1. PAC34, JLab, January 27 1 Harut Avakian (JLab) PAC34 JLab, January 27, 2009 Proposal PR12-09-09: Measure helicity distributions and the Collins fragmentation of kaons in SIDIS Studies of spin-orbit correlations in kaon electroproduction in DIS with longitudinally polarized hydrogen and deuterium targets Spokespersons: H. Avakian, E. Cisbani, K. Griffioen, K. Hafidi, P. Rossi

2. PAC34, JLab, January 27 2 The CLAS Collaboration

3. PAC34, JLab, January 27 3 Outline Introduction k T -effects with longitudinally polarized target Double spin asymmetries and k T -widths Single Spin Asymmetries and the Collins effect Projections for 12 GeV Summary Transverse structure of the nucleon and correlations between longitudinal and transverse degrees of freedom.

4. PAC34, JLab, January 27 4 z sin2  moment of the cross section for unpolarized beam and longitudinal target U unpolarized L long.polarized T trans.polarized SIDIS kinematical plane and observables Transverse spin effects are observable as correlations of transverse spin and transverse momentum of quarks.

5. PAC34, JLab, January 27 5 Single hadron production in hard scattering h Target fragmentationCurrent fragmentation Fracture Functions xFxF M 0 1 h h PDF GPD k T -dependent PDFsGeneralized PDFs Wide kinematic coverage of large acceptance detectors allows studies of hadronization both in the target and current fragmentation regions x F - momentum in the CM frame x F >0 (current fragmentation) x F <0 (target fragmentation) h

6. PAC34, JLab, January 27 6 Transverse Momentum Dependent (TMD) Distributions Quark polarization Nucleon polarization Real and imaginary parts of the  L≠0 interference contributions k T – leads to 3D description with 8PDFs  Factorization of k T -dependent PDFs proven at low P T of hadrons (Ji et al) Twist-3

7. PAC34, JLab, January 27 7 A 1 P T -dependence in SIDIS M.Anselmino et al hep-ph/0608048  + A LL can be explained in terms of broader k T distributions for f 1 compared to g 1  0 2 =0.25GeV 2  D 2 =0.2GeV 2 In perturbative limit predicted to be constant Como-2005 constituent quark model ( Pasquini et al ).

8. PAC34, JLab, January 27 8  u/u (dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian Helicity distributions: Diquark model Difference in q + =f 1 +g 1 (quark aligned with proton spin) and q - =f 1 -g 1 - (anti-aligned) k T -dependences may lead to observable effects JMR model Jakob, Mulders, Rodrigues, Nucl. Phys. A 1997 q Dq M R, R=s,a For given x the sign of the polarization is changing at large k T

9. PAC34, JLab, January 27 9 A 1 P T -dependence in SIDIS M.Anselmino et al hep-ph/0608048  + A 1 suggests broader k T distributions for f 1 compared to g 1  - A 1 may require non-Gaussian k T -dependence for different helicities and/or flavors  0 2 =0.25GeV 2  D 2 =0.2GeV 2 0.4<z<0.7

10. PAC34, JLab, January 27 10 Collins asymmetry with longitudinally pol. proton Collins effect measurement with longitudinally pol. target provide access to the chiral-odd Ralston-Soper-Mulders-Tangerman (RSMT) distribution functions and probes the polarized fragmentation function Correlation between the transverse momentum and transverse spin of quarks in longitudinally polarized proton First discussed by Kotzinian & Mulders (1996) - Clean observable: no Sivers type contributions, no twist-3 contributions

11. PAC34, JLab, January 27 11 Transversely polarized quarks in the long. polarized nucleon Light cone constituent quark model Pasquini,Cazzaniga & Boffi, Phys.Rev.D78:034025,2008 Brodsky & Yuan (2006)

12. PAC34, JLab, January 27 12 Collins SSA measurements  +  (u,d) K +  (u,s) K + and  + asymmetries consistent within error bars K - and  - asymmetries may have opposite sign e + e - →hhX Observed SSA show strong dependence on the final state hadron BRAHMS p ↑ p→hX

13. PAC34, JLab, January 27 13 Collins effect Simple string fragmentation (Artru model) Sub-leading pion opposite to leading (into page) L=1  production may produce an opposite sign A UT Leading  opposite to leading  (into page)  hep-ph/9606390 Fraction of  in e  X% left from e  X asm 20% 40% ~75% ~50% Fraction of direct kaons may be significantly higher than the fraction of direct pions. LUND-MC

14. PAC34, JLab, January 27 14 The Collins function First calculation of the Collins function Bacchetta et al, Phys.Lett.B659:234-243,2008 The Kaon Collins effect may be significant! Kaon Pion HERMES/COMPASS/Belle spectator model

