Dirac vs Majorana Neutrinos

23

( )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:

Dirac vs Majorana Neutrinos

24

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:

Neutrino Masses

25

(0.05 eV)2

(0.01 eV)2

Neutrino Mass Constraints

26

Relic neutrino density: 336 ν / cm3

Experimental

Neutrino Mass Measurement

27

„Direct“ kinematic measurement

MAC-E Filter - Principle

28

Solenoid Solenoid

Electrostatic spectrometer:

q E⋅

q E⋅

U

B

maxkinE e U= ⋅No electron flux for:

MAC-E Filter – Principle II

29

Adiabatic variation of B-field leads to alignment of momentum vector.

KATRIN = Karlsruhe Tritium Neutrino Exp.

30

Goal: measure neutrino mass w/ sensitivity of 0.2 eV (90%CL)

< 1e / s

Main Spectrometer

31

Journey of KATRIN

32

33

KARTRIN Reach

34

After 3 years:

Starts now!

Holmium Electron Capture

35

How to measure 2.8 keVw/ high precision?

Dy = Dyprosium

Micro Calorimeters: MMCs

36

Slide by K.Valerius

L. GastaldoC. Enss

ECHo Experiment

37

Uni Heidelberg:C. Enss, L. Gastaldo

Majorana? - Double Beta Decays (2β)

38

Mass parabola from Weizsäcker formula

Normal β-decay energetically forbidden for 74Ge.Double β-decay allowed: even-even nuclei.

Neutrinoless Double Beta Decay

39

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=

Helicities – Mass dependence

40

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=∑

Resolve mass hierarchy

41

0νββ Search with Germanium

42

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

GERDA Experiment

43

Gerda Construction

44

GERDA Results

45

@90% C.L.

Limit on effective neutrino mass

Phys. Rev. Lett. 111 (2013) 122503

Pulse shapediscrimination

Gerda Results

46

Heidelberg-Moscow Experiment

CUORE - 130Te Bolometer Experiment

47

T0ν > 6.6 × 1024 yrmββ < 210 - 590 meV

July 2017, preliminary

Constraints on mass hierarchy

48