1 DIS - Madrid, April 2009 E.C. Aschenauer The Quest for the spin of the proton ! or You think you understand something? Now add spin - R. Jaffe Nobel Prize, 1943: "for his contribution to the development of the molecular ray method and his discovery of the magnetic moment of the proton" p = 2.5 nuclear magnetons, 10% (1933) Otto Stern Proton spins are used to image the structure and function of the human body using the technique of magnetic resonance imaging. Paul C. Lauterbur Sir Peter Mansfield Nobel Prize, 2003: "for their discoveries concerning magnetic resonance imaging" The Spin of the Proton E.C. Aschenauer 2 DIS - Madrid, April 2009 How do the partons contribute 3 DIS - Madrid, April 2009 E.C. Aschenauer qqqqqqqq GGGG LgLgLgLg qLqqLqqLqqLq qqqq qqqqqqqq GGGG LgLgLgLg qLqqLqqLqqLq qqqq Is the proton looking like this? Helicity sum rule total u+d+s quark spin angular momentum gluon spin Where do we stand solving the spin puzzle ? q & G contributions to the proton spin E.C. Aschenauer 4 DIS - Madrid, April 2009 **** u,d, s,g polarized DIS q q, G **** u,d,s ,K polarized SIDIS q f polarized pp scattering q f, G u,d,s, g ,K jet Existing data from: to extract polarized PDFs ! a global QCD analysis is required ! all processes tied together: universality of pdfs & Q 2 evolution each reaction provides insights into different aspects and kinematics in NLO DSSV PRL101:072001,2008 Inclusive World data 5 DIS - Madrid, April 2009 E.C. Aschenauer new : input to the old GRSV-analysis : input to the DIS & SIDIS analysis by DNS Inclusive DIS-Data: Semi-Inclusive World Data 6 DIS - Madrid, April 2009 E.C. Aschenauer not in DNS Semi-inclusive DIS-Data: 7 DIS - Madrid, April 2009 E.C. Aschenauer includes all world data from DIS, SIDIS and pp includes all world data from DIS, SIDIS and pp Kretzer FF favor SU(3) symmetric sea, not so for KKP, DSS ~25-30% in all cases D. De Florian et al. arXiv: Q 2 =10 GeV 2 NLO FIT to World Data Kretzer KKP DIS SIDIS uvuv uu dvdv dd ss gg DSSV Polarized Strangeness 8 DIS - Madrid, April 2009 E.C. Aschenauer Driven by SIDIS K-Asymmetries K-FF dominated by Driven by SU(3); (3F-D) New Results from isoscaler method A K++K- & A incl Purity Method using FF Results are completely consistent with Hermes sea quark polarizations ~ 0 9 DIS - Madrid, April 2009 E.C. Aschenauer More on Strangeness PDF Kaon multiplicities from Deuterium target Kaon multiplicities from Deuterium target strange quark sea in proton and neutron identical strange quark sea in proton and neutron identical fragmentation simplifies fragmentation simplifies Only assumptions used: Only assumptions used: isospin symmetry between proton and neutron isospin symmetry between proton and neutron charge-conjugation invariance in fragmentation charge-conjugation invariance in fragmentation Fit x-dependence of multiplicities using PDFs from CTEQ-6 dotted: CTEQ-6L & fit dotted: dashed:dashed: solid:S(x)= Q(x): CTEQ-6L & DSS solid:S(x)= s(x) + sbar(x) dashed-dotted:dashed-dotted: The Gluon Polarization 10 DIS - Madrid, April 2009 E.C. Aschenauer unpolarised cross sections nicely reproduced in NLO pQCD in NLO RHIC: many sub-processes with a dominant gluon contribution high-p T jet, pion, heavy quark, RHIC Data 11 DIS - Madrid, April 2009 E.C. Aschenauer STAR GRSV curves with cone radius 0.7 and < < jet data: PRL 100, (2008) 2005: PRD 76, : arXiv: 200 GeV The Gluon Polarization 12 DIS - Madrid, April 2009 E.C. Aschenauer x RHIC range 0.05 x 0.2 small-x x 0.05 large-x x 0.2 g(x) very small at medium x best fit has a node at x ~ 0.1 huge uncertainties at small x small-x behavior completely unconstrained g(x) small !? 