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Neutrino masses

Neutrino masses. Determination of absolute mass scale with beta decays: single beta decays: energy spectra search for neutrinoless double beta decays The latter is extremely important in order to understand the Universe and sources of particle masses. }. or. (Mass) 2. }.

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Neutrino masses

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  1. Neutrino masses Determination of absolute mass scale with beta decays: • single beta decays: energy spectra • search for neutrinoless double beta decays The latter is extremely important in order to understand the Universe and sources of particle masses

  2. } or (Mass)2 } Neutrino (mass)2 spectrum Normal Inverted From neutrinos... DK&ER lecture11

  3. Various and complementary ways to measure neutrino mass Cosmology Oscillation Beta decay From neutrinos... DK&ER lecture11

  4. Three roads to neutrino masses

  5. Direct measurements of neutrino masses • νe: tritium β decay • νμ: πdecay • ντ: τ decay Information from the end of the energy spectrum. „Mass” of flavor α – combination of mass states. Very high precision of measurements needed. Up to now only limits. From neutrinos... DK&ER lecture11

  6. β-decay and neutrino mass Model independent neutrino mass from ß-decay kinematics experimental observable is mν2 • ß-source requirements : • high ß-decay rate (short t1/2) • low ß-endpoint energy E0 • superallowed ß-transition • few inelastic scatters of ß‘s • ß-detection requirements : • - high resolution (ΔE< few eV) • - large solid angle • - low background E0 = 18.6 keV T1/2 = 12.3 y

  7. History of tritium measurements From neutrinos... DK&ER lecture11

  8. Electrostatic filter with magnetic adiabatic collimation From neutrinos... DK&ER lecture11

  9. Status of previous tritium measurements Mainz & Troitsk have reached their intrinsic limit of sensitivity Troitsk Mainz windowless gaseous T2 source quench condensed solid T2 source analysis 1994 to 1999, 2001 analysis 1998/99, 2001/02 both experiments now used for systematic investigations From neutrinos... DK&ER lecture11

  10. Designing a next-generation experiment • experimental observable in ß-decay is mν2 • aim :improve mνby one order of magnitude (2 eV  0.2 eV ) • requires : improve mν by two orders of magnitude (4 eV2 0.04 eV2 ) • problem : count rate close to ß-end point drops very fast (~δE3) • improve statistics : • stronger tritium source (factor 80) (& large analysing plane, Ø=10m) • - longer measuring period (~100 days  ~1000 days) • improve energy resolution : • large electrostatic spectrometer with ΔE=0.93 eV (factor 4 improvement) • reduce systematic errors : • - better control of systematics, energy losses (reduce to less than 1/10) 2 L=23 m From neutrinos... DK&ER lecture11

  11. Katrin From neutrinos... DK&ER lecture11 KATRIN will reach a final sensitivity of 200 meV at 90\% C.L. on the absolute neutrino mass scale.

  12. KATRIN experiment Karlsruhe Tritium Neutrino Experiment at Forschungszentrum Karlsruhe unique facility for closed T2 cycle: Tritium Laboratory Karlsruhe TLK ~ 75 m linear setup with 40 s.c. solenoids From neutrinos... DK&ER lecture11

  13. Transport of KATRIN Complicated transport of the spectrometer in Dec. 2006 From neutrinos... DK&ER lecture11

  14. KATRIN sensitivity sensitivity optimisation: LoI (2001) reference design (2004) • improved statistics: source luminosity, scanning • reduced systematics: ß-energy losses in source improved sensitivity sensitivity (90% CL) m(ν) < 0.2 eV discovery potential m(ν) = 0.35 eV (5σ) From neutrinos... DK&ER lecture11

  15. Search for neutrinoless double beta decays • Why so important? • What it would tell us (if seen)? Reminder: • Leptons are (mostly) left handed • Anti-leptons are (mostly) right handed • Contribution of states with „wrong helicity” is proportional to:  for m=0 particle – no such contribution From neutrinos... DK&ER lecture11

  16. Dirac particles Majorana particles Special case: particle is it’s own anti-particle Dirac neutrino vs Majorana neutrino Lorentz Boost, E, B C P T C P T only neutral particles are candidates for beeing Majorana particle Example of such isπ0 Spinor is fermion representation (in Dirac equation) For particles with m=0 reduces to 2 non-zero states

