1 The Physics of Jefferson Lab 12 GeV Upgrade Xiaochao Zheng (Univ. of Virginia) Nov. 3, 2010 Jefferson Lab: its mission and current status The Physics from 6 to 12 GeV: A few selected topics Current status of the Upgrade Summary and Outlook

2 Scientific Mission In 1985: How are hadrons constructed from quarks and gluons of QCD? What is the QCD basis for the nucleon-nucleon force? Where are the limits of our understanding of nuclear structure? Where does the transition from nucleon-meson to QCD quark-gluon description occur? Today also include: What is the mechanism of confinement? How does Chiral symmetry breaking occur? Symmetry Tests in Nuclear Physics

3 JLab Accelerator (Present) 20 cryomodules End Stations with complementary equipments Recirculation arcs Helium Refrigerator 0.4-GeV linac 45 MeV Injector 20 cryomodules State-of-art, superconducting RF cavities, combined with polarized electron source, provide high intensity, yet continuous-wave polarized beam for the past 15 years.

4 Structure of the Nucleon Nucleon Electromagnetic Form Factors

5 Before JLab and Recent non-JLab Data Figure credit: S. Riordan JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

6 Today, with JLab 6 GeV Data, compared with theory Figure credit: S. Riordan JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue Inferences to date: Relativity essential Quark angular momentum important Pion cloud makes critical contributions

7 JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue Today, with JLab Data

8 JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue with JLab 12 GeV expected results

9 Structure of the Nucleon Valence Quark Structure

10 After 35 years: Miserable Lack of Knowledge of Valence d-Quarks pQCD (Helicity Conservation) di-quark correlations SU(6) Unpolarized Parton Distribution Function in the Valence Quark Region

11 >70MeV/c BONUS Detector F 2n /F 2p ratio by tagging almost unbound neutrons using detection of low momentum protons in a radial time projection chamber (BONUS). e-D→e-psXe-D→e-psX n psps p e-e- e-e- First model-independent measurement of F 2n /F 2p and F 2n. At 12 GeV F 2n will be measured up to x B =0.85. CLAS Neutron structure in spectator tagging pQCD (HHC) di-quark SU(6) SLAC (PLC suppression) SLAC (Fermi corrected) CTEQ6X BoNUS preliminary

12 Hall A 11 GeV with Super BigBite + HRS, 3 H/ 3 He DIS with SoLID proton target PVDIS Hall B 11 GeV with CLAS12 2 H w/ recoil detection Helicity Conservation Unpolarized Parton Distribution Function in the Valence Quark Region pQCD (HHC) di-quark correlations SU(6) d/u x

13 Valence Polarized Structure Functions and PDFs Before JLab di-quark pQCD (HHC) SU(6) proton A 1 p neutron A 1 n di-quark SU(6) pQCD (HHC)

14 pQCD with HHC RCQM RCQM Valence Polarized Structure Functions and PDFs with JLab 6 GeV data proton (CLAS 2006) CQM LSS(BBS):pQCD+HHC Statistical Model LSS neutron (Hall A 2004)

15 pQCD with HHC RCQM RCQM Valence Polarized Structure Functions and PDFs with JLab 6 GeV data proton (CLAS 2006) CQM LSS(BBS):pQCD+HHC Statistical Model LSS neutron (Hall A 2004) HHC not valid, quark OAM?

16 H. Avakian, S. Brodsky, A. Deur, F. Yuan, Phys. Rev. Lett.99:082001(2007) Figure credit: A. Deur Polarized Structure Functions and PDFs in the Valence Quark Region

17 Polarized Structure PDFs in the Valence Quark Region at JLab 12 GeV Neutron (Hall C) D q/q with JLab 12 GeV projected results Proton (CLAS12)

18 3D Imaging of the Nucleon GPDs and TMDs

19 Beyond form factors and quark distributions – Generalized Parton Distributions (GPDs) Proton form factors, transverse charge & current densities Structure functions, quark longitudinal momentum & helicity distributions Correlated quark momentum and helicity distributions in transverse space - GPDs 4 GPDs: X. Ji, D. Mueller, A. Radyushkin ( )

20 GPDs Transverse momentum of partons Quark spin distributions Form factors (transverse quark distributions) Quark longitudinal momentum distributions Pion cloud Pion distribution amplitudes Quark angular momentum Beyond form factors and quark distributions – Generalized Parton Distributions (GPDs)

