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Neutrino masses Determination of absolute mass scale with beta decays:  single beta decays: energy spectra  search for neutrinoless double beta decays.

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Presentation on theme: "Neutrino masses Determination of absolute mass scale with beta decays:  single beta decays: energy spectra  search for neutrinoless double beta decays."— Presentation transcript:

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 1

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

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

4 Three roads to neutrino masses 4

5 Direct measurements of neutrino masses   e : tritium  decay    :  decay     decay 5From neutrinos... DK&ER lecture11 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. 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.

6 experimental observable is m  2 Model independent neutrino mass from ß-decay kinematics ß-source requirements : -high ß-decay rate (short t 1/2 ) -low ß-endpoint energy E 0 -superallowed ß-transition -few inelastic scatters of ß‘s ß-detection requirements : - high resolution ( Δ E< few eV) - large solid angle - low background E 0 = 18.6 keV T 1/2 = 12.3 y β-decay and neutrino mass 6

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

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

9 Status of previous tritium measurements From neutrinos... DK&ER lecture11 9 Troitsk Mainz windowless gaseous T 2 source quench condensed solid T 2 source Mainz & Troitsk have reached their intrinsic limit of sensitivity analysis 1994 to 1999, 2001 analysis 1998/99, 2001/02 both experiments now used for systematic investigations

10 experimental observable in ß-decay is m ν  aim : improve m  by one order of magnitude (2 eV  0.2 eV ) requires : improve m  by two orders of magnitude (4 eV 2  0.04 eV 2 ) problem : count rate close to ß-end point drops very fast (~  E 3 ) 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 Designing a next-generation experiment From neutrinos... DK&ER lecture11 10 L=23 m

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

12 TLK Karlsruhe Tritium Neutrino Experiment at Forschungszentrum Karlsruhe unique facility for closed T 2 cycle: Tritium Laboratory Karlsruhe KATRIN experiment From neutrinos... DK&ER lecture11 12 ~ 75 m linear setup with 40 s.c. solenoids

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

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

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 15From neutrinos... DK&ER lecture11

16 Dirac neutrino vs Majorana neutrino Dirac particles Majorana particles Special case: particle is it’s own anti-particle CPTCPT CPTCPT Lorentz Boost, E, B Spinor is fermion representation (in Dirac equation) For particles with m=0 reduces to 2 non-zero states only neutral particles are candidates for beeing Majorana particle Example of such is  0

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

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

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

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

21 Majorana Phases only 0  Neutrino mixing and oscillations Atmospheric Reactor Solar 3 mixing angles + 1 phase weak eigenstates mass eigenstates Pontecorvo – Maki – Nakagawa - Sakata (PMNS) matrix ν21

22 48 Ca → 48 Ti Ge → 76 Se Se → 82 Kr Zr → 96 Mo Mo → 100 Ru Pd → 110 Cd Cd → 116 Sn Sn → 124 Te Te → 130 Xe Xe → 136 Ba Nd → 150 Sm Candidate Nuclei for Double Beta Decay Q (MeV) Abundance(%) 22From neutrinos... DK&ER lecture11

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

24  history   (2  ) rate first calculated by Maria Goeppert-Mayer  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 82 Se  Why it took so long? Background  1/2 (U, Th) ~ years  while signal:  1/2 (2νββ) ~ years  But next we want to look for a process with:  1/2 (0νββ) ~ years 24From neutrinos... DK&ER lecture11

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

26 26From neutrinos... DK&ER lecture11

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

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

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

30 30 Exposure (total): 71.7 kg.y 76 Ge 76 Ge spectrum with a possible 0νββ peak 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 … 31

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

33 33 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 E 1 + E 2 (normalized to Q  )  spectrum (normalized to 1)  spectrum (5% FWHM) (normalized to )  spectrum (5% FWHM) (normalized to ) Separation of  from  Energy resolution is essential

34 3 m 4 m B (25 G) 20 sectors Source : 10 kg of ββ isotopic foils area = 20 m 2, thickness ~ 60 mg/cm 2 Tracking detector : drift wire chamber operating (9 layers) in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H 2 O 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) Fréjus Underground Laboratory : 4800 m.w.e. NEMO-3 detector 34 Particle ID: e , e ,  and 

35 Source : 10 kg of isotopic foils area = 20 m 2, thickness ~ 60 mg/cm 2 Tracking detector : drift wire chamber operating (9 layers) in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H 2 O 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) Fréjus Underground Laboratory : 4800 m.w.e. NEMO-3 detector 35

36 100 Mo kg Q  = 3034 keV  decay isotopes NEMO-3 82 Se kg Q  = 2995 keV 116 Cd 405 g Q  = 2805 keV 96 Zr 9.4 g Q  = 3350 keV 150 Nd 37.0 g Q  = 3367 keV Cu 621 g 48 Ca 7.0 g Q  = 4272 keV nat Te 491 g 130 Te 454 g Q  = 2529 keV  measurement External bkg measurement  search (All enriched isotopes produced in Russia) 36

37  isotope foils scintillators PMTs Calibration tube Cathod rings Wire chamber 37

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

39 During installation AUGUST

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

41 (Data Feb – Dec. 2004) T 1/2 = 7.11  0.02 (stat)  0.54 (syst)  y 7.37 kg.y Cos( ϑ ) Angular Distribution events 6914 g 389 days S/B = 40 NEMO Mo E 1 + E 2 (keV) Sum Energy Spectrum events 6914 g 389 days S/B = 40 NEMO Mo Background subtracted Data ββ2ν Monte Carlo Data ββ2ν Monte Carlo Background subtracted 100 Mo ββ2ν results From neutrinos... DK&ER lecture11 41

42 E 1 + E 2 (MeV) 133 events S/B days 7g 48 Ca 150 Nd 925 days S/B g 932 g, 389 days 2750 events S/B = 4 82 Se NEMO g, 534 days 109 events S/B = Te NEMO-3 96 Zr 2.8 ± 0.1 (stat) ± 0.3 (sys) y E 1 + E 2 (MeV) 7.6 ± 1.5 (stat) ± 0.8 (sys) y 2.3 ± 0.2 (stat) ± 0.3 (sys) y (stat) ± 0.63 (sys) y (stat)± 0.4 (sys) y 9.6 ± 0.3 (stat) ± 1.0 (sys) y Other results from NEMO-3: 2  42

43 Results for 2  0  searches IsotopeExperiment 48 CaHEP Beijing>1.1x10 22* GeHeidelberg-Moscow>5.7x IGEX>0.8x SeIrvine>2.7x NEMO 2>9.5x ZrNEMO 2>1.3x MoLBL>2.2x10 22* UCI>2.6x10 21 Osaka5.5x NEMO2>5x TeMilano>1.4x XeCaltech/PSI/Neuchatel>4.4x NdUCI>1.2x Germanium diode cal. Te0 2 cryo calorim. Xe TPC Upper limits 43From neutrinos... DK&ER lecture11

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

45 Neutrino mass and mass ordering 45 ? ? Normal Inverted m(“  e ”) < 2.2 eV Mainz-Troitsk 3 H decay m(“   ”) < 190 keV m(“   ”) < 18.2 MeV Σm  < eV Cosmological models

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

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

48 Summary  Direct neutrino mass measurements – sensitivity good enough only for ν e - 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 ( 0  ββ possible only for Majorana neutrinos) - essential for understanding the source of particle masses 48From neutrinos... DK&ER lecture11


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