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HERMES in 2002

HERMES in 2002. Gerard van der Steenhoven, Dec. ‘02. The origin of proton spin. HERMES run II (2002-2006). Transversity: Spin structure of the nucleon without gluons: Generalized Parton Distributions: Orbital angular momentum Parton correlations. Transverse magnetic field

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HERMES in 2002

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  1. HERMES in 2002 Gerard van der Steenhoven, Dec. ‘02 The origin of proton spin

  2. HERMES run II (2002-2006) • Transversity: • Spin structure of the nucleon without gluons: • Generalized Parton Distributions: • Orbital angular momentum • Parton correlations Transverse magnetic field orienting the spin of the target protons in a direction perpendicular to the e+-beam.

  3. Spin Physics: Transversity ½ = ½ Sq + DG + Lq • The origin of spin: • Three leading order distributions: momentum carried by quarks longitudinal quark spin, DS lattice QCD:DS= 0.18 (10) transverse quark spin, dS lattice QCD:dS= 0.56 (9) [“Traffic Lights” – P.J. Mulders]

  4. HERMES data taking in ‘02 Goal for March 2003: 1.3 Million DIS events

  5. Polarization at HERA 35% e+-polarization observed H.P. Blok, P. van der Nat, B. Zihlmann

  6. ~1.5m The HERMES spectrometer TRD + Calo RICH Magnet Target area e+BEAM Beam Loss Monitor Lambda Wheels

  7. Lambda Wheels • Physics: •  spin structure • Transverse spin • Operations: • Commissioned • Interference with transverse field  Shut down ’03: new capacitive couplings M. van Beuzekom, V. Mexner, A.J. Reischl, J.J.M. Steijger

  8. Lambda Wheels results I Energy loss in ohmic () and junction (j) side of one counter Bethe Bloch Energy loss in two counters of one LW silicon module Single Si-strip ADC overflow J.J.M. Steijger

  9. Normal HERMES detector acceptance Lambda Wheels results II Hits with Eloss > 6 MIP in LW at z = 45 cm Broken bond Lambda Wheels are operational! J.J.M. Steijger

  10. Beam Loss Monitor • Purpose: • Generate trigger in case of excessive beam losses • Trigger to HERA kicker • Monitor radiation • Custom built • Operational since Febr ‘02 e+ M. van Beuzekom, V. Mexner, A.J. Reischl, J.J.M. Steijger

  11. Integrated dose from BLM Maximum dose HELIX > 200 krad  Lambda Wheels ok M. Demey

  12. Physics Results: 4 PhD’s • Higher twist effects in DIS on 1,2H – J. Visser • Flavour decomposition of nucleon spin – M.C Simani • Semi-inclusive DIS off 84Kr – E. Garutti* • Hyperon and C+ photo-production – D. Heesbeen *next talk: first evidence for (QCD prediction!)

  13. Higher twist effects  No evidence for higher twist at low Q2 J. Visser

  14. Gottfried Sumrule Isospin asymmetry of the sea is Q2-independent! J. Visser

  15. Flavour decomposition I • Sea quarks: unpolarized • for strange sea? M.C. Simani

  16. Flavour decomposition II • First data on: • Data  zero • Calculations: • Instantons (QSM): • Gas of massless quarks: (Goeke) M.C. Simani

  17. f0(980)Scalar Meson • f0(980)structure: • Glue ball (comp.) f0(980) • No strong A-dependence: • Q2 and Pt2 dep.: E. Garutti

  18. LC+photoproduction I Charm photoproduction • First observation of LC+ near threshold: D. Heesbeen

  19. LC+photoproduction II • Spin-dependent LC+ production: • Partial LC+ rec.: D. Heesbeen

  20. Outlook • What to expect in 03+04: • Lambda Wheel data • Transversity data • Beyond 2004: • Recoil Detector (GPDs) • Orbital angular momentum • …. Spin physics @ STAR? The cast: Henk Blok, Erika Garutti Michiel Demey, David Heesbeen Willem Hesselink, Louk Lapikas Armen Laziev, Vanessa Mexner Paul van der Nat, Andreas Reischl Chiara Simani, Jos Steijger Gerard van der Steenhoven Jan Visser Gabriel Ybeles Smit Beni Zihlmann

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