Non-Accelerator Physics with the Homestake “Megaton Array”

• 1) Nucleon Decay P o + e+, & P K+ +e

(improved PMTs may permit spatial & time recognition of K+ +e)

• 2) Prompt SN neutrinos – our Galaxy and nearby galaxies

• 3) Relic SN neutrinos (greater depth provides critical C.R. muon background reduction)

• 4) Low background shield

• (Used Hank Sobel talk-Korea 2005 & Ed Kearns talk -NNN07)

Various Detection Techniques

%Free Protons

% Nuclei Features

Water 11% 89% Cerenkov radiation

Liquid ScintillatorCould insert into center of 100 kton water detector

~10% ~90% Signal from slow particles

Liquid Argon 0% 100% Tracking

Detector Location Constraints

• 1) Depth

• 2) Distance from Power Reactors –

• Lead, SD is ~ 500 km from “nearby” U.S. power reactors – factor 30 (1/r2) better than Kamioka location

Vertex Reconstruction of Vertex Reconstruction of EventsEventsN16

PMT times used to reconstruct event position

Resolution ~15 cm

UNTAGGEDUNTAGGED

TAGGEDTAGGED

8 inch 10 inch13 inch

20 inch

13 inch PMT is very low profiledespite its diameter.

Large Format PMTsLarge Format PMTs

Applications:Neutrino Experiment

For Better Detection EfficiencyFor Better Detection Efficiency

Trial for High QE

R7081R7081R5912R5912

R8055R8055

R3600R3600

Hamamatsu PMT Characteristics

PMT Dia. Quantum Efficiency

Rise Time

Transit time jitter

3600 20” 20% 10 ns 5.5 ns

7081 10.5” >35% 4.3 ns 2.9 ns

Bialkali QE ComparisonBialkali QE Comparison

0

10

20

30

40

50

200 300 400 500 600 700Wavelength [nm]

Qu

an

tum

Effi

cien

cy [

%] Example Data for

UBA : R7600-200SBA : R7600-100STD : R7600

UBA:43%

SBA:35%

STD:26%

x1.3

x1.6

0

5

10

15

20

25

30

35

40

200 300 400 500 600 700 800

Wavelength [nm]

Qu

an

tum

Effi

cie

ncy [

%]

Example data R7081 (10 Example data R7081 (10 inch)inch)

StandardStandard26% at 380 nm26% at 380 nm

High QE TypeHigh QE TypeChampion DataChampion Data35% at 380 nm35% at 380 nm

0

2

4

6

8

10

12

~28 ~30 ~32 ~34 ~36QE at 380 nm (%)

Samples:22 pcsAverage:31.6%