1 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

2 Where Are We With Sterile Neutrinos? Several hints of oscillations through sterile neutrino state with  m 2  1 eV 2 –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 > 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 fits with one or two sterile neutrino models - App vs Disapp - vs 

3 Has  e Disappearance Been Observed?  Reactor Antineutrino Anomaly Red: 3 sin 2 (2θ 13 ) = 0.15 Blue: 4 ∆m 2 new = 2 eV 2 and sin 2 (2θ new )=0.12, with sin 2 (2θ 13 ) = arXiv: Current Reactor Experiments Older Reactor Exps at Close Distances R =  (3.0  ) Region to Explore for Sterile Neutrinos 3 4  e  s ? RENO Daya Bay near detectors

4 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/L 2 ) to search for oscillations Backgrounds produce fake events that do not show the oscillation L/E behavior and can be separated from signal - Detector - Source Radioactive Source or Isotope Source or Reactor Source or Proton into Dump Source

5 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. 8 Li) –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

6 IsoDAR Experiment Isotope Decay-at-Rest Neutrino Source (  e Disappearance )

7 DAE  DALUS 800 MeV Cyclotron System (Under Development) H 2 + Ion Source 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. DAR Target-Dump (about 6x6x9 m 3 ) IsoDAR Cyclotron

8 Submitted to NIM Columbia, Huddersfield, IBA, Maryland, MIT, PSI, INFN-Catania, INFN –Legnaro, RIKEN, Wisconsin Academics: Neutrino Physicists, Accelerator Physicists And also Scientists at a Corporation

9 Ion source Injector Superconducting Ring Cyclotron Target/ Dump Phase I: The Ion Source

10 source solenoid lens slits & diagnostics Ion Source: By our collaborators at INFN Catania. Produces sufficient H 2 + ! (>30 mA required in order to accelerate 5 mA. Most beam is lost in the first turns.)

11 Beam to be characterized at Best Cyclotrons, Inc, Vancouver This spring (NSF funded) Results to be available by Cyclotrons’13 Conference, Sept 2013, Vancouver

12 Ion source Injector Superconducting Ring Cyclotron Target/ Dump We have a workable ion source for a Phase II IsoDAR: A sterile neutrino experiment On its own!

13 High intensity  e source using  -decay at rest of 8 Li isotope  IsoDAR 8 Li 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. Overview IsoDAR  e Disappearance Exp Detector Blanket/ Shield Targetcyclotron protons Phys Rev Lett (2012) arXiv:

14 IsoDAR Neutrino Source and Events arXiv: p (60 MeV) + 9 Be  8 Li + 2p –plus many neutrons since low binding energy n + 7 Li (shielding)  8 Li 8 Li  8 Be + e  +  e –Mean  e energy = 6.5 MeV –2.6   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 10ma rate –Observe changes in the IBD rate as a function of L/E 5 yrs

15 IsoDAR at Kamland Potential Location of Source Currently working with the Kamland collaboration on the details of siting and installation of the cyclotron, beamline, and neutrino source.

16 Detect  e Events using Inverse Beta Decay (IBD)

17 IsoDAR  e Disappearance Oscillation Sensitivity (3+1) 5 yrs  e  e 55

18 IsoDAR Measurement Sensitivity

19 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 Observed/Predicted event ratio vs L/E including energy and position smearing  e  e

20 Possibility to Probe Lower  m 2 using Super-K

21 Beyond Oscillations: IsoDAR sin 2  W Measurement

22  e e Elastic Scattering  Measure sin 2  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 sin 2  W with pure lepton process antineutrino-electron elastic scattering:  e + e   e + e

23 Kamland Backgrounds to  e e Signal Backgrounds are large since signal is single outgoing electron Visible energy is low since outgoing  e takes away energy From L. Winslow electron kinematics Cuts: - Evis > 3 MeV -  (to source) < 25 0  Reduce isotropic bkgnd by x2 Use large sample of IBD events to constrain normalization to 0.2%

24 IsoDAR sin 2  W Measurement Sensivity 5yr data (7200 evts with E vis >3MeV)  IsoDAR/Kamland:  sin 2  W = (~3%) –Not as good as NuTeV: sin 2  W =  (0.7%) –But would be best  e e elastic scattering measurement (See 3% band below)

25 Final Comments Establishing the existence of sterile neutrinos would be a major result for particle physics Several hints in the  m 2 ~1 eV 2 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)

26 Backup

27 LSND and MiniBooNE Indications of  e Appearance    e MiniBooNE Allowed Regions

28 Future Experimental Oscillation Proposals/Ideas Type of ExpApp/DisappOsc ChannelExperiments Reactor SourceDisapp  e  e Nucifer, Ricochet, SCRAMM, NIST, Neutrino4, DANSS Radioactive SourcesDisapp  e  e ( e  e ) Baksan, LENS, Borexino, SNO+, CeLAND, Daya- Bay Isotope SourceDisapp  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, LAr1kton+MicroBooNE, CERN SPS Low-Energy -Factory Appearance & Disapp e  ,  e     , e  e STORM at Fermilab ()()

29 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

30 Visible Energy Spectrum for LAr and LNe Integral = 690 events E thresh > 1keV 10m 1ton for 1 yr 10m 1ton for 1 yr E thresh > 1keV

31 Example Coherent Rates with 1ton LArgon with IsoDAR

32 Visible Energy Spectrum for Ge Detectors 475 events/yr E Thresh > 20 eV 10m 100kg for 1 yr

33 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 8 Li 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

34 Engineering design, Assembly Plan, Structural analysis, Cryo system design Engineering Study of Sector Magnet for the Daedalus Experiment,