Neutrino mass, Double beta decay, Low background, Low energy, deep underground exexperimental partic

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Neutrino mass, Double beta decay, Low background,
Low energy, deep underground ex-experimental
partical physics.
Dr. Vladimir Vasiliev UCL Physics building C14,
vv at hep.ucl.ac.uk www.hep.ycl.ac.uk/vv/lectu
res
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Neutrino, the story

• Proposed by W. Pauli in 1930
• Reactor ne observed,1953
• ne? nm, 1960-64
• Electro-weak theory GWS
• Neutral current discovered, 1973
• Z, W observed at LEP, 1983
• Z width ? 3 n families
• nt,
• SM almost complete.

Neutrino oscillate!
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Neutrino oscillations.
v do have mass!!!
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Absolute neutrino mass
How to weight a particle?
NO

• resonance in cross section

YES!

• decay kinematics

• Cosmology, gravitation

YES!

• double beta decay

YES!
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Kinematical experiments
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Kinematical experiments

• Challenges
• Small rate at the tail ? low Qb
• Energy resolution mn ? non-traditional
  detectors
• Effect is at the scale of atomic energy (H line
  13.6 eV) ? enormous effort to control
  systematic error
• 3H 18 keV b-decay (Troitsk, Maiz, Katrin) ? Use
  of MAC-E filter
• 187Re 2.47 keV b-decay (MARE) ? Use of cryogenic
  bolometer (see CUORE experiment for bolometer
  detector)

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Kinematical experiments
Magnetic Adiabatic Collimation Electrostatic
Filter

• Two superconducting
  solenoids make a guiding magnetic field
• Electron source in left solenoid
• Electrons emitted in forward direction are
  magnetically guided
• Adiabatic transformation

• Parallel beam at
• analyzing plane

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Kinematical experiments
Mainz result Current best limit mn lt 2.2 eV
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Kinematical experiments
KATRIN
DE EBmin/Bmax 0.93 eV
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Cosmology
galaxy formation movie millennium
simulations http//www.mpa-garching.mpg.de/galform
/virgo/millennium/
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Cosmology
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Cosmology
http//video.google.com/videoplay?docid-825270510
2362324792qsdss
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Cosmology
http//space.mit.edu/home/tegmark/cmb/movies.html
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Cosmology
GALAXIES
CMB
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Cosmology
Key problems what data to use? what are the
systematic errors in the data? Ex. SELJAK,
SLOSAR MCDONALD (ASTRO-PH/0604335) FIND
SELJAK, SLOSAR MCDONALD
SDSS LYMAN-ALPHA
WMAP-3 NORMALIZATION
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Cosmology
Key problems what data to use? what are the
systematic errors in the data? Ex. Degeneracy
between dark energy state equation and neutrino
mass
STH, ASTRO-PH/0505551 (PRL)
DE LA MACORRA ET AL. ASTRO-PH/0608351
DE LA MACORRA ET AL. ASTRO-PH/0608351
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Absolute neutrino mass
DE LA MACORRA ET AL. ASTRO-PH/0608351
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Dirac neutrino
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Charge conjugation and bar
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Majorana neutrino
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See-Saw
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Leptogenesis

• Generate DL in out of equilibrium decay of heavy
  Majorana neutrinos
• Convert DL ? DB
• Leptogenesis is consistent with
• neutrino masses and cosmology
• Leptogenesis is predictive

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Neutrinoless bb decay

• Golden plated channel
• 2 electrons
• Eb1 Eb2Qbb

ltmgt2/E2
(A,Z)?(Z2,A)2e-
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Double beta (bb2n) decay
(A,Z)?(Z2,A)2e-2ne
allowed in Standard Model very rare,
GF4 typical T1/21018-1021 years First indirect
confirmation for 82Se, 130Te by geochemical
analysis First direct observation TPC with 82Se
foil, 32 events. Elliott SR Hahn AA and Moe MK,
1987
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Double beta (bb) decay
1935 by Carl von Weizsäcker
(A,Z)?(Z2,A)2e-2ne
(A,Z)?(Z-2,A)2e2ne
(A,Z)?(Z2,A)ge2ne (EC)
(A,Z)?(Z2,A)2g2ne (ECEC)
69 stable and 28 a-unstable bb isotopes
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Double beta (bb0n) decay, experimental signatures
(A,Z)?(Z2,A)2e-

• Experimental signatures
• two e- from same place at the same time
• daughter (Z2,A) nuclei appears
• the sum of e- kinetic energy equals to Qbb

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Big questions

• What are the absolute masses?
• Direct mass measurement, Cosmology, bb0n
• What is the mass ordering, 123 or 312?
• Long baseline oscillations, bb0n
• Are v's Dirac or Majorana Particles
• bb0n

bb0n is the key experiment for neutrino physics
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Home problems questions
3) Why tritium is the isotope of choice for
kinematical experiments? 4) What if dark matter
sector has other light particles similar to
neutrinos (in terms of mass and interaction cross
section). What would happen with neutrino
cosmological mass boundaries? 5) Why not to
search double beta decay of beta-unstable
isotopes? 6) What do you know about Occam's
razor? How one can apply it to argue against
simple extension of SM with massive Dirac
neutrinos?
1)
2) derive m1,2 for the slide 21