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Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction

Roadmap to the CLAS12 Physics Program. Ralf W. Gothe. Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction Connections: Not everything is difficult that sounds difficult. Users Group Workshop and Annual Meeting June 8-10, 2009

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Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction

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  1. Roadmap to the CLAS12 Physics Program Ralf W. Gothe Basic Tools: Experiment and Theory Goals:Unveil the dynamics of the strong interaction Connections:Not everything is difficult that sounds difficult Users Group Workshop and Annual Meeting June 8-10, 2009 Jefferson Lab, Newport News, VA

  2. Jefferson Lab Today A C B Hall B Hall A Large acceptance spectrometer electron/photon beams Two high-resolution 4 GeV spectrometers Hall C 7 GeV spectrometer 1.8 GeV spectrometer

  3. 6 GeV CEBAF Upgrade magnets and power supplies CHL-2 12 11 Two 0.6 GeV linacs 1.1 1.1 Enhanced capabilities in existing Halls

  4. Overview of Upgrade Technical Performance Requirements .

  5. CLAS12 CLAS12 Forward Detector • Luminosity > 1035 cm-2s-1 • Baryon Spectroscopy • N and N* Form Factors • GPDs and TMDs • DIS and SIDIS • Nucleon Spin Structure • Color Transpareny • … Central Detector 1m

  6. CLAS12 Approved Experiments

  7. Physics Goals Quark mass extrapolated to the chiral limit, where q is the momentum variable of the tree-level quark propagator using the Asqtad action. q quark mass(GeV) e.m. probe • Study the structure of the nucleon spectrum in the domain where dressed quarks are the major active degree of freedom. • Explore the formation of excited nucleon states in interactions of dressed quarks and their emergence from QCD. resolution p,r,w… low N,N*,D,D*… LQCD (Bowman et al.) LQCD, DSE and … 3q-core+MB-cloud 3q-core high pQCD

  8. Hadron Structure with Electromagnetic Probes lgp=1/2 gv N lgp=3/2

  9. Hadron Structure with Electromagnetic Probes

  10. Cross Section Decomposition

  11. What do we really know? Spectroscopy

  12. Quark Model Classification of N* D13(1520) S11(1535) D(1232) Roper P11(1440) + q³g + q³qq + N-Meson + …

  13. “Missing” Resonances? Problem: symmetric CQM predicts many more states than observed (in pN scattering) Possible solutions: 1. di-quark model old but always young fewer degrees-of-freedom open question: mechanism for q2 formation? 2. not all states have been found • possible reason: decouple from pN-channel • model calculations: missing states couple to • Npp (Dp, Nr), Nw, KY 3. coupled channel dynamics new all baryonic and mesonic excitations beyond the groundstate octets and decuplet are generated by coupled channel dynamics (not only L(1405), L(1520), S11(1535) or f0(980))

  14. γp→K+Λ FROST/HD gN pN’, hN, KL, KS, Npp • Process described by 4 complex, parity conserving amplitudes • 7 well-chosen measurements are needed to determine amplitude. • For hyperon finals state 16 observables will be measured in CLAS ➠ huge redundancy in determining the photo-production amplitudes ➠ allows many cross checks. • 7 observables measured in reactions without recoil polarization. L weak decay has large analyzing power

  15. Quasi-Real Electroproduction Meson spectroscopy: exotic, high t, coherent, J/Y Baryon spectroscopy: heavy mass N*, hyperons Time-like Compton scattering: GPDs, …

  16. Quasi-Real Electroproduction DDVCS? Missing momentum analysis of all final state particles Meson spectroscopy: exotic, high t, coherent, J/Y Baryon spectroscopy: heavy mass N*, hyperons Time-like Compton scattering: GPDs, … Double Deep Virtual Compton scattering

  17. Photoproduction of Lepton Pairs CLAS/E1-6 CLAS/G7 w Mee > 1.2 GeV for TCS analysis f r g’e+e-

  18. Color Transparency A CLAS12 projected • Color Transparencyis a spectacular prediction of QCD: under the right conditions, nuclear matter will allow the transmission of hadrons with reduced attenuation. • Unexpected in a hadronic picture of strongly interacting matter, butstraightforward in quark gluon basis. • Small effects observed at lower energy. Expect significant effects at higher energy. e+ e-

  19. Dynamical Mass of Light Dressed Quarks per dressed quark DSE and LQCD predict the dynamical generation of the momentum dependent dressed quark mass that comes from the gluon dressing of the current quark propagator. These dynamical contributions account for more than 98% of the dressed light quark mass. DSE: lines and LQCD: triangles Q2 = 12 GeV2 = (p times number of quarks)2 = 12 GeV2 p = 1.15 GeV The data on N* electrocouplings at 0<Q2<12 GeV2 will allow us to chart the momentum evolution of dressed quark mass, and in particular, to explore the transition from dressed to almost bare current quarks as shown above.

