present and future of super-kamiokande experiment chen shaomin center for high energy physics...

Present and Future of Super-Kamiokande

Experiment

Chen Shaomin

Center for High Energy Physics

Tsinghua University

Super-Kamiokande detector

41.4

m

39.3 m

A 50k tons water Č detectorlocated at 1k m underground

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

…

Super-Kamiokande collaboration

Initially (1992):

Japan, USA

Later:

Korea, Poland

Now:

China

~ 140 Scientists and ~ 35 Institutions

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

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

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

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

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?

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

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)

Supernova neutrino burst

SN1987A

BeforeAfter

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

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

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

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

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

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

Muon background

Invisible

Decay ePossible -ray emission

T = ~ 2 sec

16OPre-activity

Post-activity

e

possible + production

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.

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

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

A proposed forced trigger logic

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.

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.

Tsinghua conditionally accepted by Super-K collaboration

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: suzuki@suketto.icrr.u-tokyo.ac.jp15-July, 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

Tsinghua students at Kamioka

Around ICRR researchbuilding “Kenkyu-tou”

Inside the mine

Work has been done since then

Work in last year

Work in this year

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.