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## Contalbrigo Marco INFN Ferrara

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**Overview of**TmDMeasurements Contalbrigo Marco INFN Ferrara Partons in Nucleons and Nuclei September 30, 2011 Marrakech**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**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**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**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**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**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**Number**Helicity Number Density & Helicity (TheBaseline) Boer-Mulders Density nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity**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**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**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**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**Number**Helicity Transversity (the Collinear Missing piece) Chirally-odd Boer-Mulders Density First evidence: 2005 nucleon polarisation Worm-gear Transversity Sivers Worm-gear Pretzelosity + - + -**The Collins fragmentation**Correlation between quark polarization and observed hadron transverse momentum PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 14**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**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**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**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**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**Transversity signals**No significant asymmetries seen in pp reactions at mid-rapidity. PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 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 + + + -**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**The Sivers signals**HERMES vs COMPASS comparison: are data consistent ? New ! HERMES COMPASS PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 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**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**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**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**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**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**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**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**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**The TMDs Landascape**A very active field to explore for various upcoming experiments ! PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 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**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**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**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**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**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**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**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**Higher-twist effects**Non zero up to the COMPASS energies PANIN 11, 30th September 2011, Marrakech Contalbrigo M. 43