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 20 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. }. or. (Mass) 2. }. - PowerPoint PPT Presentation
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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
The latter is extremely important in order to understand the Universe and sources of particle masses
2 0
1
Normal Inverted
(Mass)2
}
}
or
Neutrino (mass)2 spectrum
From neutrinos... DK&ER lecture11
2
3
1 3
1
2
2
sin2ϑ 13
sin2ϑ 13
δmsol2
δmsol2
Δmatm2
Δmatm2
δmsol2 ≅ 8g10−5 eV2
δmatm2 ≅ 2.5g10−3 eV2
e Uei
2 μ Uμi
2 τ Uτ i2
Various and complementary ways
to measure neutrino massCosmology Oscillation
Beta decay
Σ =m1 + m2 + m3 δmij2 = mi
2 − m j2
3From neutrinos... DK&ER lecture11
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m = Uei2 mi
2
i=1
3
∑
Three roads to neutrino masses
4
Direct measurements of neutrino masses
32 2
1i i
i
m U m
3 3 - 2.2e: VH He+e ee em
+ 170k: eV mμμ μ μ
e: tritium decay
μ: decay
τ τ decay-: +5 18MeVmτ τ ττ
5From neutrinos... DK&ER lecture11
m = U i2mi
2
i=1
3
∑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.
experimental observable is mexperimental observable is m22
Model independent neutrino mass from ß-decay kinematics
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
EE00 = 18.6 keV = 18.6 keV
TT1/21/2 = 12.3 y = 12.3 y
3 3 -H He+e e
β-decay and neutrino mass
6 ΔΩ : 2π
History of tritium measurements
From neutrinos... DK&ER lecture11
7
Electrostatic filter with magnetic adiabatic collimation
2004 – controversial claim of observation of 0νββ:
25From neutrinos... DK&ER lecture11
26From neutrinos... DK&ER lecture11
Experiments with active targets
From neutrinos... DK&ER lecture11
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28From neutrinos... DK&ER lecture11
76Ge spectrum
76Ge spectrum with a possible 0νββ peak
29From neutrinos... DK&ER lecture11
30
Exposure(total):71.7 kg.y
76Ge
76Ge spectrum with a possible 0νββ peak
Clearly this needs to be verified...Clearly this needs to be verified...
New experiment with Ge: GERDATo check the questionable result – new experiment with Ge is prepared GERDA (with contribution from Jagiellonian Uniw.), the background reduction will be better …
31
Experimental techniques
32
Background, isotope choice
Tracking and calorimeterSource ≠ detector
TPC (Xe)
Efficiency, Mass
CalorimeterSource=detector
Resolution, efficiency
0
Main features:High energy resolutionModest background rejection
Main features:High background rejectionModest energy resolution
0
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
E1 + E2 (normalized to Q)
2 spectrum(normalized to 1)
0 spectrum(5% FWHM)(normalized to 10-6)
0 spectrum(5% FWHM)(normalized to 10-2)
Separation of 0 from 2
Energy resolution is essentialEnergy resolution is essential
3 m
4 m
B (25 G)
20 sectors 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 GaussGamma shield: pure iron (d = 18cm)Neutron shield: 30 cm water (ext. wall)
40 cm wood (top and bottom) (since March 2004: water boron)