Contalbrigo Marco INFN Ferrara Partons in Nucleons and Nuclei September 30, 2011 Marrakech

PDFs f p u (x),… TMD PDFs: f p u (x,k T ),… d2kTd2kT  =0,t=0 W p q (x,k T,r) “Mother” Wigner distributions d3rd3r d2kTd2kT Exclusive Measurements Momentum transfer to target Direct info about spatial distribution Semi-inclusive measurements Momentum transfer to quark Direct info about momentum distribution (FT) GPDs: H p u (x, ,t), … p T < 2 GeV/c √s = 20 GeV xFxF ANAN May solve proton spin puzzle May explain SSA & Lam-Tung Probability to find a quark q in a nucleon P with a certain polarization in a position r & momentum k 2 PANIN 11, 30 th September 2011, Marrakech Contalbrigo M.

N/q ULT U L T quark polarisatio n nucleon polarisation 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 Off-diagonal elements: Sivers Survives transverse momentum integration (missing leading-twist collinear piece) Differs from helicity due to relativistic effects and no mix with gluons in the spin-1/2 nucleon Transversity: Worm-gear 3 Contalbrigo M. Transversity PANIN 11, 30 th September 2011, Marrakech N/q ULT U L T quark polarisatio n nucleon polarisation Unpolarized Collins Boer-Mulders Worm-gear Pretzelosity Helicity Number T-odd elements: Strict prediction from TMDs + QCD ! sign change between DY and SIDIS universality of TMDs Number density and helicity: Focusing here in transverse momentum dependence Density

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

N/q ULT U L T quark polarisatio n nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear 5 Contalbrigo M. Transversity Pretzelosity SIDIS cross section (transversely polarized target): PANIN 11, 30 th September 2011, Marrakech

N/q ULT U L T quark polarisatio n nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear 6 Contalbrigo M. Transversity DFDF FF Pretzelosity SIDIS cross section (transversely pol. target): PANIN 11, 30 th September 2011, Marrakech Involved phenomenology due to the convolution over transverse momentum TMD factorization for P T <<Q

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

N/q ULT U L T nucleon polarisation Number Sivers Boer-Mulders Density Worm-gear Transversity Pretzelosity Helicity

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

Disentanglement of z and : access to the transverse intrinsic quark k T and fragmentation p T, i.e. from gaussian anstaz 10 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech T PhPh T PhPh 2 T PhPh 2 T PhPh 2 T PhPh arXiv: arXiv: Joosten, DIS 2011 Hall C - JLab

11 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Drell-Yan z ~ 0.5 SIDIS arXiv: arXiv: Is p T independent of z ? arXiv: Gaussian ansatz f1uf1u Indirect indication of a k T and p T broadening with c.m. energy: TMD Q 2 evolution f1uf1u New !

12 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Hint of different transverse momentum widths for helicity vs number density T PhPh arXiv: CLAS HERMES COMPASS arXiv:

N/q ULT U L T nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear Transversity Pretzelosity Chirally-odd First evidence: 2005

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

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

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

17 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Flavor separation with various targets and detected hadrons Puzzle in (low-statistics) kaon amplitudes: K + larger than  + K - controversial K-K- K+K+ Jlab Hall-A n COMPASS d COMPASS p HERMES p New !

xh 1 (x) 18 Contalbrigo M. First extraction of Transversity! Anselmino et al. Phys. Rev. D 75 (2007) -Existing data limited to x < 0.3 -Gaussian ansatz -Evolution from high energy colliders Soffer bound xh 1 (x) d u xh 1 (x, k ) T u T d PANIN 11, 30 th September 2011, Marrakech Tensor charge M. Anselmino et al hep-ph: M. Wakamatsu hep-ph:

19 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech NEW !! Issue with unknown pp-terms in partial wave expansion -Survives P h integration -Collinear factorization (simple product) -DGLAP volution -Universality New !

20 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Bacchetta et al., PRL 107 (11) 1 st collinear extraction ! NEW !! arXiv: q1q1 quark spin e+e+ q2q2 z2z2 z1z1 φ R1 φ R2 e-e- Different from zero correlations ! New !

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

N/q ULT U L T nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear Transversity Pretzelosity Naïve-T-odd Non-trivial gauge link Process dependence Naïve-T-odd Non-trivial gauge link Process dependence

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

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

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

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

27 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech  A UT is vanishing at low p T  Q 2 increases with p T approaching DIS regime  Study transition from perturbative to non-perturbative regime Non-zero signals for positive hadrons resembling Sivers Sivers modulation sin(  -  S ) can survives as sin(  )

N/q ULT U L T nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear Transversity Pretzelosity Naïve-T-odd Chirally-odd Spin effect in unpolarized reactions

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

EMC (1987) 30 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Kinematical effect redicted since 1978 by Cahn due to non-zero intrinsic k T Non perturbative contribution P T (GeV/c) No hadron identification No charge separation Poor statistics for cos2  Till 2008: qualitative agreement with Cahn expectations Leading-twist contribution introduced by Boer & Mulders in 1998 Boer & Mulders PRD 57 (1998) Cahn PLB 78 (1978)

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

32 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Significant difference in hadron charge might signal Much larger expectations but largely sensitive on and k T cutoff Large and negative increasing with z and P h arXiv:

33 Contalbrigo M. TMDs describe a new class of phenomena providing novel insights into the rich nuclear structure  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  Universality Fundamental test of QCD SIDIS and e + e - experiments provide evidence of non-zero TMDs First generation experiments provide promises but also open questions PANIN 11, 30 th September 2011, Marrakech

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

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

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

37 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Asymmetry expected to go As sin 2 (  )/(1+cos 2 (  )) At low thrust spherical events and gluon emission

N/q ULT U L T nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear Transversity Pretzelosity Sensitive to the D-wave component and the non spherical shape of the nucleon

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

N/q ULT U L T nucleon polarisation Number Helicity Sivers Boer-Mulders Density Worm-gear Transversity Pretzelosity Worm-gear The only T-even and chirally-even off-diagonal TMD Proton wave- components with different OAM

41 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Unexpected pattern needs more statistics to be verified arXiv: arXiv: COMPASS Deuteron Proton arXiv:

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

43 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech Non zero up to the COMPASS energies