JPARC DY Workshop, April 7 Ralf Seidl (RBRC) R.Seidl: Transverse Spin 1RIKEN, April 7 In JPARC Drell Yan accessible with: UU(unpolarized beam, unpolarized target) UT(unpolarized beam, transversely polarized target) TU (transversely polarized beam, unpolarized target) TT (transversely polarized beam, transversely polarized target)

Outline Introduction of TMDs and Transversity Boer-Mulders Function Existing DY results COMPASS, RHIC(?), FAIR(??) Sivers Function SIDIS results and global analysis Current inclusive RHIC SSAs, future DY, COMPASS, FAIR(??) Transversity SIDIS results, global analysis Comparison to Lattice predictions  Evolution of Collins FF(?) other measurements at RHIC(Collins, IFF), SIDIS (IFF,  ) R.Seidl: Transverse Spin RIKEN, April 72 In DY: UU In DY: TU or UT In DY: TT

Unpol. DF Helicity Transversity Transversity and friends Sivers function Boer-Mulders function q(x)  q(x)  q(x) R.Seidl: Transverse Spin 3RIKEN, April 7

Boer Mulders measurements Lam Tung relation:  in leading order term should be zero Experiments see large cos  asymmetries in  +nuclear Drell Yan possible explanations  vacuum polarization (Nachtmann, Brandenburg)  Boer Mulders function: R.Seidl: Transverse Spin RIKEN, April 74 In DY: UU

Boer Mulders E866 sees vanishing asymmetries on p+d DY R.Seidl: Transverse Spin RIKEN, April 7 5 In DY: UU

Is it the isoscalar target? Or maybe the valence like antiquark in  Models and Lattice suggest, that u and d Boer Mulders function have similar sign Unless the sea has opposite signs for  u and  d then this cannot explain smallness However valence Boer mulders function in pion could Gluon radiative effect becomes dominant at higher Q T Does that effect behave differently? R.Seidl: Transverse Spin RIKEN, April 7 6 In DY: UU

Boer Mulders in SIDIS and future DY Difficult A UU Asymmetry which contains convolution of Boer- Mulders function and Collins fragmentation function Concurrent with Cahn- effect For unpolarized asymmety acceptance effects in non 2  detectors Analysis ongoing in HERMES, COMPASS and CLAS In DY: COMPASS  DY measurements (again large asymmetries?) PANDA (FAIR) : only one they can do, some day R.Seidl: Transverse Spin RIKEN, April 7 7 In DY: UU

RIKEN, April 7 8 Sivers function measurements I    asymmetries clearly positive First evidence of a nonzero TMD   K - asymmetries consistent with zero K + asymmetries 2.3 times larger than   hard to explain Consistent sign of Sivers functions as from M.Burkhardt’s chromodynamic lensing R.Seidl: Transverse Spin In DY: TU or UT

RIKEN, April 7 9 R.Seidl: Transverse Spin Sivers function measurements II Results for all 3 pion states consistent with isospin symmetry In DY: TU or UT

10 R.Seidl: Transverse Spin deuteron target transversely polarised charged hadrons (mostly pions) 2004: results from 2002 data PRL94(2005) confirmed by 2006: results from data NPB765(2007)31 Sivers asymmetry III asymmetries compatible with zero within the statistical errors (systematic errors much smaller) RIKEN, April 7 In DY: TU or UT

RIKEN, April 7 11 R.Seidl: Transverse Spin Sivers measurements IV Again, data for identified hadrons In DY: TU or UT

RIKEN, April 7 12 R.Seidl: Transverse Spin Sivers global analysis Simultaneous fit of HERMES (02-04) and COMPASS (03-04) data on charged pions u and d Sivers functions of nearly equal size and opposite sign Vogelsang, Yuan Anselmino et al Collins et al Anselmino et al Also available: Efremov,Goeke, Schweitzer In DY: TU or UT

measurements in the near future COMPASS proton target Important test of the HERMES results in the overlap region JLAB 6 and 12 GeV Low energies and multiplicities R.Seidl: Transverse Spin RIKEN, April 7 13 COMPASS, arXiv: In DY: TU or UT

Improvements in theoretical understanding will allow RHIC A N to be used Fitting HERMES and COMPASS Sivers data, Take Collins contribution into account and Calculate phases to describe RHIC A N results Pion asymmetries fairly well described At least same sign for both K asymmetries as in data Theoretical interpretations not yet consistent  F.Yuan (Phys.Rev.Lett. 100:032003,2008. ) R.Seidl: Transverse Spin RIKEN, April 7 14 Boglione, D’Alesia, Murgia e-Print: arXiv: [hep-ph] STAR asymmetries: Brahms asymmetries (200GeV): In DY: TU or UT

Sivers back-to-back jet measurements R.Seidl: Transverse Spin RIKEN, April 7 15 Emphasizes (50%+ ) quark Sivers A N consistent with zero in central region Partial cancellation of SIDIS –like and DY –like contributions from Sivers function -VY 1, VY 2 are calculations by Vogelsang & Yuan, PRD 72 (2005) Bomhof et al PRD 75, (2007) STAR,PRL,99(2007) In DY: TU or UT

RIKEN, April 7 16 R.Seidl: Transverse Spin x Sivers Amplitude 0 Experiment SIDIS vs Drell Yan: Sivers| DIS = − Sivers| DY *** Test QCD Prediction of Non-Universality *** HERMES Sivers Results Markus Diefenthaler DIS Workshop Műnchen, April RHIC II Drell Yan Projections Feng Yuan Werner Vogelsang In DY: TU or UT

