The Physics of Jefferson Lab 12 GeV Upgrade

Transcription

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 1

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 2

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

4 Structure of the Nucleon Nucleon Electromagnetic Form Factors d d E, = M p GE G p M = [ 2 E 2 2 M 2 G Q G Q Pt E E ' Pl 2 M 1 2 G 2M tan 2 /2 ] M= 2 E ' cos 2 / 2 4 E 3 sin 4 /2 tan /2 4 1 Q4

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

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

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

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 8

9 Structure of the Nucleon Valence Quark Structure Q2 x= 2M Model prediction at x=1 F2n/F2p d/d A1 n A1p d/u u/u SU(6) = SU3 flavor + SU2 spin 2/3 1/2 2/3-1/3 0 5/9 Valence Quark + Hyperfine 1/ /3 1 1 pqcd + HHC 3/7 1/

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

11 Neutron structure in spectator tagging CLAS F2n/F2p ratio by tagging almost unbound neutrons using detection of low momentum protons in a radial time projection chamber (BONUS). F n2 e-d e-psx p F2 1 4 d / u 4 d / u ee - BoNUS preliminary SLAC (Fermi corrected SLAC (PLC suppression) CTEQ6X SU(6) n p ps>70mev/c pqcd (HHC) BONUS Detector di-quark First model-independent measurement of F2n/F2p and F2n. At 12 GeV F2n will be measured up to xb =

12 Unpolarized Parton Distribution Function in the Valence Quark Region Hall A 11 GeV with Super BigBite + HRS, 3H/3He DIS with SoLID proton target PVDIS 0.6 Hall B 11 GeV with CLAS12 2 H w/ recoil detection d/u SU(6) pqcd (HHC) di-quark correlations x Helicity Conservation

13 Valence Polarized Structure Functions and PDFs neutron A1n p proton A1 Before JLab pqcd (HHC) di-quark SU(6) pqcd (HHC) di-quark SU(6) 13

14 neutron (Hall A 2004) proton (CLAS 2006) Valence Polarized Structure Functions and PDFs with JLab 6 GeV data 1.0 RCQM pqcd with HHC RCQM CQM LSS(BBS):pQCD+HHC Statistical Model LSS

15 neutron (Hall A 2004) proton (CLAS 2006) Valence Polarized Structure Functions and PDFs with JLab 6 GeV data 1.0 RCQM 0.5 HHC not valid, quark OAM? pqcd with HHC RCQM CQM LSS(BBS):pQCD+HHC Statistical Model LSS

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

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

18 3D Imaging of the Nucleon GPDs and TMDs 18

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

20 Beyond form factors and quark distributions Generalized Parton Distributions (GPDs) 1 J q = q Lq 2 Transverse momentum of partons Quark angular momentum GPDs Pion distribution amplitudes Pion cloud Quark spin distributions Form factors (transverse quark distributions) Quark longitudinal momentum distributions 20

21 GPDs: Results from JLab 6 GeV and Elsewhere Deeply Virtual Compton Scattering: The simplest process that can be Jd described by GPDs model dependent analysis PRL99, (2007) 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 Ju 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 π0 production Compass data with muon beam (~2013) 21

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

23 Parity Violating Electron Scattering at JLab Weak Neutral Current (WNC) Interactions at Q2 << MZ2 Longitudinally Polarized Electron Scattering off Unpolarized Fixed Targets longitudinally A Aweak 2 polarized Q2 Asym 100 ppm GeV 2 23

24 e e Parity Quality of JLab polarized beam HAPPEx-I (1999): strained GaAs (PB~69%) 40 µa beam current HAPPEx-II (2005): superlattice (PB>85%) PREX (2010): superlattice (PB>85%) 35 µa µa Beam Parameter HAPPEx-I HAPPEx-II PREX Charge asymmetry < 0.1 ppm 0.41 ppm 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 ppm 0.08 ± 0.03 ppm 200 ppb 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 GEp and less than 20% to GMp 24

25 Quark Weak Neutral Couplings A V V A C 1i 2 g ea g Vi C 2i 2 g ev g ia Vector quark coupling Axial-vector quark coupling 25

26 Quark Weak Neutral Couplings C1,2q without recent PVES data SAMPLE all are 1 limit without JLab data SLAC/ Prescott PDG best fit C2u+C2d PDG best fit C2u C2d

27 Quark Weak Neutral Couplings C1,2q with recent PVES data SAMPLE all are 1 limit without JLab data SLAC/ Prescott C2u+C2d HAPPEx: H, He G0: H, PVA4: H SAMPLE: H, D PDG best fit C2u C2d