15. PAC34, JLab, January 27 15 CLAS12 LTCC FTOF PCAL EC HTCC Lumi = 10 35 cm -2 s -1 High beam polarization 80% High target polarization 85% NH 3 (30 days) ND 3 (50 days) Wide detector and physics acceptance (current/target fragmentation) Replace 2 sectors of LTCC with a proximity RICH detector 2/3 cm 60/80 cm pad cathode coated with CsI film Proximity Gap ~4  K-  separation at ~5 GeV/c

16. PAC34, JLab, January 27 16 Q 2 >1GeV 2 W 2 >4 GeV 2 (10) y<0.85 M X >2GeV SIDIS kinematics Kaon distributions in ep  e’KX High energy kaons are at small angles (  <30 o ) LUND-MC More kaons at small x forward

17. PAC34, JLab, January 27 17 A LL P T -dependence Azimuthal asymmetry sensitive to the difference of widths in PDFs Proton and deutron data provide a complete set required for the flavor decomposition Anselmino et al, Phys.Rev.D74:074015,2006. proton deuteron GRSV-2000+Kretzer

18. PAC34, JLab, January 27 18 Collins fragmentation: Longitudinally polarized target Study the Collins function of kaons Provides independent information on the RSMT TMD Kotzinian-Mulders Asymmetry protondeuteron Pasquini et al.

19. PAC34, JLab, January 27 19 Collins Effect: from asymmetries to distributions Combined analysis of Collins fragmentation asymmetries from proton and deuteron may provide independent to e+e- (BELLE) Information on the underlying Collins function. need

20. PAC34, JLab, January 27 20 Summary  Probe the Collins polarized fragmentation function of kaons  Provide complementary to pions info on the flavor and helicity dependence of quark transverse momentum distributions  Study the transverse polarization of quarks in the longitudinally polarized nucleon through measurements of the leading twist chiral-odd Ralston-Soper-Mulders-Tangerman distribution function.  Study higher twist effects and probe T-odd distributions in a wide range of Q 2 Beam request: 80 days of CLAS12 @ 11 GeV with L=10 35 cm -2 sec -1 (shared with E12-07- 107) with longitudinally polarized NH 3 (30days) and ND 3 (50 days) with RICH upgrade  Latest experimental data indicate that spin-orbit correlations may be significant, leading to hadron flavor dependent observable spin and azimuthal asymmetries Precision measurement of spin and azimuthal asymmetries (sin2 , cos  and sin  in kaon production in DIS will allow us to:

21. PAC34, JLab, January 27 21 Support slides….

22. PAC34, JLab, January 27 22 A Rich detector for CLAS12 A Rich detector would strongly enhance the CLAS12 capabilities in particle identification and would open possibilities for new physics Contalbrigo Marco PAC34 27 January 2009 2/3 cm 60/80 cm pad cathode coated with CsI film Proximity Gap Replacement of LTCC with proximity focusing CsI Rich detector  good separation of  /K/p in the 2-5 GeV/c momentum range  no impact on the baseline design of CLAS 12  minimum impact on spectrometer performaces RICH

23. PAC34, JLab, January 27 23 Low energy electromagnetic processes, especially Møller scattering of beam electrons off atomic electrons are the main contributor to the background load in an open large acceptance spectrometer such as CLAS12. The full event and background load has been measured with CLAS, e.g. for DVCS process at 5.7 GeV. The GEANT simulation reproduces hit occupancy on tracking chambers. We used the calibrated simulation code to extrapolate to 11 GeV and simulate the same process at higher luminosity for CLAS12 situation. This background was also studied in a full Geant4 simulation. CLAS12 - Electromagnetic Background

24. PAC34, JLab, January 27 24 5 T Magnetic Field and Shielding Photons One Event Electrons Photons One Event Shielding Background at L=10 35 cm -2 s -1,  T = 150ns CLAS12

25. PAC34, JLab, January 27 25 CLAS12 – Electromagnetic & Hadronic Rates Deposited Energy detector > 20 KeV 32.3 0.85 RICH (5 o -30 o ) (in 2 sectors) Photons Hadrons (in MHz) L1 31.3 2.5 L2 31.1 2.2 L3 24.6 2.2 SVT (5 o -35 o ) Photons Hadrons DC1 (5 o -35 o ) 1.7 3.1 Photons Hadrons Comment: For deposited energy of 20 KeV RICH would see about 35 hits in 1μsec window, randomly distributed over ~20 m 2 and uncorrelated with track in DC. This is a very conservative estimate as for electrons to be knocked out from the RICH radiator > 500 KeV energy deposition is needed.

