Megaton Water Cherenkov Detectors and Astrophysical Neutrinos

Megaton Water Cherenkov Detectors and

Astrophysical Neutrinos

Maury Goodman, Argonne National Lab

http://www.ba.infn.it/~now2004/Program/plan/plan.htm

September 2004 Now 2004; Maury Goodman

Megaton Water Detectors

1 Megaton = 1000 milli-Megaton

UNO (650 milli-Megaton) US Collaboration, focusing on Henderson Mine Frejus/CERN initiative

Hyper-Kamiokande (1000 milli-Megaton)



Outline

AGN ’s “A Search for AGN ’s in Soudan 2”

[Astroparticle Physics 20 (2004) 533-547]

A taste of UNO & astrophysics Sources Supernova Relic ’s Shopping list of other possible sources of

astrophysical ’s

Status of Thousand-Milli-Megaton Water Cherenkov projects



Search for AGN ’s in Soudan 2



Soudan 2

♣ M = 1 milli-Megaton

♣ Very fine-grained iron calorimeter drift chamber built to study proton decay

♣ Use horizontal muons to identify neutrino induced sample

♣ Use energy loss to search for AGN ’s



Horizontal muons are neutrino induced.

z > 82 o

Must take topography into account

Slant depth > 14kmwe Multiple scattering cut



induced

Acceptance is 1.77 sr or 14% of 4



N = 65; t = 2 108 s live; = .56; Aeff=87m2

() = 4.01 0.50 0.30 10-13 cm-2s-1sr-1

( E > 1.8 GeV)

The 65 events are presumably all atmospheric neutrinos. AGN neutrinos would presumably have added energy loss along the tracks



Muon Energy Lossabove 1 TeV

1 TeV

Example of a horizontal muon in a 20m x 3m fine grained detector



Expected energy loss in Soudan 2

No event had any visible catastrophic energy loss

Efficiency was calculated using a predetermined cut of 5 GeV

E(TeV) clCM-2SR-1S-1

5 60% 2.2 10-14

20 91 1.5

100 99 1.4



Soudan 2 limits



Search for AGN ’s in

Water Detectors



Up-’s in Super-K

• For “SK-I”– 4/96 to 7/01

• 1680 live-days– More than other SK

analyses, this is insensitive to poor detector conditions

• For >7m path (>1.6 GeV):– 1901 thru-

• 354 are showering

– 468 stop-– <1.4o tracking res.



UNO and UHE

Area matters for detecting up-going Take Super-K as baseline (50 milli MT)

Effective area ~1200m2 for entering events UNO is 13x SK’s volume (650 milli MT)

Only 5.5x the area, ~6600m2

Low background sensitivity will increase by 5.5Large background sensitivity will increase by 2.3

km3 detectors will be ~1,000,000m2

and are already under constructionUNO won’t compete for anything triggered by km3



Lower Energies?

But long-string PMT detectors such as AMANDA, Antares, Baikal, etc. have very high Energy thresholds

UNO will have a ~5 MeV or ~10 MeV depending on final PMT density

Strategy would be similar to Soudan 2



Astro Issues

(The next several slides courtesy Alec Habig) In searching for sources, previous

experiments have taken a hodge podge approach

Experience says: you look at noise in enough different ways, you will see surprising things! Needed-

A priori tests!! Blind analyses? (Avoids some penalties for trials.)



Backgrounds

• Our background for source searches (and most all our data) are atmospheric

• Two approaches :– Bootstrap– Monte Carlo



Bootstrap

• Take the observed events• Randomly re-assign directions and live times• Pros:

– Easily generates background which matches angular and live time distribution of real data

– Any astrophysical will be scrambled in RA and disappear from the background sample

• Cons:– For low statistics samples backgrounds are too granular,

introducing non-Poissonian effects– Trying to smear space or time to combat granularity

introduces different non-Poissonian effects



Monte Carlo

• Use the experiment’s atmospheric Monte Carlo events, assigned times from the experimental live time distribution

• Pros:– Guaranteed to contain no point sources– Directly simulates your background

• Cons:– Only as good as your MC– More work to make, especially the live-time

distribution (given rates << clock ticks, need to save down-going CR distribution)



All-sky survey

• Do we see anything anywhere sticking out over background?1. break the data into spatial bins on the sky, sizes

chosen for good S/N (not obvious)

2. Calculate the expected atm. background in bins

3. Apply Poisson statistics, discover things or set limits



Bins

• Being a spherical sky, an igloo pixelization works better than the alternatives

• Problem: a source on a bin boundary would be unnoticed– Doing multiple offset

surveys solves this but kills sensitivity with trials factors



Cones

• Another approach: overlapping cones– Any point in the sky is

near center of at least one cone

– Fewer bin-edge problems, but must deal with odd oversampling effects



Unbinned Searches

How about avoiding bin edges entirely?

