Astrophysical neutrino oscillations after pulsar timing array analyses

The pattern of neutrino flavor oscillations could be altered by the influence of noisy perturbations such as those arising from a gravitational wave background (GWB). A stochastic process that is consistent with a GWB has been recently reported by the independent analyses of pulsar timing array (PTA) datasets collected over a decadal timescale by the North American Nanohertz Observatory for gravitational waves, the European PTA jointly with the Indian Pulsar Timing Array, the Parkes PTA, and the Chinese PTA collaborations. We investigate the modifications in the neutrino flavor oscillations under the influence of the GWB reported by the PTA collaborations and we discuss how such effects could be potentially revealed in near-future neutrino detectors, possibly helping the discrimination of different models for the GWB below the nHz frequency range.

Figure 1

The black contour lines bound the region in the parameter space $(\gamma ,A_{*})$ above which flavor oscillations in a neutrino wave packer are suppressed for different values for the minimum frequency $f_{\min }$. The threshold energy of the detector is fixed at $E_{\mathrm{thr}}=1\mathrm{MeV}$. Results are compared with the fit obtained by the NANOGrav collaboration [58] after analyzing the 15 years data set (blue) and the PPTA collaboration [65] (green), with different shades marking the 1, 2, and $3\sigma$ confidence regions.

Figure 2

Same as Fig. 1 for a minimum frequency in the ELF band, $f_{\min }=[{10}^{-18},{10}^{-15}]\mathrm{Hz}$. The threshold energy of the detector is fixed at $E_{\mathrm{thr}}=1\mathrm{PeV}$.

Figure 3

The threshold energy $E_{\mathrm{thr}}$ in MeV below which flavor oscillations in the neutrino propagation are suppressed, for an outburst of neutrinos detected from a nearby supernova for $\gamma =13/3$. The vertical axis shows the minimal frequency at which Eq. (7) holds and the horizontal axis shows $A_{*}$ value. Also shown are the black hole mass $M_{\mathrm{BH}}$ yielding $f_{\min }$ (horizontal red dashed line) and the threshold energy (purple dotted-dashed line).