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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/lectures. Neutrino, the story. Proposed by W. Pauli in 1930

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slide1

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/lectures

Double beta decay primer

neutrino the story
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!

Double beta decay primer

neutrino oscillations
Neutrino oscillations.

v do have mass!!!

Double beta decay primer

absolute neutrino mass
Absolute neutrino mass

How to weight a particle?

NO

  • resonance in cross section

YES!

  • decay kinematics
  • Cosmology, gravitation

YES!

YES!

  • double beta decay

Double beta decay primer

kinematical experiments
Kinematical experiments

Double beta decay primer

kinematical experiments1
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)

Double beta decay primer

kinematical experiments2
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

Double beta decay primer

kinematical experiments3
Kinematical experiments

Mainz result

Current best limit mn < 2.2 eV

Double beta decay primer

kinematical experiments4
Kinematical experiments

KATRIN

DE = E×Bmin/Bmax = 0.93 eV

Double beta decay primer

cosmology
Cosmology

galaxy formation movie

millennium simulations

http://www.mpa-garching.mpg.de/galform/virgo/millennium/

Double beta decay primer

cosmology1
Cosmology

Double beta decay primer

cosmology2
Cosmology

Double beta decay primer

http://video.google.com/videoplay?docid=-8252705102362324792&q=sdss

cosmology3
Cosmology

http://space.mit.edu/home/tegmark/cmb/movies.html

Double beta decay primer

cosmology4
Cosmology

GALAXIES

CMB

Double beta decay primer

cosmology5
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

Double beta decay primer

cosmology6
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

Double beta decay primer

DE LA MACORRA ET AL. ASTRO-PH/0608351

absolute neutrino mass1
Absolute neutrino mass

Double beta decay primer

DE LA MACORRA ET AL. ASTRO-PH/0608351

dirac neutrino
Dirac neutrino

Double beta decay primer

charge conjugation and bar
Charge conjugation and bar

Double beta decay primer

majorana neutrino
Majorana neutrino

Double beta decay primer

see saw
See-Saw

Double beta decay primer

leptogenesis
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

Double beta decay primer

neutrinoless bb decay
Neutrinoless bb decay
  • Golden plated channel:
  • 2 electrons
  • Eb1+ Eb2=Qbb

~<m>2/E2

(A,Z)→(Z+2,A)+2e-

Double beta decay primer

slide24

Double beta (bb2n) decay

(A,Z)→(Z+2,A)+2e-+2ne

allowed in Standard Model

very rare, ~GF4

typical T1/2=1018-1021 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

24

slide25

Double beta (bb) decay

1935 by Carl von Weizsäcker

(A,Z)→(Z+2,A)+2e-+2ne

(A,Z)→(Z-2,A)+2e++2ne

(A,Z)→(Z+2,A)+g+e++2ne (EC)

(A,Z)→(Z+2,A)+2g+2ne (ECEC)

~ 69 stable and 28 a-unstable bb isotopes

25

slide26

Double beta (bb0n) decay, experimental signatures

(A,Z)→(Z+2,A)+2e-

  • Experimental signatures:
    • two e- from same place at the same time
    • daughter (Z+2,A) nuclei appears
    • the sum of e- kinetic energy equals to Qbb

26

slide27

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

27

home problems questions
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

Double beta decay primer