Results from the GDH experiment at Mainz and Bonn

1
Results from the GDH experiment at Mainz and Bonn

• Alessandro Braghieri, INFN Pavia
• A2 and GDH Collaborations

October 12-15, 2005

• First measurements in double polarization
  physical motivation
• Experimental set-up
• Results Gerasimov-Drell-Hearn sum rule and
  resonance contribution
• Comments

2
Proton 205 mb
Neutron 233 mb
3
Derivation of the GDH sum rule

• Forward (J 0) Compton scat tering amplitude
  (Lorentz and gauge invariance)

• Dispersion relation without subtraction

• Optical theorem

• Low energy theorem

4

• GDH sum rule
• Fundamental check of our knowledge of the gN
  interaction
• Important comparison for nucleon models
• Valid for any system with k ¹ 0 (2H, 3He) .
  Bridge between nuclear and particle physics
• The same formalism leads to a relation for the
  so-called forward spin polarizability

5
Connection with the Spin Crisis

• Measurement of the polarized structure function
  on the nucleon (D.I.S., EMC 1985 )

• How the proton spin is shared between partons?

• Anselmino , Ioffe, Leader, Sov. J. Nucl. Phys.
  49136, 1989

6
(No Transcript)
7
Milestones
1966 A SUM RULE FOR MAGNETIC MOMENTS AND THE
DAMPING OF THE NUCLEON MAGNETIC MOMENT IN
NUCLEI.By S.B. Gerasimov (Dubna, JINR), Sov. J.
Nucl. Phys. 2430-433, 1966 EXACT SUM RULE FOR
NUCLEON MAGNETIC MOMENTS.By S.D. Drell (SLAC),
A. C. Hearn (Stanford U., ITP), Phys. Rev. Lett.
16908-911, 1966 1973 SATURATION OF THE
DRELL-HEARN-GERASIMOV SUM RULE.By I. Karliner
(SLAC), Phys. Rev. D72717, 1973 1989 ON
POSSIBLE RESOLUTIONS OF THE SPIN CRISIS IN THE
PARTON MODEL.By M. Anselmino (Cagliari U.
INFN), B.L. Ioffe (Moscow, ITEP), E. Leader
(Birkbeck Coll.), Sov. J. Nucl. Phys. 49136,
1989 1990 MEASURING THE DRELL-HEARN GERASIMOV
SUM RULE.By N. de Botton (Saclay CERN),In
Bonn 1990, Proceedings, High energy spin
physics, vol. 1, 419-423.
8
Milestones
1991, Oct HELICITY STRUCTURE OF PION
PHOTOPRODUCTION Spokeperson D. Sober
(CUA), Proposal E91-015 at CEBAF MEASUREMENT OF
POLARIZED STRUCTURE FUNCTIONS IN INELASTIC
ELECTRON PROTON SCATTERING USING THE CEBAF LARGE
ACCEPTANCE SPECTROMETER Spokepersons V. Burkert
(Jlab), D. Crabb(Virginia U.), Minehart (Virginia
U.)Proposal E91-023 at CEBAF 1992, Apr PROPOSAL
TO MEASURE THE DRELL-HEARN-GERASIMOV SUM
RULE April 1992, proposal at ELSA 1993,
Apr EXPERIMENTAL CHECK OF THE DRELL-HEARN-GERASIMO
V SUM RULE Spokeperson J. Ahrens (Mainz
U.) Proposal A2/2-93 2000 HELICITY DEPENDENCE OF
g p --gt N p BELOW 450-MeV AND CONTRIBUTION TO THE
GERASIMOV-DRELL-HEARN SUM RULEBy GDH and A2
Collaborations (J. Ahrens et al.),Published in
Phys. Rev. Lett. 845950-5954, 2000
9
The GDH collaboration
J.Ahrens9,S.Altieri15,16,J.R.M.Annand6,G.Anton3,H.
-J.Arends9,K.Aulenbacher9,R.Beck9,
C.Bradtke1,A.Braghieri15,N.Degrande4, N.d'Hose5,
H.Dutz2, S.Goertz1, P.Grabmayr17, K.Hansen8,
J.Harmsen1, S.Hasegawa13,T.Hasegawa11, E.Heid9,
K.Helbing3, H.Holvoet4, L.VanHoorebeke4,
N.Horikawa14,T.Iwata13, P.Jennewein9, T.Kageya14,
B.Kiel2,F.Klein2, R.Kondratiev12,K.Kossert7,J.Krim
mer17,M.Lang9,B.Lannoy4,R.Leukel9,V.Lisin12,
T.Matsuda11,J.C.McGeorge6,A.Meier1,D.Menze2,W.Meye
r1,T.Michel3,J.Naumann3, A.Panzeri15,16,
P.Pedroni15, T.Pinelli15,16, I.Preobrajenski9,12,
E.Radtke1, E.Reichert10, G.Reicherz1,Ch.Rohlof2,D
.Ryckbosch4,F.Sadiq6,M.Sauer17,B.Schoch2,
M.Schumacher7, B.Seitz7,T.Speckner3,M.Steigerwald9
, N.Takabayashi13, G.Tamas9, A.Thomas9, R.van de
Vyver4, A.Wakai14, W.Weihofen7, F.Wissmann7,
F.Zapadtka7, G.Zeitler3 1Institute of
Experimental Physics, Ruhr-University, Bochum,
Germany 2 Physics Institute,
University of Bonn, Germany
3 Physics Institute,
University of Erlangen-Nuernberg, Erlangen,
Germany 4 Nuclear Physics
Laboratory, Gent, Belgium
5 CEA Saclay,
DSM/DAPNIA/SPhN, Gif-sur-Yvette, France
6 Department of Physics
Astronomy, University of Glasgow, U.K.
7 II.Physics Institute,
University of Goettingen, Germany
8 Department of Physics,
University of Lund, Sweden
9,10 Institute of Nucl. Physics
and Inst. of Physics, University of Mainz,
Germany 11 Faculty of Engineering, Miyazaki
University, Miyazaki, Japan
12 INR, Academy of Science, Moscow, Russia