Try 2-point correlation functionUsed for galactic large-

scale structure searchesProblem – best for large

scale structure, not so sensitive to small clusters

Protheroe statistic …



• Haven’t seen any sources in an all-sky survey, so limits can be set on any given potential point source

• To test your favorite model of production at some high energy astrophysical source:– Up- near sources counted,

4o ½ angle cone shown here– Expected count from atm.

background calculated– Compute flux limits for

modelers to play with– SGR’s/Magnetars of current

interest

Pick a Source, Any Source

Source BG

Acceptance

x106cm2

90% c.l. limit

x10-14cm-2s-1

Cyg X-1 6 2.54 3.731 1.486

Cyg X-3 3 2.40 3.083 1.049

Her X-1 2 2.53 3.718 0.680

Sco X-1 3 2.95 6.533 0.465

Vela X-1 8 3.69 8.040 0.798

Crab N. 1 2.57 4.776 0.420

3C273 5 2.70 5.814 0.795

Per A 2 2.49 3.010 0.842

Vir A 4 2.76 5.329 0.712

Coma cl. 4 2.67 4.358 0.881

Gal. C. 1 3.51 7.144 0.269

Geminga 3 2.90 5.034 0.607

Mrk 421 2 2.62 3.414 0.734

Mrk 501 3 2.33 3.233 1.008

1ES1426 1 2.33 2.830 0.713

SGR 1900+14 2 2.51 5.483 0.461

SGR 0526-66 6 5.17 12.070 0.341

1E 1048-5937 5 5.98 11.920 0.273

SGR 1806-20 2 2.84 6.734 0.365

GX339-4 4 4.39 9.194 0.345

SMC X-1 5 4.90 12.203 0.293



Supernova Remnant Neutrinos



SN Relic

Look for the sum of all SNe long long ago in galaxies far far awaySupernovae Relic Neutrinos (SRN)

Provides a direct test of various early star-formation models by integrating over all stars and the whole universe

Expected signal !

1Lucas, G., 1975



SN Relic S/N

8B flux

hep flux

atm. e flux

SRN window!



Super-K SNR limit

• Flux limit < 1.2 cm-2 s-1

above 18 MeV• Super Kamiokande

Collaboration Phys.Rev.Lett. 90 (2003) 061101

atm. e

Michel e

DataTotal bg90%cl SRN



Recent estimates



SNR an expected UNO signal

• With 450 kton fiducial volume, expect 20-60 events per year

• This is a background limited search• Deeper underground – better sensitivity

• One sigma “hint” expected in 0.5 to 6 years.



Other searches in large water detectors



WIMP Detection

• WIMPs could be seen indirectly via their annihilation products (eventually ) if they are captured and settle into the center of a gravitational well

• WIMPs of larger mass would produce a tighter beam – Differently sized angular windows allow searches to be

optimized for different mass WIMPs SK Paper submitted to PRD



WIMPs in the Earth

Unosc atm MCDataOsc atm MC

• WIMPs could only get trapped in the Earth by interacting in a spin-independent way– All those even heavy nuclei

in the Earth with no net spin

• from WIMP annihilation would come from the nadir– No excess seen in any sized

angular cone (compared to background of oscillated atmospheric Monte Carlo)



Earth WIMP-induced Up- Limits

• Resulting upper limits on the WIMP-induced up- from the center of the Earth vs. WIMP mass– Varies as a function of

possible WIMP mass– Lower limits for higher

masses are due to the better S/N in smaller angular search windows

– Lowest masses ruled out anyway by accelerator searches



Earth WIMP-induced Up- Limits

• Resulting upper limits on the WIMP-induced up- from the center of the Earth vs. WIMP mass– Varies as a function of

possible WIMP mass– Lower limits for higher

masses are due to the better S/N in smaller angular search windows

– Lowest masses ruled out anyway by accelerator searches

UNO



Sun WIMP-induced Up- Limits

• Resulting upper limits on the WIMP-induced up- from the Sun vs. WIMP mass

• Same features as from Earth– But probes different

WIMP interactions– Unfortunately hard for

South Pole detectors to see the Sun (it’s always near the horizon)



Other searches

• WIMP’s from the galactic core• Galactic “Atmospheric” ’s• Diffuse AGN Search• Coincidence with Gamma Ray Bursts• Coincidence with xxx



Status of Megaton Water Cherenkov proposals



UNO goal

Reminder, the main goal is proton decay



UNO sensitivity(t)

Super-K

91.6 ktyr

5.7x1033 yr



UNO Conceptual Design



FREJUS

2) Components of the Project

-> a very large Laboratory to allow the installation of a Megaton-scale Cerenkov Detector ( 106 m3)

Present Tunnel

FutureSafety Tunnel

Present Laboratory

Future Laboratorywith Water Cerenkov Detectors

CERN

FRÉJUS

and (or) neutrino beta-beam

Three types of geometry that will be consideredin the preliminary study for the future Lab.



