Detecting supernova neutrinos with iron and lead detectors

Supernova (SN) neutrinos can excite the nuclei of various detector materials beyond their neutron emission thresholds through charged current (CC) and neutral current (NC) interactions. The emitted neutrons, if detected, can be a signal for the supernova event. Here we present the results of our study of SN neutrino detection through the neutron channel in ${}^{208}\mathrm{Pb}$ and ${}^{56}\mathrm{Fe}$ detectors for realistic neutrino fluxes and energies given by the recent Basel/Darmstadt simulations for an 18 solar mass progenitor SN at a distance of 10 kpc. We find that, in general, the number of neutrons emitted per kiloton (kTon) of detector material for the neutrino luminosities and average energies of the different neutrino species as given by the Basel/Darmstadt simulations are significantly lower than those estimated in previous studies based on the results of earlier SN simulations. At the same time, we highlight the fact that, although the total number of neutrons produced per kTon in a ${}^{56}\mathrm{Fe}$ detector is more than an order of magnitude lower than that for ${}^{208}\mathrm{Pb}$, the dominance of the flavor blind NC events in the case of ${}^{56}\mathrm{Fe}$, as opposed to the dominance of ${\nu }_e$ induced CC events in the case of ${}^{208}\mathrm{Pb}$, offers a complementarity between the two detector materials so that simultaneous detection of SN neutrinos in a ${}^{208}\mathrm{Pb}$ and a sufficiently large ${}^{56}\mathrm{Fe}$ detector suitably instrumented for neutron detection may allow estimating the fraction of the total $\mu$ and $\tau$ flavored neutrinos in the SN neutrino flux and thereby probing the emission mechanism as well as flavor oscillation scenarios of the SN neutrinos.

Figure 1

Left: Temporal profiles of the neutrino luminosity (upper three panels) and average energy of the neutrinos (lower three panels) corresponding to the neutronization phase, accretion phase, and cooling phase (from left to right, respectively) for different neutrino flavors, obtained from the results of the Basel/Darmstadt simulation [13] of a $18M_{\odot }$ progenitor SN (from Ref. [20]). Right: The normalized time-averaged energy spectra of the neutrinos of different flavors.

Figure 2

The one-, two-, and three-neutron emission probabilities ($P_{1n}$, $P_{2n}$, and $P_{3n}$, respectively) of excited ${}^{56}\mathrm{Fe}$ nucleus (left) and excited ${}^{56}\mathrm{Co}$ nucleus (right) as a function of the excitation energy.

Figure 3

Number of neutrons emitted due to ${\nu }_e$ CC interactions per kTon of ${}^{208}\mathrm{Pb}$ as a function of neutrino energy for NO (left panel) and IO (right panel) of neutrino mass hierarchy. “1n” and “2n” indicate neutrons from one- and two-neutron emission events, respectively.

Figure 4

Number of neutrons emitted due to NC interaction of all six species of neutrinos per kTon of ${}^{208}\mathrm{Pb}$ as a function of neutrino energy. “1n” and “2n” indicate neutrons from one- and two-neutron emission events, respectively.

Figure 5

Total ${}^{56}\mathrm{Fe}({\nu }_e,e^{-}){}^{56}\mathrm{Co}$ cross section as a function of neutrino energy. For comparison, the cross sections obtained in Refs. [9] (K-L), [41] (L-V), and [42] (Paar et al.) are also shown.

Figure 6

Number of neutrons emitted due to ${\nu }_e$ CC interactions per kTon of ${}^{56}\mathrm{Fe}$ as a function of neutrino energy for NO (left panel) and IO (right panel) of neutrino mass hierarchy. “1n” and “2n” indicate neutrons from one- and two-neutron emission events, respectively.

Figure 7

Number of neutrons emitted due to NC interaction of all six species of neutrinos per kTon of ${}^{56}\mathrm{Fe}$ as a function of neutrino energy. “1n” and “2n” indicate neutrons from one- and two-neutron emission events, respectively.