1 60th-PRC – DESY NOV E.C. Aschenauer News from HERMES since May 2005

2 60th-PRC – DESY NOV E.C. Aschenauer HERMES data taking Very efficient data taking in 2005 Data taking: efficiency > 98 % Spectrometer: in excellent shape Transverse polarized target: |P T | ~ 0.85 molecular frac. < 4% Main worry: P B =+1 ~ 0.4 – 0.5 P B =-1 ~ Data taking: efficiency > 98 % Spectrometer: in excellent shape Transverse polarized target: |P T | ~ 0.85 molecular frac. < 4%

3 60th-PRC – DESY NOV E.C. Aschenauer News on the spin structure of the nucleon Naïve parton model BUT 1989 EMC measured  = ± ± Spin Puzzle Unpolarised structure fct. Gluons are important ! Sea quarks  q s GGGG Full description of J q and J g needs orbital angular momentum

4 60th-PRC – DESY NOV E.C. Aschenauer Polarised quark distributions Correlation between detected hadron and struck q f “Flavor – Separation” “Flavor – Separation” Inclusive DIS: Semi-inclusive DIS: Extract  q by solving: In LO-QCD: MC

5 60th-PRC – DESY NOV E.C. Aschenauer Polarized Quark Densities  u(x) > 0 First complete separation of pol. PDFs without assumption on sea polarization Polarised parallel to proton spin good agreement with NLO-QCD  d(x) < 0 Polarised opposite to proton spin  u(x),  d(x) ~ 0 No indication for< 0 No indication for  s(x) < 0 In measured range (0.023 – 0.6)

6 60th-PRC – DESY NOV E.C. Aschenauer Results for  Q and  S Inclusive Asymmetry Kaon Asymmetry Fit x-dependence of multiplicities using PDFs from CTEQ-6 This Work Kretzer KKP This Work Kretzer KKP 1.20±0.06± ±0.36± Need a longitudinal polarized deuterium target strange quark sea in proton and neutron identical strange quark sea in proton and neutron identical fragmentation simplifies fragmentation simplifies All needed information can be extracted from data inclusive A 1,d (x,Q 2 )and kaon A K 1,d (x,Q 2 ) double spin asym. inclusive A 1,d (x,Q 2 )and kaon A K 1,d (x,Q 2 ) double spin asym. Kaon fragmentation functions Kaon fragmentation functions 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

7 60th-PRC – DESY NOV E.C. Aschenauer Results for  Q and  S Direct measurement of a 8 =  Q – 2  S = ± (0.02<x<1) SU(3) value: a8 = ± 0.033(0.12) Earlier HERMES conclusions of unpolarised strange sea confirmed factor 2 smaller error bars factor 2 smaller error bars

8 60th-PRC – DESY NOV E.C. Aschenauer The Hunt for L q Study of hard exclusive processes leads to a new class of PDFs Generalized Parton Distributions possible access to orbital angular momentum exclusive: all products of the reaction are detected missing energy (  E) and missing Mass (M x ) = 0 missing energy (  E) and missing Mass (M x ) = 0 from DIS: HERMES ~0.3

9 60th-PRC – DESY NOV E.C. Aschenauer GPDs Introduction What does GPDs charaterize? unpolarized polarized conserve nucleon helicity flip nucleon helicity not accessible in DIS DVCSDVCSDVCSDVCS quantum numbers of final state select different GPD pseudo-scaler mesons vector mesons A C,A LU, A UT, A UL A UT,   + A UT,  

10 60th-PRC – DESY NOV E.C. Aschenauer DVCS two experimentally undistinguishable processes: DVCS Bethe-Heitler (BH) p +  HERMES kinematics: BH c.s. >> DVCS c.s. isolate BH-DVCS interference term non-zero azimuthal asymmetries transverse target spin asymmetry:

11 60th-PRC – DESY NOV E.C. Aschenauer DVCS-TTSA first model dependent extraction of J u possible factor 2 more data on tape

