Abstract
Measurements of cosmic neutrinos have a reach potential for providing an insight into fundamental neutrino properties. For this a precise knowledge about an astrophysical environment of cosmic neutrinos propagation is needed. However this is not always possible, and the lack of information can bring about theoretical uncertainties in our physical interpretation of the results of experiments on cosmic neutrino fluxes. We formulate an approach that allows one to quantify the uncertainties using the apparatus of quantum measurement theory. We consider high-energy Dirac neutrinos emitted by some distant source and propagating towards the earth in the interstellar space. It is supposed that neutrinos can meet on their way to the detector at the earth a dense cosmic object serving as a filter that stops active, left-handed neutrinos and letting only sterile, right-handed neutrinos to propagate further. Such a filter mimics the strongest effect on the neutrino flux that can be induced by the cosmic object and that can be missed in the theoretical interpretation of the lab measurements due to the insufficient information about the astrophysical environment of the neutrino propagation. Treating the neutrino interaction with the cosmic object as the first, neutrino-spin measurement, whose result is not recorded, we study its invasive effect on the second, neutrino-flavor measurement in the lab.
Highlights
Measurements of cosmic neutrinos have a reach potential for providing an insight into fundamental neutrino properties
We present numerical illustrations of the robust invasive effect showing that the quantum witness as a function of the distance between Earth and a cosmic object can be an asymptotically nonvanishing quantity despite the thermalization of the neutrino spin induced by stochastic interstellar magnetic fields
Our approach employs the concepts of invasiveness and quantum witness that are used in the theory of quantum measurements
Summary
Many objects in the Universe produce vast amount of cosmic neutrinos with different energies. We have already been waiting a decade for a supernova explosion in our cosmic neighborhood—an event that is expected to occur a few times a century Neutrino flux from such an event will give us a bonanza of astrophysical and particle physics information [8] that will significantly advance our understanding of high-energy astrophysical phenomena. Assuming a turbulent spectrum of extragalactic magnetic fields, we may estimate a small-scale stochastic component to reach up to 0.3 μG amplitudes [17] These weak fields can affect ultrahigh-energy neutrinos that travel up to Gpc distances. We consider evolution of neutrinos that are emitted from a distant source and traverse the cosmic space diluted with the stochastic magnetic fields until they reach the detector in the lab. We deliver details of solving the Lindblad master equation for neutrino evolution
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