1. Hamish Robertson, CENPA, University of Washington Direct probes of neutrino mass Neutrino Oscillation Workshop NOW2014, Otranto Italy Sept. 8

2. Particle Physics Cosmology What is the neutrino mass scale? Some things are simply missing from the standard model (dark matter, gravity…) but neutrino mass is the only contradiction to the SM.

3. NEUTRINO MASS FROM BETA SPECTRA neutrino masses mixing With flavor mixing : from oscillationsmass scale 3

4. PRESENT LABORATORY LIMIT FROM 2 TRITIUM EXPERIMENTS: 4 Together:… m v < 1.8 eV (95% CL)

5. MASS AND MIXING PARAMETERS  m 21 2 7.54 +0.21 -0.21 x 10 -5 eV 2  m 32 2 | 2.42 +0.12 -0.11 x 10 -3 eV 2 mimi > 0.055 eV (90% CL)< 5.4 eV (95% 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 Marginalized 1-D 1-  uncertainties. *C. Kraus et al., Eur. Phys. J. C40, 447 (2005); V. Aseev et al. PRD 84 (2011) 112003. Other refs, see Fogli et al. 1205.5254 5 OscillationKinematic

6. TLK KATRIN At Karlsruhe Institute of Technology unique facility for closed T 2 cycle: Tritium Laboratory Karlsruhe 6 A direct, model- independent, kinematic method, based on β decay of tritium. ~ 75 m long with 40 s.c. solenoids

7. 7 ES

8. Molecular excitations 8 Energy loss A WINDOW TO WORK IN

9. KATRIN’S UNCERTAINTY BUDGET 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(m v 2 ) 00.01 eV 2 σ(m v 2 ) total = 0.025 eV 2 9 m v < 0.2 eV (90 % CL)

10. Overview of KArlsruhe TRItium Neutrino Experiment Windowless gaseous sourceTransport sectionPre-spectrometer Main-spectrometerDetector V Monitor-spectrometer 70 m 10 -3 mbar10 -11 mbar

11. 11 K. Valerius

12. NEUTRINO MASS SIGNAL 12

13. SENSITIVITY WITH TIME 13

14. MASS RANGE ACCESSIBLE Present Lab Limit 1.8 eV starting 2016 KATRIN 14

15. THE LAST ORDER OF MAGNITUDE If the mass is below 0.2 eV, how can we measure it? KATRIN may be the largest such experiment possible. Size of experiment now: Diameter 10 m. Rovibrational states of THe +, HHe + molecule Source T 2 column density near max Next diameter: 300 m! σ(m v ) 2 ~ 0.38 eV 2

16. 16 A new idea.

17. CYCLOTRON RADIATION FROM TRITIUM BETA DECAY 17 (B. Monreal and J. Formaggio, PRD 80:051301, 2009) Surprisingly, this has never been observed for a single electron.

18. THE ENERGY IS MEASURED AS A FREQUENCY 18 Tritium endpoint

19. ENERGY RESOLUTION 19

20. POWER RADIATED 20

21. 21 G-M cooler (35K) 26-GHz amplifiers 83m Kr source (behind) SC Magnet (0.95 T) Prototype at University of Washington

22. 22 Gas cell is a small section of WR-42 waveguide

23. 23 52 mm

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25. SUPERHETERODYNE RECEIVER 25

26. WHAT WOULD A SIGNAL FROM AN ELECTRON LOOK LIKE? 26 Digitize the amplifier output. Make short-time Fourier transforms. Plot the spectra sequentially (a “spectrogram”). Simulation: M. Leber

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32. ENERGY SPECTRUM 32 83m Kr

33. “JUMP” SPECTRUM 33 83m Kr 30.4 keV line Most probable jump is 14 eV.

34. NEXT: A TRITIUM EXPERIMENT 34 Fill a volume with tritium gas at low pressure Instrument with antennas and receivers Apply uniform magnetic field Measure the spectrum

35. PROJECT 8 SENSITIVITY 35 and OPTIMISTIC

36. PROJECT 8: A PHASED APPROACH

37. MASS RANGE ACCESSIBLE Present Lab Limit 1.8 eV starting 2016 KATRIN 37

38. NEUTRINO MASS LIMITS FROM BETA DECAY 38

39. 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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41. 41 Fin

42. 2013201420152016201720182019 ConstructionRunning KATRIN: Phase IProof concept Prototype Project 8: NEUTRINO MASS: SOME MILESTONES 42

43. NEUTRINO MASS PHYSICS IMPACT 43

44. 44 Battye and Moss, PRL 112, 051303 (2014)  Planck  SPT Lensing power spectrum Shear correlation spectrum  CFHTLenS Some tensions in ΛCDM resolved with neutrino mass:

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48. (B. Monreal and J. Formaggio, PRD 80:051301, 2009) Radiated power ~ 1 fW CYCLOTRON RADIATION FROM TRITIUM BETA DECAY Working on the UW prototype Early 25.5-GHz waveguide cell

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50. IS AN ATOMIC SOURCE FEASIBLE? Must reject molecules to 10 -5 (endpoint is 8 eV 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. 5T ~ 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.

51. 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 μeV) Trap density initially ~10 7 cm -3 Trap lifetime ~ 1000 s

52. AN EARLY H TRAP (AT&T, MIT) Hess et al. PRL 59, 672 [1987] 6 x 10 12 cm -3 40 mK 400 s Effect of dipolar spin flips

53. ALPHA’s antihydrogen trap ALPHA Collaboration: Nature Phys.7:558-564,2011; arXiv 1104.4982

54. CURRENT STATUS: Mainz: solid T 2, MAC-E filter C. Kraus et al., Eur. Phys. J. C40, 447 (2005) Troitsk: gaseous T 2, MAC-E filter V. Aseev et al., PRD 84 (2011) 112003 Together:… m v < 1.8 eV (95% CL) 54

55. 55 K. Valerius

56. 56 K. Valerius

57. 57 K. Valerius

58. 58 K. Valerius

59. KATRIN’S STATISTICAL POWER 59