12 60th-PRC – DESY NOV E.C. Aschenauer longitudinally polarized quarks and nucleons  q(x): helicity difference   axial charge known unpolarised quarks and nucleons q(x): spin averaged  vector charge well known transversely polarized quarks and nucleons  q(x): helicity flip  tensor charge measuring! The 3 rd Twist-2 structure function

13 60th-PRC – DESY NOV E.C. Aschenauer transversely polarized quarks and nucleons  q(x): helicity flip  tensor charge measuring ! single helicity flip CHIRAL ODD NOT ALLOWED IN E.M. INTERACTIONS Peculiarities of transversity chiral odd FF double helicity flip relativistic nature of quark: in absence of relativistic effects h 1 (x)=g 1 (x) Q 2 –evolution: unlike for g 1 p (x), the gluon doesn’t mix with quark inh 1 p (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 h 1 (large from lattice QCD) angular momentum sum rule for transversity

14 60th-PRC – DESY NOV E.C. Aschenauer [PRL94(2005),012002; hep-ex ] Transverse single spin asymmetry Collins moment:  + > 0  - 0  - < 0  - unexpected large role of unfavoured FF role of unfavoured FF first data for Collins FF available from Belle extraction of h 1 from extraction of h 1 from Hermes asymmetries Hermes asymmetries 2005 data: 2 dimensional binning 2 dimensional binning disentangle x (PDF) and z (FF) dependence Soon results for Kaons &  0

15 60th-PRC – DESY NOV E.C. Aschenauer The end of polarized targets at HERMES DVCS exclusivity by missing mass M x Improve Exclusivity Detect recoiling proton modify target region Detector to measure recoiling proton

16 60th-PRC – DESY NOV E.C. Aschenauer The HERMES Recoil Detector Build by DESY, Erlangen, Ferrara, Frascati, Gent, Giessen and Glasgow detection of the recoiling proton detection of the recoiling proton P: 135 – 1200 MeV/c 76%  acceptance  /p PID via dE/dx background suppression background suppression semi-incl.: 5 %  associated: 11%  improved t-resolution improved t-resolution study kinematical dependences data taking 2006/2007 data taking 2006/2007

17 60th-PRC – DESY NOV E.C. Aschenauer Status of the recoil detector Detector completely assembled for cosmic data taking since March 05 In total 100 Million cosmic events ( ) calibration SCIFI and photon detector all fibers/strips calibration per module for Silicion Test of complete read out under realistic conditions Different sub-detectors Photon-detector: extremely stable over the whole period improved amplifier range to avoid fast aging of PMTs SCIFI-detector: GMS installed and working at 1PE (good gain monitoring) found and corrected some design flaws in readout backplanes Silicon-detector Solved several problems with common mode noise for MIPs (remember dynamic range: MIP) S/N MIP: 4-5 DVCS-p: S/N MIP: 4-5 DVCS-p: Very important exercise to remove big problems smooth detector performance in 06/07 smooth detector performance in 06/07

18 60th-PRC – DESY NOV E.C. Aschenauer First Results on detector performance Detector Residuals: Magnet is off – straight line as a track model Need fine tuning of alignment parameters like: use information from alignment test run for Scifi-detector accuracy:  = 80  m still ongoing effort to align all sub-detectors to each other SiliconSCIFI  meas = strips /  calc = strips Layer-efficiency: ~80%  meas = mm /  calc = mm Layer-efficiency: 85%-88.0% Module-efficency: ~98%

19 60th-PRC – DESY NOV E.C. Aschenauer Summary and Very successful data taking in 2005 doubled statistics of with transverse polarized hydrogen target end-of-fill running with unpolarised targets 7.2 M D 2 doubled statistics from  + paper 2.0 M Krypton and Xenon for hadron attenuation A lot of new exciting results and always more to come  S from isoscalar method DVCS-TTSA -----> J u Transversity and Sivers Ready to install recoil detector in upcoming shutdown Finalize last analysis on HERA-I data G1 and the corresponding QCD-fit DVCS data from pre-recoil detector phase Fragmentation functions Analysis of HERA-II data in full swing already first publications Running till 2007: Hermes would like to stick to plan switching back to e+ in the middle of the remaining period. need charged balanced data sets with high lumi and polarization to make recoil detector running a success