Probing Neutrino Masses Using Frequency Techniques J. A. Formaggio - PowerPoint PPT Presentation

Probing Neutrino Masses Using Frequency Techniques J. A. Formaggio Massachusetts Institute of Technology (for the Project 8 Collaboration)

Outline: Outline: 1. Scientific Motivation 1. Scientific Motivation 2. Principle of Technique 2. Principle of Technique 3. Status of Project 3. Status of Project

The Sudbury Neutrino Observatory S O N I M sin 2 ( θ 13 ) = 0 . 0241 ± 0 . 0025 Body of Evidence Reactor & Long Baseline sin 2 ( θ 12 ) = 0 . 307 ± 0 . 016 Super-Kamiokande S O N I M 12 = (7 . 54 ± 0 . 26) × 10 − 5 eV 2 ∆ m 2 KamLAND SNO Solar sin 2 ( θ 23 ) = 0 . 386 ± 0 . 022 The phenomena of 23 = (2 . 43 ± 0 . 09) × 10 − 3 eV 2 ∆ m 2 neutrino oscillations is now Super-Kamiokande firmly established. Atmospheric KamLAND Camilieri, Lisi, Wilkerson Ann. Rev. 57 (2008). Fogli et al, arXiv:1205.5254 (hep-ph)

What do we learn? m ν > 2 eV (eV scale, current) Neutrinos ruled out as primary dark matter candidate m ν > 0.2 eV (degeneracy scale) Impact on cosmology and 0 νββ reach m ν > 0.05 eV (inverted hierarchy) Resolve hierarchy if null result m ν > 0.01 eV (normal hierarchy) Oscillation limit; possible C ν B detection

Direct Probes 3 H ➟ 3 He + + e - + ν e Beta decay allows a kinematic determination of the neutrino mass No dependence on cosmological models or matrix elements

The KATRIN Experiment

Error Budget and Sensitivity 2 ) 0 0.01 eV 2 σ (m v Δ m β ,stat2 = 0.018 Statistical eV 2 Final-state spectrum T - ions in T 2 gas Unfolding energy loss Column density Background slope Δ m β ,sys2 = 0.017 HV variation eV 2 Potential variation in source B-field variation in source Elastic scattering in T 2 gas Neutrino Mass Goals Discovery: 350 meV (at 5 σ ) Sensitivity: 200 meV (at 90% C.L.)

Can we push further? • KATRIN will achieve 200 meV scale. Can direct measurements push lower to the 50 meV scale? 10 meters across • Any future experiment needs to be able to (a) have a better scaling 10 -11 mbar vacuum law for increased target mass and (b) improve its energy resolution. KATRIN Sensitivity

Outline: 1. Scientific Motivation 2. Principle of Technique Probing Neutrino Masses Using 3. Status of Project Frequency Techniques

Project 8 “Never “Never measure measure anything but anything but frequency.” frequency.” Source ≠ Detector I. I. Rabi I. I. Rabi A. L. Schawlow A. L. Schawlow • Use cyclotron Simulation run eB (10 5 events) frequency to extract ω ( γ ) = ω 0 γ = electron energy. 6 Power (arb. units) K + m e 5 • Non-destructive many overlapping rare high-energy low-energy electrons measurement of electrons 4 electron energy. 3 E = 17572 eV Theta = 1.565 B field 2 signal T 2 gas 1 Frequency Approach 0 25.6 25.8 26 26.2 26.4 26.6 26.8 27 27.2 Frequency (GHz) 3 He + + e − + ¯ 3 H → ν e B. Monreal and J. Formaggio, Phys. Rev D80:051301 B. Monreal and J. Formaggio, Phys. Rev D80:051301

Cyclotron Frequency eB ω ( γ ) = ω 0 The Concept γ = K + m e Coherent radiation emitted can be Radiative Power Emitted collected and used to measure the � 2 2 e 2 ! 2 1 energy of the electron in a non- k 0 P tot ( � k , � ) = destructive manner. 4 ⇡✏ 0 3 c 1 − � 2 B. Monreal and J. Formaggio Phys. Rev. D80:051301 (2009). • Uniform B field • Low pressure T 2 gas. B field T 2 gas • Antenna array for cyclotron radiation detection.

The Spectrum Unique Advantages: • Source = Detector • Frequency measurement • Full spectrum sampling • Look at a simulated tritium spectrum watched by a synthetic array (evenly spaced antennas over 10 meter uniform field). • Low energy electrons dominate at higher frequencies. • Rare, high energy electrons give a clean signature near endpoint.

