W. Bauer

Slide 1

Neutrinos, Double Beta Decay, and Supernova Dynamics

Wolfgang Bauer Michigan State University

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1 meV/c2 1 eV/c2 1 keV/c2 1 MeV/c2 1 GeV/c2 1 TeV/c2

tbτντ

csµνµ

udeνe

Mass Hierarchy

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1 GeV/c2 1 TeV/c2

t

b

c

s

u

d− 13 e

+ 23 e

q

m

W +W −

0

1 MeV/c2

Beta Decays β

− : q→ q '+ − + ν; mq > mq ' + m + mν

β+ : q→ q '+ + + ν; mq > mq ' + m + mν

Largest Suppressed Highly Suppressed

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π ±π 0

η K ±

KL0

KS0

J /ψ

ϒ

D

B

η 'ωρ

φK *

Composites: Mesons!

Strong

Electromagnetic

Weak

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Composites: Isotopes!

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Favorite Decay Channels

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d W −

ue−

νe

md > mu + me−+ mνe

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d W −

u

e−

νe

d

du

un p

mn > mp + me−+ mνe

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d W −

u

e−

νe

d

du

un p

mNZ A

> mN−1Z+1 A

+ me−+ mνe

NZ A

N −1Z +1 A

Already counted in atomic mass that contains Z+1 electrons

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u W +

d

e+

νe

d

du

unp

mNZ A

> mN+1Z−1 A

+ 2me++ mνe

NZ A

N +1Z −1 A

Beta+ decay: positron emission

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uW +

d

e− νe

d

du

unp

mNZ A

> mN+1Z−1 A

+ mνe

NZ A

N +1Z −1 A

Beta+ decay: electron capture

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Favorite Decay Channels

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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N

Z

3482 Se34

81 Se3480 Se 34

83 Se

3582Br35

81Br3580Br 35

83Br 3584Br

3681Kr 36

82Kr 3683Kr 36

84Kr 3685Kr

3479Se

3782Rb 37

83Rb 3784Rb 37

85Rb 3786Rb

3378As 33

79As 3380As 33

81As 3382As

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3482 Se

3682Kr

3582Br 37

82Rb

3882Sr

3982 Y 40

82 Zr

4182Nb31

82Ga

3282Ge

3382As

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Double Beta Decay Isotopes •  Only 12 known isotopes exhibit this

decay •  48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd,

128Te, 130Te, 134Xe, 136Xe, 150Nd, and 160Gd

•  Typical lifetimes ~ 1019 years (billion times the lifetime of universe)

•  First observed in 1986 by Michael Moe et al. for 82Se

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Life Times and Q-Values

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3678Kr

54124 Xe

N +1 -1 -2

Z Z-1 Z-2

Z+1

+2 Z+2

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Double Beta+ Candidate 78Kr •  Mass(78Kr) = 77.9203 GeV

Mass(78Se) = 77.9173 GeV Mass difference = 2.85 MeV

•  2 EC, e+EC (threshold 1.022 MeV), and e+e+ (threshold 2.044 MeV) channels are all open (in principle!)

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Double Beta+ Candidate 78Kr •  Typical predicted half-life* ~ 1022 years •  Need N ~ 1025 atoms of 78Kr •  Natural abundance of 78Kr = 0.35% •  Need N ~ 3•1028 atoms of natKr •  Need 0.168 kg*(3•1028)/(6•1023) =

90 tons = 40,000 liters of natKr •  Cost: ~$200,000

* A.Staudt, K.Muto and H.V.Klapdor-Kleingrothaus, “Nuclear matrix elements for double positron emission”, Phys. Lett. B268 (1991) 312

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Detection

•  Gamma ray detectors for 511 keV Photons and/or photons from K-shell ionization cascades

•  Detection of single atom of Selenium a la Ray Davis

•  Detection of positron paths in TPC (perhaps liquid Kr, or perhaps even better high pressure gas Kr (0.1g/cm3)

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Liquid Argon TPC •  One example for

LANNDD (Liquid Argon Neutrino and Nucleon Decay Detector)

•  Smallest shown: V = 125 m3

•  Design can be taken over with slight modifications (rhoAr /rhoKr = 1.65/2.41) D.B. Cline and F. Sergiampietri, “A Concept for a Scalable 2 kTon Liquid Argon TPC Detector for Astroparticle Physics”, http://arxiv.org/abs/astro-ph/0509410

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Previous Experiment •  tau > 0.9•1020 years •  J.M. Gavriljuk et al.,

Phys. Atom. Nuclei 61, 1287 (1998)

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Neutrino-less Double Beta decay •  Only possible if neutrino is its own anti-particle •  Violation of Standard Model

From: DUSEL_121306.pdf

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Current lower half-life limits

Compiled by Steven Elliott, LANL, 2006)

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Could it be detected? •  Monte Carlo:

5 body vs. 3 body phase space with constant or Fermi cross sections

•  Importance sampling with N-body event generator GENBOD (F. James, CERN library)

•  Lorentz-invariant Fermi phase space •  Respects all conservation laws (energy,

momentum) and uses proper reaction Q-value

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Monte Carlo Events Neutrino Positron Recoil Nucleus

3d momentum space event displays in cm-system

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Positron Energy distributions •  Monte Carlo:

5 body vs. 3 body phase space with constant or Fermi cross sections

•  Here: 106 events •  More realistic:

101-102 events

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Coincidence Counts •  In 0nu case the

daughter nucleus receives almost vanishing recoil energy

•  Clear signal •  (Note: not true for

recoil momentum of daughter nucleus)

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Background: 2 simult. Beta+ decays •  Very rare •  But we are dealing

a very rare signal!