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Contalbrigo Marco INFN Ferrara

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  1. Overview of TmDMeasurements Contalbrigo Marco INFN Ferrara Partons in Nucleons and Nuclei September 30, 2011 Marrakech

  2. Quantum phase-space distributions of quarks Wpq(x,kT,r) “Mother” Wigner distributions Probability to find a quarkqin a nucleon P with a certain polarization in a position r &momentum k d3r d2kT (FT) TMD PDFs: fpu(x,kT),… GPDs: Hpu(x,x,t), … Semi-inclusive measurements Momentum transfer to quark Direct info about momentum distribution Exclusive Measurements Momentum transfer to target Direct info about spatial distribution x=0,t=0 d2kT May explain SSA & Lam-Tung May solve proton spin puzzle √s = 20 GeV PDFs fpu(x),… AN pT< 2 GeV/c xF PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 2

  3. Leading Twist TMDs Number Helicity quark polarisation Number density and helicity: Focusing here in transverse momentum dependence Transversity: Boer-Mulders Density Survives transverse momentum integration (missing leading-twist collinear piece) Differs from helicitydue to relativistic effects and no mix with gluons in the spin-1/2 nucleon nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity quark polarisation Off-diagonal elements: Interference between wave functions with different angular momenta: contains information about parton orbital angular motion and spin-orbit effects Testing QCD at the amplitude level Collins Unpolarized sign change between DY and SIDIS • universality of TMDs T-odd elements: nucleon polarisation Strict prediction from TMDs + QCD ! PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 3

  4. Physics reactions SIDIS: rich phenomenology, the most exploredso far SIDIS e+e-: B-factories as powerful fragmentation laboratories e+e- DY: challenging for experiments (only unpolarized so far) DY FF FF FF DF DF DF DF DF Hadron reactions: challenging for theory (ISI + FSI) FF pp PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 4

  5. The SIDIS case Number Helicity quark polarisation SIDIS cross section (transversely polarized target): Boer-Mulders Density nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 5

  6. The SIDIS case Number Helicity quark polarisation SIDIS cross section (transversely pol. target): Boer-Mulders Density TMD factorization for PT<<Q nucleon polarisation Worm-gear Transversity Involved phenomenology due to the convolution over transverse momentum Sivers Worm-gear Pretzelosity FF DF PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 6

  7. First evidences SIDIS: epe’hX A. Airapetian et al, Phys. Rev. Lett. 94 (2005) 012002 2005: First evidence from HERMES measuring SIDIS on proton Non-zero transversity !! Non-zero Collins function !! Non-zero Sivers function !! PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 7

  8. Number Helicity Number Density & Helicity (TheBaseline) Boer-Mulders Density nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity

  9. The hadron multiplicities LO interpretation: Proton-deuteron asymmetry: Reflects different flavor content Correlated systematics cancels SIDIS data constrain fragmentation at low c.m. energy and bring enhanced flavor sensitivity PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 9

  10. The Ph-unintegratedmultiplicities T arXiv: 1008.5125 Ph Disentanglement of z and : access to the transverse intrinsic quark kT and fragmentation pT, i.e. from gaussiananstaz T 2 2 2 Ph Ph Ph T T T arXiv: 0709.3020 Hall C - JLab Ph Joosten, DIS 2011 T PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 10

  11. The evolution arXiv: 1008.5125 Gaussian ansatz Is pT independent of z ? arXiv: 1003.2190 SIDIS New ! f1u z ~ 0.5 f1u arXiv: 1101.5057 Drell-Yan Indirect indication of a kT and pT broadening with c.m. energy: TMD Q2 evolution PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 11

  12. The ALL Asymmetry arXiv: 1007.1562 COMPASS CLAS HERMES arXiv: 1003.4549 Hint of different transverse momentum widths for helicityvs number density Ph T PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 12

  13. Number Helicity Transversity (the Collinear Missing piece) Chirally-odd Boer-Mulders Density First evidence: 2005 nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity + - + -

  14. The Collins fragmentation Correlation between quark polarization and observed hadron transverse momentum PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 14

  15. The Collins fragmentation Different from zero signal! New ! At low z little memory of the struck quark At low thrust spherical events and gluon emission PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 15

  16. The Collins SIDIS amplitude HERMES p New ! Opposite sign for pions reveals Collins features Consistent non-zero signals for charged pions PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 16

  17. Transversity signals • Existingdata limitedto x < 0.3 • Gaussian ansatz • Evolution from high energy colliders First extraction of Transversity! d d u u xh1(x, k ) xh1(x, k ) xh1(x) xh1(x) T T Soffer bound Tensor charge xh1(x) M. Anselminoet al hep-ph:0812.4366 M. Wakamatsu hep-ph:0811.4196 Anselmino et al. Phys. Rev. D 75 (2007) PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 18

  18. Two hadron asymmetries New ! Issue with unknown pp-terms in partial wave expansion NEW !! • Survives Phintegration • Collinear factorization • (simple product) • DGLAP volution • Universality PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 19

  19. Transversity signals Different from zero correlations ! New ! e- q1 φR1 φR2 q2 e+ quark spin quark spin 1st collinear extraction ! z2 z1 NEW !! arXiv: 1104.2425 Bacchetta et al., PRL 107 (11) PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 20

  20. Transversity signals No significant asymmetries seen in pp reactions at mid-rapidity. PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 21

  21. Number Helicity Sivers (The TMD challenge) Naïve-T-odd Non-trivial gauge link Process dependence Boer-Mulders Density nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity + + + -

