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Research Perspectives at Jefferson Lab

Research Perspectives at Jefferson Lab. Kees de Jager Jefferson Lab Duality05 Workshop LFN Frascati June 6-8, 2005. CEBAF @ 12 GeV, WHY?. Gluonic Excitations and the Origin of Confinement Developing a Unified Description of Hadron Structure

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Research Perspectives at Jefferson Lab

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  1. Research Perspectives at Jefferson Lab Kees de Jager Jefferson Lab Duality05 Workshop LFN Frascati June 6-8, 2005

  2. CEBAF @ 12 GeV, WHY? • Gluonic Excitations and the Origin of Confinement • Developing a Unified Description of Hadron Structure • Valence Quark Structure and Parton Distributions • Form Factors – Constraints on the GPDs • The Generalized Parton Distributions (GPDs) as Accessed via Deep(ly) Exclusive Reactions • Other Topics in Hadron Structure • The Physics of Nuclei • The Quark Structure of Nuclei (resolving the EMC effect) • The Short-Range Behavior of the N-N Interaction and Its QCD Basis • Quark propagation through Nuclear Matter (hadronization) • Symmetry Tests in Nuclear Physics • Precision Tests of the Standard Model • Spontaneous Symmetry Breaking

  3. Enhanced Kinematical Access to the DIS Regime 12 GeV will access the regime (x > 0.3), where valence quarks dominate

  4. with enough luminosity to reach the high-Q2, high-x region Counts/hour/ (100 MeV)2 (100 MeV2) for L=1035 cm-2 sec-1

  5. Gluonic Excitations from Alex Dzierba

  6. Gluonic Excitations and the Origin of Confinement The quarks in a meson are sources of a color electric flux which is trapped in a flux tube connecting the quarks. The formation of the flux tube is related to the self-interaction of gluons via their color charge. From G. Bali linear potential • Flux tubes result in a linear confining potential • Do flux tubes apply to light-quark systems? • Very little is known about gluonic (or flux-tube) excitations

  7. Photons Preferred for Flux Tube Excitations Normal mesons:JPC = 0-+1+-2-+ First excited state of flux tube has JPC=1+- or 1-+ combined with S=1 for quarks results in 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)

  8. Strategy for Exotic Meson Search • Use photons to produce meson final states with a mass up to 2.5 GeV • 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

  9. Hadron Structure from Zein-Eddine Meziani and Volkert Burkert

  10. Unpolarized Neutron to Proton ratio • Impact: • determine valenced quark momentum distribution • extract helicity dependent quark distributions through inclusive DIS • high x and Q2 background in high energy particle searches. • construct moments of structure functions • In the large x region (x>0.5) the • ratio F2n/F2p is not well determined • due to the lack of a free neutron target

  11. Unpolarized Neutron to Proton ratio DIS from A=3 nuclei Spectator tagging • Mirror symmetry of A=3 nuclei • Extract F2n/F2p from ratio of 3He/3H structure functions and superratio R R = ratio of ”EMC ratios” for 3He and 3H can be calculated to within 1% • Most systematic and theoretical uncertainties cancel • Nearly free neutron target by tagging low-momentum proton from deuteron at backward angles • Small p (70-100 MeV/c) • Minimize on-shell extrapolation (neutron only 7 MeV off-shell) • Backward angles (pq> 110o) • Minimize final-state interactions

  12. Unpolarized Neutron to Proton Ratio Hall C 11 GeV with HMS Hall B 11 GeV with CLAS12

  13. Inclusive measurements of asymmetries W>1.2 A1n at 11 GeV A1p at 11 GeV

  14. Flavor decomposition At RHIC with W production Ee = 11 GeV polarizedNH3 and 3He

  15. Flavor decomposition: polarized sea JLab @11 GeV • Predictions: • Instantons (cQSM): • First data from HERMES •  0

  16. Quark-gluon correlations and g2

  17. g2 at JLab with 11 GeV

  18. Moments of Structure Functions target mass correction term dynamical twist-3 matrix element dynamical twist-4 matrix element • Both d2 and f2 are required to determine thecolor polarizabilities • To extract f2, d2 needs to be determined first