26. PAC34, JLab, January 27 26 R pd- Both ratios agree with PDF models for z 1.4 GeV)

27. PAC34, JLab, January 27 27 Unfavored to favored ratio consistent with HERMES and EMC for z=0.55 D - /D + from Deuteron  + to  - ratio

28. PAC34, JLab, January 27 28  multiplicities in SIDIS ep→e’  X  +/- multiplicities at large z diverge from SIDIS predictions  0 multiplicities less affected by higher twists 0.4<z<0.7 kinematical range, where higher twists are expected to be small DSS (Q 2 =2.5GeV 2 ) DSS (Q 2 =25GeV 2 ) M.Aghasyan Hall-C

29. PAC34, JLab, January 27 29 Uncertainties

30. PAC34, JLab, January 27 30 Collins Effect: from asymmetries to distributions Combined analysis of Collins fragmentation asymmetries from proton and deuteron may provide independent to e+e- (BELLE) Information on the underlying Collins function. need

31. PAC34, JLab, January 27 31 Higher Twist SSAs and Quark-Gluon Correlations Target sin  SSA (Bacchetta et al. 0405154) Discussed as main sources of SSA due to the Collins fragmentation In jet SIDIS only contributions ~ D 1 (Sivers type) With H 1 ┴ (  0 )≈0 (or measured) Target and Beam SSA can be a valuable source of info on HT T-odd distribution functions Transversely polarized quarks

32. PAC34, JLab, January 27 32 SSA with unpolarized target quark polarization

33. PAC34, JLab, January 27 33 SSA with unpolarized target quark polarization

34. PAC34, JLab, January 27 34 SSA with long. polarized target quark polarization

35. PAC34, JLab, January 27 35 SSA with long. polarized target quark polarization

36. PAC34, JLab, January 27 36 CLAS: Fraction from baryonic decays in SIDIS Significant fraction from target fragmentation at pion momenta below 2 GeV

37. PAC34, JLab, January 27 37 Dilution factor in SIDIS Multiple scattering and attenuation in nuclear environment introduces additional P T -dependence for hadrons Fraction of events from polarized hydrogen in NH3 N u,N p -total counts from NH3 and carbon normalized by lumi  u,  p -total areal thickness of hydrogen (in NH3), and carbon target Cn=Nitr/Carbon ratio (~0.98) Diff. symbols for diff x-bins --

38. PAC34, JLab, January 27 38 CLAS12: Acceptance deformation due to incomplete azimuthal coverage No significant effect seen from limited  coverage by RICH Lab

39. PAC34, JLab, January 27 39 Inbendin/outbending configurations Different polarities increase the acceptance of positive and negative hadrons.

40. PAC34, JLab, January 27 40 Critical for separation moment range 2<P K <5 and  <25 degree Kinematic dependence of K/  ratios

41. PAC34, JLab, January 27 41 Q 2 >1GeV 2 W 2 >4 GeV 2 (10) y<0.85 M X >2GeV SIDIS kinematics Kaon distributions in ep  e’KX High energy kaons are at small angles

42. PAC34, JLab, January 27 42 A Rich detector for CLAS12 MC simulation:  3 cm thick C 5 F 12 radiator  80 cm CH 4 proximity gap  1 cm pixel pad size  5 o -30 o radiator polar angle 4  K-  separation at 5 GeV/c 80 % kaon eff. with 1:1000  rejection 95 % kaon eff. with 1:100  rejection Contalbrigo Marco PAC34 27 January 2009 Already with 2 sectors gain of factor ~3 in the relevant z region of interest

43. PAC34, JLab, January 27 43 Transverse Momentum Dependent (TMD) Distributions Quark polarization Nucleon polarization Real and imaginary parts of the L=0 and L=1 interference contribution Related to transversity by Lorentz Invariant relations. In constituent quark model (Pasquini et al). k T – leads to 3D description with 8PDFs

44. PAC34, JLab, January 27 44 Compare SIDIS experiments COMPASS/HERMES/CLAS cover different Q 2 for the same x-range x=0.3 → Q 2 =~2 GeV 2 (CLAS), ~7 GeV 2 (HERMES) ~30 GeV 2 (COMPASS)

45. PAC34, JLab, January 27 45 HERMES: Diffractive corrections to DIS

46. PAC34, JLab, January 27 46 Collins Effect: from asymmetries to distributions Combined analysis of Collins fragmentation asymmetries from SIDIS and e+e- (BELLE) would allow separation of transverse spin distributions (Anselmino et al., arXiv:0707.1197 ) need Brodsky & Yuan (2006) CLAS12

