There is currently interest in testing possible Lorentz invariance violation (LIV) in different physical processes. LIV effects have also been searched in the neutrino sector, mainly in neutrino oscillation experiments. However, there are LIV effects induced by a Lorentz-violating operator in the Standard Model extension (SME) theory, called countershaded operator, which does not affect the neutrino oscillations. Such effects, related to the time-like component of this operator, which are controlled by the oscillation-free (of) coefficient (aof3)00, would produce small deviations in the
shape of the energy spectra of electrons emitted in double-beta decays. Such investigations are currently been conducted in several double beta decay experiments as EXO, GERDA, SuperNEMO, CUORE and CUPID-0. These analysis are based on accurate theoretical predictions of the electron spectra and their angular correlations in 2νββ decay.
In my talk I will give a current review of this topic. I will first present the precise calculation of the summed energy electron spectra and their deviations due to LIV, and the constraints of the (aof3)00 coefficient obtained from these analyzes. Next, I show that current investigations of LIV can be complemented by searches in the single electron spectra and angular correlations between the emitted electrons. Distortions due to LIV occur in the single electron spectra (maximal at small electron energies) and other effects may be highlighted by analyzing the angular correlation spectra and the ratio between the SME electron spectra and their SM forms. Finally, I will present an
alternative, new method to constrain (aof3)00 through the measurement of the angular correlation coefficient, and show that future experiments can improve these limits significantly.
1. S. Stoica, Investigation of Lorentz symmetry violation in double-beta decay, MEDEX’19, Prague, May 28-June 2, 2019 (invited lecture).
2. O. Nitescu, S. Ghinescu, and S. Stoica, J. Phys. G 47, 055112 (2020).
3. O. Nitescu, S. Ghinescu, and S. Stoica, Phys. Rev. D 103, L031701 (2021).
4. S. Stoica, Study of kinematic factors in double-beta decay, Conference on Neutrino and Nuclear Physics (CNNP2020), February 20-24, Cape Town, South Africa (invited lecture).
|Reference to paper (DOI or arXiv)||O. Nitescu, S. Ghinescu, and S. Stoica, J. Phys. G 47, 055112 (2020); Phys. Rev. D 103, L031701 (2021)|