dirac vs majorana neutrinos - heidelberg universitywesthoff/lecture... · 2018. 2. 2. ·...
TRANSCRIPT
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Dirac vs Majorana Neutrinos
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( )mass D D L R R LL m mνν ν ν ν ν= = +
Do not interact ifneutrinos arehighly relativistic.D R Lm ν ν Lν
DmRν
chirality flip
Dirac neutrinos:
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Dirac vs Majorana Neutrinos
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C TL LCν ν= is a right handed field
CL Lν ν ν= + is a self-conjiugated state:
ν ν=
( )
( )
1212
C Cmass L
C CL L L L L
L m
m
ν ν νν
ν ν ν ν
= +
= +
CL L Lm ν ν
( ) CLRν ν=
Lm
Lν
lepton number violating
ν=
Majorana neutrinos:
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Neutrino Masses
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(0.05 eV)2
(0.01 eV)2
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Neutrino Mass Constraints
26
Relic neutrino density: 336 ν / cm3
Experimental
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Neutrino Mass Measurement
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„Direct“ kinematic measurement
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MAC-E Filter - Principle
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Solenoid Solenoid
Electrostatic spectrometer:
q E⋅
q E⋅
U
B
maxkinE e U= ⋅No electron flux for:
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MAC-E Filter – Principle II
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Adiabatic variation of B-field leads to alignment of momentum vector.
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KATRIN = Karlsruhe Tritium Neutrino Exp.
30
Goal: measure neutrino mass w/ sensitivity of 0.2 eV (90%CL)
< 1e / s
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Main Spectrometer
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Journey of KATRIN
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KARTRIN Reach
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After 3 years:
Starts now!
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Holmium Electron Capture
35
How to measure 2.8 keVw/ high precision?
Dy = Dyprosium
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Micro Calorimeters: MMCs
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Slide by K.Valerius
L. GastaldoC. Enss
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ECHo Experiment
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Uni Heidelberg:C. Enss, L. Gastaldo
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Majorana? - Double Beta Decays (2β)
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Mass parabola from Weizsäcker formula
Normal β-decay energetically forbidden for 74Ge.Double β-decay allowed: even-even nuclei.
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Neutrinoless Double Beta Decay
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Allowed in SM, ∆L=0Half-life: 2 18 24
1/2 ~ (10 10 )yrT ν −2 76 21
1/2 ( Ge) (1.93 0.10) 10 yrT ν = ± ⋅
Allowed only if neutrinosare Majorana particles
νν ν=
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Helicities – Mass dependence
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Lν ν ε ν↓ ↑= + ⋅
CR Lν ν ν ε ν↑ ↓= = + ⋅ ~
2mOEν
ν
ε
i.e. no 0ν2β für vanishing mν
→ Probability to oberserve 0ν2βis suppressed by ( )2/ 2m Eν ν
If the flavor state νe is a mixture of mass states:
222
2(0 2 ) ~ ~ei iU mm
E ββν
ν βΓ ∑ with 2ei iU m mββ=∑
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Resolve mass hierarchy
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0νββ Search with Germanium
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Germanium 76Ge:• Candidate for 2β decay• Same decay and detctor material• Germanium detectors have
excellent energy resolution:FWHM ~ 1.5 10-3
• Enrichment of 76Ge up to 86%
Ge diode w/ reverse biasing
Source = Detector
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GERDA Experiment
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Gerda Construction
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GERDA Results
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@90% C.L.
Limit on effective neutrino mass
Phys. Rev. Lett. 111 (2013) 122503
Pulse shapediscrimination
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Gerda Results
46
Heidelberg-Moscow Experiment
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CUORE - 130Te Bolometer Experiment
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T0ν > 6.6 × 1024 yrmββ < 210 - 590 meV
July 2017, preliminary
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Constraints on mass hierarchy
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