Megaton Water Cherenkov Detectors and Astrophysical Neutrinos

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Megaton Water Cherenkov Detectors and
Astrophysical Neutrinos
Maury Goodman, Argonne National Lab
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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)

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Outline

• AGN ns
• A Search for AGN ns in Soudan 2
  Astroparticle Physics 20 (2004) 533-547
• A taste of UNO astrophysics
• Sources
• Supernova Relic ns
• Shopping list of other possible sources of
  astrophysical ns
• Status of Thousand-Milli-Megaton Water Cherenkov
  projects

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• Search for AGN ns in Soudan 2

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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 ns

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• Horizontal muons are neutrino induced.
• Qz gt 82 o
• Must take topography into account
• Slant depth gt 14kmwe
• Multiple scattering cut

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n induced m
Acceptance is 1.77 sr or 14 of 4p
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• N 65 t 2 108 s live e .56 Aeff87m2
• F (nm) 4.01 ? 0.50 ? 0.30 10-13 cm-2s-1sr-1
• ( Em gt 1.8 GeV)
• The 65 events are presumably all atmospheric
  neutrinos. AGN neutrinos would presumably have
  added energy loss along the tracks

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Muon Energy Lossabove 1 TeV
Example of a horizontal muon in a 20m x 3m fine
grained detector
1 TeV
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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) e 90 cl CM-2SR-1S-1
5 60 2.2 10-14
20 91 1.5
100 99 1.4
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Soudan 2 limits
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• Search for AGN ns in
• Water Detectors

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Up-ms 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 gt7m path (gt1.6 GeV)
• 1901 thru-m
• 354 are showering
• 468 stop-m
• lt1.4o tracking res.

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UNO and UHE n

• Area matters for detecting up-going m
• Take Super-K as baseline (50 milli MT)
• Effective area 1200m2 for entering events
• UNO is 13x SKs volume (650 milli MT)
• Only 5.5x the area, 6600m2
• Low background sensitivity will increase by 5.5
• Large background sensitivity will increase by 2.3
• km3 detectors will be 1,000,000m2
• and are already under construction
• UNO wont compete for anything triggered by km3

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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

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n 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.)

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Backgrounds

• Our background for source searches (and most all
  our data) are atmospheric nm
• Two approaches
• Bootstrap
• Monte Carlo

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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 n 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

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Monte Carlo

• Use the experiments atmospheric n 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 n rates ltlt clock ticks, need
  to save down-going CR distribution)

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All-sky survey

• Do we see anything anywhere sticking out over
  background?
• break the data into spatial bins on the sky,
  sizes chosen for good S/N (not obvious)
• Calculate the expected atm. n background in bins
• Apply Poisson statistics, discover things or set
  limits

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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

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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

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Unbinned Searches

• How about avoiding bin edges entirely?
• Try 2-point correlation function
• Used for galactic large-scale structure searches
• Problem best for large scale structure, not so
  sensitive to small clusters
• Protheroe statistic

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Pick a Source, Any Source
Source n 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 190014 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

• Havent 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 n production at
  some high energy astrophysical source
• Up-m near sources counted, 4o ½ angle cone shown
  here
• Expected count from atm.n background calculated
• Compute flux limits for modelers to play with
• SGRs/Magnetars of current interest

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• Supernova Remnant Neutrinos

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SN Relic n

• Look for the sum of all SNe long long ago in
  galaxies far far away
• Supernovae 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
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SN Relic n S/N
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Super-K SNR limit

• Flux limit lt 1.2 cm-2 s-1 above 18 MeV
• Super Kamiokande Collaboration Phys.Rev.Lett. 90
  (2003) 061101

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Recent estimates
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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.

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• Other searches in large water detectors

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WIMP Detection

• WIMPs could be seen indirectly via their
  annihilation products (eventually nm) if they are
  captured and settle into the center of a
  gravitational well
• WIMPs of larger mass would produce a tighter n
  beam
• Differently sized angular windows allow searches
  to be optimized for different mass WIMPs

SK Paper submitted to PRD
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WIMPs in the Earth

• 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
• nm from WIMP annihilation would come from the
  nadir
• No excess seen in any sized angular cone
  (compared to background of oscillated atmospheric
  n Monte Carlo)

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Earth WIMP-induced Up-m Limits

• Resulting upper limits on the WIMP-induced up-m
  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

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Earth WIMP-induced Up-m Limits

• Resulting upper limits on the WIMP-induced up-m
  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
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Sun WIMP-induced Up-m Limits

• Resulting upper limits on the WIMP-induced up-m
  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 (its always near the horizon)

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Other searches

• WIMPs from the galactic core
• Galactic Atmospheric ns
• Diffuse AGN Search
• Coincidence with Gamma Ray Bursts
• Coincidence with xxx

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• Status of Megaton Water Cherenkov proposals

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UNO goal

• Reminder, the main goal is proton decay

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UNO sensitivity(t)
Super-K 91.6 ktyr 5.7x1033 yr
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UNO Conceptual Design
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FREJUS
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Frejus
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US sites
Henderson
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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 day Mine 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
Ap, 2004 UNO Collaboration Meeting
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Underground Lab layout
Two access tunnels. 20 by 18 ft. 23600 ft _at_
10 grade. Estimated access costs 11
million Estimated UNO ex. cost 81
million Total excavation cost 120 million
(30 cont.)
Ap, 2004 UNO Collaboration Meeting
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Tochibora
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Rock Properties at Proposed Sites for
Hyper-KAMIOKANDE Cavern
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Twin Detector Hyper-Kamiokande
2 detectors48m 50m 250m, Total mass 1 Mton

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UNO Meeting

• http//nngroup.physics.sunysb.edu/uno/UNO04-Keysto
  ne/
• 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 alpinist_at_nngroup.physics.sunysb.ed
  u, 631-632-8108

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Conclusion

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

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(No Transcript)
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Megaton detectors superbeams

• Experiments at neutrino superbeams, and new
  off-axis experiments to measure q13 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 hasnt been the favored scheme (e.g. P929)
  for two main reasons
• A proton decay detector needs to be underground
• 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.

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Previous estimates
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WIMPs in the Galactic Core

• WIMPs could get caught in the Really Big gravity
  well at the center of the Milky Way
• Make a cos(q) Galactic Center plot for all the
  up-m events
• No excess seen compared to background of
  oscillated atmospheric n Monte Carlo