  17. Double beta decays From neutrinos... DK&ER lecture11

  18. Double Beta Decay Candidates From neutrinos... DK&ER lecture11

  19. Phenomenology of 0νββ and 2νββ • pairing interaction between nucleons (even-even nuclei more bound than the odd-odd nuclei) • e.g. 136Xe and 136Ce are stable against β decay, but unstable against ββ decay (β-β- for 136Xe and β+β+ for 136Ce) odd-odd even-even m(A,Z) > m(A,Z+2)

  20. Phenomenology of 0νββ and 2νββ Phase space (very well known) Nuclear matrix element (NME) (challenging to calculate)

  21. Neutrino mixing and oscillations Pontecorvo – Maki – Nakagawa - Sakata (PMNS) matrix weak eigenstates mass eigenstates 3 mixing angles + 1 phase Majorana Phases only 0νββ Solar Atmospheric Reactor Atmospheric

  22. Candidate Nuclei for Double Beta Decay Q (MeV) Abundance(%) From neutrinos... DK&ER lecture11

  23. Electron spectrum from double β decays • Missing energy • Energy resolution • High rates capabilities From neutrinos... DK&ER lecture11

  24. ββ history • 1935 - ββ(2ν) rate first calculated by Maria Goeppert-Mayer • 1937 - Majorana proposes his theory of two-component neutrino • 1987 – Direct laboratory evidence for 2νββ: S. Elliot et al., Phys. Rev. Lett. 59, 2020, 1987 Direct evidence for two-neutrino double-beta decay in 82Se • Why it took so long? Background t1/2(U, Th) ~ 1010 years • while signal: t1/2(2νββ) ~ 1020 years • But next we want to look for a process with: t1/2(0νββ) ~ 1025-27 years From neutrinos... DK&ER lecture11

  25. ββ history • 2004 – controversial claim of observation of 0νββ: From neutrinos... DK&ER lecture11

  26. From neutrinos... DK&ER lecture11

  27. Experiments with active targets From neutrinos... DK&ER lecture11

  28. 76Ge spectrum From neutrinos... DK&ER lecture11

  29. 76Ge spectrum with a possible 0νββ peak From neutrinos... DK&ER lecture11

  30. 76Ge spectrum with a possible 0νββ peak 76Ge Exposure (total): 71.7 kg.y Clearly this needs to be verified...

  31. New experiment with Ge: GERDA To check the questionable result – new experiment with Ge is prepared GERDA(with contribution from Jagiellonian Uniw.), the background reduction will be better …

  32. Tracking and calorimeter Source ≠ detector Calorimeter Source=detector TPC (Xe) Efficiency,Mass Resolution, efficiency Background, isotope choice Experimental techniques Main features: High energy resolution Modest background rejection Main features: High background rejection Modest energy resolution 0νββ 0νββ

  33. Separation of 0νββ from 2νββ 0nbb spectrum (5% FWHM) (normalized to 10-6) 2νββ spectrum (normalized to 1) E1 + E2 (normalized to Qββ) Energy resolution is essential 0νββ spectrum (5% FWHM) (normalized to 10-2) F. T. Avignone, G. S. King and Yu. G. Zdesenko, ``Next generation double-beta decay experiments: Metrics for their evaluation,’’ New J. Phys. 7, 6 (2005). from S. Elliott and P. Vogel

  34. 20 sectors B (25 G) 3 m 4 m Particle ID: e-, e+, γ and α Fréjus Underground Laboratory : 4800 m.w.e. NEMO-3 detector Source: 10 kg of ββ isotopic foils area = 20 m2, thickness ~ 60 mg/cm2 Tracking detector: drift wire chamber operating (9 layers) in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: pure iron (d = 18cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since March 2004: water + boron)

  35. NEMO-3 detector Fréjus Underground Laboratory : 4800 m.w.e. Source: 10 kg of isotopic foils area = 20 m2, thickness ~ 60 mg/cm2 Tracking detector: drift wire chamber operating (9 layers) in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs Magnetic field: 25 Gauss Gamma shield: pure iron (d = 18cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since March 2004: water + boron)