Frejus

13 km (12 870 m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2122 232425262728293031323334

70m x 70m x 250m

France Italy

Future Lab.

Present road Tunnel at Fréjus (grey)andfuture Tunnel (black) for safety (*) and for an independent access to the Fréjus Lab(s)______________________________________________________ (*) with 34 bypasses (shelters) connecting the two Tunnels



US sites

Henderson



Henderson Mine Overview

Mine is owned by:Climax Molybdenum Company,a subsidiary of Phelps Dodge Corporation

Mine product: Molybdenum ore (Moly)Mining method: Panel Caving (Block Caving)Production rate: 21,000 tons per dayMine life: About another 20 years

Henderson is the 6th or 7th largest underground hard rock mine in the world.A 28 ft diameter shaft from surface (10,500 ft) to 7500 level capable of hauling up to 200 people at a time. Trip down takes about 5

minutes.


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Henderson Mine Overview


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Underground Lab layout

Two access tunnels. 20 by 18 ft.

2*3600 ft @ 10% grade.

Estimated access costs $11 million

Estimated UNO ex. cost $81 million

Total excavation cost $120 million (30% cont.)



Tochibora



Rock Properties at Proposed Sites Rock Properties at Proposed Sites for Hyper-KAMIOKANDE Cavernfor Hyper-KAMIOKANDE Cavern

Spacing

Condition

Orientation

Poisson's Ratio 0.26 0.25

Location

Items MOZUMI Mine TOCHIBORA MINE Overburden (Subsurface Depth)

Rock Types

870 m 700 m

Hornblende Gneiss, Migmatite, partly with Limestone

Hornblende Biotite Gneiss, and Migmatite

Density 0.026 MN/m3 0.026 MN/m3 Compressive Strength 105 MPa - 120 MPa 150 MPa - 250 MPa Tensile Strength 9 MPa 8 - 10 MPa Young's Modulus 48 GPa 45 - 55 GPa

0.6 - 2 m

Very Rough

Very Favorable

Ground Water None None

0.2 - 0.6 m

Slightly Rough

Favorable

Rock Quality Designation (RQD) 78 % 85 % Rock Mass Ratings (RMR) 79 89

Rock Class (Japanese ) B - CH A - B

Discontinuities

Rock Mass Classification Ⅱ Ⅰ Good Rock Mass Very Good Rock Mass


September 2004 Now 2004; Maury Goodman2 detectors×48m × 50m ×250m, Total mass = 1 Mton

Twin Detector Hyper-Kamiokande



UNO Meeting

• http://nngroup.physics.sunysb.edu/uno/UNO04-Keystone/

• UNO Collaboration Meeting (UNO04) / Unification Day Workshop

• Keystone Resorts & Conference Center, Keystone, Colorado Oct. 14-16, 2004

• This meeting will include one-day workshop dedicated to Proton Decays in Unification Theories on Oct. 15 and a tour of the Henderson mine on Oct. 16.

• Chang Kee Jung: [email protected], 631-632-8108



Conclusion

• Astrophysical neutrinos will be an interesting topic for study by huge Water Cherenkov detectors, if they are built

• I don’t think astrophysical neutrinos will be a strong part of the motivation for building Thousand-milli-Megaton Water Cherenkov detectors

• Proton decay is a strong motivation– But that would be another talk





Megaton detectors & superbeams

Experiments at neutrino superbeams, and new off-axis experiments to measure 13 need to measure neutrino interactions in the 1-5 GeV region.

Proton decay detectors need to well measure event energies around 1 GeV

It makes sense to many to combine these two in a diverse physics program

This hasn’t been the favored scheme (e.g. P929) for two main reasons1. A proton decay detector needs to be underground2. A water detector quickly loses its e/NC rejection power from

1 GeV to 2 GeV This dual program should be kept in mind as

developments proceed.



Previous estimates



WIMPs in the Galactic Core

Unosc atm MCDataOsc atm MC

• WIMPs could get caught in the Really Big gravity well at the center of the Milky Way

• Make a cos() Galactic Center plot for all the up- events– No excess seen

compared to background of oscillated atmospheric Monte Carlo


Documents

Megaton Water Cherenkov Detectors and Astrophysical Neutrinos