • Remove a parton & put another back in!  Microsurgery of Baryons! Access to skewed or off-forward PDFs Polarized structure: Access to quark orbital angular momentum

34. A Color Glass Condensate? • At small x, partons are rapidly fluctuating gluons interacting weakly with each other, but still strongly coupled to the high x parton color charges which act as random static sources of COLOR charge • Analogous to spin GLASS systems in condensed matter: a disordered spin state coupled to random magnetic impurities • Gluon occupation number large; being bosons they can occupy the same state to form a CONDENSATE • Bose-Einstein condensate leads to a huge overpopulation of ground states • A new “state matter”(??): Color Glass Condensate (CGC) at high energy density would display dramatically different, yet simple properties of glassy condensates • Experimental measurements: Gluon distributions inclusive semi-inclusive methods, specific predictions regarding enhancement of diffractive processes in e-A vs. e-p at identical (x,Q2), measurement of FL to access gluon distribution in nuclei • An e-A collider/detector experiment with high luminosity and capability to have different species of nuclei in the same detector would be ideal…  Low x --> Need EIC

35. The eRHIC Ring-Ring Lay Out & Plans • Full energy injection • Polarized e- source & unpolarized e+ --> (polarization via synchrotron radiation) • 10 GeV main design but up to 5 GeV reduction possible with minimal polarization loss • Fill in bunch spacing 35ns Present conservative estimates Lep ~ 4 x 1032 cm-2 sec-1work on luminosity enhancement continues. Advantages: both positrons and electrons Disadvantages: No multiple detectors or/and Interaction Regions?

36. eRHIC: Linac-Ring Option Features: • Lep up to ~1034 cm-2sec -1 • Polarization transparency at all energies • Multiple IRs and detectors • Long element free regions • STAR & PHENIX still run • Full range of CM Energies • Future upgrades to 20 GeV seem straightforward Limitations: Positron beams not possible Physics implications?

37. ELIC Layout One accelerating & one decelerating pass through a 7 GeV/pass CEBAF Max CoM energy √s 65 GeV Max luminosity 8.1034 cm-2s-1 Polarized ions p, d, 3He Unpolarized ions up till 40Ca

38. A Detector for EIC  A 4p Detector • Scattered electrons to measure kinematics of DIS • Scattered electrons at small (~0°) to tag photo production • Central hadronic final state for kinematics, jet measurements, quark flavor tagging, fragmentation studies, particle ID • Central hard photon and particle/vector detection (DVCS) • ~Zero angle photon measurement to control radiative corrections and in e-A physics to tag nuclear de-excitations • Missing ET for neutrino final states (W decays) • Forward tagging for 1) nuclear fragments, 2) diffractive physics • At least one second detector should be incorporated… if not more • EIC will provide: • 1) Variable beam energies • 2) different hadronic species, some of them polarized • 3) high luminosity

39. Where do electrons and quarks go? q,e  p 10 GeV x 250 GeV 1770 1600 100 10 GeV 5 GeV 5 GeV 900 scattered electron scattered quark

40. Detector Design: HERA like…+ PID (Not to scale) HCAL EMCal Solenoid AEROGEL TOF A HERA like Detector with dedicated PID: >>Time of flight >>Aerogel Ckov Beam elements e p/A Inner trackers AND Forward detectors including Roman Pots etc… 5 m Outer trackers

41. eRHIC/ELIC Status & Design Ideas • 2001 LRP: NSAC enthusiastically supported R&D and stated its would be the next major for nuclear physics (after 12 GeV JLab upgrade) • 2003 NSAC committee on facilities’ high recommendation • Level 1 for physics, and level 2(eRHIC)/3(ELIC) for readiness • ZDR (Zero Design Report) for eRHIC: Ring-Ring design • Identify R&D topics toward significant luminosity enhancement • ELIC analysis and simulations: • electron cooling and short bunches • beam-beam physics • energy recovery linac physics • Development on both projects will continue until the time to make the decisions to freeze technology and design options

42. The case for hadronic beams • Goals of the baryon physics program: • Determine relevant degrees of freedom in baryons, and the nature of their short-range interactions • Find “missing” conventional qqq excitations and identify new kinds of states • pentaquarks, hybrids, baryon-meson quasi-bound states • To meet baryon physics goals we require: • High precise data using electromagnetic beams in new channels: underway at JLab and other facilities • You could get lucky and find an isolated missing resonance near a new channel’s threshold • Recent experience has shown: adding a new resonance has consequences in several channels, convincing evidence will come from a simultaneous fit • Polarization experiments: beam, target, recoil: • E.g. all three possible, and planned, in

43. The case for hadronic beams… • Hadron beams! • Hadron-beam information complementary to that of photoproduction • Simultaneous unitary analysis of data from gN and pNrequired to find new N*, D* states • Kaon-beam experiments could map out spectrum of a persistent Q+ and its partners • Would make enormous improvement in our understanding of S, L and X resonances • No plans for such beams at GSI or JPARC • Is this something the US nuclear/hadron physics community should plan for the future?

44. SciDAC Initiative for Lattice QCD • DOE Scientific Discovery through Advanced Computing Initiative: develop software/hardware infrastructure for next generation computers • U.S. Lattice QCD Collaboration consists of 64 senior scientists. Research closely coupled to DOE’s experimental program: • Weak Decays of Strongly Interacting Particles: BaBar (SLAC), B-Tevatron (FNAL), CLEO-c (Cornell) • Quark-Gluon Plasma: RHIC (BNL) • Structure and Interactions of Hadrons: Bates, BNL, FNAL, JLAB, SLAC SciDAC Project: • $6M, 30% JLab, 30% FNAL, 15% BNL, 25% universities • Unify software development and porting efforts for diverse hardware platforms • Hardware prototyping efforts: clusters, QCDOC • No direct physics support • Hope for significant funding for QCDOC-type machine in FY04/FY05 • Proposal for corresponding LGT funding at JLAB from FY06

45. LQCD Roadmap at Jefferson Lab First data from CEBAF @12 GeV 102 GPD measurements shown at JLAB 101 FY05-06 Clusters ~5 Teraflops Precise moments, decay widths 100 Current Clusters 0.3 Teraflops Moments of GPD’s, N-> 10-1 Low moments, quenched resonances 10-2 Lattice Spectrum agrees with Experiment for Conventional Mesons. 10-3 10-4 Flux tubes between Heavy Quarks 10-5 First numerical simulations 10-6 Lattice gauge theory invented 1974 1990 2000 2010

46. The DOE-OSc “20-year plan” includes the JLab 12 GeV Upgrade in its near-term (<7 year) prospects and eRHIC in its far-term (>14 year) prospects

47. CEBAF Upgrade EIC

48. Summary • Broad active program in hadronic physics (JLab@6GeV, RHIC-spin) • Many important questions remain to be answered in detail (OAM, transversity, hadronization, gluonic structure,……) • Confident that JLab@12GeV will happen, but need to keep pressure on DOE • Vibrant and active community essential for future funding • Excellent scientific case for Electron-Ion Collider • Next NSAC Long Range Plan (starting ~2005) will probably be asked to evaluate need and options for electron-ion collider • However, funding outlook at present not optimistic