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Register a new userNeutrino quantum decoherence engendered by neutrino radiative decay
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Added by
Alexander Studenikin
Publication date
2020
fields
Physics
and research's language is
English
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A new theoretical framework, based on the quantum field theory of open systems applied to neutrinos, has been developed to describe the neutrino evolution in external environments accounting for the effect of the neutrino quantum decoherence. The developed new approach enables one to obtain the explicit expressions of the decoherence and relaxation parameters that account for a particular process, in which the neutrino participates, and also for the characteristics of an external environment and of the neutrino itself, including the neutrino energy. We have used this approach to consider a new mechanism of the neutrino quantum decoherence engendered by the neutrino radiative decay to photons and dark photons in an astrophysical environment. The importance of the performed studies is highlighted by the prospects of the forthcoming new large volume neutrino detectors that will provide new frontier in high-statistics measurements of neutrino fluxes from supernovae.
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The radiative decay of neutral fermions has been studied for decades but $CP$ violation induced within such a paradigm has evaded attention. $CP$ violation in these processes can produce an asymmetry between circularly polarised directions of the radiated photons and produces an important source of net circular polarisation in particle and astroparticle physics observables. The results presented in this work outlines the general connection between $CP$ violation and circular polarisation for both Dirac and Majorana fermions and can be used for any class of models that produce such radiative decays. The total $CP$ violation is calculated based on a widely studied Yukawa interaction considered in both active and sterile neutrino radiative decay scenarios as well as searches for dark matter via direct detection and collider signatures. Finally, the phenomenological implications of the formalism on keV sterile neutrino decay, leptogenesis-induced right-handed neutrino radiative decay and IceCube-driven heavy dark matter decay are discussed.
In our previous studies (see [1] and references therein) we developed a new theoretical framework that enabled one to consider a new mechanism of neutrino quantum decoherence engendered by the neutrino radiative decay. In parallel, another framework was developed (see [2] and references therein) for the description of the neutrino quantum decoherence due to the non-forward neutrino scattering processes. Both mechanisms are described by the master equations in the Lindblad form. We study the influence of the neutrino quantum decoherence on collective neutrino oscillations. In the present studies we are are not interested in a specific mechanism of neutrino quantum decoherence. Therefore, we use the general Lindblad master equation for the description of the neutrino quantum decoherence and do not fix an analytical expressions for the decoherence and relaxation parameters.
Neutrino interactions with an external environment can in influence the neutrino oscillation pattern and the oscillations can be damped as a result of the neutrino quantum decoherence. In particular, the quantum decoherence of neutrino states engendered by the neutrino radiative decay accounting for the nonstandard interactions (NSI) leads to the suppression of flavor neutrino oscillations in the solar neutrino fluxes.
In this work we perform global fits of microscopic decoherence models of neutrinos to all available current data, including LSND and KamLAND spectral distortion results. In previous works on related issues the models used were supposed to explain LSND results by means of quantum gravity induced decoherence. However those models were purely phenomenological without any underlying microscopic basis. It is one of the main purposes of this article to use detailed microscopic decoherence models with complete positivity, to fit the data.The decoherence in these models has contributions not only from stochastic quantum gravity vacua operating as a medium, but also from conventional uncertainties in the energy of the (anti)neutrino beam. All these contributions lead to oscillation-length independent damping factors modulating the oscillatory terms from which one obtains an excellent fit to all available neutrino data, including LSND and Kamland spectral distortion.
We study decoherence effects in neutrino flavor oscillations in curved spacetime with particular emphasis on the lensing in a Schwarzschild geometry. Assuming Gaussian wave packets for neutrinos, we argue that the decoherence length derived from the exponential suppression of the flavor transition probability depends on the proper time of the geodesic connecting the events of the production and detection in general gravitational setting. In the weak gravity limit, the proper time between two events of given proper distance is smaller than that in the flat spacetime. Therefore, in presence of a Schwarzschild object, the neutrino wave packets have to travel relatively more physical distance in space to lapse the same amount of proper time before they decoher. For non-radial propagation applicable to the lensing phenomena, we show that the decoherence, in general, is sensitive to the absolute values of neutrino masses as well as the classical trajectories taken by neutrinos between the source and detector along with the spatial widths of neutrino wave packets. At distances beyond the decoherence length, the probability of neutrino flavor transition due to lensing attains a value which depends only on the leptonic mixing parameters. Hence, the observability of neutrino lensing significantly depends on these parameters and in-turn the lensing can provide useful information about the latter.
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