--- New Results from HERMES --- The Spin of the Nucleon --- New Results from HERMES --- E.C. Aschenauer DIS-06 - Tsukuba April 2006

News on the spin structure of the nucleon Naïve parton model BUT 1989 EMC measured S = 0.120 0.094 0.138 ± Spin Puzzle Unpolarised structure fct. Gluons are important ! Sea quarks Dqs DG Full description of Jq and Jg needs orbital angular momentum E.C. Aschenauer DIS-06 - Tsukuba April 2006

Polarised quark distributions Correlation between detected hadron and struck qf “Flavor – Separation” Inclusive DIS: Semi-inclusive DIS: In LO-QCD: MC Extract Dq by solving: E.C. Aschenauer DIS-06 - Tsukuba April 2006

Polarized Quark Densities First complete separation of pol. PDFs without assumption on sea polarization Du(x) > 0 Dd(x) < 0 Polarised opposite to proton spin Polarised parallel to proton spin good agreement with NLO-QCD Du(x), Dd(x) ~ 0 No indication for Ds(x) < 0 In measured range (0.023 – 0.6) E.C. Aschenauer DIS-06 - Tsukuba April 2006

NLO FIT to inclusive and semi-inclusive Data D. De Florian et al. hep-ph/0504155 Sidis-data improve description of all Dq’s; crucial for light sea FF very crucial : Kretzer favors SU(3) flavor symmetric sea; KKP broken one E.C. Aschenauer DIS-06 - Tsukuba April 2006

Results for DQ and DS Inclusive Asymmetry Kaon Asymmetry Need a longitudinal polarized deuterium target strange quark sea in proton and neutron identical fragmentation simplifies All needed information can be extracted from HERMES data alone inclusive A1,d(x,Q2)and kaon AK1,d (x,Q2) double spin asym. Kaon multiplicities Only assumptions used: isospin symmetry between proton and neutron charge-conjugation invariance in fragmentation Fit x-dependence of multiplicities using PDFs from CTEQ-6 This Work Kretzer KKP 0.379±0.002±0.009 1.103 1.111 1.722±0.024±0.108 0.783 0.296 E.C. Aschenauer DIS-06 - Tsukuba April 2006

Results for DQ and DS Earlier HERMES conclusions of unpolarised strange sea confirmed factor 2 smaller error bars Errors very sensitive to FF input E.C. Aschenauer DIS-06 - Tsukuba April 2006

The 3rd Twist-2 structure function unpolarised quarks and nucleons q(x): spin averaged vector charge well known longitudinally polarized quarks and nucleons Dq(x): helicity difference  axial charge known transversely polarized quarks and nucleons dq(x): helicity flip  tensor charge measuring! E.C. Aschenauer DIS-06 - Tsukuba April 2006

Peculiarities of transversity relativistic nature of quark: in absence of relativistic effects h1(x)=g1(x) Q2 –evolution: unlike for g1p(x), the gluon doesn’t mix with quark inh1p(x) (no gluon analog for spin-½ nucleon) sensitive to the valence quark polarisation q and q have opposite sign. _ tensor charge: first moment of h1 (large from lattice QCD) chiral odd FF CHIRAL ODD NOT ALLOWED IN E.M. INTERACTIONS transversely polarized quarks and nucleons dq(x): helicity flip  tensor charge measuring ! double helicity flip single helicity flip E.C. Aschenauer DIS-06 - Tsukuba April 2006

Collins moments Collins moment: p+ > 0 p- < 0 [PRL94(2005),012002; hep-ex0507013] p- unexpected large role of unfavoured FF first data for Collins FF available from Belle extraction of h1 from Hermes asymmetries K+ > 0 K- > 0 K+ in agreement with p+ 2005 data: 2 dimensional binning disentangle x (PDF) and z (FF) dependence E.C. Aschenauer DIS-06 - Tsukuba April 2006

Azimuthal angles and asymmetries angle of hadron relative to final quark spin (Collins) (Collins) angle of hadron relative to initial quark spin (Sivers) (Sivers) chiral-even naïve T-odd DF related to parton orbital momentum violates naïve universality of PDF peculiarity of f^1T different sign of f^1T in DY E.C. Aschenauer DIS-06 - Tsukuba April 2006

