Evidence for Neutrinoless Double Beta Decay
Abstract
The data of the HeidelbergMoscow double beta decay experiment for the measuring period August 1990May 2000 (54.9813 kg y or 723.44 molyears), published recently, are analyzed using the potential of the Bayesian method for low counting rates. First evidence for neutrinoless double beta decay is observed giving first evidence for lepton number violation. The evidence for this decay mode is 97% (2.2σ) with the Bayesian method, and 99.8% c.l. (3.1σ) with the method recommended by the Particle Data Group. The halflife of the process is found with the Bayesian method to be T_{1/2}^{0ν }=(0.818.3)x 10^{25} y (95% c.l.) with a best value of 1.5 × 10^{25} y. The deduced value of the effective neutrino mass is, with the nuclear matrix elements from Ref. 1, <m> = (0.110.56) eV (95% c.l.), with a best value of 0.39 eV. Uncertainties in the nuclear matrix elements may widen the range given for the effective neutrino mass by at most a factor 2. Our observation which at the same time means evidence that the neutrino is a Majorana particle, will be of fundamental importance for neutrino physics.
 Publication:

Modern Physics Letters A
 Pub Date:
 2001
 DOI:
 10.1142/S0217732301005825
 arXiv:
 arXiv:hepph/0201231
 Bibcode:
 2001MPLA...16.2409K
 Keywords:

 14.69.Pq;
 23.40.Bw;
 23.40.s;
 Weakinteraction and lepton aspects;
 Beta decay;
 double beta decay;
 electron and muon capture;
 High Energy Physics  Phenomenology
 EPrint:
 14 pages, psfile, 7 figures, Published in Modern Physics Letters A, Vol. 16, No. 37 (2001) 24092420, World Scientific Publishing Company, Home Page: http://ejournals.wspc.com.sg/mpla/16/1637/S0217732301005825.html, Home Page of Heidelberg NonAccelerator Particle Physics Group: http://www.mpihd.mpg.de/non_acc/