21 JdJd JuJu P PRL99, (2007) GPDs: Results from JLab 6 GeV and Elsewhere Remaining JLab 6 GeV program Hall B (relative asymmetries) ALU, AUL, DVCS on He4: data taken ( ), analysis on-going AUT (HD-ice) : experiment to be scheduled Hall A (absolute cross-sections): LH2 and LD2 targets, data taking fall Rosenbluth-type separation of BH2 and DVCS-BH interference L/T separation of the deeply virtual  0 production Compass data with muon beam (~2013) Deeply Virtual Compton Scattering: The simplest process that can be described by GPDs model dependent analysis

22 Projected results (CLAS12) Projected precision in extraction of GPD H at x =  Spatial Image

23 Parity Violating Electron Scattering at JLab Weak Neutral Current (WNC) Interactions at Q 2 << M Z 2 Longitudinally Polarized Electron Scattering off Unpolarized Fixed Targets longitudinally polarized

24 “Parity Quality” of JLab polarized beam Beam Parameter HAPPEx-IHAPPEx-IIPREX Charge asymmetry< 0.1 ppm0.41 ppm200 ppb Position difference -11±2.3 nm, -10±1.0 nm 0.56±0.53 nm, 1.69±0.83 nm 2 nm angle difference 0.2±0.6 nrad, 3±0.2 nrad -0.26±0.24 nrad, 0.21±0.25 nrad 1 nrad Energy difference -4±1 ppb 0.2ppb (0.6 eV)1 eV Total correction-0.02 ± 0.02 ppm0.08 ± 0.03 ppm HAPPEx-II (2005): superlattice (P B >85%) 35  A ee PREX (2010): superlattice (P B >85%)  A HAPPEx-I (1999): strained GaAs (P B ~69%) 40  A beam current High “parity-quality”, negligible uncertainties due to beam; Most of 6 GeV experiments measured strange quark contribution to proton form factors: less than 5% to G E p and less than 20% to G M p

25 Quark Weak Neutral Couplings A V V A Vector quark coupling Axial-vector quark coupling

26 SAMPLE C 2u +C 2d C 2u -C 2d SAMPLE C 2u +C 2d C 2u -C 2d Quark Weak Neutral Couplings C 1,2q without recent PVES data without JLab data all are 1 s limit PDG best fit SLAC/ Prescott PDG best fit

27 SAMPLE C 2u +C 2d C 2u -C 2d SAMPLE C 2u +C 2d C 2u -C 2d HAPPEx: H, He G0: H, PVA4: H SAMPLE: H, D Quark Weak Neutral Couplings C 1,2q with recent PVES data without JLab data all are 1 s limit PDG best fit SLAC/ Prescott

28 SAMPLE C 2u +C 2d C 2u -C 2d Factor of 5 increase in precision of Standard Model test PRL99,122003(2007) Quark Weak Neutral Couplings C 1,2q with recent PVES data without JLab data all are 1 s limit PDG best fit SLAC/ Prescott

29 SAMPLE C 2u +C 2d C 2u -C 2d Quark Weak Neutral Couplings C 1,2q with recent PVES data and Qweak without JLab data all are 1 s limit PDG best fit SLAC/ Prescott Qweak in Hall C (2010-): another factor of 5 improvement in knowledge of C 1q, New Physics scale from 0.9 to 2 TeV 1 H + e  e’ + p

30 Quark Weak Neutral Couplings C 1,2q with recent PVES data and Qweak with JLab 6 GeV all are 1 s limit SAMPLE SLAC/ Prescott C 2u +C 2d C 2u -C 2d PVDIS in Hall A (Oct-Dec 2009): potential to improve C 2q knowledge if hadronic effects are small.

31 SAMPLE R. Young ( combined ) all are 1 s limit PVDIS with 11 GeV beam and SoLID spectrometer in Hall A: potential to improve C 2q knowledge by another order of magnitude and better separation from hadronic effects. Knowledge on C 1,2q with Projected JLab 12 GeV Results C 2u -C 2d C 2u +C 2d

32 N  ee ~ 25 TeV JLab Møller LHC New Contact Interactions Møller Parity-Violating Experiment: New Physics Reach (a large installation experiment with 11 GeV beam energy) Czarnecki and Marciano (2000) Erler and Ramsey-Musolf (2004) Expected precision comparable to the two most precise measurements from colliders, but at lower energy. No other experiment with comparable precision in the forseeable future! 12 GeV 6 GeV

33 Search for Gluonic Degree of Freedom – predicted by theories of confinement

34 Gluonic Excitations and the Origin of Confinement Flux-tubes – a possible mechanism of confinement – comes naturally from self-interaction nature of gluons in QCD. PRD31, 2910 (1985) PLB124,247 (1983)

35 Gluonic Excitations and the Origin of Confinement Flux-tubes – a possible mechanism of confinement – comes naturally from self-interaction nature of gluons in QCD. ground state 1 st excitation:  /r ~ 1 GeV J pc = 1 -+ PRD31, 2910 (1985) PLB124,247 (1983) This gluonic degree of freedom predicts glueballs and hybrid mesons, with exotic quantum numbers. Yet no solid observation of these states.

