Contalbrigo Marco INFN Ferrara Partons in Nucleons and

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

Quantum phase-space distributions of quarks Wpq(x, k. T, r) “Mother” Wigner distributions 2 d d 3 r Probability to find a quark q in a nucleon P with a certain polarization in a position r & momentum k k. T T) (F TMD PDFs: fpu(x, k. T), … Semi-inclusive measurements Momentum transfer to quark Direct info about momentum distribution May explain SSA & Lam-Tung AN √s = 20 Ge. V p. T< 2 Ge. V/c GPDs: Hpu(x, x, t), … d 2 k T 0 t, = 0 x= Exclusive Measurements Momentum transfer to target Direct info about spatial distribution PDFs fpu(x), … May solve proton spin puzzle x. F Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 2

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

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

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

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

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

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

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

The Ph -unintegrated multiplicities T Disentanglement of z and Ph : access to the transverse intrinsic quark k. T and fragmentation p. T, ar. Xiv: 1008. 5125 T i. e. from gaussian anstaz Ph 2 T T Contalbrigo M. Ph Ph 2 T Joosten, DIS 2011 PANIN 11, 30 th September 2011, Marrakech ar. Xiv: 0709. 3020 Ph 2 T Hall C - JLab 10

The evolution ar. Xiv: 1008. 5125 Is p. T independent of z ? Gaussian ansatz f 1 u New ! ar. Xiv: 1101. 5057 ar. Xiv: 1003. 2190 Drell-Yan SIDIS z ~ 0. 5 Indirect indication of a k. T and p. T broadening with c. m. energy: TMD Q 2 evolution Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 11

The ALL Asymmetry ar. Xiv: 1007. 1562 COMPASS CLAS HERMES T Ph ar. Xiv: 1003. 4549 Hint of different transverse momentum widths for helicity vs number density Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 12

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

The Collins fragmentation Correlation between quark polarization and observed hadron transverse momentum Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 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 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 15

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

Transversity signals Tensor charge M. Wakamatsu hep-ph: 0811. 4196 xhu 1(x, k ) - xhd 1(x, k ) T xhd 1(x) Soffer bound Existing data limited to x < 0. 3 Gaussian ansatz Evolution from high energy colliders xh 1(x) T xhu 1(x) First extraction of Transversity! M. Anselmino et al hep-ph: 0812. 4366 Anselmino et al. Phys. Rev. D 75 (2007) Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 18

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

Transversity signals Different from zero correlations ! e- φR 2 z 2 quark spin 1 st collinear extraction ! q 1 e+ quark spin φR 1 z 1 NEW !! New ! ar. Xiv: 1104. 2425 Bacchetta et al. , PRL 107 (11) Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 20

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

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

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

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

The Sivers challenges Coverage at large p. T and relation with twist-3 collinear approach ar. Xiv: 1107. 4446 x Sivers effect from SIDIS to Drell-Yan: Sivers effect from SIDIS to pp: Sign change as a crucial test of TMDs factorization A possible candidate to explain SSA ar. Xiv: 0901. 3078 Sivers from SIDIS and collinear twist-3 as candidates for SSA explanation ar. Xiv: 0801. 2990 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 25

The inclusive hadron SSA Persistent with energy ANL s=4. 9 Ge. V BNL s=6. 6 Ge. V s=6. 6 FNAL s=19. 4 Ge. V RHIC s=62. 4 Ge. V Sivers effect from SIDIS to pp: ar. Xiv: 0801. 2990 Sign mismatch between SIDIS and pp SSA ? ar. Xiv: 1103. 1591 T 3 correlator from pp Contalbrigo M. Asymptotic 1/p. T not reached Issues on factorization New ! Sivers moment from SIDIS PANIN 11, 30 th September 2011, Marrakech 26

Inclusive hadron SSA in SIDIS Sivers modulation sin(f-f. S) can survives as sin(f) AUT 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 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 27

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

The Lam-Tung relation Preserved by NLO and resummation Analogous of SIDIS Callan-Gross E 615 (pp) NA 10 (pp) 194 Ge. V 140 Ge. V 286 Ge. V p. T (Ge. V) Boer-Mulders offers a possible explanation E 615 E 866 (pp, p. D) NA 10 E 866 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 29

The azimuthal modulation Kinematical effect redicted since 1978 by Cahn due to non-zero intrinsic k. T Cahn PLB 78 (1978) Leading-twist contribution introduced by Boer & Mulders in 1998 Boer & Mulders PRD 57 (1998) Non perturbative contribution PT (Ge. V/c) Till 2008: qualitative agreement with Cahn expectations • No hadron identification • No charge separation • Poor statistics for cos 2 f EMC (1987) Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 30

The SIDIS cos 2 f dependence Non-zero ! Issue on DATA consistency ar. Xiv: 0912. 5194 Can be explained by large uncertainty on Cahn and neglected HT effects Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 31

The SIDIS cosf dependence Significant difference in hadron charge might signal Large and negative increasing with z and Ph Much larger expectations but largely sensitive on <k. T> and k. T cutoff ar. Xiv: 1106. 6177 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 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 Ø Full coverage of valence region not achieved Ø Limited knowledge on transverse momentum dependences Ø Role of the higher twist to be quantified Ø Evolution properties to be defined Ø Flavor decomposition to be refined Ø Universality Contalbrigo M. Fundamental test of QCD PANIN 11, 30 th September 2011, Marrakech 33

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

The 3 D description of the nucleon Distribution Functions (DF) BOER-MULDERS Spin orbit effect ┴ ┴ ct a p Im ┴ s e ┴ ┴ r te ce a p GPD E am r a p Deformations by ~ GPD ET+2 HT SIVERS Quark orbital angular momentum a m u nt e m om 3 - sp green quark ce anti-green remnant i. e. Sivers: spin-orbit correlations with same matrix element of anomalus magnetic moment, and GPD E Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 35

The hadron multiplicities Seek for flavor dependences Nuclear effects should be taken into account for not pure targets Hermes, ar. Xiv: 1107. 3496 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 36

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

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

The Pretzelosity HERMES p COMPASS p Statistical power of existing data is not enough to observe significant signals h+ deuteron h- deuteron Positivity bound Avakian, PRD 78 Covariant model ar. Xiv: 0812. 3246 Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech 39

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

The AUL Asymmetry Proton ar. Xiv: 1007. 1562 Deuteron Unexpected pattern needs more statistics to be verified ar. Xiv: 0902. 0689 COMPASS Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech ar. Xiv: 1003. 4549 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: Contalbrigo M. PANIN 11, 30 th September 2011, Marrakech ar. Xiv: 0903. 1271 42

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