Searching for Sterile Neutrinos with an Isotope

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Searching for Sterile Neutrinos with an Isotope
ß-decay Source The IsoDAR Experiment

• Mike Shaevitz - Columbia University
• Aspen Winter Workshop--New Directions in Neutrino
  Physics      
• February 8, 2013

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Where Are We With Sterile Neutrinos?

• Several hints of oscillations through sterile
  neutrino state with ?m2 ? 1 eV2
• LSND / MiniBooNE ?e /??e appearance
• Reactor??e disappearance (Reactor Anomaly)
• Radioactive source ?e disappearance
• But still no indication of ?? disappearance
• Establishing the existence of sterile neutrinos
  would be a major result for particle physics but
  ..
• Need definitive experiments
• Significance at the gt 5? level
• Observation of oscillatory behavior within
  detector
• Several directions for next generation
  experiments
• Multi-detector accelerator neutrino beam
  experiments
• Very short baseline (VSBL) experiments with
  compact neutrino sources

Some difficulty for fitswith one or twosterile
neutrino models - App vs Disapp- ? vs??
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Has??e Disappearance Been Observed?
? Reactor Antineutrino Anomaly
near detectors
Red 3? sin2(2?13) 0.15 Blue 4? ?m2new 2 eV2
and sin2(2?new)0.12, with
sin2(2?13) 0.085 arXiv 1204.5379
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Very-short Baseline Oscillation Experiments
? - Source
? - Detector
Radioactive SourceorIsotope SourceorReactor
SourceorProton into Dump Source

• Can observe oscillatory behavior within the
  detector if neutrino source has small extent .
• Look for a change in event rate as a function of
  position and energy within the detector
• Bin observed events in L/E (corrected for the
  1/L2) to search for oscillations
• Backgrounds produce fake events that do not show
  the oscillation L/E behavior and can be
  separated from signal

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Possible Sources for VSBL Experiments
Need experiments with L/E 1 m/MeV

• Reactor sources
• E? 3 MeV ? optimum distance around 3 to 20 m
• Reactor core size can also be an issue
• Radioactive sources
• E? few MeV ? see oscillations with wavelengths
  1m
• Compact source can be placed directly into
  detector or just outside
• Isotope neutrino source
• E? 8 MeV (typical of short lived isotopes,
  i.e. 8Li)
• Distance to source can be longer 10m to 20m
• Compact source that can be set up near an
  existing large detector
• Beam can be turned off periodically to measure
  background
• Higher energy neutrinos with less background

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IsoDAR ExperimentIsotope Decay-at-Rest Neutrino
Source (??e Disappearance )
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DAE?DALUS 800 MeV Cyclotron System (Under
Development)
IsoDARCyclotron
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Columbia, Huddersfield, IBA, Maryland, MIT, PSI,
INFN-Catania, INFN Legnaro, RIKEN,
Wisconsin Academics Neutrino Physicists,
Accelerator Physicists And also Scientists at a
Corporation
Submitted to NIM
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Phase I The Ion Source
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solenoid lens
source
slits diagnostics
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Beam to be characterized at Best Cyclotrons, Inc,
Vancouver This spring (NSF funded)
Results to be available by Cyclotrons13
Conference, Sept 2013, Vancouver
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We have a workable ion source for a
Phase II
IsoDAR
A sterile neutrino experiment On its own!
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Overview IsoDAR??e Disappearance Exp

• High intensity??e source using ?-decay at rest of
  8Li isotope ? IsoDAR
• 8Li produced by high intensity (10ma) proton beam
  from 60 MeV cyclotron? being developed as
  prototype injector for DAE?ALUS cyclotron system
• Put a cyclotron-isotope source near one of the
  large (kton size) liquid scintillator/water
  detectors such as KAMLAND, SNO, Borexino,
  Super-K.
• Physics measurements
• ??e disappearance measurement in the region of
  the LSND and reactor-neutrino anomalies.
• Measure oscillatory behavior within the detector
  as a function of L and E.

Phys Rev Lett 109 141802 (2012) arXiv1205.4419
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IsoDAR Neutrino Source and Events

• p (60 MeV)    9Be  ?  8Li    2p
• plus many neutrons since low binding energy
• n 7Li (shielding) ? 8Li
• 8Li ? 8Be e? ??e
• Mean??e energy 6.5 MeV
• 2.6?1022??e / yr
• Example detector Kamland (900 t)
• Use IBD??e p ? e n process
• Detector center 16m from source
• 160,000 IBD events / yr
• 60 MeV protons _at_ 10ma rate
• Observe changes in the IBD rate as a function of
  L/E

arXiv1205.4419
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IsoDAR at Kamland
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Detect??e Events using Inverse Beta Decay (IBD)
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IsoDAR ??e Disappearance Oscillation Sensitivity
(31)
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IsoDAR Measurement Sensitivity
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Oscillation L/E Waves in IsoDAR
Observed/Predicted event ratio vs L/E including
energy and position smearing
??e ???e
??e ???e
IsoDARs high statistics and good L/E resolution
has potential to distinguish (31) and (32)
oscillation models
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Possibility to Probe Lower ?m2 using Super-K
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Beyond OscillationsIsoDAR sin2?W Measurement
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??ee Elastic Scattering ? Measure sin2?W

