gdh sum rule experiment at spring-8 leps
DESCRIPTION
Nov. 19. 2002 Japan-Italy Sympo. Miyazaki. GDH sum rule experiment at SPring-8 LEPS. Takahiro Iwata Yamagata Univ. GDH sum rule Overview of the SPring-8 LEPS facility Plan of the GDH experiment at SPring-8. GDH sum rule. Gerasimov-Drell-Hearn sum rule. S.B.Gerasimov: - PowerPoint PPT PresentationTRANSCRIPT
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GDH sum rule experiment at SPring-8 LEPS
Nov. 19. 2002Japan-Italy Sympo. Miyazaki
Takahiro IwataYamagata Univ.
GDH sum ruleOverview of the SPring-8 LEPS facilityPlan of the GDH experiment at SPring-8
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GDH sum rule• Gerasimov-Drell-Hearn sum rule
23/ 2 1/ 2 22
GDHN
I dm
p p
n n
,p ,
: photon energy: pion threshold energy
: anomalous magnetic moment( ) / 1.79
( 0) / 1.91
205 , 233
N N
N
GDH GDH nI b I b
•S.B.Gerasimov: Yad.Fiz. 2 (1965) 598 / Sov. J. Nucl. Phys. 2, 430(1966)•S.D.Drell and A.C.Hearn: Phys.Rev. Lett. 16, 430 (1966) •M.Hosoda and K.Yamamoto: Prog. Theor Phys. 36 (1966) No.2, Lett. to Editor 425 “ DHGHY sum rule” called by Jaffe ( SPIN200 0 )
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spin non-flip spin fli
†2
p
1
Forward Compton Amplitud
[ ]
e
f f i if if f if
22 2 2
0
unsubtracted dipersion relation
mfef P d
2lim 0f
2 3/ 2 1/ 2
optical theorem
8mf
222 2
0
low energy theo
2
rem
ff
m
23/ 2 1/ 2 22
N
dm
GDH sum rule
ASSUMPTION:spin flip amplitudevanishes at infinite energy
General Principles
Lorenz invariance, gauge invariance, causality, relativity, crossing symmetry, analytic amplitude
nucleon spin structure
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SPring-8 (Super Photon ring-8 GeV)
• Third-generation synchrotron radiation facility
Circumference: 1436m
• Electron Energy: 8GeV
• Max. beam current: 100mA
• 62 beam lines
• LEPS beam line for high energy nuclear physics (RCNP beam line)
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LEPS Beam Line• Backward Compton scattering of a laser light agai
nst 8GeV electrons in the storage ring• Laser Electron Photon at SPring-8 : LEPS• Photon energy :
Experiments in higher energy regions Polarized photons(linear & circular) available with
a polarized laser Polarization experiments
2.maxeEE
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Polarization
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Layout of the Beam Line
Laser Hutch(36m from I.R.)Interaction
RegionExperimental Hutch (69mfrom I.R.)
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Laser System
laser
Gamma
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Energy Spectrum
2.4 GeV
8 GeV
0
200
400
600
800
1000
1200
1400
1600
05 0 100 150 200 250 300 350 400
0
100
200
300
400
500
600
05 0 100 150 200 250 300 350 400
BCS
background
measured by PWO
Intensity(typ.)
