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Present and Future of Super-Kamiokande Experiment

Present and Future of Super-Kamiokande Experiment. Chen Shaomin Center for High Energy Physics Tsinghua University. Super-Kamiokande detector. A 50k tons water Č detector located at 1k m underground. 41.4 m. 39.3 m. Physics topics in Super-Kamioka nde.

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Present and Future of Super-Kamiokande Experiment

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  1. Present and Future of Super-Kamiokande Experiment Chen Shaomin Center for High Energy Physics Tsinghua University

  2. Super-Kamiokande detector A 50k tons water Č detector located at 1k m underground 41.4 m 39.3 m

  3. Physics topics in Super-Kamiokande • Nucleon decay • Solar neutrino • Atmospheric neutrino • Neutrinos from supernova burst • Long baseline neutrino oscillation • Massive neutrino dark matter search • Gamma-ray burst search …

  4. Super-Kamiokande collaboration Initially (1992): Japan, USA Later: Korea, Poland Now: China ~ 140 Scientists and ~ 35 Institutions

  5. History of Super-Kamiokande # of PMTs Threshold Achievement Start Discovery of atmosphere  oscillation 11,146 (40%) 5 MeV SK-I Discovery of Solar  oscillation Accident Partial reconstruction Discovery of Atmosphere  L/E effect 5,182 (19%) SK-II 7 MeV K2K final result Full reconstruction 11,129 (40%) SK-III 4 MeV(plan)

  6. From SK-II to SK-III 5,182 PMTs SK-I in 2006 accidence Partial reconstruction SK-II in 2002 Full reconstruction 11,129 PMTs SK-III in 2006 PMT with FRP mask

  7. Detector goals in SK-III • Lower energy threshold • Extend energy range • Special trigger logic? • Change electronic threshold? • Lower water temperature from 13°C to 10°C? • Adding Gd in water? • … Down to 4 MeV Improved from 0 – 300 p.e.s/PMT to 0 – 1250 p.e.s./PMT with newly designed electronics. Up to multi TeV scale

  8. Neutrino detection in SK If +/– is fully contained in the inner tank Cone vertex and # of PMT and total charge collected used for measuring Evis Ring pattern diff. used for PID If e+/e– is fully contained in the inner tank

  9. Far detector for K2K/T2K KEK-TO-KAMIOKANDE TOKAI-TO-KAMIOKANDE KEK Tokai Near detector L K2K L=250km E~1GeV T2K L=295km E~0.75GeV Far detector To Beijing?

  10.  Beam @Super-K GPS Tspill Tsk Time-of-Flight <1 msec SK ND To detect  beam @SK • Fully contained • Evis20MeV • Fiducial volume (<2m) • Timing requirement: K2K -0.2<Tsk-Tspill-T.O.F<1.3sec

  11. Solar/Supernova neutrinos Neutrino from the Sun/Supernova (low energy neutrinos) QSUN Neutrino scatters electron in detector We observe the electron and can know the origin

  12. Supernova neutrino burst After Before SN1987A

  13. Key issues in Supernova study When and where? “BANG” Precise measurement on 1st bounce of e’s can be a key step to determine absolute neutrino mass. Time spectrum of supernova neutrinos

  14. ~7,300 ne+p events ~300 n+e events ~100 ne+16O events for 10 kpc supernova (-) Supernova event rate at SK 5MeV threshold T.Totani, K.Sato, H.E.Dalhed and J.R.Wilson, ApJ.496,216 (1998) Lower the energy threshold can get more sensitivity

  15. ne+p Direction to Supernova Direction of supernova can be determined with an accuracy of 2-3 degrees. n+e n+e Separation between +e   + e and e + p  n + e+ can improve the accuracy

  16. Neutrinos from all past core-collapse supernovas Population synthesis (Totani et al., 1996) Constant SN rate (Totani et al., 1996) Cosmic gas infall (Malaney, 1997) Cosmic chemical evolution (Hartmann et al., 1997) Heavy metal abundance (Kaplinghat et al., 2000) LMA noscillation (Ando et al., 2002) is the easiest to detect @SK Golden region Electron-type antineutrino energy (MeV)

  17. What do we learn from SK-I? Total background 90% CL limit of SRN Atmospheric nm → invisible m → decay e Atmospheric ne

  18. SK SRN limit vs. predictions We hope to improve the limit by tagging neutron in process SK-I upper limit: < 1.2 /cm2/sec

  19. Muon background possible p+ production nm p+ m+  e 16O Post-activity Pre-activity Invisible m Decay e Possibleg-ray emission DT = ~ 2 msec

  20. Possibilities of taggingneutron n g ne 2.2 MeV  t ~ 200 s p p Gd e+ g 8 MeV  t ~ 30 s Positron and gamma ray vertices are within ~50cm. e could be identified by tagging the delay neutron.

  21. Trigger logic to tag neutrons 2.2MeV  # of PMT hits Average # of PMT hits ~ 7 @ SK, lower than the trigger threshold and the requirement for a good gamma vertex reconstruction

  22. PMT timings for 2.2MeV ’s # of PMT hits # of PMT hits Time of flight (TOF) Time smearing PMT timings (ns) PMT timings (ns) Timing coincidence among the PMT hits for a 2.2 MeV  diluted by different TOFs

  23. A proposed forced trigger logic

  24. PMT hits in a given window 2.2 MeV ’s 3.5kHz PMT dark noise assumed After TOF correction, 56% neutrons can be tagged with event Rate increase due to PMT dark noise less than 20Hz.

  25. Goal for SRN search @SK-III Relic model: S.Ando, K.Sato, and T.Totani, Astropart.Phys.18, 307(2003) with flux revise in NNN05. 10-year with SK-I SRN signal:　 22.7 Background: 115 If we do not tag neutrons If we can tag neutrons with 80% efficiency and suppress BG by 90%. 10-year with SK-III SRN signal:　 18 Background: 12 May lead to a discovery of SRN.

  26. Tsinghua conditionally accepted by Super-K collaboration

  27. Formally accepted in 2005 KAMIOKA OBSETVATORY INSTITUTE FOR COSMIC RAY RESEARCH, UNIVERSITY OF TOKYO Higashi-Mozumi, Kamioka-cho, Hida-city Gifu 506-1205, JAPAN TEL +81-578-5-9601, FAX +81-578-5-2121 e-mail: suzuki@suketto.icrr.u-tokyo.ac.jp 15-July, 2005 Shaomin Chen Center for High Energy Physics Tsinghua University Beijing 100084 P.R. of China Dear Professor Chen, We are happy to inform you that the Super-Kamiokande Collaboration Council decided to welcome the Tsinghua University group into the collaboration and appointed you as the team leader of Tsinghua neutrino physics group. Your interest in participating in the detector upgrade together with the relevant physics research programmes was well appreciated by the council. The council stressed the importance of establishing a close cooperation between the Center for High Energy Physics in Tsinghua University and Kamioka observatory, Institute for Cosmic Ray Research in University of Tokyo. We are very much looking forward to seeing a fruitful collaboration. Yours Sincerely Yoichiro Suzuki Spokesman of the Super-Kamiokande Collaboration

  28. Tsinghua students at Kamioka Around ICRR research building “Kenkyu-tou” Inside the mine

  29. Work has been done since then Work in last year Work in this year

  30. Summary • Super-K starts a new life this year (SK-III) • Many physics researches can continue • Efforts made for lowering energy threshold and broad dynamic range • Tsinghua university has been a member of Super-K collaboration, making its effort in detecting supernova neutrinos.

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