Neutrino mass, Double beta decay, Low background, Low energy, deep underground ex-experimental partical physics.

1. 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

2. 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

3. Neutrino oscillations. v do have mass!!! Double beta decay primer

4. 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

5. Kinematical experiments Double beta decay primer

6. 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

7. 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

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

9. Kinematical experiments KATRIN DE = E×Bmin/Bmax = 0.93 eV Double beta decay primer

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

11. Cosmology Double beta decay primer

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

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

14. Cosmology GALAXIES CMB Double beta decay primer

15. 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

16. 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

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

18. Dirac neutrino Double beta decay primer

19. Charge conjugation and bar Double beta decay primer

20. Majorana neutrino Double beta decay primer

21. See-Saw Double beta decay primer

22. 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

23. Neutrinoless bb decay • Golden plated channel: • 2 electrons • Eb1+ Eb2=Qbb ~<m>2/E2 (A,Z)→(Z+2,A)+2e- Double beta decay primer

24. 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

25. 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

26. 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

27. 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

28. 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