1. SSA in the target fragmentation region of SIDIS
Aram Kotzinian
Torino University & INFN
On leave in absence from YerPhI, Armenia and JINR, Russia
M.Anselmino, M.Boglione, U.D’Alesio, A.K., F.Murgia and A.Prokudin: PRD 71, (2005)
A.K.: arXiv:hep-ph/
Cahn and Sivers effects
Phenomenology & Data in the CFR
Intrinsic transverse momentum of partons in LEPTO
Results for TFR of SIDIS
Discussion & Conclusions
SIR05, JLab, May 20, 2005
Aram Kotzinian

2. Unpolarized SIDIS & Cahn effect
Ji et al: QCD factorization holds for
approximation
Quadratic in
Linear in and proportional to
SIR05, JLab, May 20, 2005
Aram Kotzinian

3. Comparison with data
Non Gaussian tail; x, z and flavor dependence of intrinsic and fragmentation transv. momentum
SIR05, JLab, May 20, 2005
Aram Kotzinian

4. Interpretation of Sivers effect
Brodsky, Hwang & Schmidt, 2002: FSI + 2
Collins, 2002; Belitski, Ji &Yuan, 2003: Wilson gauge link
Boer, Mulders & Teryaev, 1997: twist three gluonic pole
In standard approach the effective treatment of the Sivers effect is
adopted as correlation in quark distribution in
transversely polarized nucleon
SIR05, JLab, May 20, 2005
Aram Kotzinian

5. Parameterization for Sivers effect
SIR05, JLab, May 20, 2005
Aram Kotzinian

6. Data
SIR05, JLab, May 20, 2005
Aram Kotzinian

7. New HERMES data
SIR05, JLab, May 20, 2005
Aram Kotzinian

8. CFR: TMD dependent descriptionq h
Well clasified correlations in distribution and fragmentation functions
Sivers effect
Boer-Mulders distribution
Helicity distribution
Collins effect in quark fragmentation
SIR05, JLab, May 20, 2005
Aram Kotzinian

9. TFR & Fracture Functionsq h
1994: Trentadue & Veneziano; Graudenz; … Fracture functions:
probability of finding a parton q with momentum
fraction x and a hadron h with the CMS energy fraction Eh/EN
More correlations for TMD dependent FracFuncs
SIR05, JLab, May 20, 2005
Aram Kotzinian

10. Azimuths in SIDIS
In one-photon approximation the general structure of azimuthal
angles dependences in polarized SIDIS can be found from very
general principles (A.K. 1995). Valid both for CFR and TFR.
SIR05, JLab, May 20, 2005
Aram Kotzinian

11. Hadronization Soft Strong Interaction SIR05, JLab, May 20, 2005
Aram Kotzinian

12. Quark intrinsic transverse momentum in LEPTO
- Generate virtual photon – quark scattering in collinear configuration:
- Before
- After hard scattering
- Generate intrinsic transverse momentum of quark (Gaussian kT)
- Rotate in l-l’ plane
- Generate uniform azimuthal distribution of quark (flat by default)
- Rotate around virtual photon
SIR05, JLab, May 20, 2005
Aram Kotzinian

13. Implementing Cahn and Sivers effects in LEPTO
The common feature of Cahn and Sivers effects
Unpolarized initial and final quarks
Fragmenting quark-target remnant system is similar to that in default LEPTO but the direction of is now modulated
Cahn:
Sivers:
Generate the final quark azimuth
according to above distributions
SIR05, JLab, May 20, 2005
Aram Kotzinian

14. Results: Cahn Imbalance of measured in TFR and CFR: neutrals?
SIR05, JLab, May 20, 2005
Aram Kotzinian

15. Results: Sivers Predictions for JLab 12 GeV xF-dependence
Red triangles with error bars – projected statistical accuracy for 1000h data taking
(H.Avagyan).
z and xBj-dependences
SIR05, JLab, May 20, 2005
Aram Kotzinian

16. Results: Sivers JLab 12 GeV
SIR05, JLab, May 20, 2005
Aram Kotzinian

17. SSA in PP-interactions
E704. Curves: by Anselmino et al,
STAR (hep-ex/ )
xF<0 in PP corresponds to xF>0 in SIDIS. In both cases backward
with respect to polarized proton flight direction in CMS.
Both the active quark and the proton remnant are flying in forward
direction. Which particles provide transverse momentum balance?
SIR05, JLab, May 20, 2005
Aram Kotzinian

18. Discussion & Conclusions
Both Cahn and Sivers effects are implemented in LEPTO. Possible effects of polarized hadronization were neglected.
Existing data in CFR are well described by modified LEPTO
The measured Cahn effect in the TFR is not well described
Is there an universal mechanism describing SSA in SIDIS and PP interactions?
It will be interesting to implement Cahn and Sivers effects in PHYTIA
It is important to perform new measurements of both effects in the TFR (JLab, HERMES, Electron Ion Colliders)
This will help better understand hadronization mechanism
Do the neutral hadrons compensate Cahn effect in CFR?
Is there a similarity with PP-reaction?
Multihadron final states distributions can enhance effects
Fracture Function
“Global” analysis
Classification of spin and TMD dependent correlations in Fracture Functions
SIR05, JLab, May 20, 2005
Aram Kotzinian