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Status of Super-Kamiokande and early data from SK-III

Status of Super-Kamiokande and early data from SK-III. M.Miura (Kamioka Observatory, ICRR) for Super-Kamiokande Collaboration. Introduction Reconstruction for SK-III Calibration Early data from SK-III Summary. C Scientific American. 1. Introduction: History of Super-Kamiokande.

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Status of Super-Kamiokande and early data from SK-III

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  1. Status of Super-Kamiokande and early data from SK-III M.Miura (Kamioka Observatory, ICRR) for Super-Kamiokande Collaboration Introduction Reconstruction for SK-III Calibration Early data from SK-III Summary

  2. C Scientific American 1. Introduction: History of Super-Kamiokande • 1996.4 Started data taking (SK- I) Evidence of Atm. n ocsillation(98’) • 1999.6 K2K started Evidence of Solar n oscillation(01’) • 2001.7 Stopped data taking for detector upgrade • 2001.11 Accident • partial reconstruction of the detector • 2002.10 Resumed data taking (SK- II) • 2002.12 Resumed K2K beam (K2K-II) • 2004.11 K2K finished Confirm n oscillation by accelerator n • 2005.10 Stopped data taking for full reconstruction Water Cherenkov detector • 1000 m underground • 50,000 ton (22,500 ton fid.) • 11,146 20 inch PMTs • 1,885 anti-counter PMTs • E > 5 MeV • E resolution: 14 %@10MeV • 5,182 20 inch PMTs • E > 7 MeV • E resolution: 21 %@10MeV n 42m SK- I 39m SK- II

  3. 2005Jul Oct 2006Jan Apr Jul PMT case Assembly PMT installation in tank Water filling SK-III started (Jul.12, 2006) 2. Reconstruction for SK-III Acrylic cover Same case as SK-II FRP

  4. Hardware improvement:Outer Detector (OD) segmentation less light creeps around the detector corner Cosmic ray mwill have hits in both endcap AND wall. Wall and endcaps are optically separated. Cosmic ray m OD segmentation enables more robust and effective cuts in the 1st stage of PC reduction (~30 % reduced background). Number of endcap hits Number of wall hits

  5. 3. CalibrationGain calibration • Pre-calibrated PMTs are installed in the tank (red). • Put scinti.ball at the center of the tank and flashed by Xe lamp. • PMTs with same distance are grouped (yellow). A target charge of the group is decided by pre-calib. PMTs. • HV of other PMTs are decided adjusting to the target charge. • RMS of Q/Qtarget < 2 % Xe lamp Other calibrations were also successfully done ! Scintillator ball

  6. 4. Early data from SK-III 4-1 Atmospheric n • Data: Jul06’-Mar07’ (livetime 166 days) • Same reconstruction tools as SK-II (except obvious change, i.e. #of PMTs). • Event rates of preliminary sample after all reduction (stat. error only) FC: 8.31±0.22 event/day (SK-II:8.22±0.10) PC: 0.57±0.06 event/day (SK-II:0.54±0.03) upmu: (without background subtraction) stopm 0.32±0.04 event/day (SK-II:0.28±0.02) thrum 1.05±0.07 event/day (SK-II:1.07±0.04) ==> Consistent with previous data! FullyContained PatiallyContained up-stopm up-through m

  7. Zenith angle distribution for each sample Preliminary Plot: SK-III data Box: MC without oscillation Sub-GeV e-like p<400MeV/c Sub-GeV m-like p<400MeV/c Even though preliminary results, we can see zenith angle distortion. Sub-GeV m-like p>400MeV/c Sub-GeV e-like p>400MeV/c Multi-GeV e-like Multi-GeV m-like +PC

  8. SK-III has been started with Low Energy (LE) trigger and Super Low Energy (SLE) trigger has been ON since Jan.24th ,2007. SLE trigger efficiency is; 100%@5.0MeV 50%@4.2MeV MC is tuned by Linear Accelerator (LINAC) data and energy response is well reproduced by MC. Now ready for analysis! --> Detail analysis of solar n is presented in the next talk. 4-2 Solar n analysis LINAC 8.8MeV Black:Data Red: MC Entry/Total Energy (MeV)

  9. 5. Summary • Full reconstruction work was finished and now we have 11,129 20-inch PMTs in the inner detector. • SK-III data taking started from July 2006. • Calibration works have been successfully done. • Early data of SK-III are analyzed for atmospheric n and it seems promising. • SLE trigger has been ON from Jan. 24th ,2007 and detail analysis of solar n is presented in the next talk.

  10. Backup

  11. 945 940 935 930 925 920 Early  time Late nsec] 3-2 Timing Calibration • To calibrate time-walk, a diffuser ball flashed by laser is put at the center of tank and take data with various light intencity. • To obtain correction function, timing distributions are made for each Q slice. • In conventional method, we took mean value for each Q. But it suffers reflection effect in the corner of the wall. • It is improved by taking peak position of T and improvement can be seen in Cf+Ni g source run. Log scale Liner scale Time before correction [nsec] 1 2 5 10 50 100 Charge [P.E] New method Top Old method Layer number in wall Bottom Tisk-Tof-T0[nsec] Tisk-Tof-T0[nsec]

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