Double - beta decay of 96zr and double - electron capture of 156dy to excited final states

1.

Double-Beta Decay of 96Zr and
Double-Electron Capture of 156Dy to
Excited Final States
Sean Finch
Thesis Defense
March 25, 2015

2.

Outline
• Introduction to second-order weak decays
– Nature of the neutrino
• Double-β decay of 96Zr
– Two-coaxial HPGe apparatus
– Analysis and results
• Resonantly enhanced double-electron capture of
156Dy
– Two-clover HPGe apparatus
– Analysis and results
• Concluding remarks
2

3.

Outline
• Introduction to second-order weak decays
– Nature of the neutrino
• Double-β decay of 96Zr
– Two-coaxial HPGe apparatus
– Analysis and results
• Resonantly enhanced double-electron capture of
156Dy
– Two-clover HPGe apparatus
– Analysis and results
• Concluding remarks
3

4.

Weak Nuclear Decays
• β decay:
n → p + e - + νe
• Double-β decay:
2n → 2p + 2e- + 2νe
• 35 nuclides capable of ββ; Observed in 11
eνe
n
e-
p
νe
n
p
Spectator Nucleons
4

5.

Neutrinoless-ββ Decay
• n1 → p1 + e-1 + “νe”
“νe” + n2 → p2 + e-2
• Never observed (one questionable claim)
e-
e-
νe
n
e-
p
n
νe
n
νe
p
νe
p
Spectator Nucleons
e-
n
p
Spectator Nucleons
5

6.

Majorana Neutrinos
0νββ requires:
• Helicity flip
– Solved by massive
neutrinos
• Neutrinos are their own
antiparticle
– Solved by Majorana
neutrinos
Why is this interesting?
• 0νββ violates lepton number
conservation
• Allows measurement of
neutrino mass:
–