  36. ββ2ν measurement ββ0ν search ββdecay isotopes NEMO-3 116Cd405 g Qbb = 2805 keV 96Zr 9.4 g Qbb = 3350 keV 150Nd 37.0 g Qbb = 3367 keV 48Ca 7.0 g Qbb = 4272 keV 130Te454 g Qbb = 2529 keV External bkg measurement natTe491 g 100Mo6.914 kg Qbb = 3034 keV 82Se0.932 kg Qbb = 2995 keV Cu621 g (All enriched isotopes produced in Russia)

  37. Cathod rings Wire chamber PMTs Calibration tube scintillators bb isotope foils

  38. Side view Top view ββ events in NEMO-3 experiment Typical ββ2ν event observed from 100Mo From neutrinos... DK&ER lecture11

  39. During installation AUGUST 2001

  40. Laboratoire Souterrain de Modane 4700 m.w.e COMMISSARIAT À L’ÉNERGIE ATOMIQUE DIRECTION DES SCIENCES DE LA MATIÈRE Built for taup experiment (proton decay) in 1981-1982

  41. Data • Data ββ2ν Monte Carlo ββ2ν Monte Carlo Background subtracted Background subtracted 100Mo ββ2ν results (Data Feb. 2003 – Dec. 2004) Angular Distribution Sum Energy Spectrum 219 000 events 6914 g 389 days S/B = 40 219 000 events 6914 g 389 days S/B = 40 NEMO-3 NEMO-3 100Mo 100Mo E1 + E2 (keV) Cos(ϑ) 7.37 kg.y T1/2 = 7.11 ± 0.02 (stat) ± 0.54 (syst) x 1018 y From neutrinos... DK&ER lecture11

  42. Other results from NEMO-3: 2νββ NEMO-3 454 g, 534 days 109 events S/B = 0.25 130Te NEMO-3 932 g, 389 days 2750 events S/B = 4 82Se E1 + E2 (MeV) 2.8 ± 0.1 (stat) ± 0.3 (sys) 1019 y 7.6 ± 1.5 (stat) ± 0.8 (sys) 1020 y 9.6 ± 0.3 (stat) ± 1.0 (sys) 1019 y 133 events S/B 6.76 48Ca 96Zr 150Nd 948 days 7g 925 days S/B 1.01 9.41g E1 + E2 (MeV) 9.11 +0.25-0.22(stat) ± 0.63 (sys) 1018 y 2.3 ± 0.2 (stat) ± 0.3 (sys) 1019 y 4.4 +0.5-0.4 (stat)± 0.4 (sys) 1019 y

  43. Upper limits Results for 2β0ν searches Germanium diode cal. Te02 cryo calorim. Xe TPC From neutrinos... DK&ER lecture11

  44. Neutrinoless ββ-decay limits From Elliot and Vogel, hep-ph/0202264 From neutrinos... DK&ER lecture11

  45. Neutrino mass and mass ordering Quasi Degenerate Inverted Normal ? ? Σmν < 0.14 - 1.3 eV m(“νe”) < 2.2 eV m(“νμ”) < 190 keV m(“ντ”) < 18.2 MeV Mainz-Troitsk 3H decay Cosmological models

  46. What is the scale of neutrino masses? • Strumia and F. Vissani, ``Neutrino masses and mixings.’’ • arXiv:hep-ph/0606054. • F. Feruglio, C. Hagedorn, Y. Lin and L. Merlo, • ``Theory of the Neutrino Mass,’’ arXiv:0808.0812 [hep-ph]. mββ may be very tiny in case of cancellations due to phases

  47. Projections – ββ0ν HM Claim NEMO 3 CUORICINO, EXO-200 GERDA(PII) SuperNEMO CUORE,EXO >2020, 1t experiments ( ≥ 2) Cosmologically disfavoured region (WMAP) >>2020, >10t experiment 47

  48. Summary • Direct neutrino mass measurements – sensitivity good enough only for νe - may be successful in case of inverted hierarchy • Search for 0νββ–extremely important because: It may answer the following basic questions: • Is the total lepton number conserved? Essential for understanding the matter-antimatter asymmetry in Universe • What is nature of neutrinos: Dirac or Majorana ( 0νββ possible only for Majorana neutrinos) - essential for understanding the source of particle masses From neutrinos... DK&ER lecture11

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