Probing nonstandard neutrino interactions with supernova neutrinos

We analyze the possibility of probing nonstandard neutrino interactions (NSI, for short) through the detection of neutrinos produced in a future galactic supernova (SN). We consider the effect of NSI on the neutrino propagation through the SN envelope within a three-neutrino framework, paying special attention to the inclusion of NSI-induced resonant conversions, which may take place in the most deleptonized inner layers. We study the possibility of detecting NSI effects in a Megaton water Cherenkov detector, either through modulation effects in the ${\overline{\nu }}_e$ spectrum due to (i) the passage of shock waves through the SN envelope, (ii) the time dependence of the electron fraction, and (iii) the Earth matter effects; or, finally, through the possible detectability of the neutronization ${\nu }_e$ burst. We find that the ${\overline{\nu }}_e$ spectrum can exhibit dramatic features due to the internal NSI-induced resonant conversion. This occurs for nonuniversal NSI strengths of a few %, and for very small flavor-changing NSI above a $\mathrm{\text{few}}\times {10}^{-5}$.

Figure 1

Density (upper panel) and electron fraction (bottom panel) profiles for the SN progenitor and at different instants after the core bounce, from Ref. 67. The regions where the $H$ (light-shaded, yellow) and the $L$ (dark-shaded, cyan) resonance take place are also indicated, as well as the NSI-induced $I$ (gray) resonance for the parameters ${\epsilon }_{ee}=0$, ${\epsilon }_{\tau \tau }\lesssim 0.07$, and $|{\epsilon }_{\mu \tau }|\lesssim 0.05$.

Figure 2

Contours of $Y_e^I$ as function of ${\epsilon }_{ee}$ and ${\epsilon }_{\tau \tau }^{\prime }$ according to Eq. (19) for different values of $Y_e$. The shaded region (yellow) represents the region of parameters that gives rise to $I$-resonance before the collapse. The arrows indicate how this region widens with time.

Figure 3

Level-crossing schemes, left panels for the case with only oscillations, and right panels in the presence of NSI. The upper and lower panels represent normal and inverted mass hierarchy, respectively.

Figure 4

Contours of constant jump probability at the $I$-resonance in terms of ${\epsilon }_{\tau \tau }$ and ${\epsilon }_{e\tau }$ for two profiles corresponding to Fig. 1 at 2 s with $a=0.235$ and $b=0.175$ (left panel) and 15.7 s with $a=0.26$ and $b=0.195$ (right panel). For simplicity the other $\epsilon$’s have been set to zero.

Figure 5

Angle $\alpha$ as function of ${\epsilon }_{\tau \tau }$ for different values of ${\epsilon }_{ee}$ and ${\epsilon }_{\mu \tau }$, in the case of neutrinos of energy 10 MeV, with normal mass hierarchy, and $s_{13}^2={10}^{-5}$. The other NSI parameters take the following values: ${\epsilon }_{e\mu }=0$ and ${\epsilon }_{e\tau }={10}^{-3}$.

Figure 6

Landau-Zener jump probability isocontours at the $H$-resonance in terms of ${\epsilon }_{e\tau }$ and ${\epsilon }_{\tau \tau }$ for 10 MeV antineutrinos in the case of inverted mass hierarchy. Left panel: $\alpha$ given by Eq. (24). Right panel: $\alpha$ set to zero. The remaining parameters take the following values: ${sin}^2{\vartheta }_{13}={10}^{-5}$, ${\epsilon }_{ee}={\epsilon }_{e\mu }={\epsilon }_{\mu \tau }=0$. See text.

Figure 7

Landau-Zener jump probability isocontours at the $H$-resonance in terms of ${\epsilon }_{e\tau }$ and ${\vartheta }_{13}$ for ${\epsilon }_{\tau \tau }={10}^{-4}$. Antineutrinos with energy 10 MeV and inverted mass hierarchy has been assumed.

Figure 8

Survival probability ${\overline{P}}_{\mathrm{surv}}(E,t)$ for ${\overline{\nu }}_e$ as function of energy at different times averaged in energies with the energy resolution of Super-Kamiokande; for the profile shown in Fig. 1. Upper panel: case $B$ is assumed for ${sin}^2{\vartheta }_{13}={10}^{-2}$. Bottom panel: case $BI$, with ${\epsilon }_{\tau \tau }=0.07$, ${\epsilon }_{e\tau }={10}^{-4}$, and the rest of NSI parameters put to zero.

Figure 9

Range of ${\epsilon }_{\tau \tau }$ and ${\epsilon }_{e\tau }$ for which the effect of the shock wave will be observed. In the upper panels a minimum value of $Y_e^{\min }=0.06$ based on the numerical profiles at $t=2\mathrm{s}$ has been assumed, see Fig. 1. In the lower panels we have considered a case with $Y_e^{\min }=0.01$ inspired in the profile at $t=15.7\mathrm{s}$. The value of ${sin}^2{\vartheta }_{13}$ has been assumed to be ${10}^{-2}$ and ${10}^{-7}$ in the left and right panels, respectively. We have also superimposed isocontours of constant hopping probability 0.1 (darker, blue) and 0.9 (lighter, red) in the $I$ (solid lines) and $H$ (dashed lines) resonances for inverted mass hierarchy and $E=10\mathrm{MeV}$ and antineutrinos. The light-shaded area (yellow) represents the parameter space where both resonances will be adiabatic. In the dark-shaded area (cyan) the $I$-resonance is assumed to be adiabatic whereas $H$ lies in the transition region.

Figure 10

The average energy of $\overline{\nu }p\to n{e}^{+}$ events binned in time for case $B$ (dashed blue line) and $BI$ (solid red line). In each panel different values of ${\epsilon }_{\tau \tau }$ have been assumed. The error bars represent $1\sigma$ errors in any bin. ${\epsilon }_{e\tau }={10}^{-4}$.

Figure 11

The average energy of $\overline{\nu }p\to n{e}^{+}$ events binned in time for case $AI$ and $CIa$ and different values of ${\epsilon }_{\tau \tau }$. The error bars represent $1\sigma$ errors in any bin. ${\epsilon }_{e\tau }={10}^{-4}$.

Figure 12

Number of events from the elastic scattering on electrons, per time bin in a Megaton water Cherenkov detector for a SN at 10 kpc for cases $C$ (thin lines) and $BI$ (thick lines). Different progenitor masses have been assumed: $13M_{\odot }$ (n13) (dash-dotted lines), $15M_{\odot }$ (s15s7b2) (dashed lines), and $25M_{\odot }$ (s25a28) (solid lines). 1-sigma errors are also shown for the $15M_{\odot }$ case.