1 Searching for Sterile Neutrinos with an Isotope β-decay Source: The IsoDAR Experiment Mike Shaevitz - Columbia University Aspen Winter Workshop--New

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Searching for Sterile Neutrinos with an Isotope β-decay Source:

The IsoDAR Experiment

Mike Shaevitz - Columbia UniversityMike 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– Reactore 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 > 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

3Hase Disappearance Been Observed? Reactor Antineutrino Anomaly

Red: 3 sin2(2θ13) = 0.15Blue: 4 ∆m2

new = 2 eV2 and sin2(2θnew)=0.12, with sin2(2θ13) = 0.085 arXiv: 1204.5379

QuickTime™ and a decompressor

are needed to see this picture.

Current ReactorExperiments

Older ReactorExps at Close DistancesR = 0.927 0.023 (3.0 )

Region to Explorefor Sterile Neutrinos

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4

e s ? RE

NO

Day

a B

ay

near detectors

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Very-short Baseline Oscillation Experiments

• 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





- Detector

1 / L2 flux rate modulated by Probosc =sin2 2θ ⋅sin2 m2L / E( )

- Source

Radioactive Sourceor

Isotope Sourceor

Reactor Sourceor

Proton into Dump Source

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Possible Sources for VSBL Experiments

• 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

Need experiments with L/E ~ 1 m/MeV

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IsoDAR Experiment

Isotope Decay-at-Rest Neutrino Source (e Disappearance )



7DAEDALUS 800 MeV Cyclotron System (Under Development)





H2+ Ion

Source

InjectorCyclotron(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.

DAR Target-Dump (about 6x6x9 m3)

IsoDARCyclotron

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Submitted to NIM

Columbia, Huddersfield, IBA, Maryland, MIT,PSI, INFN-Catania, INFN –Legnaro, RIKEN, Wisconsin

Academics: Neutrino Physicists, Accelerator PhysicistsAnd also Scientists at a Corporation

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Ionsource

InjectorSuperconductingRing Cyclotron

Target/Dump

Phase I: The Ion Source

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source solenoidlens slits &

diagnostics



11Beam to be characterized at Best Cyclotrons, Inc, VancouverThis spring (NSF funded)

Results to be available by Cyclotrons’13 Conference, Sept 2013, Vancouver

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Ionsource

InjectorSuperconductingRing Cyclotron

Target/Dump

We have a workable ion source for a Phase II

IsoDAR: A sterile neutrino experimentOn its own!

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• High intensitye 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 DAEALUS 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.

Overview IsoDARe Disappearance Exp

DetectorBlanket/Shield

Targetcyclotronprotons

Phys Rev Lett 109 141802 (2012) arXiv:1205.4419

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IsoDAR Neutrino Source and Events



arXiv:1205.4419

• p (60 MeV) + 9Be 8Li + 2p– plus many neutrons since low

binding energy

• n + 7Li (shielding) 8Li

• 8Li 8Be + e +e

– Meane energy = 6.5 MeV

– 2.61022e / yr

• Example detector: Kamland (900 t)

– Use IBDe + 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



5 yrs

15IsoDAR at Kamland



Potential Location of Source

Currently working with the Kamland collaborationon the details of siting and installation of thecyclotron, beamline, and neutrino source.

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Detecte Events using Inverse Beta Decay (IBD)



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IsoDAR e Disappearance Oscillation Sensitivity (3+1)



5 yrs

e e

5

18IsoDAR Measurement Sensitivity



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IsoDAR’s high statistics and good L/E resolution has potential to distinguish (3+1) and (3+2) oscillation models

Oscillation L/E Waves in IsoDAR



5 yrs 5 yrs

Observed/Predicted event ratio vs L/E including energy and position smearing

e e

e e

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Possibility to Probe Lower m2 using Super-K



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Beyond Oscillations:

IsoDAR sin2θW Measurement

22ee Elastic Scattering Measure sin2θW



• 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 sin2θW with pure lepton process

antineutrino-electron elastic scattering:e + e e + e

23Kamland Backgrounds toee Signal



• Backgrounds are large since signal is single outgoing electron

• Visible energy is low since outgoinge takes away energy

From L. Winslow



electron kinematics

Cuts:- Evis > 3 MeV- θ (to source) < 250

Reduce isotropic bkgnd by x2

Use large sample of IBD eventsto constrain normalization to 0.2%

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IsoDAR sin2θW Measurement Sensivity

• 5yr data (7200 evts with Evis>3MeV)

IsoDAR/Kamland: sin2θW = 0.0075 (~3%)

– Not as good as NuTeV: sin2θW = 0.2277 0.0016 (0.7%)– But would be bestee elastic scattering measurement

(See 3% band below)



25Final 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 ofe Appearance



e

MiniBooNEAllowed Regions

28Future 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, DAEALUS, KDAR

Accelerator using Pion Decay-in-Flight

Appearance & Disapp

e , e

, e e

MINOS+, MicroBooNE,

LAr1kton+MicroBooNE, CERN SPS

Low-Energy -Factory

Appearance & Disapp

e ,e

, e e

STORM at Fermilab

()

29Use IsoDARe 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 eventsEthresh > 1keV

LAr @ 10m1ton for 1 yr

LNe @ 10m1ton for 1 yr

Ethresh > 1keV

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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 @ 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 , compacte source from 8Li isotope decay.– Synergy with industrial interest in medical isotope production

• High intensity IsoDAR typee 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 design,Assembly Plan,Structural analysis,Cryo system design

Engineering Study of Sector Magnet for the Daedalus Experiment,http://arxiv.org/abs/1209.4886

Documents

1 Searching for Sterile Neutrinos with an Isotope β-decay Source: The IsoDAR Experiment Mike Shaevitz - Columbia University Aspen Winter Workshop--New