Direct probes of neutrino mass Neutrino Oscillation Workshop
Direct probes of neutrino mass Neutrino Oscillation Workshop NOW 2014, Otranto Italy Sept. 8 Hamish Robertson, CENPA, University of Washington
What is the neutrino mass scale? Particle Physics Cosmology Some things are simply missing from the standard model (dark matter, gravity…) but neutrino mass is the only contradiction to the SM.
NEUTRINO MASS FROM BETA SPECTRA With flavor mixing: mixing from oscillations neutrino masses mass scale 3
PRESENT LABORATORY LIMIT FROM 2 TRITIUM EXPERIMENTS: Together: … mv < 1. 8 e. V (95% CL) 4
MASS AND MIXING PARAMETERS Oscillation m 212 7. 54+0. 21 -0. 21 x 10 -5 e. V 2 m 322| 2. 42+0. 12 -0. 11 x 10 -3 e. V 2 mi > 0. 055 e. V (90% CL) 12 34. 1+0. 9 -0. 9 deg 23 39. 2+1. 8 -1. 8 deg 13 9. 1+0. 6 -0. 7 deg sin 2 13 0. 025+. 003 -. 003 Kinematic < 5. 4 e. V (95% CL)* Marginalized 1 -D 1 - uncertainties. *C. Kraus et al. , Eur. Phys. J. C 40, 447 (2005); V. Aseev et al. PRD 84 (2011) 112003. Other refs, see Fogli et al. 1205. 5254 5
At Karlsruhe Institute of Technology unique facility for closed T 2 cycle: Tritium Laboratory Karlsruhe KATRIN TLK ~ 75 m long with 40 s. c. solenoids A direct, model-independent, kinematic method, based on β decay of tritium. 6
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A WINDOW TO WORK IN Molecular excitations Energy loss 8
KATRIN’S UNCERTAINTY 2 BUDGET σ(mv ) 0 0. 01 e. V 2 Statistical Final-state spectrum T- ions in T 2 gas Unfolding energy loss Column density Background slope HV variation Potential variation in source B-field variation in source Elastic scattering in T 2 gas σ(mv 2)total= 0. 025 e. V 2 mv< 0. 2 e. V (90 % CL) 9
Overview of KArlsruhe TRItium Neutrino Experiment Windowless gaseous source Transport section Pre-spectrometer 10 -3 mbar Main-spectrometer 10 -11 mbar V 70 m Monitor-spectrometer Detector
K. Valerius 11
NEUTRINO MASS SIGNAL 12
SENSITIVITY WITH TIME 13
MASS RANGE ACCESSIBLE KATRIN starting 2016 Present Lab Limit 1. 8 e. V 14
THE LAST ORDER OF MAGNITUDE If the mass is below 0. 2 e. V, how can we measure it? KATRIN may be the largest such experiment possible. σ(mv)2 ~ 0. 38 e. V 2 Size of experiment now: Diameter 10 m. Next diameter: 300 m! Source T 2 column density near max Rovibrational states of THe+, HHe+ molecule
A new idea. 16
CYCLOTRON RADIATION FROM TRITIUM BETA DECAY (B. Monreal and J. Formaggio, PRD 80: 051301, 2009) Surprisingly, this has never been observed for a single electron. 17
THE ENERGY IS MEASURED AS A FREQUENCY Tritium endpoint 18
ENERGY RESOLUTION 19
POWER RADIATED 20
G-M cooler (35 K) 26 -GHz amplifiers 83 m. Kr source (behind) SC Magnet (0. 95 T) Prototype at University of Washington 21
Gas cell is a small section of WR-42 waveguide 22
52 mm 23
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SUPERHETERODYNE RECEIVER 25
WHAT WOULD A SIGNAL FROM AN ELECTRON LOOK LIKE? Digitize the amplifier output. Make short-time Fourier transforms. Plot the spectra sequentially (a “spectrogram”). Simulation: M. Leber 26
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ENERGY SPECTRUM 83 m. Kr 32
“JUMP” SPECTRUM 83 m. Kr 30. 4 ke. V line Most probable jump is 14 e. V. 33
NEXT: A TRITIUM EXPERIMENT Fill a volume with tritium gas at low pressure Instrument with antennas and receivers Apply uniform magnetic field Measure the spectrum 34
PROJECT 8 SENSITIVITY and OPTIMISTIC 35
PROJECT 8: A PHASED APPROACH
MASS RANGE ACCESSIBLE KATRIN starting 2016 Present Lab Limit 1. 8 e. V 37
NEUTRINO MASS LIMITS FROM BETA DECAY 38
SUMMARY Direct mass measurements are largely model independent: • Majorana or Dirac • No nuclear matrix elements • No complex phases • No cosmological degrees of freedom One experiment in construction (KATRIN); 2016 start. Three experiments in R&D (Project 8, ECHo, PTOLEMY) Success of Project 8 proof-of-concept. • New spectroscopy based on frequency • First step toward frequency-based determination of neutrino mass 39
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Fin 41
NEUTRINO MASS: SOME MILESTONES Construction Running KATRIN: Project 8: Proof concept 2013 Prototype 2014 2015 Phase I 2016 2017 2018 2019 42
NEUTRINO MASS PHYSICS IMPACT 43
Battye and Moss, PRL 112, 051303 (2014) Lensing power spectrum § Planck § SPT Some tensions in ΛCDM resolved with neutrino mass: Shear correlation spectrum § CFHTLen. S 44
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CYCLOTRON RADIATION FROM TRITIUM BETA DECAY (B. Monreal and J. Formaggio, PRD 80: 051301, 2009) Radiated power ~ 1 f. W Early 25. 5 -GHz waveguide cell Working on the UW prototype
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IS AN ATOMIC SOURCE FEASIBLE? • • • Must reject molecules to 10 -5 (endpoint is 8 e. V higher) Produce T in RF discharge: 90: 10 T 2: T Cool to 140 K in aluminum or sapphire tube. Inject into trap, trap low-field seeking polarization. Trap and cool to ~1 K by scattering from 4 He. Trap in same magnetic field configuration that is trapping the electrons: bathtub axial trap + added barrel conductors. High fields are essential: complicated SC magnet. 5 T ~ 3. 1 K. • Neither T 2 nor 4 He are trapped magnetically. Surprisingly, all of this looks sort of feasible, not easy. The statistical accuracy alone doesn’t convey the added confidence an atomic source would give.
MAGNETIC CONFIGURATION OF TRAP Solenoidal uniform field for electron cyclotron motion Pinch coils to reflect electrons Ioffe conductors (multipole magnetic field) to reflect radially moving atoms. The ALPHA antihydrogen trap parameters: Magnetic well depth 0. 54 K (50 μe. V) Trap density initially ~107 cm-3 Trap lifetime ~ 1000 s
AN EARLY H TRAP (AT&T, MIT) 6 x 1012 cm-3 40 m. K 400 s Effect of dipolar spin flips Hess et al. PRL 59, 672 [1987]
ALPHA’s antihydrogen trap ALPHA Collaboration: Nature Phys. 7: 558 -564, 2011; ar. Xiv 1104. 4982
CURRENT STATUS: Mainz: solid T 2, MAC-E filter C. Kraus et al. , Eur. Phys. J. C 40, 447 (2005) Troitsk: gaseous T 2, MAC-E filter V. Aseev et al. , PRD 84 (2011) 112003 Together: … mv < 1. 8 e. V (95% CL) 54
K. Valerius 55
K. Valerius 56
K. Valerius 57
K. Valerius 58
KATRIN’S STATISTICAL POWER 59
- Slides: 59