47. PAC34, JLab, January 27 47 JLab@12GeV: Inclusive DIS BBS/LSS no OAM PDF measurements at large x provide additional information on OAM BBS/LSS with OAM

48. PAC34, JLab, January 27 48 The Large-Nc Behavior of the PDFs Use the large Nc limit of QCD to study TMD PDFs qg interaction constant In color singlet Feynman diagrams every vertex loop Introduced by ‘t Hooft in1974 isospin Nc-power P.Pobylitsa hep-ph/0301236

49. PAC34, JLab, January 27 49 The Large-Nc limit of QCD to study TMD PDFs  3 – isospin Pauli matrice t 1,t 2 – isospin projection of quark fields (  3 ) uu =1, (  3 ) dd =-1 Change sign from + (SIDIS) to – (DY) Nucleon mass M=O(Nc) Large-Nc approach predicts signs and relative Nc power of TMDs, used in phenomenology.  3 – nucleon isospin P.Pobylitsa hep-ph/0301236 Do not change sign (isoscalar) All others change sign u→d (isovector) Introduced by ‘t Hooft in1974 qg interaction constant In color singlet Feynman diagrams every vertex loop

50. PAC34, JLab, January 27 50 GSIM12 Events for exclusive  + production on proton (ep→e’  +n) Typical event

51. PAC34, JLab, January 27 51 SIDIS (  *p→  X) cross section at leading twist (Ji et al.) structure functions = pdf × fragm × hard × soft (all universal) e Unpolarized target Longitudinally pol. target Transversely pol. target e e p p Boer-Mulders 1998 Kotzinian-Mulders 1996 Collins-1993 To observe the transverse polarization of quarks in SIDIS spin dependent fragmentation is required! Do we understand well the helicity distributions?

52. PAC34, JLab, January 27 52 Azimuthal Asymmetries in SIDIS Due to color coherence the configuration with gluon inside the quark cone is more probable Why < 0 ? Chay,Ellis,Stirling-1991   x  =180  =0

53. PAC34, JLab, January 27 53 HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980, A.Brandenburg, V. Khoze, D. Muller 1995 A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997 ++ Fragmentation  + 00 Azimuthal asymmetries with opposite sign from HT effects Effect may be suppressed for semi-exclusive  0 compared to  +/-

54. PAC34, JLab, January 27 54 Flavor Decomposition Use double spin asymmetries for different targets and final state particles to extract the helicity distributions for different flavors Sum over quark flavors Extraction of k T -dependent distributions q+ (f 1 +g 1 ) and q- (f 1 -g 1 ) will require unfolding of spin independent and spin dependent contributions BBS/LSS no OAM BBS/LSS with OAM H.A.,S.Brodsky,A.Deur,F.Yuan (2007)

55. PAC34, JLab, January 27 55 HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980, A.Brandenburg, V. Khoze, D. Muller 1995 A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997 ++ Fragmentation  + 00 Azimuthal asymmetries with opposite sign from HT effects Effect may be suppressed for semi-exclusive  0 compared to  +/-

56. PAC34, JLab, January 27 56 3D structure of the nucleon Wide kinematic coverage of large acceptance detectors allows studies of exclusive (GPDs) and semi-inclusive (TMDs) processes providing complementary information on transverse structure of nucleon h TMDs Semi-Inclusive processes and transverse momentum distributions ,h Hard exclusive processes and spatial distributions of partons GPDs

57. PAC34, JLab, January 27 57 Flavor Decomposition Sum over quark flavors Extraction of k T -dependent distributions q+ (f 1 +g 1 ) and q- (f 1 -g 1 ) will require unfolding of spin independent and spin dependent contributions BBS/LSS BBS/LSS +OAM H.A.,S.Brodsky,A.Deur,F.Yuan (2007) Large contribution from orbital motion

58. PAC34, JLab, January 27 58 Non-perturbative TMDPerturbative region Boer-Mulders Asymmetry: P T -dependence In the perturbative limit 1/P T 2 behavior expected (F.Yuan) Missing: predictions for K-, dedicated predictions for K+ CLAS12 2<Q 2 <5 (2000h @ 11 GeV with 10 35 sec -1 cm -2 )

59. PAC34, JLab, January 27 59 SSA in ep→e’  X  contribution to SSA (~20%) may be responsible for the difference in    and    beam SSA at large z Larger fraction of  from  at low x and large z PYTHIA at 5.7 GeV

60. PAC34, JLab, January 27 60 Target SSA in exclusive   production Large positive  0 target SSA in the exclusive limit confirmed by CLAS at 5.7 GeV HERMES 27.5 GeV CLAS @5.7GeV ep->e’   p

61. PAC34, JLab, January 27 61 Space and size of RICH sector (LTCC option)