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Status of XMASS experiment

Status of XMASS experiment. Cygnus 2013@Toyama 2013/06/05 Nagoya univ . H.Uchida for XMASS collaboration. XMASS-II. XMASS-I. Overview. XMASS-1.5. 835 kg, 100 kg Fiducial volume (FV) φ80 cm, 642 PMTs. 5 ton, 1 ton FV φ1.5 m, ~1000 PMTs. 25 ton, 10 ton FV φ2.5 m

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Status of XMASS experiment

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  1. Status of XMASS experiment Cygnus 2013@Toyama 2013/06/05 Nagoya univ. H.Uchida for XMASS collaboration

  2. XMASS-II XMASS-I Overview XMASS-1.5 835 kg, 100 kgFiducial volume (FV) φ80 cm, 642 PMTs 5 ton,1 ton FV φ1.5 m, ~1000 PMTs 25 ton, 10 ton FV φ2.5 m 　・ Dark matter 　・ pp solar neutrino 　・ 0n2b decay ・ Dark matter search Y. Suzuki, hep-ph/0008296 • A purpose of XMASS-I and 1.5 experiment is dark matter search. • Commissioning data was taken with XMASS-I at the Kamioka Observatory in Japan between Nov. 2010 and May. 2012. And now refurbishment work is on going. • XMASS-II has multi purpose of dark matter, pp solar neutrino and 0ν2β decay.

  3. 800kg detector • XMASS is a single phase detector with ultra pure liquid xenon. • Background is reduced by a self-shielding of liquid xenon. • This detector has high light yield (~14p.e./keV) & low energy threshold (~0.3keVee). • This detector is sensitivefor electromagnetic signals.

  4. Detector configuration There is a this detector at Kamioka observatory. Elec. hut OFHC copper vessel Water tank Refrigerator 11m 835kg liq. xenon 642 PMTs ~ 1.2m 10m 700L reservoir 72 20inch PMTs (veto)

  5. Source calibration • Calibration sources are used for checking detector response. • The sources can be moved along the vertical axis in the detector. Stepping motor Linear and rotary motion feed-through Gate valve (*1) Ka X-rays from the copper used for housing. (*2) Ka X-rays from the tungsten used for housing. ~5m 0.21mmf for 57Co source 4mmf Top photo tube Source rod with a dummy source • We can use one of five sources. • Right hand animation shows a procedure of calibration data taking. First, installation of a source to a calibration rod, opening the top PMT, and insertion of the rod. 5

  6. Calibration data • Calibration dataでreal dataを 57Co calibration data (122keV) Real data MC ４０ ３０ 40 40 30 30 20 20 z [cm] 10 10 0 0 -10 -10 -20 -20 -30 -30 -40 -40 -10 10 0 -20 20 10 0 -20 20 -10 y [cm] y [cm]

  7. Background • Background level of XMASS-I is a fewevent/day/keV/kg [dru] without fiducualization. • It is similar level with DAMA and CoGeNT. • The origin of BG for more than 5 keV were almost identified(lower figure). Also for less than 5 keV, Gore-Tex may explain the events. • Events originate at the inner surface must explain major part of the observed events.. PMT写真と アルミの位置の 説明 ● Black line: Real data ● Colored histogram: BG (MC) Surface Cu 210Pb PMT Al 235U-231Pa 210Pb 232Th 238U-230Th PMT gamma Gore-Tex 210Pb Gore-Tex 14C Full volume dru[/day/keVee/kg] 7 5 20 10 15

  8. Light mass WIMP search • Full volume (835 kg) analysis • 6.70 days×835kg in 2012 Feb. • 0.3 keVee threshold 5 4 3 Counts/day/kg/keVee 2 1 0 0 0.5 2 1.5 1 Energy [keVee]

  9. solar axionsearch • Axion is a hypothetical particle to solve the strong CP problem • Produced in the Sun and detected in the detector • XMASS is suitable to search because of a large mass and low BG Bremsstrahlung and Compton effect Axio-electric effect gaee gaee ma= Our data Max allowed 50 keV

  10. WIMP-Xe129 inelastic scattering 他の非弾性散乱実験についての言及。 I127を使った（DAMA、PICORON）？ 論文があるか見ておくこと。 Inelasticの図

  11. Reduction of surface background

  12. Optimization of the cut parameters

  13. Systematic error

  14. Upper limit for the inelastic cross section

  15. 1.5

  16. Refurbishment

  17. Summary

  18. Back up

  19. Cross section of DM100GeV Event Event/keV Scaled energy(13.9PE/keV) Reconstructed R (cm) # of events of no cut in DM100GeV MC are 82625. If these events occur in 55.6days, (explanation of this function in backup slide) Calculation of cross section DM100GeV: 82625/835/0.264/55.6 = 6.74 event/kg(Xe129)/day NA of Xe129 = 3.758×10-37×6.74×100/0.3 = 8.4×10‐34cm2 (8.4×102pb) When cross section is 8.4×102pb, inelastic events by DM100GeV occur 82625 events in 55.6days.

  20. Cross section of DM200GeV Event Event/keV Scaled energy(13.9PE/keV) Reconstructed R (cm) # of events of no cut in DM200GeV MC are 82640. If these events occur in 55.6days, (explanation of this function in backup slide) Calculation of cross section DM200GeV: 82640/835/0.264/55.6 = 6.74 event/kg(Xe129)/day NA of Xe129 = 3.758×10-37×6.74×200/0.5 = 1.0×10‐33cm2 (1.0×103pb) When cross section is 1.0×103pb, inelastic events by DM200GeV occur 82640 events in 55.6days.

  21. Cross section of DM400GeV Event Event/keV Scaled energy(13.9PE/keV) Reconstructed R (cm) # of events of no cut in DM400GeV MC are 82175. If these events occur in 55.6days, (explanation of this function in backup slide) Calculation of cross section DM200GeV: 82175/835/0.264/55.6 = 6.70 event/kg(Xe129)/day NA of Xe129 = 3.758×10-37×6.70×400/0.53 = 1.9×10‐33cm2 (1.9×103pb) When cross section is 1.9×103pb, inelastic events by DM400GeV occur 82175 events in 55.6days.

  22. Reduction of best parameter set Live time: 55 days # of events Energy(keV) Signal region # of events Reconstructed R

  23. Origin of BG in XMASS-I Main BG source (≧5keV) Al seal BG candidate (< 5keV) • In refurbishment, Al seal will be covered • by copper rings and GORE-TEX will be • removed • In XMASS-1.5, Al seal will be replaced • with ultra pure one 24

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