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GDH sum rule experiment at SPring-8 LEPS

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:

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GDH sum rule experiment at SPring-8 LEPS

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  1. Nov. 19. 2002 Japan-Italy Sympo. Miyazaki GDHsum rule experiment at SPring-8LEPS Takahiro Iwata Yamagata Univ. • GDH sum rule • Overview of the SPring-8 LEPS facility • Plan of the GDH experiment at SPring-8

  2. GDH sum rule • Gerasimov-Drell-Hearn sum rule • 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（SPIN200０)

  3. nucleon spin structure ASSUMPTION: spin flip amplitude vanishes at infinite energy General Principles Lorenz invariance, gauge invariance, causality, relativity, crossing symmetry, analytic amplitude GDH sum rule

  4. 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)

  5. LEPS Beam Line • Backward Compton scattering of a laser light against 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

  6. Polarization

  7. Laser Hutch (36m from I.R.) Interaction Region Experimental Hutch (69mfrom I.R.) Layout of the Beam Line

  8. Laser System Gamma laser

  9. Energy Spectrum measured by PWO Intensity(typ.) 2.5x106 BCS background 8 GeV 2.4 GeV

  10. LEPS Spectrometer TOF wall Dipole Magnet (0.7 T) Liquid Hydrogen Target (50mm thick) • f photo-production; • further study with pol. target 　　（ss-content in nucleon) • K+ photo-production; beam asymmetry • L(1405) photo-production • further study by TPCto identify the decay products (Sp) beam DCｓ Aerogel Cerenkov (n=1.03)

  11. 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<Eg<2.4GeV, Ig=106/s(full spectrum), <Pol.>=85% • 2nd phase: Emax=2.8GeV (λ=275nm, 0.3W) • 2.3< Eg <2.8GeV, Ig=105/s(full spectrum), <Pol.>=80% • Polarized polyethylene target • 4pi-detector system

  12. 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

  13. Forward Detector (TOF wall) Large Angle Detector geometrical acceptance 97% of 4p Polarized Target Gas Cerenkov Inner Detector Gamma beam Forward Gamma Detector (lead-glass, PWO) PT-Magnet Large Angle Gamma Detector (lead-plastic) Inner Gamma Detector 1 m SP8-GDH Setup

  14. 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%

  15. PT-Magnet Superconducting Solenoid B=2.5T(max=2.6T) DB/B~130ppm (f20x50mm) warm bore: 60cm length: 100cm cooled by cryocooler (GM-refrigerator)  no need of lid. He

  16. 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

  17. Inner Gamma Detector lead-plastic-scintillator Sandwich detector clear fiber 3m long to PMT WLS fiber d=1mm 18 sampling layers (lead:1.6mm, Scin.:8mm) total thickness~5X0

  18. Test of Prototype electron beam simulation photon beam simulation Eff. > 90% for Eg>50MeV the results published: NIM A 481(2002) 188-199

  19. Inner Detector • Charged particle detection • Surrounding target • Plastic-scintillator, 25mm thick • 10 segments x 8 sectors • 80 modules • neighboring segments rotated by half a sector • Readout: WLS fiber(d=1mm) + clear fiber(3m long) • 4-dimensional readout • PMT: 16CH multi-anode-PMT • Melbourne group made preliminary study 40cm

  20. 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 Test Module 300 MeV electron <Np.e.>=6.7 thre.=1p.e.

  21. 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

  22. Summary • The polarized photon beam facility at SPring8 has been established. • The experiments with the common spectrometer are currently running. They are giving interesting results. • The GDH sumrule 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.

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