  22. The Sivers signals HERMES p Jlab Hall-A n New ! x z Non zero ! for positive hadrons on proton Flavor tagging: K+ signals larger than p+ No signal on deuteron target COMPASS p h+ h- Ph(GeV/c) T PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 23

  23. The Sivers signals HERMES vs COMPASS comparison: are data consistent ? New ! HERMES COMPASS PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 24

  24. The Sivers challenges Coverage at large pTand relation with twist-3 collinear approach arXiv: 1107.4446 x Sivers effect from SIDIS to pp: A possible candidate to explain SSA Sivers effect from SIDIS to Drell-Yan: Sign change as a crucial test of TMDs factorization arXiv: 0901.3078 Sivers from SIDIS and collinear twist-3 as candidates for SSA explanation arXiv: 0801.2990 PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 25

  25. The inclusive hadron SSA Persistent with energy New ! Asymptotic 1/pT not reached Issues on factorization Sivers effect from SIDIS to pp: arXiv: 0801.2990 Sign mismatch between SIDIS and pp SSA ? arXiv: 1103.1591 ANL s=4.9 GeV BNL s=6.6 GeV RHIC s=62.4 GeV BNL s=6.6 GeV ANL s=4.9 GeV FNAL s=19.4 GeV FNAL s=19.4 GeV RHIC s=62.4 GeV Sivers moment from SIDIS T3 correlator from pp PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 26

  26. Inclusive hadron SSA in SIDIS Sivers modulation sin(f-fS) can survives as sin(f) • AUT is vanishing at low pT • Q2 increases with pT • approaching DIS regime • Study transition from • perturbative to • non-perturbative regime Non-zero signals for positive hadrons resembling Sivers PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 27

  27. Number Helicity CaHn & Boer-mulders (TheNeglected Effects) Naïve-T-odd Chirally-odd Spin effect in unpolarized reactions Boer-Mulders Density nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity

  28. The Lam-Tung relation E615 NA10 E866 Preserved by NLO and resummation Analogous of SIDIS Callan-Gross E615 (pp) NA10 (pp) 194 GeV 286 GeV 140 GeV pT (GeV) pT (GeV) Boer-Mulders offers a possible explanation E866 (pp, pD) PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 29

  29. The azimuthal modulation EMC (1987) Kinematical effect redicted since 1978 by Cahn due to non-zero intrinsic kT Cahn PLB 78 (1978) Leading-twist contribution introduced by Boer & Mulders in 1998 Boer & Mulders PRD 57 (1998) Till 2008: qualitative agreement with Cahn expectations • No hadron identification • No charge separation • Poor statistics for cos2f Non perturbative contribution PT (GeV/c) PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 30

  30. The SIDIS cos2f dependence Non-zero ! Issue on DATA consistency arXiv: 0912.5194 Can be explained by large uncertainty on Cahn and neglected HT effects PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 31

  31. The SIDIS cosf dependence Significant differencein hadron charge might signal Large and negative increasing with z and Ph Much larger expectations but largely sensitive on <kT> and kT cutoff arXiv: 1106.6177 PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 32

  32. Summary TMDs describe a new class of phenomena providing novel insights into the rich nuclear structure SIDIS and e+e- experiments provide evidence of non-zero TMDs First generation experiments provide promises but also open questions • Full coverage of valence region not achieved • Limited knowledge on transverse momentum dependences • Role of the higher twist to be quantified • Evolution properties to be defined • Flavor decomposition to be refined • UniversalityFundamental test of QCD PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 33

  33. The TMDs Landascape A very active field to explore for various upcoming experiments ! PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 34

  34. The 3D description of the nucleon GPD E GPD ET+2HT green quark anti-green remnant Distribution Functions (DF) BOER-MULDERS Spin orbit effect Impact parameter space ┴ ┴ Deformations by ~ ┴ ┴ ┴ SIVERS Quark orbital angular momentum 3-momentum space i.e. Sivers: spin-orbit correlations with same matrix element of anomalus magnetic moment, and GPD E PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 35

  35. The hadron multiplicities Seek for flavor dependences Nuclear effects should be taken into account for not pure targets Hermes, arXiv: 1107.3496 PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 36

  36. The Collins fragmentation Asymmetry expected to go As sin2(q)/(1+cos2(q)) At low thrust spherical events and gluon emission PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 37

  37. Number Helicity Pretzelosity (the D-Wave) Sensitive to the D-wave component and the non spherical shape of the nucleon Boer-Mulders Density nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity

  38. The Pretzelosity HERMES p COMPASS p Statistical power of existing data is not enough to observe significant signals h+ deuteron h- deuteron Positivity bound h+ deuteron Avakian, PRD78 Covariant model arXiv: 0812.3246 PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 39

  39. Number Helicity Worm gear (the standard OAM effect) Proton wave-components with different OAM Boer-Mulders Density nucleon polarisation Worm-gear The only T-even and chirally-even off-diagonal TMD Transversity Sivers Worm-gear Pretzelosity

  40. The AUL Asymmetry Proton arXiv: 1007.1562 Unexpected pattern needs more statistics to be verified arXiv: 0902.0689 Deuteron arXiv: 1003.4549 COMPASS PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 41

  41. The ALT Asymmetry HERMES p COMPASS p Worm-gear function: longitudinally polarized quarks in a transversely polarized nucleon Statistics not enough to investigate relations supported by many theoretical models: (supported by Lattice QCD and first data) (Wandura-Wilczek type approximation) Jlab Hall-A n From constituent quark model: arXiv: 0903.1271 PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 42

  42. Higher-twist effects Non zero up to the COMPASS energies PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 43