13 DIS - Madrid, April 2009 E.C. Aschenauer Compass & Hermes: The golden channels for g Idea: Direct measurement of G Isolate the photon gluon fusion process detection of hadronic final states detection of hadronic final states charmed mesons charmed mesons high p T pairs of hadrons high p T pairs of hadrons single high p T hadrons single high p T hadrons hhhhhhhh hhhh less sub-processes contributing less sub-processes contributing more sub-processes contributing higher statistics higher statistics less sub-processes contributing less sub-processes contributing more sub-processes contributing higher statistics higher statistics Several possible contributions to the measured asymmetry MC needed to determine R and a LL q g q g qg Important at Q2> DVCS Deeply Virtual Compton Scattering DVCS two experimentally undistinguishable processes: DVCS Bethe-Heitler (BH) p + isolate BH-DVCS interference term non-zero azimuthal asymmetries most clean channel for interpretation in terms of GPDs I can measure DVCS cross section and I 19 DIS - Madrid, April 2009 E.C. Aschenauer HERMES: combined analysis of charge & polarization dependent data separation of interference term + DVCS 2 DVCS Beam Charge Asymmetry higher twist Beam Spin Asymmetry DVCS DVCS from & 20 DIS - Madrid, April 2009 E.C. Aschenauer Archiv: only some appetizers on existing data lets see what theory says Hermes BCA CLAS BSA Hall A different GPD parametrisations Results from Theory 21 DIS - Madrid, April 2009 E.C. Aschenauer contribution to nucleon spin m 2 GeV 2 LHPC Collab. hep-lat/ Lattice: K. Kumericki & D. Mueller arXiv: t=0 t=-0.3 First hints for a small J q L q More insights to the proton - TMDs 22 DIS - Madrid, April 2009 E.C. Aschenauer Unpolarized distribution function q(x), G(x) Helicity distribution function q(x), G(x) Transversity distribution function q(x) Correlation between and Sivers distribution function Boer-Mulders distribution function Explore spin orbit correlations peculiarities of f 1T chiral even nave T-odd DF related to parton orbital angular momentum violates nave universality of PDFs QCD-prediction: f 1T,DY = -f 1T,DIS Transverse Polarization RHIC 23 DIS - Madrid, April 2009 E.C. Aschenauer Left -Right Naive pQCD (in a collinear picture) predicts A N ~ m q /sqrt(s) ~ 0 However, large A N observed in forward pions / Kaons. Proposed mechanisms - Sivers - Collins - twist-3 process -... need correlations between particles ( jet) to disentangle underlying process Boer-Mulders 24 DIS - Madrid, April 2009 E.C. Aschenauer Unpol. SIDIS cross section: Boer-Mulders x Collins FF remember Collins FF: Boer-Mulders fct. for u and d quark seem to have same sign consistent with Fermi-lab DY-experiments E605++ K + > 0 K - ~ 0 K + > 0 K - ~ 0 K + > + K + > + importance of sea quarks? importance of sea quarks? Deuterium ~ 0 Deuterium ~ 0 u and d quark cancel u and d quark cancel 25 DIS - Madrid, April 2009 E.C. Aschenauer HERMES & COMPASS Measurements Proton Proton: Proton: Sivers moment: Sivers moment: + > 0 - ~ 0 hep-ex/ Deuterium Fit M. Anselmino et al. arXiv: Sivers function and OAM 26 DIS - Madrid, April 2009 E.C. Aschenauer Anselmino et al. arXiv: Model dependent statement: anomalous magnetic moment: u = 1.67 d = x M. Burkardt et al. Lattice: P. Haegler et al. lowest moment of distribution of unpol. q in transverse pol. proton and of transverse pol. quarks in