HERMES in 2002

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HERMES in 2002
The origin of proton spin

• Gerard van der Steenhoven, Dec. 02

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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.
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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
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HERMES data taking in 02
Goal for March 2003 1.3 Million DIS events
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Polarization at HERA
35 e-polarization observed
H.P. Blok, P. van der Nat, B. Zihlmann
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The HERMES spectrometer
TRD Calo
RICH
Magnet
Target area
e BEAM
Beam Loss Monitor
Lambda Wheels
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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
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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
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Lambda Wheels results II
Hits with Eloss gt 6 MIP in LW at z 45 cm
Broken bond
Lambda Wheels are operational!
J.J.M. Steijger
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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
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Integrated dose from BLM
Maximum dose HELIX gt 200 krad ? Lambda Wheels ok
M. Demey
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Physics Results 4 PhDs

• 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!)
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Higher twist effects
? No evidence for higher twist at low Q2
J. Visser
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Gottfried Sumrule
Isospin asymmetry of the sea is Q2-independent!
J. Visser
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Flavour decomposition I

• Sea quarks unpolarized
• for strange sea?

M.C. Simani
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Flavour decomposition II

• First data on
• Data ? zero
• Calculations
• Instantons (?QSM)
• Gas of massless quarks

(Goeke)
M.C. Simani
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f0(980) Scalar Meson

• f0(980) structure
• Glue ball (comp.)

f0(980)

• No strong A-dependence
• Q2 and Pt2 dep.

E. Garutti
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LC photoproduction I
Charm photoproduction

• First observation of LC near threshold

D. Heesbeen
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LC photoproduction II

• Spin-dependent LC production
• Partial LC rec.

D. Heesbeen
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Outlook

• What to expect in 0304
• Lambda Wheel data
• Transversity data
• Beyond 2004
• Recoil Detector (GPDs)
• Orbital angular momentum
• . Spin physics _at_ 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