John WilkersonA National Underground Science Laboratory at Homestake

How do you weigh a neutrino?

Recent underground experiments have demonstrated that ’s must have mass!• Atmospheric neutrinos: SuperKamiokande (1998)• Solar neutrinos: Chlorine (1970s) --> SNO (2001, 2002)• Reactor antineutrinos: KamLAND (2002)

These results also disagree with physicists’ long held “standard” model

In the standard model - massless neutrinos were frankly a bit dull,

perhaps even boring

And why would one want to do that!

These results tell us neutrinos have mass, but don’t tell us what the mass is.

John WilkersonA National Underground Science Laboratory at Homestake

’s with mass: exciting “superhero” particles

As ’s travel through space or matter they transform from one type (flavor)of neutrino to another?

Neutrinos play important roles in• how stars burn• how stars die (supernovae explosions)• the creation of the heavier elements

There are lots of neutrinos in the universe (~330 / cm3). So even with a small mass, they collectively are equal to the mass of all the stars and luminous gases in the universe! Thus they can influence the evolution of the early universe

They could potentially be the reason for the observed matter - antimatter asymmetry. (We don’t know yet!)

Neutrinos may even be their own anti-particle! (don’t know yet!)

John WilkersonA National Underground Science Laboratory at Homestake

physics - more questions than answers!

Since the current model is wrong, what is the correct model? Mass opens up an array of interesting theoretical possibilities.

What is the nature of these “massive” neutrinos?• What is the relationship between the neutrino “flavors”

we observe in nature and the neutrino “mass” states.

• Is there a connection between neutrinos and other fundamental particles (quarks) and the origin of mass?

• What symmetry laws do neutrinos obey?Might neutrinos be their own anti-particle?

• What are the neutrino masses?

John WilkersonA National Underground Science Laboratory at Homestake

NeutrinolessDouble Beta decay

How do you weigh a neutrino?

Z

Z+1e-

e

Beta decay:

Nucleus (A, Z) Nucleus (A, Z+1) + e- + e n p + e- + e

2 Double Beta decay:

Nucleus (A, Z) Nucleus (A, Z+2) + e- + e + e- + e 76Ge 76Se + e- + e + e- + e Z

Z+2e-

e

e-

e

Neutrinoless Double Beta decay: Nucleus (A, Z) Nucleus (A, Z+2) + e- + e-

76Ge 76Se + e- + e-

Z

Z+2e-

e

e-

e

John WilkersonA National Underground Science Laboratory at Homestake

NeutrinolessDouble Beta decay

If neutrinos are their own anti-particles, a nucleus that decays via double beta decay will do so at a rate proportional to effective neutrino mass. (The slower the decay, the longer lifetime for the nucleus.)

Crucial Challenge - measuring extremely rare decay rates:

Best experiments to date (10 kg) T1/2 > 2 1025 years (~.3 eV)

Requirements for next generation experiments:• Sufficient mass, ~ 500 - 1000 kg (a factor of 100 increase!)• Extremely low backgrounds

deep underground, ultra clean materials• Good detector energy resolution

Goal: T1/2 ~ 1026 - 1027 years

John WilkersonA National Underground Science Laboratory at Homestake

Next generation 0 -decay experiments

Next Generation Double Beta Decay ExperimentsIsotope Experiment Technique Isotope

Mass (t)Enriched Q

(MeV)Expected

Sensitivity

T1/20 (y)

48Ca CANDLES CaF2 crystals in liq. scint. ~1-3 No 4.27 1 x 1026

76Ge GEM Ge diodes in LN 1 Yes 2.04 7 x 1027

76Ge GENIUS Ge diodes in LN 1 86% 2.04 1 x 1028

76Ge MAJORANA Segmented Ge crystals .5 86% 2.04 3 x 1027

82Se, 100Mo,116Cd, 150Nd

NEMO3 drift chamber-scintillator .001, .007, .001, .001

Yes 3.0,3.0,2.8,3.4

4 x 1024

100Mo MOON Scint+Foils (or Bolometer) 34 No 3.03 1 x 1027

116Cd CAMEO CdWO4 - Borexino CTF ~1 Yes 2.8 > 1027

116Cd CWO CdWO4 ~1 Yes 2.8 1 x 1026

130Te COBRA CdZnTe or TeO2 semiconductors .01 No 2.6 1 x 1024

130Te CUORICINO Cryogenic TeO2 crystals .04 No 2.6 1 x 1024

130Te CUORE Cryogenic TeO2 crystals .75 No 2.6 2 x 1026

136Xe EXO Liquid Xe 1-10 Ye s 2.47 8 x 1026

136Xe Xe Xe in liquid scintillator 1.6 Yes 2.47 5 x 1026

136Xe XMASS liquid Xe (solar ) 10 No 2.47 3 x 1026

150Nd DCBA-II(2) foils and tracking chambers .02 Yes 3.37 2 x 1025

160 Gd GSO Gd2SiO5 :Ce crystal scint. in liq. scint. 2 No 1.73 2 x 1026

EXO

MajoranaCUORE

MOON

John WilkersonA National Underground Science Laboratory at Homestake

Majorana Collaboration Proposed Detector

Requires:• 500 kg enriched 85% 76Ge• many crystals, each segmented• advanced signal processing

Pulse shape discrimination

• special low bkg materials• deep underground location

Sensitive to effective Majorana mass as low as 0.02-0.07 eV

0 decay of 76Ge potentially measured at 2039 keV

Based on well known 76Ge detector technology plus:• Pulse-shape analysis• Detector segmentation• Ready to begin now