  19. Color “Polarizabilities”

  20. d2 with 11 GeV at JLab

  21. Charged Pion Electromagnetic Form Factor • Where does the dynamics of the q-q interaction make a transition from • the strong QCD (confinement) to the pQCD regime? • It will occur earliest in the simplest systems • the pion form factor Fp(Q2) provides a good starting system to • determine the relevant distance scale experimentally • In asymptotic region, F  8s ƒ  Q-2 HMS+SHMS (11 GeV)projection

  22. Proton Charge Form Factor

  23. CLAS 12 : Neutron GMn With 12 GeV Upgrade eD en(ps) ep ep+n

  24. GPDs & Deeply Virtual Exclusive Processes hard vertices –t – Fourier conjugate to transverse impact parameter H(x,x,t), E(x,x,t), . . “handbag” mechanism Deeply Virtual Compton Scattering (DVCS) x g x – longitudinal quark momentum fraction x+x x-x 2x – longitudinal momentum transfer t xB x = 2-xB

  25. overlap with other experiments unique to JLab High xB only reachable with high luminosity H1, ZEUS Upgraded JLab has complementary & unique capabilities Kinematics Coverage of the 12 GeV Upgrade JLab Upgrade

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

  27. DVCS/BH Transverse Target Asymmetry Sample kinematics E = 11 GeV Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2 • Asymmetry highly sensitive to the u-quark contributions to proton spin Transversely polarized target Ds ~ sinfIm{k1(F2H– F1E) +…}df AUTx Target polarized in scattering plane AUTy Target polarized perpendicular to scattering plane

  28. Exclusive 0 production on transverse target AUT  xB 2D (Im(AB*))/p T A~ 2Hu + Hd AUT = - r0 |A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB2 B~ 2Eu + Ed A~ Hu - Hd B ~ Eu - Ed r+ Asymmetry depends linearly on the GPDE, which enters Ji’s sum rule. CLAS12 K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001

  29. Physics of Nuclei from Will Brooks

  30. Unpacking the EMC effect • With 12 GeV, we have a variety of tools to unravel the EMC effect: • Parton model ideas are valid over fairly wide kinematic range • High luminosity • High polarization • New experiments, including several major programs: • Precision study of A-dependence; x>1; valence vs. sea • g1A(x) “Polarized EMC effect” – influence of nucleus on spin • Flavor-tagged polarized structure functions uA(xA) and dA(xA) • x dependence of axial-vector current in nuclei (can study via parity violation) • Nucleon-tagged structure functions from 2H and 3He with recoil detector • Study x-dependence of exclusive channels on light nuclei, sum up to EMC

  31. Hadronization How do energetic quarks transform into hadrons? How quickly does it happen? What are the mechanisms?

  32. Expected Results on Hadronization 12 12 12 12

  33. Parity Violation from Krishna Kumar

  34. Electron-Quark Phenomenology V A A V C1u and C1d will be determined to high precision by other experiments C2u and C2d are small and poorly known: can be accessed in PV DIS New physics such as compositeness, new gauge bosons: Deviations to C2u and C2d might be fractionally large Proposed JLab upgrade experiment will make it possible to improve knowledge of 2C2u-C2d by more than a factor of 20

  35. Parity Violating Electron DIS e- e- * Z* X N fi(x) are quark distribution functions For an isoscalar target like 2H, structure functions largely cancel in the ratio: Provided Q2 >> 1 GeV2 and W2 >> 4 GeV2 and x ~ 0.2 - 0.4 Must measure APV to fractional accuracy better than 1% • 11 GeV at high luminosity makes very high precision feasible • JLab is uniquely capable of providing beam of extraordinary stability • Systematic control of normalization errors being developed at 6 GeV

  36. 2H Experiment at 11 GeV 1000 hours (APV)=0.65 ppm (2C2u-C2d)=±0.0086±0.0080 PDG (2004): -0.08 ± 0.24 Theory: +0.0986 lab = 12.5o E’ = 5.0 GeV ± 10% 60 cm LD2 target Ibeam = 90 µA • Use both HMS and SHMS to increase solid angle • ~2 MHz DIS rate, π/e ~ 2-3 APV = 217 ppm xBj ~ 0.235, Q2 ~ 2.6 GeV2, W2 ~ 9.5 GeV2 • Advantages over 6 GeV: • Higher Q2, W2, f(y) • Lower rate, better π/e • Better systematics: 0.7%