13,14 Department of Physics and CIRSE, Nagoya
University, Nagoya, Japan
15,16 INFN Sezione di Pavia and
Dept. of Nucl. Physics of the University , Pavia,
Italy 17 Physics Institute, University of
Tuebingen, Germany
10
Experimental set-up

• Tagged photon beam Mainz mp Eg 800 MeV
• Bonn
  0.6 GeV Eg 2.9 GeV
• Circularly polarized photons
• Bremsstrahlung of linearly polarized
  electrons

• Longitudinally polarized Protons/Deuterons
• Frozen spin butanol target (Bonn, Bochum,
  Nagoya)

• Large acceptance hadron detectors

• Mainz DAPHNE detector (Pavia, Saclay)
  forward angle detectors (Pavia, Mainz,
  Tübingen, Gent)
• Bonn GDH Detector (Erlangen, Tübingen, Gent)

11
Experimental Programme at MAMI and ELSA
Measurements of s3/2- s1/2 over a large photon
energy range for proton and neutron (D/3He)
MAMI mp lt Eg lt 0.8 GeV
ELSA 0.7 lt Eg lt 3.1 GeV

• Inclusive cross section
• Partial channels

• Inclusive cross section

Status and planning
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
Target Polarisation
D-butanol
H-butanol
Chemically doped with trityl radicals (Bochum,
2003)
18
Summary of results on the Proton
19
D(1232)
D13(1520)
F15(1680)
F35(1905)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
Exclusive reactions
g NNp and g NNpp
Interference enhances contribution of some
multipoles
An important tool to understand resonances
ß
Multipole Analysis
SAID MAID
27
J. Ahrens et al, PRL 88, 232002 (2002)
SAID SM95 UIM
SAID SM02K
mod. UIM
28
Change of sign / interference terms between
multipoles
29
(No Transcript)
30

• Differential cross sections
• h3/2
• h1/2
• MAID 03
• SAID (SM02K)

31
The GDH sum rule for the neutron

• No free n target ? 2H and 3He
• Extract GDH from bound Nucleon
• Kinematics and Nuclear corrections
• 3He m _at_ mn ? ? ? (S-state 90)
• 2H m _at_ mp mn ? ? (Partial channels)
• Data analysis in progress. Preliminary Results

32
Comparison between p and n
33
(No Transcript)
34
(No Transcript)
35

• sD sp sn ??

36
Comparison between p and nH. Dutz et al, PRL 94
(2005)
37
Arenhövel, Fix, Schamb, Phys. Rev. Lett. 93
(2004)
38
Ref. Schwamb et al., Nucl. Phys. A690 (2001)
647, 682 and Nucl. Phys. A696 (2001) 556
39

• Model features
• NN-ND coupled channel
• approach,
• Complete retardation in
• hadronic interaction and
• pion-MEC
• Offshell contributions
• to e.m. current
• No free parameters
• concerning

Ref. Schwamb et al., Nucl. Phys. A690 (2001)
647, 682 and Nucl. Phys. A696 (2001) 556
40
Preliminary
polarized results
M.Martinez-Fabregate, PhD thesis

• Deut.data
• Deuteron model
• A.Fix Priv. communication
• Free proton
• g p -gt p p0
• I.Preobrajenski, PhD Thesis,
• Mainz, 2001

41
Preliminary

• GDH preliminary
• Deuteron model
• A.Fix, private communication

? free data EPJA 21,323 (04)
42
M.Martinez-Fabregate, PhD thesis
GDH data Preliminary
Arenhoevel model
43
Conclusions

• Data taking to check the GDH sum rule was
  completed
• Proton and Deuteron targets have been used
• Most of the analysis on the proton finished
  (inclusive and partial channels)
• Analysis on Deuteron in progress
• Check of the partial channels on the bound
  neutron
• Check of the methods using the bound proton
• Comparison with the results with the (free)
  proton
• Theoretical calculations

44
Conclusions