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Spin Physics with CLAS12

Spin Physics with CLAS12. Yelena Prok CNU/JLab April 12 2011. XIX International Workshop on Deep Inelastic Scattering. The Spin Puzzle: Key Question in Standard Model QCD. g. . spin 1/2. spin 1. QED. QCD.

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Spin Physics with CLAS12

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  1. Spin Physics with CLAS12 Yelena Prok CNU/JLab April 12 2011 XIX International Workshop on Deep Inelastic Scattering

  2. The Spin Puzzle: Key Question in Standard Model QCD g  spin 1/2 spin 1 QED QCD 99.9% of mass of the visible universe composed of quarks and gluons - the building blocks of the nucleon How do partonic degrees of freedom - mass, charge, color, SPIN - manifest as the nucleon degrees of freedom? No access to free partons due to confinement! The proton is a stable and abundant source of partons

  3. k’ k Elastic q p’ xP= p P Inclusive DIS of lepton off nucleon k’ k Virtual photon probes the structure q p’ Important variables: xP=p P W

  4. The nucleon parton model and TMDs In the collinear approximation: DIS distribution functions Parton transverse momentum more complex dist. functions Transverse Momentum Distributions (TMDs) of partons describe the distribution of quarks and gluons in a nucleon with respect to x and the intrinsic transverse momentum pT carried by the quarks

  5. Target polarization • orbital motion of quarks • parton distributions • factorization studies Semi-inclusive DIS: U unpolarized L long.polarized T trans.polarized z Beam polarization azimuthal asymmetries due to correlations of spin and transverse momentum of quarks

  6. CLAS12 LTCC DC R1, R2, R3 CHL-2 PCAL Beam Current: 90 µA Max Pass energy: 2.2 GeV Max Enery Hall A,B,C: 11 GeV Solenoid 5T Primary goal of experiments using CLAS12: study of the internal nucleon dynamics by accessing GPDs & TMDs  detector tuned for studies of exclusive and semi-inclusive reactions in a wide kinematic range. Large acceptance detector and high luminosity capabilities EC HTCC FTOF L = 1035 cm-2s-1 May 2012 6 GeV Accelerator Shutdown starts May 2013 Accelerator Commissioning starts 2013-2015 Pre-Ops (beam commissioning)

  7. The Polarized Target • NH3/ND3 targets (also C, empty)3.3 cm length, 16 nA beam rastered over 3 cm diameter • Pt=80(40)% p(d) via DNP • Horizontal 1 K cryostat, 5 T field from CLAS12 CT solenoid, 140 GHz µwave

  8. A RICH detector for CLAS12 • A RICH detector would strogly enhance the CLAS12 capabilities in particle identification and would open possibilities for new physics • A proximity focusing RICH detector could replace the LTCC • Several options are under study: • geometry optimization • radiator • photocatode Photocathode drift electrode charged particle radiator Proximity gap

  9. DIS coverage CLAS12: Kinematic coverage • Large kinematic ranges accessible with CLAS12 are important for separation of • Valence region • Higher Twist contributions (Q2) • Perturbative regime (PT ≥ 1) epX

  10. Large-x behavior of the A1 asymmetry Large x region dominated by valence quarks can test quark models

  11. Predicted Data from CLAS12 Proton Deuteron W > 2; Q2 > 1

  12. BBS/LSS +OAM Quark polarization in the valence region Simulated Data for EG12 Extracted from A1p, A1d and d/u Existing Data Hall B

  13. Anticipated Effect of CLAS12 data on NLO fits of PDFs

  14. Sum Rules • Expected error bars for CLAS12 Γ1p • Coverage predicted for CLAS12 Γ1p

  15. A1 – PT dependence @ 12 GeV A1 A1 proton Curves: M. Anselmino et al PRD74:074015, 2006 deuteron A1 PT-dependence provides access to helicity dependence of kT-distributions of quarks Deuteron and hydrogen data required for PT-dependent flavor decomposition.

  16. Conclusions • Study of the spin-structure of the nucleon is one of the main driving forces behind the upgrade of Jefferson Lab • An extensive and rich experimental program using CLAS12 and polarized targets will provide new insights into all components of the nucleon’s spin • The anticipated data will allow for the separation of leading-twist TMDs in the valence region, providing important information on spin-orbit correlations and the role of angular momentum

  17. Extra slides

  18. Status of g1(x,Q2) • Data mostly for DIS and low x • Remains to be done: • G (RHIC,COMPASS) • L (DVCS: COMPASS, HERMES,Jlab) • Transversity(HERMES, Jlab, RHIC) • Large x precision measurements (Jlab) • Measurement in non-perturbative region (Jlab)

  19. Boer-Mulders asymmetry @ CLAS12 /K measurement with CLAS12 will provide a more detailed knowledge of spin-orbit correlations in hadronization 56 days at L=1x1035 cm-2s-1

  20. Spin Structure Function g1 S+SN=1/2 S+SN=3/2 1/2 ≈ q+(x) 3/2 ≈ q-(x) • Virtual photon couples to quarks of opposite helicity

  21. World data on the proton before JLab (without COMPASS) World data on the proton including EG1(without COMPASS) Status of g1(x,Q2) for the proton

  22. TheCLASDetector • High luminosity, polarized CW beam • Wide physics acceptance, including exclusive, semi-inclusive processes, current and target fragmentation • Wide geometric acceptance, allowing detection of multi-particle final states ~ 200 physicists 37 institutions Q2 Forward CALO H. Avakian, Trento, June 10

  23. Existing Data from CLAS Close and Melnitchouk, PRC 68, 035210 (2003) Isgur, PRD 59, 034013 (2003) W > 2; Q2 > 1 } Proton Deuteron

  24. Flavor Decomposition from SIDIS

  25. Sum Rules • Expected errors for CLAS12 G1d • Expected errors for CLAS12 G1p-n Greater x-coverage for 1

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