The total intrinsic k ┴ carried by quarks - PowerPoint PPT Presentation

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The total intrinsic k ┴ carried by quarks

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  1. The total intrinsic k┴carried by quarks • Extraction of the Sivers function • What do we learn from it? • k┴and orbital angular momentum • Orbiting quarks … ? ? Mauro Anselmino,Parton Orbital Angular Momentum,RBRC-UNM Workshop, Albuquerque,24-26/02/2006

  2. uncertainty principle gluon radiation k┴ ±1 ± ± l+ Q2 = M2 l– γ* qT p p qL Partonic intrinsic motion Plenty of theoretical and experimental evidence for transverse motion of partons within nucleons qT distribution of lepton pairs in D-Y processes

  3. pT distribution of hadrons in SIDIS estimates of

  4. S The Sivers distribution function number density of partons with longitudinal momentum fraction x and transverse momentum k┴, inside a proton with spin S M. Burkardt, PR D69, 091501 (2004)

  5. Transverse single spin asymmetries in SIDIS y Φπ ΦS x S PT p z X in collinear configurations there cannot be (at LO) any PT needsk┴dependent quark distribution in p↑ (Sivers mechanism)

  6. Sivers mechanism in SIDIS p┴= PT– zk┴+ O(k┴2/Q2)

  7. Other approaches, with some simplifying assumptions: J.C. Collins et al. W. Vogelsang, F. Yuan

  8. “Sivers moment”

  9. from Sivers mechanism M.A., U.D’Alesio, M.Boglione, A.Kotzinian, A Prokudin

  10. Deuteron target

  11. M.A, M. Boglione, U. D’Alesio, A. Kotzinian, F. Murgia, A. Prokudin comparison of different extractions: hep-ph/0511017 first p┴ moments of extracted Sivers functions, compared with models data from HERMES and COMPASS

  12. M. Anselmino, M. Boglione, J.C. Collins, U. D’Alesio, A.V. Efremov, K. Goeke, A. Kotzinian, S. Menze, A. Metz, F. Murgia, A. Prokudin, P. Schweitzer, W. Vogelsang, F. Yuan The first and 1/2-transverse moments of the Sivers quark distribution functions, defined in Eqs. (3, 9), as extracted in Refs. [20, 21, 23]. The fits were constrained mainly (or solely) by the preliminary HERMES data in the indicated x-range. The curves indicate the 1-σ regions of the various parameterizations.

  13. Predictions for K production at HERMES

  14. Q2 > 1 (GeV/c)2 W2 > 25 GeV2 PT > 0.1 GeV/c Eh > 4 GeV 0.2 < zh < 0.9 0.1 < y < 0.9 Predictions for COMPASS, hydrogen target

  15. predictions for JLab, proton target

  16. SSA in p↑p → π X fit to ANwith Sivers effect U. D’Alesio, F. Murgia E704 data, E = 200 GeV

  17. l+ Q2 = M2 l– γ* qT p p QCD test: qL SSA in p↑p → l+ l- X

  18. SSA in p↑p → D X only Sivers effect: no transverse spin transfer in dominance of gluonic channel, access to gluon Sivers function assuming saturated Sivers function

  19. What do we learn from Sivers distribution? total amount of intrinsic momentum carried by partons of flavoura for a proton moving along the+z-axisand polarization vector S

  20. Numerical estimates from fitting data on Cahn effect from fitting HERMES and COMPASS data on AN M.A., M. Boglione, U. D’Alesio, A. Kotzinian, F. Murgia and A. Prokudin

  21. Sivers functions extracted from ANdata in give also opposite results, with

  22. k┴and orbital angular momentum (case of 2 quarks) ? Does imply It depends on space distribution …… to be continued ……