Probing Possible Decoherence Effects in Atmospheric Neutrino Oscillations

Abstract

It is shown that the results of the Super-Kamiokande atmospheric neutrino experiment, interpreted in terms of nu(mu)<-->nu(tau) flavor transitions, can probe possible decoherence effects induced by new physics (e.g., by quantum gravity) with high sensitivity, supplementing current laboratory tests based on kaon oscillations and on neutron interferometry. By varying the (unknown) energy dependence of such effects, one can either obtain strong limits on their amplitude or use them to find an unconventional solution to the atmospheric nu anomaly based solely on decoherence.

On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

“…On the other hand, an earlier analysis [22] by means of the super-Kamiokande data [26] for ν µ − ν τ oscillations yields a somewhat weaker bound for the QG-decoherence effects < 3.5 × 10 −23 GeV in the massive neutrino case, using the super Kamiokande value [26] for the neutrino squared mass difference ∆m 2 = m 2 2 − m 2 1 = 3 × 10 −3 eV 2 between the oscillating states. In the massless neutrino case, the analysis of [22] yields more stringent bounds for the decoherence parameter(s), of order 10 −27 GeV, as in [23]. However, theoretically, for massive neutrino models of decoherence, more conservative estimates have been presented for some models [27] according to which the decoherence parameters are of order…”

“…Such effects may then be bounded (or tested!) experimentally by taking into account that their presence may induce decoherence and oscillations in, say, neutral mesons [18,19,20,21], neutrinos [22,23] etc.. We shall discuss first the neutral meson case, concentrating on the most sensitive probe that of neutral kaons.…”

“…We remind the reader that neutrinos, viewed as open string excitations on the brane, transform in the fundamental representation of appropriate gauge groups, while a string-D-particle 'composite', describing the capture stage, behaves as a gauge field excitation in the model, transforming in the adjoint representation of the unbroken standard model group 8 . However, in other models of QG, where gravitational fluctuations imply the existence of an 'environment' [31,22] neutrinos may have non trivial refractive indices (for the massless species). Such modifications, as we discussed in previous sections, may lead to CPTV and LIV effects of order g s E 2 /M s , where E is a typical neutrino energy at the frame of observation.…”

“…Given that in a space-time foam model the quantum numbers of the 'vacuum' must be preserved [42] by the interactions of matter with the foam d.o.f., we must conclude from the above considerations that only string modes which transform in the adjoint representation of the (unbroken) standard model group U (3) ≃ SU (2) ⊗ U (1), and are therefore gauge excitations, can interact in the above sense with the D-particles and have modified dispersion relations of the type (22).…”

“…Finally, when the above-described formalism of open quantum systems [18] is applied to neutrinos, induced oscillations between neutrino flavours may occur as a result of decoherence [22,23], which may be independent of neutrino masses. Fitting currently available data from atmospheric and solar neutrinos [22] one may obtain sensitivities which exceed the Planck scale by far. For instance, concentrating on the QG-decoherence-induced transition probability P νe→νµ (t), and assuming that the dissipative environmental (QG) effects are of order…”