36 Gluonic Excitations and the Origin of Confinement PRD82: (2010) Lattice QCD gives more detailed predictions exotics

37 q q after q q before  beam With the upgraded CEBAF, a linearly polarized photon beam, and the GlueX detector, Jefferson Lab will be uniquely poised to: - discover these states - map out their spectrum - measure their properties Searching for Gluonic Excitations in Hall D

38 For many physics topics such as GPDs, valence quark structure, PVDIS etc., 6 GeV experiments have demonstrated the feasibility of measurements in a regime that we have barely touched. For some topics such as Moller and searching for gluonic degree of freedom, we have not yet started. Our pursuit of these topics rely on the higher beam energy and more sophisticated equipment of the JLab 12 GeV Upgrade.

39 NSAC 2007 Long Range Plan Recommendation I “We recommend completion of the 12 GeV Upgrade at Jefferson Lab. The Upgrade will enable new insights into the structure of the nucleon, the transition between the hadronic and quark/gluon descriptions of nuclei, and the nature of confinement.”

40 ONGOING CONSTRUCTION EFFORTS Hall D - Central Drift Chamber CMU Hall C – Drift HU & JMU Hall B - Drift JLab, ODU and ISU 12 GeV Groundbreaking (Apr2010) Hall D Concrete Wall Erection (Apr 2009)

41 The Hadron spectra as probes of QCD The transverse structure of the hadrons The longitudinal structure of the hadrons The 3D structure of the hadrons Hadrons and cold nuclear matter Low-energy tests of the Standard Model and Fundamental Symmetries Jefferson Lab is fulfilling its scientific mission. Its 12 GeV Upgrade is well underway and will greatly enhance its scientific reach. 32 proposals already approved and program already established in: Summary and Perspectives Beam off 2012 for the upgrade. Hall commissioning (experiments start) ,. Stay tuned! PAC37 (Jan 2011) new proposal welcome, come join us! Plan for the next “upgrade”!

42 Backup Slides

43

44 12 GeV Upgrade Physics Instrumentation GLUEx (Hall D): exploring origin of confinement by studying hybrid mesons CLAS12 (Hall B): 3D imaging of the nucleon via generalized parton distributions SHMS (Hall C): precision determination of valence quark properties in nucleons and nuclei, form factors Hall A: short range correlations, form factors, hypernuclear physics, & new “installation” experiments (SBS, Møller, SOLID,…..)

45 The Upgrade to the accelerator can be done in a relatively cost-efficient way. 12 GeV Upgrade Accelerator

46 Staff: ~650 User community: ~1300 A CB

47 Three Experimental Halls (Present) Hall A: pair of high resolution spectrometers (HRS), E' up to 4 GeV/c, = 7 msr luminosity up to cm -2 s -1 Hall C: High Momentum (HMS and Short-Orbit Spectrometers (SOS) luminosity up to cm -2 s -1 Hall B: CEBAF Large Acceptance Spectrometer (CLAS) luminosity up to cm -2 s -1

48 Topics not covered in this Talk 6 GeV: GDH sum rule, short-range correlation, PRIMEX, Hadron spectroscopy (N* program) Hadrons and cold nuclear matter (Medium modification of the nucleons, quark hadronization, N-N correlations, hypernuclear spectroscopy, few-body experiments)

49 Beam was first delivered in 10/95 In full operation for ~13 years (since 11/97); 283 PRL and PL to date: ½ expt, ½ theory) 334 PhDs to date and 249 in progress (~1/3 of US PhDs in Nuclear Physics)

50 Medium & High Energy Physics Facilities for Lepton Scattering High luminosity, yet “continuous” polarized beam makes JLab an unique facility. ~ns: “continuous” >>ns: “pulsed”

51 Today, with JLab Data Figure credit: S. Riordan JLab Data on the EM Form Factors Provide a Testing Ground for Theories Constructing Nucleons from Quarks and Glue

52 Main Physics Programs: Nucleon structure functions in the valence quark region; Nucleon form factors (electromagnetic and strange); Hadronic-Partonic transition: Sum rules and duality; Hadron spectroscopy; Nuclear Physics: form factor and structure of light nuclei nuclear medium effects (“EMC” effects) Standard Model test (parity violation in electron scattering)...

