# Presentation: 611783

## Hyper-Kamiokande project andR&D status

-  Hyper-K project
-  Motivation
-  Detector
-  Physics potential study
-  photo-sensor development
-  Summary

**Kamioka Observatory  **_**Masato Shiozawa**_
**For JHF-Kamioka νworking group**

- Jan.-2002 @CERN

## Next generation proton decay detector

** ****τ/B(p→e****+****π****0****) > 5.0 × 10****33**** years (90% CL)**
** ****τ/B(p→ν K****+****) > 1.9 × 10****33**** 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**

- Jan.-2002 @CERN

## Hyper-K as a far detector of 2nd JHF ν

_**Enable higher statistics physics (22.5 kton **__****__** **__**~**__**1000 kton) **_
** ****improved sensitivity for θ****13**** measurement              **
** ****CP phase measurement in lepton sector                  **
** ****test of the unitarity triangle**
_**Detector requirement**_
**good e/π****0**** separation capability at low energy**
**No magnetic field is needed **

**Hyper-K as a far detector of 2****nd**** 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 pepi0, 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 @CERN

## Possible Design of Hyper-Kamiokande

**Possible Design of Hyper-Kamiokande**

**Super-K**

- 40m

- Jan.-2002 @CERN

## Possible 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

**Total 800m   16 compartments**

- Jan.-2002 @CERN

## Possible 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

## Detector site candidate

**Super-K**

**KAMLAND**

- Mozumi site

- Tochibora site

- Super-K

- Jan.-2002 @CERN

## Analysis for discovery of p→e+π0 

**Analysis for discovery of p→e****+****π****0 **

**Tight momentum cut**
**      ⇒ ****target is mainly ****free protons**
**        ****efficiency=17.4%, 0.15BG/Mtyr**

**No Fermi momentum**
**No binding energy**
**No nuclear effect**

** ****Small systematic uncertainty of efficiency**
** ****High detection efficiency**
** ****Perfectly known proton mass and momentum**

**free proton**

**bound proton**

- Jan.-2002 @CERN

## Lifetime sensitivity     with tight cut

**Lifetime sensitivity****     with tight cut**

**With 3σ(99.73%) level**
** ****1Mton  ×20 years → ****~****1×10****35**** years lifetime**

- Jan.-2002 @CERN

## How the signal looks like

**How the signal looks like**

** ****τ****p****/B(p→e****+****π****0****)  = 1×10****35**** years**

** ****S/N = 4 for 1×10****35**** years**
**                ↓**
** ****S/N = 1 for 4×10****35**** years**

**τ****p****/B(p→e****+****π****0****) = several×10****35**** yrs**
** ****is reachable **
** ****by a large water Cherenkov detector**

** ****Proton mass peak **
** ****can be observed !**

- Jan.-2002 @CERN

## Backgrounds in p→νK+ searches

**   ****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****+****π****0****             ****~****22 events/Mtyr**

**  ****we should reject them by **
**  ****improved vertex fitter**

** ****very serious backgrounds **
** ****if both Λ and K****+**** are invisible**

_***K.Kobayashi***_

**3. other unknown background?**

- Jan.-2002 @CERN

## Lifetime sensitivity  with reduced BG

**Lifetime sensitivity****  with reduced BG**

**With 3σ(99.73%) level**
** ****1Mton  ×20 years → ****~****3×10****34**** years lifetime **

**Prompt γ tagging is essential**

- 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

- 5inch

- sensitive area 80mmφ

- e

- APD 3mmφ, GND
- bias voltage 150V

- photo-cathode –8kV

- 100% coll. efficiency
- cathode   80mmφ --------      3mm
- cathode 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 (2)

- _measured quantum efficiency_

- _time response_

- 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 voltage
- and/or larger AD

- Jan.-2002 @CERN

## Spherical HPD

** ****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)= 5×10****4****  ******** 1×10****7**** **
** ****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**

- Jan.-2002 @CERN

## Summary of Hyper-K

- Rich physics potential
- τp/B(p→e+π0)  ~ 1×1035 years (3σ CL with 20Mtyr)
- τp/B(p→ν K+)  ~ 3×1034 years (3σ CL with 20Mtyr)
-  Atmospheric, Supernova
-  other physics
-  2nd phase of JHF-Kamioka neutrino experiment
- R&D’s are in progress
- new photo-sensor

- Jan.-2002 @CERN