Polarization Experiments at MAMI

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Polarization Experimentsat MAMI
Hans-Jürgen Arends Mainz University

• The 5th International Pion-Nucleon PWA Workshop
• and Interpretation of Baryon Resonances
• ECT, Trento, Italy
• June 1 5, 2009

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K.-H. Kaiser et al., NIM A 593 (2008) 159
In full operation since Feb. 2007
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Helicity structure of g N and GDH sum rule

• Proposed in 1966
• Prediction on the absorption of circularly
  polarized photons by longitudinally polarized
  nucleons

• Based on very general quantum mechanical
  principles (causality, optical theorem, gauge
  and Lorentz invariance)?

Anomalous magnetic moment of the nucleon
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In operation at MAMI from 1991 to 2003
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Polarised Photons _at_ MAMI C
Eg 75 ... 1475 MeV DEg 4 MeV Ng 105 s-1
MeV-1
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Helicity structure of g N and GDH sum rule
previous expts. from MAMI and ELSA
Proton
Deuteron
Phys. Lett. B 672(2009)328-332
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Helicity structure of g N and GDH sum rule
experiments from MAMI and ELSA
Proton
Deuteron
Phys. Lett. B 672(2009)328-332
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Helicity structure of g N and GDH sum rule
Proton
Deuteron
Phys. Lett. B 672(2009)328-332
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Helicity structure of g N and baryon resonances
on the proton

• Electric quadrupole component of the ND
  transition
• Helicity amplitudes of the D13(1520)
• Double pion production channels

• on the deuteron
• single pion production in the D region
• double pion production in the D13(1520) region

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Electric quadrupole component of N?D
HDT model (PWAdispersion)
E2/M1 -5
E2/M1 -2.5
E2/M1 0
Previous DAPHNE data (?)
EPJA 31, 323 (2004)
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Helicity structure of the D13(1520) resonance
(Different signs and interference terms)
T. Rostymian, PhD thesis (2005), PRC 74 (2006)
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• GDH data ( PRC 74, 2006)?

Unitarity cusp ( threshold of ??production)?
SAID (FA04K)?
MAID2003
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• GDH data
• PLB 551, 49 (2003)

• D13 plays a significant role
• (?p ?D13 ??N ? ? Npp?
• ? p D ? Npp)
• Nacher-Oset model NPA 695, 295 (2001)
• Fix- Arenhoevel model EPJA 25, 114 (2005)

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intermediate p D
FA Fix, Arenhövel, EPJ A 25 (2005)
115 Valencia Nacher, Oset, NP A 697 (2002) 372
Eur.Phys. J. A 34 (2007) 11
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Helicity dependent Total inclusive cross section
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Helicity dependent cross sections
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(on quasifree p)
???GDH Preliminary Fix Arenhoevel
EPJ A25 (2005) Levchuk et al.
PRC 74 (2006) GDH ? p -gt n ??
EPJA 26, 135 (05)
Preliminary
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(on quasifree n)
? GDH Preliminary Fix
-Arenhoevel Levchuk et
al.
Preliminary
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when
mainly quasi free processes on the proton
? GDH Preliminary Fix
-Arenhoevel Levchuk et
al.
discrepancy due to p0 on n or coherent production
?
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quasi free reaction on the neutron
D13 peak
Effects due to the intermediate excitation of the
D13(1520) resonance are much smaller than the
model predictions
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Crystal Ball / TAPS
at MAMI since 2003
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Dan Watts
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N?? Single Spin Asymmetry
?
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????
????
????
Fix -Arenhoevel
Roca
Bonn-Gatchina
CB preliminary data
Krambrich et.al., submitted to PRL
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MAMI-C
without? ?(1700)?
with ?(1700)?
CrystalBall data
Kashevarov et.al., EPJA (2009)
2.0
0.67 (PDG)
?(1700)
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Helicity Asymmetry
preliminary
f
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A1
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spectrometer A
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S11(1535)
JP 1/2 -
D13(1520)
JP 3/2 -
Asymmetry with transverse polarised target T
Im (E0 (E2- M2-))
Polarisation of the recoil proton Py Im (E0
(E2- M2-))
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T Im (E0 (E2- M2-))
Breit-Wigner resonances in JP 1/2- and 3/2
partial waves
energy dependent phase shift between JP 1/2-
and 3/2 partial wave amplitudes
Tiator et al., PRC C60 (1999)
Phoenix/Bonn, A. Bock et al., PRL81(1998)
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A1 Collaboration First experiment with MAMI C
and the 3-spectrometer setup
Q²0.1 GeV/c² Qh120 deg.
Py Im (E0 (E2- M2-))
T
Merkel et al., PRL 99132301 (2007)
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A1 Collaboration First experiment with MAMI C
and the 3-spectrometer setup
Merkel et al., PRL 99132301,2007
Py Im (E0 (E2- M2-))
T
energy dependent phase shift between JP 1/2-
and 3/2 partial wave amplitudes
Breit-Wigner resonances in JP 1/2- and 3/2
partial waves
More complete energy- and angular coverage in
progress
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Developments and future plans

• polarization observables for single and double
  meson photoproduction
• spin polarizabilities (polarized Compton
  scattering)
• electroproduction of h mesons
• CB nucleon polarimeter (improved, p and n)
• polarized p, d frozen-spin target
• pol. ³He gas target

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Polarized Target for Crystal Ball
Tagged CW photon beam
4p- detector
Frozen spin target (20mKelvin, 5Tesla) Pproton
95 Pdeuteron70 All directions of
polarization
Transverse And Longitudinal Internal Holding
coil
New 3He4He-Dilution refrigerator (in
collaboration with JINR Dubna)
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Polarized ³He gas target
(with Institute of Physics, Mainz)
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Backup
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GDH sum rule predictions (2009)?
K?(?) Sumowidagdo et al., PRC 65,0321002 (02)?
N? SAID-FA07K MAID07
N??? Fix, Arenhoevel EPJA 25, 114 (2005)?
N? MAID
N? Zhao et al., PRC 65, 032201 (03)?
Regge Bianchi-Thomas , PLB 450,439(99)?
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GDH sum rule on the proton
Low energy theorems in the N??threshold
region (multipole analyses not very wrong ...)?
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Partial reaction channels and polarisation
observables deliver more information to improve
the deuteron models and our knowledge on the
neutron. (Better Models are needed.)
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Towards the complete N? experiment

• Linearly /circularly polarized photons
• Longitudinally / transversally polarized p,d
  targets
• Longitudinally polarized 3He target
• Recoil polarimeter
• MAMI-C E???? 1.5 GeV

In preparation