2.5x106
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LEPS SpectrometerDipole Magnet (0.7 T)
Liquid HydrogenTarget (50mm thick)
TOFwall
AerogelCerenkov(n=1.03)
DC s
beam
photo-production; further study with pol. target
( ss-content in nucleon) K+ photo-production; beam asymmetry
• (1405) photo-production
– further study by TPC to identify the decay products ()
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GDH experiment at SPring-8
• Study of the GDH sum rule for proton (measurement of helicity dependent photo-absorption cross-sections)
• Approved in Oct. 2001(QPAC of RCNP)• Energy region: 1.8 ~ 2.8 GeV• Energy settings
– 1st phase: Emax=2.4GeV (λ=351nm, 1W)• 1.8<E<2.4GeV, I=106/s(full spectrum), <Pol.>=85%
– 2nd phase: Emax=2.8GeV (λ=275nm, 0.3W)• 2.3< E <2.8GeV, I=105/s(full spectrum), <Pol.>=80%
• Polarized polyethylene target • 4pi-detector system
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SP8-GDH collaboration
• Yamagata Univ. T.Iwata, H.Yoshida, Y.Tajima, S.Kato 、 M.Moriya
• Nagoya Univ. N.Horikawa, I.Daito, S.Fukui, S.Hasegawa, T.Kobayashi• Miyazaki Univ. T.Hasegawa, T.Mastuda, M.Iio, Y.Toi, R.Akashi• Melbourne Univ. M.Thompson, R.Rassool, M.Geso, L.Smith• UCLA G.Igo, S.Trentalange, V.Ghazikanian• University Bonn D.Menze• CUA F.Klein• KEK S.Ishimoto• SPring-8 Y.Ohashi
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SP8-GDH SetupForward Detector(TOF wall)
InnerDetector
Gas Cerenkov
PT-Magnet
Polarized Target
Inner Gamma Detector
Gamma beam
Large AngleDetector
Forward GammaDetector(lead-glass, PWO)
Large AngleGamma Detector(lead-plastic)
1 m
geometrical acceptance97% of 4
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Polarized Target for SP8-GDH Dynamic Nuclear Polarization(DNP) technique
microwave irradiation at low temperature(100mK) and high magnetic field(2.5T)
polarization reversal by change of microwave frequency
Target material stack of polyethylene( ) foils(t=100μm )
new material developed by Nagoya Group target preparation at room temperature precise evaluation of thickness reducing systematic errors efficient cooling by foil shape
Target size: d=20mm, l=50mm, Polarization: P>60%
2CH
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PT-Magnet
SuperconductingSolenoidB=2.5T(max=2.6T)B/B~130ppm(20x50mm)warm bore: 60cmlength: 100cmcooled by cryocooler(GM-refrigerator) no need of lid. He
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KEK Dilution Cryostat
• Top part(still, heat-exchanger, mixing-chamber) to be modified• beam pipe to be rearranged(MW guide removed)
– diameter of the beam pipe is 24mm• beam size x: 40mm need an active collimator
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Inner Gamma Detector
to PMT
clear fiber3m long
WLS fiberd=1mm
lead-plastic-scintillatorSandwich detector
18 sampling layers(lead:1.6mm, Scin.:8mm)total thickness~5X0
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Test of Prototype
Eff. > 90%for EMeV
electron beam
photon beam
simulation
simulation
the results published:NIM A 481(2002) 188-199
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• Charged particle detection• Surrounding target• Plastic-scintillator, 25mm thick• 10 segments x 8 sectors
– 80 modules– neighboring segments rotated by h
alf a sector
• Readout: WLS fiber(d=1mm) + clear fiber(3m long)• 4-dimensional readout• PMT: 16CH multi-anode-PMT• Melbourne group made prelimin
ary study
Inner Detector
40cm
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Gas Cerenkov Counter
• Basic tests have been done by Nagoya group– Radiator: 90cm CO2 1atm
• n=1.00043(thre.=4.9GeV/c for pi, 17.5MeV/c for e)
– Eff. > 99.8% for a single electron track at 300MeV
• suppression of shower: 10-4
• Miyazaki group will construct the final version
300 MeV electron
<Np.e.>=6.7 thre.=1p.e.
Test Module
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Status and time schedule
• Status– R&D in progress
– lack of budget for construction
• Possible time schedule– 2003 July, Aug.
Installation of detectors and pol. target
– 2003 Sep., tuning detectors
– 2003 Oct.,Nov., data taking(1st phase)
– 2004 Jan. Feb., data taking(2nd phase)
– 2004~2005 data taking with pol. deuteron target
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Summary• The polarized photon beam facility at SPring8 has been es
tablished.
• The experiments with the common spectrometer are currently running. They are giving interesting results.
• The GDH sum rule experiment at SPring-8 aims at the study of the GDH sum rule for proton in the energy region from 1.8 GeV to 2.8GeV.
• Preparation of the experiment is in progress although we have serious budget problem.
• Possible run time is from Oct. 2003.