1. Double beta decay primer 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

2. Double beta decay primer Neutrino, the story Proposed by W. Pauli in 1930 Reactor e observed,1953 e, 1960-64 Electro-weak theory GWS Neutral current discovered, 1973 Z, W observed at LEP, 1983 Z width 3 families SM almost complete.

3. Double beta decay primer Neutrino oscillations.

4. Double beta decay primer Absolute neutrino mass How to weight a particle? resonance in cross section decay kinematics Cosmology, gravitation double beta decay NO YES!

5. Double beta decay primer Kinematical experiments

6. Double beta decay primer Kinematical experiments Challenges: Small rate at the tail low Q Energy resolution ~ m non-traditional detectors Effect is at the scale of atomic energy (H line 13.6 eV) enormous effort to control systematic error 3 H 18 keV -decay (Troitsk, Maiz, Katrin) Use of MAC-E filter 187 Re 2.47 keV -decay (MARE) Use of cryogenic bolometer (see CUORE experiment for bolometer detector)

7. Double beta decay primer Kinematical experiments Parallel beam at analyzing plane 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:

8. Double beta decay primer Kinematical experiments Mainz result Current best limit m < 2.2 eV

9. Double beta decay primer Kinematical experiments E = E×B min /B max = 0.93 eV KATRIN

10. Double beta decay primer Cosmology galaxy formation movie millennium simulations http://www.mpa-garching.mpg.de/galform/virgo/millennium/

11. Double beta decay primer Cosmology

12. Double beta decay primer Cosmology http://video.google.com/videoplay?docid=-8252705102362324792&q=sdss

13. Double beta decay primer Cosmology http://space.mit.edu/home/tegmark/cmb/movies.html

14. Double beta decay primer Cosmology CMB GALAXIES

15. Double beta decay primer 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

16. Double beta decay primer 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

17. Double beta decay primer Absolute neutrino mass DE LA MACORRA ET AL. ASTRO-PH/0608351

18. Double beta decay primer Dirac neutrino

19. Double beta decay primer Charge conjugation and bar

20. Double beta decay primer Majorana neutrino

21. Double beta decay primer See-Saw

22. Double beta decay primer Leptogenesis Generate L in out of equilibrium decay of heavy Majorana neutrinos Convert L B Leptogenesis is consistent with neutrino masses and cosmology Leptogenesis is predictive

23. Double beta decay primer Neutrinoless decay Golden plated channel: a)2 electrons b)E + E Q (A,Z)(Z+2,A)+2e - ~ 2 /E 2

24. Double beta ( ) decay (A,Z)(Z+2,A)+2e - +2 e allowed in Standard Model very rare, ~G F 4 typical T 1/2 =10 18 -10 21 years First indirect confirmation for 82 Se, 130 Te by geochemical analysis First direct observation: TPC with 82 Se foil, 32 events. Elliott SR Hahn AA and Moe MK, 1987 24

25. Double beta ( ) decay (A,Z)(Z+2,A)+2e - +2 e (A,Z)(Z-2,A)+2e + +2 e (A,Z)(Z+2,A)+ +e + +2 e (EC) (A,Z)(Z+2,A)+2 +2 e (ECEC) 1935 by Carl von Weizsäcker ~ 69 stable and 28 -unstable isotopes 25

26. Double beta ( ) 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 Q 26

27. What are the absolute masses? Direct mass measurement, Cosmology, What is the mass ordering, 123 or 312? Long baseline oscillations, Are v's Dirac or Majorana Particles Big questions is the key experiment for neutrino physics 27

28. Double beta decay primer Home problems & questions 1) 2) derive m 1,2 for the slide 21 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?