28 Quark Weak Neutral Couplings C1,2q with recent PVES data SAMPLE all are 1 limit without JLab data SLAC/ Prescott C2u+C2d PDG best fit C2u C2d PRL99,122003(2007) Factor of 5 increase in precision of Standard Model test 28

29 Quark Weak Neutral Couplings C1,2q with recent PVES data and Qweak SAMPLE all are 1 limit without JLab data SLAC/ Prescott C2u+C2d PDG best fit C2u C2d 0.25 Qweak in Hall C (2010-): 1H + e e + p another factor of 5 improvement in knowledge of C1q, New Physics scale from 0.9 to 2 TeV

30 Quark Weak Neutral Couplings C1,2q with recent PVES data and Qweak SAMPLE all are 1 limit with JLab 6 GeV SLAC/ Prescott C2u+C2d C2u C2d PVDIS in Hall A (Oct-Dec 2009): potential to improve C2q knowledge if hadronic effects are small. 30

31 Knowledge on C1,2q with Projected JLab 12 GeV Results all are 1 limit C2u+C2d SAMPLE R. Young (combined) C2u C2d PVDIS with 11 GeV beam and SoLID spectrometer in Hall A: potential to improve C2q knowledge by another order of magnitude and better separation from hadronic effects. 31

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

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

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) 34

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. 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. ground state 1st excitation: π/r ~ 1 GeV Jpc =

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

37 Searching for Gluonic Excitations in Hall D q q after γ beam q before 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 q 37

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. 38

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. 39

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

41 Summary and Perspectives 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: 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 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! 41

42 Backup Slides 42

43 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,..) 44

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

46 A B C Staff: ~650 User community: ~

47 Three Experimental Halls (Present) Hall A: pair of high resolution spectrometers (HRS), E' up to 4 GeV/c, = 7 msr luminosity up to 1039 cm-2 s-1 Hall C: High Momentum (HMS and Short-Orbit Spectrometers (SOS) luminosity up to 1039 cm-2 s-1 Hall B: CEBAF Large Acceptance Spectrometer (CLAS) luminosity up to 1034 cm-2 s-1 47

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) 48

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) 49

50 Medium & High Energy Physics Facilities for Lepton Scattering Facilities Accelerator FermiLab Tevatron Energy, polarization Luminosity, 1.96 TeV low % 6 GeV, 85% 12 GeV, 85% CW GeV low low (DESY II) 0.8/1.6 GeV GeV SLAC Stanford Linear Accelerator JLab Continuous Electron Beam Accelerator Facility (CEBAF) CERN Large e /e+ Collider (LEP) DESY.. e, e Deutsches Elektronen Synchrotron 27.5 GeV MAINZ Mainz Microtron MAMI MIT Bates MIT Bates Linear Accelerator duty factor Beam e., e. 50 GeV, 80% e.,. e, e e.. High luminosity, yet continuous polarized beam makes JLab an unique facility. (cm 2 s 1) Time CW ~ns: continuous >>ns: pulsed 50

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

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 53

54 Plan View of the Spectrometer BaBar Solenoid? 54

55 Møller Parity-Violating Experiment: New Physics Reach (example of large installation experiment with 11 GeV beam energy) JLab Møller LHC Λ ee ~ 25 TeV New Contact Interactions Not just another measurement of sin2(θ w) N AFB(b) measures product of e- and b-z couplings ALR(had) measures purely the e-z couplings Proposed APV(b) measures purely the e-z couplings at a different energy scale 55

56 Transverse Momentum Distributions CLAS12 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. 56

57 Exclusive ρ 0 production on transverse target Great opportunity for 12 GeV-Upgrade science program T AUT = - 2 (Im(AB*))/π A (1-ξ ) - B (ξ +t/4m ) - Re(AB )2ξ * 2 ρ0 AUT ρ + A ~ 2Hu + Hd B ~ 2Eu + Ed A ~ Hu - Hd B ~ E u - Ed Asymmetry depends linearly on the GPD E, which enters Ji s sum rule best known way to access quark angular momentum. ρ0 CLAS12 xb K. Goeke, M.V. Polyakov, M. Vanderhaeghen,

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 transverse momentum of quarks implies significant Final transverse momentum of the detected pion Pt arises from convolution of the struck quark transverse momentum kt with the transverse momentum generated during the fragmentation pt. P t = pt + z k t + O(kt2/Q2) z = Eπ/ν pt ~ Λ < 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 58

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

60 Experimental Evidence for Exotic Hybrids 1 +

61 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

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