Searching for Sterile Neutrinos with an Isotope -decay Source: The - PowerPoint PPT Presentation

1 Searching for Sterile Neutrinos with an Isotope β -decay Source: The IsoDAR Experiment Mike Shaevitz Shaevitz - Columbia University - Columbia University Mike 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 Δ m 2 ≈ 1 eV 2 Some difficulty for fits – LSND / MiniBooNE ν e / ν e appearance with one or two – Reactor ν e disappearance (“Reactor Anomaly”) sterile neutrino models – Radioactive source ν e disappearance - App vs Disapp – But still no indication of ν µ disappearance - ν vs ν • Establishing the existence of sterile neutrinos would be a major result for particle physics but … .. • Need definitive experiments – Significance at the > 5 σ 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

3 Has ν ν e Disappearance Been Observed? ⇒ Reactor Antineutrino Anomaly Daya Bay ν e →ν s ? RENO 3 ν 4 ν near detectors Region to Explore Current Reactor Older Reactor for Sterile Neutrinos Experiments Exps at Close Distances R = 0.927 ± 0.023 (3.0 σ ) Red: 3 ν sin 2 (2 θ 13 ) = 0.15 Blue: 4 ν ∆ m 2 new = 2 eV 2 and sin 2 (2 θ new )=0.12, with sin 2 (2 θ 13 ) = 0.085 arXiv: 1204.5379

4 Very-short Baseline Oscillation Experiments ν - Source ν - Detector Radioactive Source or Isotope Source or Reactor Source or Proton into Dump Source 1/ L 2 flux rate modulated by Prob osc = sin 2 2 ! " sin 2 # m 2 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/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

5 Possible Sources for VSBL Experiments Need experiments with L/E ~ 1 m/MeV • Reactor sources – E ν ~ 3 MeV ⇒ optimum distance around 3 to 20 m – Reactor core size can also be an issue • Radioactive sources – E ν ~ few MeV ⇒ see oscillations with wavelengths ~ 1m – Compact source can be placed directly into detector or just outside • Isotope neutrino source – E ν ~ 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

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

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

8 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

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

10 solenoid source slits & lens diagnostics

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

13 Overview IsoDAR ν ν e Disappearance Exp • High intensity ν e source using β -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 δ 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 … . cyclotron protons Blanket/ Detector Target Shield • Physics measurements: – ν 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) arXiv:1205.4419

14 IsoDAR Neutrino Source and Events • 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 − + ν e • – Mean ν e energy = 6.5 MeV – 2.6 × 10 22 ν e / yr arXiv:1205.4419 • Example detector: Kamland (900 t) – Use IBD ν 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 5 yrs

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

16 Detect ν ν e Events using Inverse Beta Decay (IBD)

17 IsoDAR ν ν e Disappearance Oscillation Sensitivity (3+1) ν e →ν e 5 σ 5 yrs

18 IsoDAR Measurement Sensitivity

19 Oscillation L/E Waves in IsoDAR Observed/Predicted event ratio vs L/E including energy and position smearing ν e →ν e ν e →ν 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

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

21 Beyond Oscillations: IsoDAR sin 2 θ W Measurement

22 ν e e Elastic Scattering ⇒ Measure sin 2 θ W ν • NuTeV weak mixing angle measurement using neutrino neutral current scattering differs from expectation by 3 σ – Is there something special with neutrinos or difficulty in NuTeV analysis? ⇒ Use IsoDAR/Kamland to measure sin 2 θ W with pure lepton process antineutrino-electron elastic scattering: ν ν e + e → ν ν e + e

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

24 IsoDAR sin 2 θ W Measurement Sensivity • 5yr data (7200 evts with E vis >3MeV) ⇒ IsoDAR/Kamland: δ sin 2 θ W = 0.0075 (~3%) – Not as good as NuTeV: sin 2 θ W = 0.2277 ± 0.0016 (0.7%) – But would be best ν 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 Δ m 2 ~1 eV 2 region – Some tension with lack of ν µ disappearance signals • Many proposals and ideas for sterile neutrino searches – New experiments to have better sensitivity (~5 σ 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)