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Neutrinoless double-electron capture: current status and prospects

M.I. Krivoruchenko

ITEP, Moscow

Abstract: Double-beta processes play a key role in the exploration of neutrino and weak interaction properties, and in the searches for effects beyond the Standard Model. During the last half century many attempts were undertaken to search for double-beta decay with emission of two electrons, especially for its neutrinoless mode ($0\nu2\beta^-$), the latter being still not observed. Double-electron capture (2EC) was not in focus so far because of its in general lower transition probability. However, the rate of neutrinoless double-electron capture ($0\nu2$EC) can experience a resonance enhancement by many orders of magnitude in case the initial and final states are energetically degenerate. In the resonant case, the sensitivity of the $0\nu2$EC process can compete with that of the $0\nu2\beta^-$ decay in the search for the Majorana mass of neutrinos, right-handed currents, and other new physics. We present an overview of the main experimental and theoretical results obtained during the last decade in this field. The experimental part of the talk outlines search results of 2EC processes and measurements of the decay energies (Q values) for possible resonant $0\nu$2EC transitions. An unprecedented precision in the determination of decay energies with Penning traps has allowed one to refine the values of the degeneracy parameter for all previously known near-resonant decays and has reduced the rather large uncertainties in the estimate of the $0\nu2$EC half-lives. The theoretical part contains an updated analysis of the electron shell effects and an overview of the nuclear structure models, in which the nuclear matrix elements of the $0\nu2$EC decays are calculated. One can conclude that the decay probability of $0\nu$2EC can experience a significant enhancement in several nuclides.

Seminar takes place on Tuesday, July 23rd 2019 at 2:00 PM
in the IEAP meeting room, Praha 1, Husova 240/5.

Ing. Bartoloměj Biskup, Ph.D.
seminar organizer
doc. Ing. Ivan Štekl, CSc.
director of IEAP
doc. Dr. André Sopczak
IEEE CS - NPSS chair

IEEE Czechoslovakia section

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