present and future of super-kamiokande experiment chen shaomin center for high energy physics...
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![Page 1: Present and Future of Super-Kamiokande Experiment Chen Shaomin Center for High Energy Physics Tsinghua University](https://reader034.vdocument.in/reader034/viewer/2022052701/56649ee15503460f94bf2557/html5/thumbnails/1.jpg)
Present and Future of Super-Kamiokande
Experiment
Chen Shaomin
Center for High Energy Physics
Tsinghua University
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Super-Kamiokande detector
41.4
m
39.3 m
A 50k tons water Č detectorlocated at 1k m underground
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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
…
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Super-Kamiokande collaboration
Initially (1992):
Japan, USA
Later:
Korea, Poland
Now:
China
~ 140 Scientists and ~ 35 Institutions
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History of Super-Kamiokande
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
Start
SK-I
Accident
Partial reconstruction
SK-II
Full reconstruction
SK-III
11,146 (40%)
5,182 (19%)
11,129 (40%)
# of PMTs Threshold
5 MeV
7 MeV
4 MeV(plan)
Achievement
Discovery ofatmosphere oscillation
Discovery ofSolar oscillation
Discovery ofAtmosphere L/E effect
K2K final result
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From SK-II to SK-III
SK-I in 2006 accidence
PMT with FRP mask
Partial reconstruction
Fullreconstruction
SK-III in 2006
SK-II in 2002
5,182 PMTs
11,129 PMTs
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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?•…
Improved from 0 – 300 p.e.s/PMT to 0 – 1250 p.e.s./PMT with newly designed electronics.
Down to 4 MeV
Up to multi TeV scale
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Neutrino detection in SK
,
,e e
If +/– is fullycontained in theinner tank
If e+/e– is fullycontained in theinner tank
Ring pattern diff.used for PID
Cone vertex and# of PMT and total charge collected usedfor measuring Evis
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Far detector for K2K/T2K
km
GeV
eV27.1sin2sin1
2
4222 L
E
cmPsurv
K2KL=250kmE~1GeV
L Far detector
Near detector
KEK-TO-KAMIOKANDETOKAI-TO-KAMIOKANDE
KEKTokai
T2KL=295kmE~0.75GeVTo Beijing?
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Beam @Super-K
ND SKTime-of-Flight < 1 msec
Fully containedEvis 20 MeV
Fiducial volume (<2m) Timing requirement:
-0.2<Tsk-Tspill-T.O.F<1.3sec
Tspill Tsk
GPS
To detect beam @SK
K2K
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Solar/Supernova neutrinos
SUNNeutrino scatters electron in detector
We observe the electron and can know the origin
Neutrino from the Sun/Supernova (low energy neutrinos)
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Supernova neutrino burst
SN1987A
BeforeAfter
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Key issues in Supernova study
“BANG”
When and
where?
Precise measurement on 1st bounce of e’s can be a key step to determine absolute neutrino mass. Time spectrum of supernova neutrinos
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Supernova event rate at SK
5MeV threshold
~7,300 e+p events~300 +e events~100 e+16O events
for 10 kpc supernova
(-)
T.Totani, K.Sato, H.E.Dalhed
and J.R.Wilson, ApJ.496,216
(1998)
Lower the energy threshold can get more sensitivity
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Direction to Supernova
Direction of supernova can be determined with an accuracy of 2-3
degrees.
+e +e
e+p
Separation between+e + eande + p n + e+
can improve the accuracy
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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 oscillation (Ando et al., 2002)
Electron-type antineutrino energy (MeV)
Golden region
is the easiestto detect @SKe
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What do we learn from SK-I?
Total background
Atmospheric → invisible → decay e
Atmospheric e
90% CL limit of SRN
Identifying
is a way out
to improve S/N
e p n e
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SK SRN limit vs. predictions
SK-I upper limit: < 1.2 /cm2/sec
We hope to improve the limit by tagging neutronin process e p n e
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Muon background
Invisible
Decay ePossible -ray emission
T = ~ 2 sec
16OPre-activity
Post-activity
e
possible + production
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Possibilities of tagging neutron
e
e+
pn
Positron and gamma ray vertices are within ~50cm.
p
Gd
2.2 MeV t ~ 200 s
8 MeV t ~ 30 s
e could be identified by tagging the delay neutron.
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Trigger logic to tag neutrons
Average # of PMT hits~ 7 @ SK, lower than the trigger threshold and the requirement fora good gamma vertex reconstruction
# of PMT hits
2.2MeV
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PMT timings for 2.2MeV ’s
it
jt
# of PMT hits
PMT timings (ns)
# of PMT hits
PMT timings (ns)
Time of flight(TOF) Time smearing
Timing coincidence amongthe PMT hits for a 2.2 MeV diluted by different TOFs
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A proposed forced trigger logic
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PMT hits in a given window
2.2 MeV ’s
3.5kHz PMTdark noise assumed
After TOF correction, 56% neutrons can be tagged with eventRate increase due to PMT dark noise less than 20Hz.
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Goal for SRN search @SK-III
10-year with SK-I
SRN signal: 22.7
Background: 115
10-year with SK-III
SRN signal: 18
Background: 12
If we do not tag neutrons
If we can tag neutrons with 80% efficiency and suppress BG by90%.
Relic model: S.Ando, K.Sato, and T.Totani, Astropart.Phys.18, 307(2003) with flux revise in NNN05.
May lead to a discovery of SRN.
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Tsinghua conditionally accepted by Super-K collaboration
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Formally accepted in 2005
KAMIOKA OBSETVATORYINSTITUTE FOR COSMIC RAY RESEARCH,UNIVERSITY OF TOKYOHigashi-Mozumi, Kamioka-cho, Hida-cityGifu 506-1205, JAPANTEL +81-578-5-9601, FAX +81-578-5-2121e-mail: [email protected], 2005 Shaomin Chen Center for High Energy PhysicsTsinghua 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
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Tsinghua students at Kamioka
Around ICRR researchbuilding “Kenkyu-tou”
Inside the mine
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Work has been done since then
Work in last year
Work in this year
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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.