Transcript NOW2004 - Nevis Laboratories

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Searching for Sterile Neutrinos with an Isotope
β-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
Some difficulty for fits
with one or two
sterile neutrino models
- App vs Disapp
-  vs
• Establishing the existence of sterile neutrinos would be a major result for
particle physics but …..
• Need definitive experiments
– Significance at the > 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
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RENO
Daya Bay
Hase Disappearance Been Observed?
 Reactor Antineutrino Anomaly
e s ?
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4
near detectors
Region to Explore
for Sterile Neutrinos
Older Reactor
Exps at Close Distances
R = 0.927  0.023 (3.0  )
Current Reactor
Experiments
Red: 3 sin2(2θ13) = 0.15
Blue: 4 ∆m2new = 2 eV2
and sin2(2θnew)=0.12,
with sin2(2θ13) = 0.085
arXiv: 1204.5379
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Very-short Baseline Oscillation Experiments
 - Source
Radioactive Source
or
Isotope Source
or
Reactor Source
or
Proton into Dump Source
 - Detector
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
1 / L2 flux rate modulated by Probosc  sin2 2  sin2 m2 L / E
• 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

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
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–
–
–
–
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 Experiment
Isotope Decay-at-Rest Neutrino Source
(e Disappearance )
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DAEDALUS 800 MeV Cyclotron System
(Under Development)
H2+ Ion
Source
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DAR Target-Dump
(about 6x6x9 m3)
IsoDAR
Cyclotron
Injector
Cyclotron
(Resistive
Isochronous)
Ring Cyclotron
(Superconducting)
“Isochronous cyclotron” where
mag. field changes with radius,
but RF does not change with time.
This can accelerate many bunches
at once.
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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
Ion
source
Injector
Superconducting
Ring Cyclotron
Target/
Dump
Ion Source:
By our collaborators at INFN Catania.
Produces sufficient H2+!
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(>30 mA required
in order to accelerate 5 mA.
.)
source
solenoid
lens
slits &
diagnostics
Beam to be characterized at Best Cyclotrons, Inc, Vancouver
This spring (NSF funded)
Results to be available by
Cyclotrons’13 Conference, Sept
2013, Vancouver
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We have a workable ion source for a
Phase II
Ion
source
Injector
IsoDAR:
Superconducting
Ring Cyclotron
Target/
Dump
A sterile neutrino experiment
On its own!
Overview IsoDARe Disappearance Exp
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• 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….
protons
cyclotron
Target
Blanket/
Shield
Detector
• Physics measurements:
– e disappearance measurement in the region of the LSND and reactorneutrino anomalies.
– Measure oscillatory behavior within the detector as a function of L and E.
Phys Rev Lett 109 141802 (2012)
arXiv:1205.4419
IsoDAR Neutrino Source and Events
• p (60 MeV) + 9Be  8Li + 2p
– plus many neutrons since low
binding energy
• n+
•
7Li
(shielding) 
8Li
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 8Be + e +e
– Meane energy = 6.5 MeV
– 2.61022e / yr
8Li
• 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 @ 10ma rate
– Observe changes in the IBD rate
as a function of L/E
arXiv:1205.4419
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5 yrs
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IsoDAR at Kamland
Potential Location of  Source
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Currently working with the Kamland collaboration
on the details of siting and installation of the
cyclotron, beamline, and neutrino source.
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Detecte Events using Inverse Beta Decay (IBD)
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IsoDAR e Disappearance Oscillation Sensitivity (3+1)
e e
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5
5 yrs
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
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e e
5 yrs
5 yrs
IsoDAR’s high statistics and good L/E resolution has potential
to distinguish (3+1) and (3+2) oscillation models
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Possibility to Probe Lower
m2 using Super-K
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Beyond Oscillations:
IsoDAR sin2W Measurement
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
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Cuts:
- Evis > 3 MeV
-  (to source) < 250
 Reduce isotropic
bkgnd by x2
electron kinematics
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From L. Winslow
Use large sample of IBD events
to constrain normalization to 0.2%
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IsoDAR sin2W Measurement Sensivity
• 5yr data (7200 evts with Evis>3MeV)
 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 spectrum
and 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
– R&D 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
MiniBooNE
Allowed Regions
e
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Future Experimental Oscillation Proposals/Ideas
Type of Exp
App/Disapp
Osc Channel
Experiments
Disapp
e e
Nucifer, Ricochet,
SCRAMM, NIST,
Neutrino4, DANSS
Radioactive Sources
Disapp
e e
(e  e)
Baksan, LENS, Borexino,
SNO+, CeLAND, DayaBay
Isotope Source
Disapp
Pion / Kaon Decayat-Rest Source
Appearance  e
& Disapp
e  e
OscSNS, CLEAR,
DAEALUS, KDAR
Accelerator  using
Pion Decay-in-Flight
Appearance   e , e
& Disapp
   , e  e
MINOS+, MicroBooNE,
LAr1kton+MicroBooNE,
CERN SPS
Low-Energy
-Factory
Appearance e   ,e 
& Disapp
   , e  e
STORM at Fermilab
Reactor Source
()
e e
IsoDAR
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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
Ethresh > 1keV
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LAr @ 10m
1ton for 1 yr
Integral = 690 events
Ethresh > 1keV
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LNe @ 10m
1ton 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 > 20 eV
Ge @ 10m
100kg 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
Engineering Study of Sector Magnet for the Daedalus Experiment,
http://arxiv.org/abs/1209.4886
Engineering design,
Assembly Plan,
Structural analysis,
Cryo system design
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