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)

• Energy region: 1.8 ~ 2.4 GeV & 2.3 ~ 2.8 GeV• Circularly polarized gamma beam • Polarized polyethylene target • 4-detector system

• 1st double polarization experiment at SPring-8 • Approved in Oct. 2001 (QPAC )• Status: in preparation

SP8-GDH collaboration• Yamagata Univ. T.Iwata, H.Yoshida, Y.Tajima, S.Kato

• Miyazaki Univ. T.Mastuda, Y.Toi

• KEK S.Ishimoto

• SPring-8 Y.Ohashi

• Chubu Univ. N.Horikawa,

• Tohoku Univ. H.Shimizu, T.Ishikawa

• Melbourne Univ. M.Thompson, R.Rassool

• Royal Melbourne Institute of Technology M.Geso

• UCLA G.Igo, O.Tsai, C.Witten, S.Trentalange, V.Ghazikanian

• Bochum Univ. G.Reicherz, W.Meyer

• CUA F.Klein

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

AnomalousMagnetic Moment(static property)

- Circularly polarized gamma &

polarized nucleon target

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

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

SP8

3 122

neutron

Mainz dataO. Jahn, Proc.GDH2004 Bonn data[PRL 94,162001(2005)]

3 122

neutron

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

SP8-GDH SetupForward Detector(FD);TOF wall

InnerDetector(ID)

Gas Cerenkov(GC)

PT-Magnet

Polarized Target(PT)

Inner Gamma Detector(IGD)

Gamma beam

Large AngleDetector(LAD)

Forward GammaDetector(FG);lead-glass+ PWO

Large AngleGamma Detector(LAG);lead-plastic

1 m

geometrical acceptance97% of 4

Layout of experiment

PT: Yamagata + Bochum IGD: UCLAID: MelbourneLAD: YamagataLAG: YamagataGC: MiyazakiFD: YamagataFG: Tohoku+YamagataDAQ: Yamagata

responsibility

beam

Polarizedtarget

Magnetfor pol. target

modified part

final heat exchanger

still

microwave cavity

beam pipefinal heat exchangerswalls

outer pipe of the final HE

Polarized target • Modification of KEK-cryostat ongoing

• a few steps for final assembly

• Most parts ready except MC, waveguide

• NMR for pol. monitor made by Bochum

G.V. JIS150

JIS250

DN160

DN160

G.V.

RSV2000

R６０１H2060

JIS65

pipe d=76.3

flange O.D.=285

pipe d=267.4flange d=350

JIS250

JIS250

JIS65

~2500

~1000

3300

500

1400

300

300

2000

2000400

300 2000400

200

1000 2000200500

200

2000

500

500

~2500

100LDewar

200LDewar

ＥＨ１２ 00

ＥＨ５００

ＥＨ８０

EXP.hatch

Ｈｅ３

Ｈｅ４

Cryogenics system for polarized target at SPring-8

PT

He4 pump systemHe3 pump system

Inner Gamma Detector (IGD)

Designed and R&D by UCLA

26 layers of 5mm thick scintillators and 1.2mm thick lead sheets

Avalanche Photodiode readout1 APD/segment

10 MeV equiv. light outputO.Tsai(UCLA) invited to Yamagata by JSPS

for 10 month( from Nov. 2005)

Budget application to DOE (280k$)

• Charged particle detection• tile scintillators 25mm thick• 10 segments x 8 sectors

– 80 tiles in total– neighboring segments rotated by ha

lf a sector

• Readout: WLS fiber(d=1mm) + clear fiber(3m long)• 4-dimensional readout(32ch)• Multi-anode-PMT(16ch)• Melbourne group made prelimin

ary study • tiles to be made at Melbourne w

orkshop

Inner Detector (ID)

40cm

Gas Cherenkov CounterMiyazaki Univ. group in charge

Gas box constructedleak check OK.

Mirror design ongoing

Electron rejection

CO2 gas at 1 bar

Other detectors

• LAD (charged particle detection)– scintillator plate 20mm thick , 4 PMTs

• LAG ( gamma detection)– scintillator+ lead, WLS readout, 10 PMTs

• FD (charged particle detection)– TOF wall (LEPS)

• 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.

Summary

GDH activities in the worldproton Neutron

MAMI 200-800MeV, complete 200-800MeV, completed

(D-butanole)

ELSA 0.68-2.9GeV, complete 0.8-1.8,complete(LiD)

JLAB 2.5-6GeV, proposed

GRAAL 0.5-1.5GeV,proposed,(HD) 0.5-1.5GeV, proposed (HD)

SLAC 4-40GeV, proposed

LEGS 130-470MeV, running,(HD) 130-470MeV, running,(HD)

SPring-8 1.8-2.8GeV, proposed, (PE) 1.8-2.8GeV, 　 to be proposed,

(D-butanole)

Q.Zhao, J.Al-Khalili and C.Bennhold（ th-nucl 0201002v2) quark model approach

Contributions from partial channels

Double polarized data for exclusive channels(Mainz data for eta p channel)

131/ 2 3/ 2

d d

d d

p p ))))))))))))) )

Forward Detector(TOF wall)

Gas Cerenkov

PT-Magnet

Gamma beam

ＬＥＰＳ　 spectrometer

TPC

TPC

Forward GammaDetector(lead-glass, PWO)

PT+TPC

80 mm

SuperconductingSolenoidB=2.5T(max=2.6T)B/B~130ppm(20x50mm)warm bore: 60cmlength: 100cmcooled by cryocooler(GM-refrigerator) no need of liq. He

PT-Magnet

proton Neutron

energyrange(GeV)

energy step(MeV)

errorstat.+sys.

energyrange(GeV)

energy step(MeV)

errorstat.+sys.

SPring-8

1.8-2.8 100 1+ 0.7 b 1.8-2.8 200 5+ 5 b

ELSA 0.7-2.9 200(above 1.5GeV

)

4+ 0.3 available data only <1.8GeV

- -

Comparison between ELSA and SPring-8