• NuTeV weak mixing angle measurement using
  neutrino neutral current scattering differs from
  expectation by 3?
• Is there something special with neutrinos or
  difficulty in NuTeV analysis?
• ? Use IsoDAR/Kamland to measure sin2?W with
  pure lepton process
• antineutrino-electron elastic
  scattering??e e ? ??e e

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Kamland Backgrounds to??ee Signal

• Backgrounds are large since signal is single
  outgoing electron
• Visible energy is low since outgoing??e takes
  away energy

• Cuts
• Evis gt 3 MeV- ? (to source) lt 250
• ? Reduce isotropic bkgnd by x2

electron kinematics
From L. Winslow
Use large sample of IBD eventsto constrain
normalization to 0.2
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IsoDAR sin2?W Measurement Sensivity

• 5yr data (7200 evts with Evisgt3MeV)
  ? IsoDAR/Kamland ?sin2?W 0.0075 (3)
• Not as good as NuTeV sin2?W 0.2277 ? 0.0016
  (0.7)
• But would be best??ee elastic scattering
  measurement(See 3 band below)

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Final Comments

• Establishing the existence of sterile neutrinos
  would be a major result for particle physics
• Several hints in the ?m2 1 eV2 region
• Some tension with lack of ?? disappearance
  signals
• Many proposals and ideas for sterile neutrino
  searches
• New experiments to have better sensitivity (5?
  level) with capabilities to see oscillatory
  behavior.
• IsoDAR could make a definitive search for sterile
  neutrinos
• Advantage over reactor and radioactive sources in
  having neutrinos with x3 higher energy
• Source is compact with a very well understood
  energy spectrumand can be setup near an existing
  large detector
• Combined L and E analysis can isolate the
  oscillatory behavior and reduce backgrounds
• Can turn beam off to measure background
• RD is well underway to produce a high-intensity
  compact 60 MeV cyclotron to drive the neutrino
  source (See talk by Matt Toups)

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Backup
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LSND and MiniBooNE Indications of??e Appearance
MiniBooNEAllowed Regions
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Future Experimental Oscillation Proposals/Ideas
Type of Exp App/Disapp Osc Channel Experiments
Reactor Source Disapp ??e ???e Nucifer, Ricochet, SCRAMM, NIST, Neutrino4, DANSS
Radioactive Sources Disapp ??e ???e (?e ? ?e) Baksan, LENS, Borexino, SNO, CeLAND, Daya-Bay
Isotope Source Disapp ??e ???e IsoDAR
Pion / Kaon Decay-at-Rest Source Appearance Disapp ??? ???e ?e ? ?e OscSNS, CLEAR, DAE?ALUS, KDAR
Accelerator ? using Pion Decay-in-Flight Appearance Disapp ?? ? ?e ,??? ???e ?? ? ?? , ?e ? ?e MINOS, MicroBooNE, LAr1ktonMicroBooNE, CERN SPS
Low-Energy ?-Factory Appearance Disapp ?e ? ?? ,??e ???? ?? ? ?? , ?e ? ?e ?STORM at Fermilab
(?)
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Use IsoDAR??e Source for Coherent NC Measurement

• High intensity isotropic neutrino beam with well
  known spectrum
• Advantages
• About x2 higher energy than reactor neutrinos
  (but lower flux)
• IsoDAR experimental site should offer a close,
  low-background location to put a ton scale
  coherent scattering detector
• Can turn off cyclotron to give measurement of
  non-beam backgrounds
• Source size 0.5m so might explore doing an
  oscillation search with coherent scattering
  events.
• Can vary distance with cyclotron beam to multiple
  ? sources
• Can go deep to reduce cosmic backgrounds
• Do dark matter searches during cyclotron-off
  periods
• Disadvantage
• To get needed rates, one needs to push the
  detection thresholds down to the few keV range
• High-intensity cyclotron needs to be developed

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Visible Energy Spectrum for LAr and LNe
Integral 690 events Ethresh gt 1keV
Ethresh gt 1keV
LNe _at_ 10m1ton for 1 yr
LAr _at_ 10m1ton for 1 yr
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Example Coherent Rates with 1ton LArgon with
IsoDAR
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Visible Energy Spectrum for Ge Detectors
475 events/yr EThresh gt 20 eV
Ge _at_ 10m100kg for 1 yr
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Overview

• High-power cyclotrons can be used to make an
  intense, compact neutrino source.
• Daedalus CP violation program using 800 MeV
  proton cyclotrons
• High intensity DAR source of??? to complement
  long-baseline neutrino oscillation program
• Use NC coherent scattering to search for ??
  ?STERILE with DAR beam
• IsoDAR sterile neutrino experiment using a 60 MeV
  proton cyclotron
• Cost effective, intense , compact??e source
  from 8Li isotope decay.
• Synergy with industrial interest in medical
  isotope production
• High intensity IsoDAR type??e source could also
  be used for a neutral current coherent neutrino
  scattering experiment
• Need to couple the IsoDAR source with a low
  threshold (few keV) 10 to 1000 kg detector

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Engineering Study of Sector Magnet for the
Daedalus Experiment, http//arxiv.org/abs/1209.488
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Engineering design, Assembly Plan, Structural
analysis, Cryo system design