unpol. proton Conclusions 27 DIS - Madrid, April 2009 E.C. Aschenauer many avenues for further important measurements and theoretical developments we have just explored the tip of the iceberg you are here L q,g ss gg u tot, d tot u, d spin sum rule Thank you for your attention & to everybody, who helped preparing the talk, especially Werner and Marco 28 DIS - Madrid, April 2009 E.C. Aschenauer BACKUP SLIDES 29 DIS - Madrid, April 2009 E.C. Aschenauer good agreement with NLO-QCD Polarised opposite to proton spin Polarized Quark Densities u(x) > 0 First complete separation of First complete separation of pol. PDFs without assumption on pol. PDFs without assumption on sea polarization sea polarization Polarised parallel to proton spin d(x) < 0 ~ 0 u(x), d(x) ~ 0 No indication for< 0 No indication for s(x) < 0 In measured range (0.023 0.6) In measured range (0.023 0.6) DSS: good global fit of all e + e -, ep, and pp hadron data 30 DIS - Madrid, April 2009 E.C. Aschenauer de Florian, Sassot, MS main results: results for , K , chg. hadrons full flavor separation for D i H (z) and D g H uncertainties (L.M.) well under control fits all LEP, HERMES, SMC, RHIC, data supersede old fits based only on e + e - data apart from cross-over trajectory ( x ) GPDs not directly accessible: deconvolution needed ! (model dependent) but only and t accessible experimentally x is mute variable (integrated over): GPD moments cannot be directly revealed, extrapolations t 0 are model dependent e.g. cross sections & beam-charge asymmetry ~ Re(T DVCS ) beam or target-spin asymmetries ~ Im(T DVCS ) accessing GPDs: some caveats t=0 q(x) =0 q(x) E.C. Aschenauer 31 DIS - Madrid, April 2009 detour: DSS kaon FFs D i K (z) 32 DIS - Madrid, April 2009 E.C. Aschenauer RHIC pp data (BRAHMS, STAR) explain different D g smaller u & larger s-frag. required by SIDIS note: some issues with K - data (slope! ) await eagerly final HERMES data 33 DIS - Madrid, April 2009 E.C. Aschenauer UT ~ sin Im{k(H - E) + } C ~ cos Re{ H + H + } ~ LU ~ sin Im{H + H + kE} ~ UL ~ sin Im{H + H + } ~ polarization observables: polarization observables: UT beam target kinematically suppressed H H H, E ~ different charges: e + e - different charges: e + e - H DVCS ASYMMETRIES = x B /(2-x B ),k = t/4M 2 34 DIS - Madrid, April 2009 E.C. Aschenauer [M. Burkardt, M. Diehl 2002] FT (GPD) : momentum space impact parameter space: probing partons with specified long. position b T polarized nucleon: [ =0] from lattice What does theory tell d-quark u-quark 35 DIS - Madrid, April 2009 E.C. Aschenauer Hermes: Charge and Beam Spin Asymmetry Heavy Targets Beam Charge Asymmetry Beam Spin Asymmetry Why nuclear DVCS: constrain nuclear GPDs constrain nuclear GPDs constrain models attempting constrain models attempting to describe nuclear matter to describe nuclear matter neutron and proton matter neutron and proton matter distribution in nuclei distribution in nuclei Beam: 27.5 GeV e ; % polarization Target: (un)-polarized gas targets; polarization Lumi: pol: 5x10 31 cm -2 /s -1 ; unpol: 3x cm -2 /s -1 Data taking finished June The contemporary experiments E.C. Aschenauer DIS - Madrid, April 2009 SM1 SM2 6 LiD Target 160 GeV RICH ECal & HCal Filter Trigger-hodoscopes Silicon Micromegas SciFi Gems Drift chambers Straws MWPC 50 m Beam: 160 GeV : 80% polarization Target: 6 LiD: 50% polarization ( ) NH 3 : 80% polarisation (2007) NH 3 : 80% polarisation (2007) Lumi: 5x10 32 cm -2 s -1 STAR Detector Beams: s=200 GeV pp; 50% polarization Lumi: 50 pb -1