Prospective constraints on neutrino masses from a core-collapse supernova

We discuss the prospects for improved upper limits on neutrino masses that may be provided by a core-collapse supernova explosion in our Galaxy, if it exhibits time variations in the neutrino emissions on the scale of a few milliseconds as suggested by recent two-dimensional simulations. Analyzing simulations of such neutrino emissions using the wavelet technique adopted in [J. Ellis, H.-T. Janka, N. E. Mavromatos, A. S. Sakharov, and E. K. G. Sarkisyan, Phys. Rev. D 85, 045032 (2012)], we find that an upper limit $m_{\nu }\sim 0.14\mathrm{eV}$ could be established at the 95% confidence level if the time variations in emissions were to be preserved during neutrino propagation to the Earth.

Figure 1

Top panel: The time series of the neutrino emission from the two-dimensional simulation of a core-collapse supernova found in 5. The time profile is sampled in 1024 ($2^{10}$) bins. Middle panel: The local wavelet power spectrum of the neutrino emission time series, obtained using the Morlet wavelet function (1) normalized by $1/{\sigma }^2$ [6]. The vertical axis is the Fourier period (in seconds), and the horizontal axis is the time of the neutrino emission. The red contours enclose regions that differ from white noise at greater than the 95% C.L. The cone of influence, where edge effects become important, is indicated by the concave solid lines at the edges of the support of the signal. Bottom panel: The average power in the 0.002–0.003 s band. The dashed line shows the 95% C.L. significance.

Figure 2

Upper panel: The time series of the neutrino emission from the two-dimensional simulation of a core-collapse supernova after applying an energy-dependent time shift ${\tau }_m=0.019\mathrm{s}·{\mathrm{MeV}}^2$. Lower panel: The strengths of the time-scale structures of the power spectrum averaged between 2 and 3 ms disappear below the 95% C.L. of significance after applying this time shift.

Figure 3

A Gaussian fit to the amount $\Sigma$ of the short time-scale signal above the 95% C.L., calculated for 21 values of the shift parameters ${\tau }_m$. Each point is obtained as the average over 25 realizations of the time-energy assignments of individual neutrinos.