Count Rate, With molecular T 2, the Background, Resolution rovibrational width of the ground state molecular ion limits the effective resolution !! = 0.36 eV For a background (b) and a count rate (r), the optimum energy window ( Δ E) to count in is: ∆ E = (2 b r ) 1 / 3 The best useful resolution with molecular tritium is then Δ E ~ 2.35*0.36 = 0.9 eV . For a given r, we then know the target level of background. σ = 0 . 36 eV

Decay Rate The total rate of decays scales inversely as the frequency squared: nC (2 π c ) 3 ∆Ω r = f geom η 4 π τ m ω 3 c Arbitrarily selecting 100 MHz we get a cavity volume of about 8 m 3 and a gross decay rate therein of 4.4 x 10 8 Bq. However there are two acceptance factors, one for the useful active volume inside the cavity, the other for the solid angle to trap an electron. Together these factors might be 0.01 – 0.1. To this level of precision, it looks feasible to reach 200 meV , except for the noise.

Background M. Leber calculated the cosmic ray delta intensity for KATRIN (about 3 Ci of tritium), for a background of about 0.01 Hz In Project 8, assuming the same source strength, this background is 3 x 10 -10 Hz/ eV near the endpoint!

Resolution Magnetic Bottle The energy resolution is related to the frequency resolution by the following relation. d ω T dT ω = − T + m 0 c 2 T The magnetic field must be uniform to at least this level. The emission interrupted after a This time scale also sets the trapping time for electrons. random time gives a Lorentzian line width. A magnetic bottle is necessary ∆ ω = Γ = 1 to ensure adequate observation & photon collection. τ

A Phased Approach Given the novelty of the project, we are pursuing a phased approach toward neutrino mass measurements: 1. Phase I Goals: Single electron detection. 2. Phase II Goals: T-He mass difference 3. Phase III Goals: Mass sensitivity to 0.2-2 eV range 4. Phase IV Goals: Mass sensitivity pushed down to inverted scale We have commenced Phase I, we are designing Phase II

Antenna Options Two possible options for cyclotron detection being explored: 1. A resonant microwave cavity containing tritium. • In this case the Doppler shift is eliminated, but the volume of the cavity, and hence the source strength, is related to the operating frequency. 2. A non-resonant chamber surrounded by receiving antennas. • The Doppler shift is present, but the size n i d e s u g of the volume, and hence the source n i e B I strength, is not directly related to the e s a h P operating frequency.

Neutrino Mass Sensitivity Source strength, resolution and background help determine the activity and frequency needed to achieve a given neutrino mass sensitivity. Table on right shows mass sensitivity versus cyclotron frequency. Parameters and statistical sensitivities for Does not correspond to the resonant-cavity experiments at various cyclotron phased approach, only a frequencies. guide.

Neutrino Mass Sensitivity Source strength, resolution and background help determine the activity and frequency needed to achieve a given neutrino mass sensitivity. Table on right shows mass sensitivity versus cyclotron frequency. Parameters and statistical sensitivities for Does not correspond to the non resonant-cavity experiments at 10 GHz cyclotron phased approach, only a frequency. guide.

Outline: 1. Scientific Motivation 2. Principle of Technique Probing Neutrino Masses Using 3. Status of Project Frequency Techniques

Magnetic Environment Main Superconducting Magnet 10 G Trapping coil 1 T field (27 GHz) Use 0.93 Tesla field, where signal occurs at ~26 GHz with quadrupole trapping coil. System monitors field in-situ using DPPH ESR and Hall probe monitoring. Overall stability of prototype Δ B B ~1 × 10 − 5

Magnetic Monitoring ESR Measurement Magnetic field monitoring Magnet Cooling Use 0.93 Tesla field, where signal occurs at ~26 GHz with quadrupole trapping coil. System monitors field in-situ using DPPH ESR and Hall probe monitoring. Overall stability of prototype Δ B B ~1 × 10 − 5

Prototype Status Monolithic assembly inserted into 2-in diameter vertical bore of 1 T s.c. magnet. Source gas flows directly through waveguide fiducial volume. Dual waveguide Cyclotron power transported in both directions to low- prototype noise 26 GHz amplifiers loaned by NRAO. Signal mixed down to lower frequency (250 MHz bandwidth) and fully digitized.

Project 8 Waveguide Prototype Rack-mounted 1 st (HF) Receive Stage Cryogenic RF (26 GHz) IF (1.5 GHz) K-connector 3 7 interface at top 40 � -50 � cable of insert 4 (~6 dB loss) WR-42 waveguide Directional BPF 6 1 2 To LF Rx with electron source Coupler Stage 25-27 GHz 25 dB 30 dB 20 dB 5 Used to examine signal with SA during digitizer use 24.5 GHz DRO 2 nd (LF) Receive Stage 12 13 14 10 From Directional 9 HPF LPF 8 15 16 To digitizer HF Rx Coupler stage 0.07 - 1000 DC – 81 MHz 20 dB 20 dB 20 dB 20 dB MHz 11 500-2200 MHz signal generator Fundamental cyclotron signal at 26 GHz is mixed down with 24.5 GHz oscillator, and again with 500+ MHz oscillator resulting in signals ~100 MHz, digitized at 500 MHz 8-bit sampling rate for ~10 hours continuously and without dead-time.

Expected Signal The signal from our waveguide prototype is expected to be a short- lived “chirp” from a trapped electron.