jan.-2002 @cern hyper-kamiokande project and r&d status hyper-k project motivation detector...
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Jan.-2002 @CERN
Hyper-Kamiokande project andR&D status
Hyper-K project Motivation Detector Physics potential study photo-sensor development
Summary
Kamioka Observatory Masato ShiozawaFor JHF-Kamioka νworking group
Jan.-2002 @CERN
Super-K has not found nucleon decays in 3.5 years data τ/B(p→e+π0) > 5.0 × 1033 years (90% CL) τ/B(p→ν K+) > 1.9 × 1033 years (90% CL)Predicted lifetime of nucleon 4 fermion interactions
2 fermion – 2 sfermion interactions (SUSY models)
One or two order of extension of Super-Kamiokande would reveal new physics!!!
Next generation proton decay detector
g4 mp4
Γ = : τ(p→e+π0) = 1035±1 years MX
4
h 4 mp4 ____
Γ = : τ(p→K+ν) = 1029-35 years MHx
2 MX2
Jan.-2002 @CERN
Same baseline with Super-K (295km)
Enable higher statistics physics (22.5 kton ~1000 kton) improved sensitivity for θ13 measurement CP phase measurement in lepton sector test of the unitarity triangle
Detector requirementgood e/π0 separation capability at low energyNo magnetic field is needed
Hyper-K as a far detector of 2nd JHF ν
Jan.-2002 @CERN
R&D Items for Hyper-K
• cavity design and assessment• rock stress analysis• excavation cost, time, optimization
• physics potential study• optimization of photo-coverage, detector volume• sensitivity for pepi0, nuK+, background estimation• SN, atmospheric nu, and others• long baseline experiment(JHF), pi0 rejection etc.
• photo-sensor development• low cost, high sensitivity• mass production rate automated production• high pressure resistant
• other detector improvement• longer light attenuation length?• reducing reflection light?
Jan.-2002 @CERNPossible Design of Hyper-Kamiokande (2)
PMT Wall 45m 45m 2 planes 16 modules = 64,800 m2
45m 46m 4 planes 4 modules = 33,120 m2 45m 47m 4 planes 12 modules = 101,520 m2
Total 199,440 m2
200,000 PMTs if 1 PMT/m2 Fiducial Volume 41m 41m 42m 4 modules = 282,408 m3
41m 41m 43m 12 modules = 867,396 m3
Total 1,149,804 m3
2.5 m2 m
3 m
45m45m46m
41m41m42m
45m45m47m
41m41m43m
Total 800m 16 compartments
Jan.-2002 @CERNPossible Design of Hyper-Kamiokande (3)
#compartments
Total volume
Fiducial volume
PMT density #PMT
Case1 8 1Mton
0.57Mton
1PMT/m2 100k
Case2 8 1Mton
0.57Mton
2PMT/m2 200k
Case3 16 2Mton
1.15Mton
1PMT/m2 200k
Case4 16 2Mton
1.15Mton
2PMT/m2 400k• PMT density should be optimized by
• gamma tagging in nuK+ search, pi0 rejection in long baseline experiment• detector volume should be optimized by
• physics goals• site, stable cavity design• excavation cost, construction time• photo-sensor cost, production time
Jan.-2002 @CERN
Analysis for discovery of p→e+π0
Tight momentum cut ⇒ target is mainly free protons efficiency=17.4%, 0.15BG/Mtyr
No Fermi momentumNo binding energyNo nuclear effect
Small systematic uncertainty of efficiency High detection efficiency Perfectly known proton mass and momentum
free proton bound proton
Lif
eti
me
sen
sit
ivit
y
w
ith
tig
ht
cu
t
Wit
h 3
σ(9
9.7
3%
) le
vel
1
Mto
n ×
20
ye
ars
→ ~
1×
103
5 ye
ars
life
tim
e
Jan.-2002 @CERN
How the signal looks like
τp/B(p→e+π0) = 1×1035 years
S/N = 4 for 1×1035 years ↓ S/N = 1 for 4×1035 yearsτp/B(p→e+π0) = several×1035 yrs
is reachable by a large water Cherenkov detector
Proton mass peak can be observed !
Jan.-2002 @CERN
2. K+ production by atmν νN → νN* ΛK+
~ 1 events/Mtyr (after pdecay cut)
Backgrounds in p→νK+ searches
1. prompt γ ~ 6 events/Mtyr most are misfitted vertex events μ spectram 2100 events/Mtyr (single-ring μ,π,proton) π+π0 ~ 22 events/Mtyr
we should reject them by improved vertex fitter
very serious backgrounds if both Λ and K+ are invisible
K.KobayashiK.Kobayashi
3. other unknown background?
Lif
eti
me
sen
sit
ivit
y
wit
h r
ed
uced
BG
Wit
h 3
σ(9
9.7
3%
) le
vel
1
Mto
n ×
20
ye
ars
→ ~
3×
103
4 ye
ars
life
tim
e
Pro
mp
t γ
tag
gin
g i
s es
sen
tial
Jan.-2002 @CERN
Photo-sensor development
• improving QE• optimizing cathode materials, production methods
• larger (30-40inch) PMTs• glass valve production is a key
• hybrid photo-detector (HPD)• photo-cathode + AD(avalanche diode)• simple structure hopefully low cost• good timing resolution ( ~ 1ns)• good single p.e. separation
Jan.-2002 @CERN
5 inch HPD prototype
5in
ch
sensi
tive a
rea 8
0m
mφ
e
APD 3mmφ, GNDbias voltage 150V
photo-cathode –8kV
100% coll. efficiency cathode 80mmφ -------- 3mmcathode 120mmφ -------- >10mm
• need higher voltage• larger AD• spherical cathode
electron bombarded gain 1000 ×avalanche gain 50 = 50,000
Jan.-2002 @CERN
5 inch HPD prototype (3)
pulse height distribution (dark current)
• good single p.e. peak• dark rate is 24kHz
Jan.-2002 @CERN
5 inch HPD prototype (4)
(a) cathode uniformity
(b) anode uniformity
geomagnetic effect is seen
need higher voltageand/or larger AD
Jan.-2002 @CERN
Spherical HPD
glass photocathode
reflector
diode-1
diode-2
light
photoelectrons
Lead and support
• high efficiency• simple structure low cost high production rate• pressure resistant
Jan.-2002 @CERN
to do list for the new photo-sensor
• gain up
1000(E.B.gain)×50(Av. gain)= 5×104 1×107
• good focusing higher voltage, spherical shape
• good control of AD position
• operation of AD in positive high voltage
• keep low dark rate
• pressure resistant (spherical shape)
• larger size