  20. Constituent Counting Rule S11 Q3A1/2 F15 Q5A3/2 P11 Q3A1/2 D13 Q5A3/2 F15 Q3A1/2 • GMa 1/Q4 * D13 Q3A1/2 • A1/2a 1/Q3 • A3/2a 1/Q5

  21. N → D Multipole RatiosREM ,RSM 1 GD = (1+Q2/0.71)2 • New trend towards pQCD behavior does not show up. • CLAS12 can measure REM and RSM up to Q²~12 GeV². • REM +1 M. Ungaro • GM 1/Q4 *

  22. Np (UIM, DR) PDG estimation Npp (JM) Np, Nppcombined analysis The good agreement on extracting the N* electrocouplings between the two exclusive channels (1p/2p) – having fundamentally different mechanisms for the nonresonant background – provides evidence for the reliable extraction of N* electrocouplings. Electrocouplings of N(1440)P11 from CLAS Data

  23. A1/22 – A3/22 Ahel = A1/22 + A3/22 A1/2 L. Tiator A3/2 Np (UIM, DR) PDG estimation Npp (JM) Np, Nppcombined analysis 10-3 GeV-1/2 world data Electrocouplings of N(1520)D13 from the CLAS 1p/2p data

  24. Kinematic Coverage of CLAS12 2p limit > 1p limit > Q2 GeV2 2p limit > 1p limit > 1h limit > W GeV 60 days L= 1035 cm-2 sec-1, W = 0.025 GeV, Q2 = 0.5 GeV2 (e’,pp+p-) detected Genova-EG

  25. Proton Electromagnetic Form Factors Pun05 Gay02 green : Rosenbluth data (SLAC, JLab) JLab/HallA recoil polarization data

  26. Quark Transverse Charge Densities in Nucleons Light-Front Formalism q+ = q0 + q3 = 0 z p p’ photon only couples to forward moving quarks quark charge density operator longitudinally polarized nucleon Miller (2007)

  27. Quark Transverse Charge Densities in Nucleons transversely polarizednucleon transverse spin e.g. along x-axis : dipolefield pattern Carlson, Vanderhaegen(2007)

  28. Quark Transverse Charge Densities in the Proton ρT ρ0 inducedEDM : dy = F2p (0) . e / (2 MN) data : Arrington, Melnitchouk, Tjon (2007) densities : Miller (2007); Carlson, Vdh (2007)

  29. Transverse Transition Densities p ->N*(1440) p ->D+ (1232) p n quadrupole pattern Tiator, Vdh (2008) Carlson, Vdh (2007)

  30. Transverse Transition Densities p -> D13(1520) ρT ρ0 Tiator, Vdh (2009)

  31. Generalized Parton Distributions Burkardt (2000,2003) Belitsky,Ji,Yuan (2004) 3-dim quark structure of nucleon DIS longitudinal quark distribution in momentum space DES (GPDs) fully-correlated quark distribution in both coordinate and momentum space Elastic Scattering transverse quark distribution in coordinate space

  32. Generalized Parton Distributions ~ ~ H,H,E,E (x, ξ ,t) * Q2 >> t = Δ2 x + ξ x - ξ P - Δ/2 P + Δ/2 GPDs ξ = 0 Fourier transform ofGPDsgives simultaneous distributions of quarks w.r.t.longitudinal momentum x Pandtransverse position b

  33. DVCS Kinematics Coverage of the 12 GeV Upgrade H1, ZEUS H1, ZEUS 27 GeV 11 GeV 200 GeV 11 GeV JLab Upgrade JLab @ 12 GeV COMPASS W = 2 GeV HERMES Study of high xB domain requires high luminosity

  34. How to Extract GPDs ?  2 ξ~ xB/(2-xB)  + -  -  + +  - = A = k = t/4M2 Polarized beam, unpolarized target: ~ LU~sin {F1H+ξ(F1+F2)H+kF2E)}d H(ξ,t) Kinematically suppressed Unpolarized beam, longitudinal target: ~ ~ H(ξ,t) UL~sin {F1H+ξ(F1+F2)(H+ξ/(1+ξ)E) -… }d Kinematically suppressed Unpolarized beam, transverse target: E(ξ,t) UT~ cossin(s-){k(F2H – F1E) + …}d Kinematically suppressed

  35. DVCS Polarized Beam Asymmetry  2  + -  -  + +  - = A = ExtractH(ξ,t) e p epg DsLU~sinf{F1H+…}df 2/25/09 40 Volker Burkert, CLAS12 Workshop, Genoa

  36. DVCS Longitudinal Target Asymmetry  2  + -  -  + +  - = A = e p epg e p epg ~ DsUL~sinfIm{F1H+x(F1+F2)H...}df ~ ExtractH(ξ,t) 2/25/09 41 Volker Burkert, CLAS12 Workshop, Genoa

  37. Transverse Momentum Distributions Semi Inclusive Deep Inelastic Scattering • TMDs are complementary to GPDs in that they allow to construct 3-D imagesof the nucleon in momentum space • TMDs can be studied in SIDIS experiments measuring azimuthal asymmetries or moments.

  38. TMDs in SIDIS Land Many spin asymmetries

  39. TMDs in SIDIS Land

  40. TMDs in SIDIS Land 4 <Q2< 5 GeV2 The cos2F moment of the azimuthal asymmetry gives access to the Boer-Mulders function, which measures the momentum distribution of transversely polarized quarks in unpolarized nucleons..

  41. TMDs in SIDIS Land The sin2F moment gives access to the Kotzinian-Mulders function, which measures the momentum distribution of transversely polarized quarks in the longitudinally polarized nucleon.

  42. Summary and Outlook per dressed quark

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