Status of the SP8-GDH experiment Yamagata University Takahiro Iwata On behalf of the SP8-GDH collaboration 2005.Oct.6 @QPAC at RCNP • SP8-GDH proposal • Introduction of GDH sum rule • Status of the world data • Status of the SP8-GDH experiment • PT, IGD, ID, GD, …
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Status of the SP8-GDH experiment Yamagata University Takahiro Iwata On behalf of the SP8-GDH collaboration 2005.Oct.6 @QPAC at RCNP SP8-GDH proposal Introduction.
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Status of the SP8-GDH experiment
Yamagata UniversityTakahiro Iwata
On behalf of the SP8-GDH collaboration
2005.Oct.6 @QPAC at RCNP
• SP8-GDH proposal• Introduction of GDH sum rule• Status of the world data• Status of the SP8-GDH experiment• PT, IGD, ID, GD, …
Proposal : GDH experiment at SPring-8
• Study of the GDH sum rule for proton (measurement of helicity dependent photo-absorption cross-sections)
Similar sum rules areformulated for any particles having non-zero spin !
Universal sum rule
spin non-flip spin fli
†2
p
1
Forward Compton Amplitud
[ ]
e
f f i if if f if
Derivation
GDH for proton
3/ 2 1/ 2
RUN
E
I E d
Running GDH integral
. .
2.9
226 5 12 RUN
stat sys
I GeV
b
GDH sum rule
205 b.tot
The running GDH integral overshoots the GDH prediction at 2.9 GeV by ~10%.
ELSA(Bonn)
MAMI(Mainz)
3 122
33P
13D
15F35 37 or ?F F
High-energy contribution
.tot
High-energy behavior evaluated by fitting DIS data with Regge parameterizations
Contribution above 2.9 GeV: Bianchi and Thomas: -14b Simula et al.: -13b
Total integral: . .(212 213) 5 12stat sys b
GDH sum rule 205 bIf the evaluations are correct, the sum rule is verified at 10% level.
SP8
Extrapolation to high energy is good?
3 122
3 122
GDH for neutron
phenomenological Regge approach
phenomenologicalanalyses with real photon data in resonance region
• Data analyses in resonance region give contrary results to GDH s.r.• Interesting to see neutron GDH
Data of neutron GDH• preliminary Mainz data ( < 800 MeV) • published Bonn data up to 1.8GeV large errors compared with proton data• no data above 1.8 GeV
Objectives of SP8-GDH experimentMeasurements of for protonin the energy range of 1.8-2.8 GeVwith high precision and finer energy binning• confirmation of ELSA data ( with different technique) • study extrapolation to high energy
• Prospects• double pol. measurements in exclusive channels ( PT+TPC+LEPS configuration )• resonance studies with double polarization technique• new GDH data for neutron with pol.d target
• new proposal to be submitted • spin study of + : d
• FG ( gamma detection)– scintillator+ lead, WLS readout, 20 PMTs– (or lead glass blocks borrowed from KEK)– PWO(LEPS)
Realistic design should be started soon
• Proton GDH– It is verified at 10% level at Mainz and Bonn– Confirmation of the data is necessary– Extrapolation to high energy is important
• Neutron GDH– No data is available above 1.8GeV
• SP8-GDH experiment can provide additional data for proton and new data for neutron
• Preparation of SP8-GDH– A few steps for completion of PT – Work for cryogenics system at SPring-8– Preparations of IGD, ID, GC are on the track– Others should be started.
• Funding is required for construction, installation and running• But , it is not reserved, yet.