Sivers moments sea quarks important Sivers moment: p+ > 0 p- ~ 0 [PRL94(2005),012002; hep-ex0507013] Sivers moment: p+ > 0 p- ~ 0 K+ > 0 K- ~ 0 K+ >= p+ sea quarks important non-zero orbital angular momentum in p-wave fct. Lq ?? opposite sign f1T^ in DIS and Drell-Yan 2005 data: FF known, extraction of Sivers function E.C. Aschenauer DIS-06 - Tsukuba April 2006

Study of hard exclusive processes leads to The Hunt for Lq Study of hard exclusive processes leads to a new class of PDFs Generalized Parton Distributions possible access to orbital angular momentum from DIS: HERMES ~0.3 exclusive: all products of the reaction are detected missing energy (DE) and missing Mass (Mx) = 0 E.C. Aschenauer DIS-06 - Tsukuba April 2006

GPDs Introduction AUT,sp+ AUT,sr,F,w AC,ALU, AUT, AUL What does GPDs charaterize? unpolarized polarized conserve nucleon helicity flip nucleon helicity not accessible in DIS DVCS quantum numbers of final state select different GPD pseudo-scaler mesons vector mesons AC,ALU, AUT, AUL AUT,sp+ AUT,sr,F,w E.C. Aschenauer DIS-06 - Tsukuba April 2006

DVCS DVCS two experimentally undistinguishable processes: HERMES kinematics: BH c.s. >> DVCS c.s. DVCS Bethe-Heitler (BH) p + D isolate BH-DVCS interference term non-zero azimuthal asymmetries transverse target spin asymmetry: E.C. Aschenauer DIS-06 - Tsukuba April 2006

DVCS-TTSA first model dependent extraction of Ju possible Code: VGG Jd assumed to be zero E.C. Aschenauer DIS-06 - Tsukuba April 2006

Can we constrain (Ju+Jd) same statistics with electron beam on tape independent data set to constrain (Ju+Jd) E.C. Aschenauer DIS-06 - Tsukuba April 2006

AUT - Exclusive r exclusivity ensured by DE background estimated by MC reconstruct r0 from h+h- Transverse Target Spin Asymmetry: 2005: factor 2 more statistics sL – sT separation AUT(F-Fs) sensitive to GPD E sensitivity to Ju E.C. Aschenauer DIS-06 - Tsukuba April 2006

Summary and And much more to come A lot of new results on the different components of the nucleon spin polarized quark distributions Transversity and Sivers Exclusive reactions: DVCS AUT (Ju+Jd) excl. r production AUT Ju And much more to come E.C. Aschenauer DIS-06 - Tsukuba April 2006

The end of polarized targets at HERMES DVCS exclusivity by missing mass Mx Improve Exclusivity Detect recoiling proton modify target region E.C. Aschenauer DIS-06 - Tsukuba April 2006

The HERMES Recoil Detector detection of the recoiling proton P: 135 – 1200 MeV/c 76% f acceptance p/p PID via dE/dx background suppression semi-incl.: 5 %® << 1% associated: 11% ® ~1% improved t-resolution study kinematical dependences data taking 2006/2007 Commissioning has started Build by DESY, Erlangen, Ferrara, Frascati, Gent, Giessen and Glasgow E.C. Aschenauer DIS-06 - Tsukuba April 2006

Transversity: L. Pappalardo Tu. 16.30 Spin is fascinating More from HERMES: Transversity: L. Pappalardo Tu. 16.30 DVCS: Z. Ye Fr. 11.10 SDME: B. Marianski Fr. 16.10 DS: M. Ehrenfried Sa. 11.30 L(1520): S. Wang Sa. 11.30 E.C. Aschenauer DIS-06 - Tsukuba April 2006

BACKUP SLIDES E.C. Aschenauer DIS-06 - Tsukuba April 2006

Purities E.C. Aschenauer DIS-06 - Tsukuba April 2006

Kaon Multiplicities E.C. Aschenauer DIS-06 - Tsukuba April 2006

VM-Contribution basically no VM contribution for Kaons E.C. Aschenauer DIS-06 - Tsukuba April 2006