53 “Classification” Categories to be Used for the Assignment of Scientific Priority to the 12 GeV Experiments The Hadron spectra as probes of QCD (GluEx and heavy baryon and meson spectroscopy) The transverse structure of the hadrons (Elastic and transition Form Factors) The longitudinal structure of the hadrons (Unpolarized and polarized parton distribution functions) The 3D structure of the hadrons (Generalized Parton Distributions and Transverse Momentum Distributions) Hadrons and cold nuclear matter (Medium modification of the nucleons, quark hadronization, N-N correlations, hypernuclear spectroscopy, few-body experiments) Low-energy tests of the Standard Model and Fundamental Symmetries (Møller, PVDIS, PRIMEX, …..) 53

54 Plan View of the Spectrometer BaBar Solenoid?

55 N  ee ~ 25 TeV JLab Møller LHC New Contact Interactions Møller Parity-Violating Experiment: New Physics Reach (example of large installation experiment with 11 GeV beam energy) A FB (b) measures product of e- and b-Z couplings A LR (had) measures purely the e-Z couplings Proposed A PV (b) measures purely the e-Z couplings at a different energy scale Not “just another measurement” of sin 2 (  w )

56 TMDs are complementary to GPDs in that they allow to construct 3-D images of the nucleon in momentum space TMDs are connected to orbital angular momentum (OAM) in the nucleon wave function – for a TMD to be non-zero OAM must be present. TMDs can be studied in experiments measuring azimuthal asymmetries or moments. Several proposals have been accepted by PAC34 that propose to upgrade CLAS12 with improved Kaon identification. CLAS12 Transverse Momentum Distributions

57 Exclusive  0 production on transverse target 2  (Im(AB*))/  T |A| 2 (1-  2 ) - |B| 2 (  2 +t/4m 2 ) - Re(AB * )2  2 A UT = - Asymmetry depends linearly on the GPD E, which enters “Ji’s sum rule”  best known way to access quark angular momentum. A ~ 2H u + H d B ~ 2E u + E d 00 K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001 A ~ H u - H d B ~ E u - E d ++ A UT xBxB 00 Great opportunity for 12 GeV-Upgrade science program CLAS12

58 Transverse Momentum Dependence of Semi-Inclusive Pion Production Not much is known about the orbital motion of partons Significant net orbital angular momentum of valence quarks implies significant transverse momentum of quarks P t = p t + z k t + O(k t 2 /Q 2 ) Final transverse momentum of the detected pion P t arises from convolution of the struck quark transverse momentum k t with the transverse momentum generated during the fragmentation p t. z = E  / p T ~  < 0.5 GeV optimal for studies as theoretical framework for Semi-Inclusive Deep Inelastic Scattering has been well developed at small transverse momentum  Emerging new area of study

59 The road to orbital motion The difference between the  +,  –, and K + asymmetries reveals that quarks and anti-quarks of different flavor are orbiting in different ways within the proton. Swing to the left, swing to the right: A surprise of transverse-spin experiments Illustration of the possible correlation between the internal motion of an up quark and the direction in which a positively-charged pion (ud) flies off. -  P T -dependences of the double and single-spin asymmetries provide important input for studies of flavor and helicity dependence of quark transverse momentum dependent distributions. e.g., lattice: Higher probability to find a d-quark at large k T Also higher probability to find a quark anti- aligned with proton spin at large k T (not shown)

Experimental Evidence for Exotic Hybrids 1−+

“Classification” Categories Used for the Assignment of Scientific Priority to the 12 GeV Experiments The Hadron spectra as probes of QCD (GluEx and heavy baryon and meson spectroscopy) The transverse structure of the hadrons (Elastic and transition Form Factors) The longitudinal structure of the hadrons (Unpolarized and polarized parton distribution functions) The 3D structure of the hadrons (Generalized Parton Distributions and Transverse Momentum Distributions) Hadrons and cold nuclear matter (Medium modification of the nucleons, quark hadronization, N-N correlations, hypernuclear spectroscopy, few-body experiments) Low-energy tests of the Standard Model and Fundamental Symmetries (Møller, PVDIS, PRIMEX, …..) 61