RIKEN, April 717R.Seidl: Transverse Spin Transversity properties Does not couple to gluons  different QCD evolution than  q(x) Valence dominated  Comparable to Lattice calculations, especially tensor charge: Test relativistic nature of quarks in the nucleon Positivity bound: Soffer bound: In DY: TT

RIKEN, April 7 18 R.Seidl: Transverse Spin How to access Transversity another chiral-odd function Drell Yan: Combine two Transversity distributions with each other SIDIS: Combine Transversity distributions with chiral-odd fragmentation function (FF) Total process is chiral- even: OK Possible Partners: Collins FF Interference FF Transverse L FF Most require single spin asymmetries in the fragmentation In DY: TT

RIKEN, April 7 19 R.Seidl: Transverse Spin First successful attempt at a global analysis for the transverse SIDIS and the BELLE Collins data HERMES A UT p data COMPASS A UT d data Belle e + e - Collins data Kretzer FF  First extraction of transversity (up to a sign) Anselmino et al: hep-ex Tensor charges obtained from this fit (from Alexei Prokudin) at Q 2 = 2.4 GeV 2 : In DY: TT

Current problems in the global transversity analysis Universaliy? Is the Collins function from e + e - the same in SIDIS, how about pp? According to Bacchetta et al. and Gamberg et al, yes Evolution? Is the evolution of transversity understood? Yes Is the evolution of the Collins function understood? Not really – is this the reason for low transversity in the global fit so far? Error treatment, first suggestions to start a CTEQ-like transversity global analysis group with contributors from Theory (Torino), COMPASS(Trieste),HERMES(Ferrara), Belle(Illinois, RBRC) R.Seidl: Transverse Spin RIKEN, April 720 In DY: TT

RIKEN, April 7 21 R.Seidl: Transverse Spin Collins measurements II K + asymmetries compatible with   asymmetries (through u quark dominance) K - asymmetries maybe slightly positive In DY: TT

Coming additions to global analysis R.Seidl: Transverse Spin RIKEN, April 722 Very important Test: COMPASS proton data- Will it be consistent in the overlap with HERMES? Will they be different arXiv: COMPASS full d data set, Charged , K and K S In DY: TT

Further additions Belle 547 fb -1 data set JLAB 6 and 12 GeV Low energies and multiplicities Higher twist an issue? R.Seidl: Transverse Spin RIKEN, April 723 In DY: TT

Other channels: IFF,  polarization HERMES,COMPASS, pp, BELLE R.Seidl: Transverse Spin RIKEN, April 724

RIKEN, April 7 25 R.Seidl: Transverse Spin DY transversity measurements at RHIC, JPARC and FAIR DY transverse double spin asymmetries golden channel to Transversity: Requires both (anti)- protons transversely polarized For mostly sensitive to u- quark transversity For pp smaller asymmetries due to sea transversity, but for tensor charge absolutely necessary Q= 8GeV Q= 3GeV Q= 5GeV Q=15GeV √s=200GeV √s=10 GeV Kawamura et. al Nucl.Phys.B777: ,2007. Assuming Soffer bound In DY: TT

RIKEN, April 7 26 R.Seidl: Transverse Spin Transversity access over DY in single spin asymmetries Instead of double spin asymmetries measure single spin asymmetries Advantage: only one proton polarized  better FOM at RHIC, earlier feasible at JPARC and GSI Disadvantage: first have to measure Boer-Mulders function with good precision Also planned at COMPASS with pion beam Q=2GeV Q=3GeV Q=4GeV Q=6GeV GSI ( collider option √s=15 GeV Kawamura et. al Nucl.Phys.B777: ,2007. Theory for A TT fairly well understood even at very low scales, if there will be PAX, it will measure mostly  u 2 – until then already relatively well known  only consistency test Transversity over p  p DY in double spin asymmetries In DY: TT

Summary Boer Mulders function: not at all well defined, hopefully some improvements until JPARC DY, but not much Important JPARC DY measurement even w/o polarization (UU) Sivers function: Fairly well known from SIDIS, but at low scales Inclusion of pp asymmetries possible, soon? Universality test will be absolutely crucial, then sea Sivers functions measurements (UT) Transversity: First global analysis available, errors still huge, evolution of Collins function? New accesses over IFF,  polarimetry soon Clean experiment, sensitive to sea transversity in (TT) R.Seidl: Transverse Spin RIKEN, April 727

Backup slides R.Seidl: Transverse Spin RIKEN, April 728

RIKEN, April 7 29 R.Seidl: Transverse Spin Transversity In helicity basis: helicity distribution and momentum difference and sum of diagonal amplitudes Transversity contains helicity flip and is not diagonal Helicity is conserved quantity for (nearly) massless quarks All interactions conserve helicity/chirality  Transversity cannot be observed in DIS

RIKEN, April 7 30 R.Seidl: Transverse Spin  q(x),  G(x) Difference of quarks with parallel and antiparallel polarization relative to longitudinally polarized proton (known from fixed target (SI)DIS experiments) q(x),G(x) Sum of quarks with parallel and antiparallel polarization relative to proton spin (well known from Collider DIS experiments)  q(x) Quark distributions in spin bases Difference of quarks with parallel and antiparallel polarization relative to transversely polarized proton (first results from HERMES and COMPASS – with the help of Belle) Unpolarized distribution function q(x) Helicity distribution function  q(x) Transversity distribution function  q(x)