  37. Physics Implications (2C2u-C2d)=0.012 (sin2W)=0.0009 Unique, unmatched constraints on axial-vector quark couplings: Complementary to LHC direct searches • 1 TeV extra gauge bosons (model dependent) • TeV scale leptoquarks with specific chiral couplings Examples:

  38. PV DIS and Nucleon Structure • Analysis assumed control of QCD uncertainties • Higher twist effects • Charge Symmetry Violation (CSV) • d/u at high x • NuTeV provides perspective • Result is 3 from theory prediction • Raised very interesting nucleon structure issues: cannot be addressed by NuTeV • JLab at 11 GeV offers new opportunities • PV DIS can address issues directly • Luminosity and kinematic coverage • Outstanding opportunities for new discoveries • Provide confidence in electroweak measurement

  39. Search for CSV in PV DIS For APV in electron-2H DIS: Strategy: • measure or constrain higher twist effects at x ~ 0.5-0.6 • precision measurement of APV at x ~ 0.7 to search for CSV • u-d mass difference • electromagnetic effects • Direct observation of parton-level CSV would be very exciting • Important implications for high-energy collider pdfs • Could explain significant portion of the NuTeV anomaly Sensitivity will be further enhanced if u+d falls off more rapidly than u-d as x -> 1

  40. APV in DIS on 1H + small corrections • Allows d/u measurement on a single proton • Vector quark current (electron is axial-vector) • Determine that higher twist is under control • Determine standard model agreement at low x • Obtain high precision at high x

  41. d/u at High x Deuteron analysis has nuclear corrections APV for the proton has no such corrections Must simultaneously constrain higher twist effects The challenge is to get statistical and systematic errors ~ 2%

  42. Large Acceptance: Concept • Need high rates at high x • For the first time: sufficient rates to make precision PV DIS measurements • solid angle > 200 msr • count at 100 kHz • online pion rejection of 102 to 103 • CW 90 µA at 11 GeV • 40-60 cm liquid H2 and D2 targets • Luminosity > 1038/cm2/s JLab Upgrade

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

  44. Hall A w/ 2.2, 4.4, 6.6, 8.8 and 11 GeV Beam • Retain High Resolution Spectrometer (HRS) pair for the continuation of research in which energy resolution comparable to nuclear level spacing is essential • Use the hall infrastructure to support specialized large-installation experiments

  45. CLAS12 -Acceptance for DVCS 70 60 50 For small t, protons recoil at large polar angles 40 30 20 10 Occupancy of DVCS events ep epg Q2 > 2.5 GeV2 E = 11 GeV Kinematic Limit Central Detector Forward Detector

  46. CLAS12 Preshower EC(not visible) Forward EC Low Threshold Cerenkov Counter (LTCC) Forward Drift Chambers Forward TOF High Threshold Cerenkov (HTCC) New Torus Coils Central Detector Beamline Inner EC (not visible) Reused CLAS element Coil EC

  47. Hall C: The SHMS and HMS SuperHMS HMS SOS

  48. GlueX Detector Event rate to processor farm: 10 kHz and later 180 kHz corresponding to data rates of 50 and 900 Mbytes/sec,respectively Lead Glass Detector Barrel Calorimeter Solenoid Coherent Bremsstrahlung Photon Beam Time of Flight Note that tagger is 80 m upstream of detector Tracking Cerenkov Counter Target Electron beam from CEBAF

  49. DOE Critical Decisions

  50. Status of 12 GeV project • The 12 GeV JLab upgrade, a formal recommendation of the NSAC Long Range Plan, will permit a major step forward in the study of “strong” QCD and hadron structure • Substantial progress has been made toward refining the experimental program and equipment designs • DOE has provided a “mission need statement” (CD-0 approval) • A recent DOE review of the science program was highly supportive • JLab is in the process of obtaining CD-1 approval • International involvement is essential to move this exciting project forward rapidly

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