Pinpointing astrophysical bursts of low-energy neutrinos embedded into the noise

Abstract

We propose a novel method to increase the probability of identifying impulsive astrophysical bursts of low-energy neutrinos. The proposed approach exploits the temporal structure differences between astrophysical bursts and background fluctuations and it allows us to pinpoint weak signals otherwise unlikely to be detected. With respect to previous search strategies, this method strongly reduces the misidentification probability, e.g. for Super Kamiokande this reduction is a factor of ∼ 9 within a distance of D ∼ 200 kpc without decreasing the detection efficiency. In addition, we extend the proposed method to a network of different detectors and we show that the Kamland & LVD background reduction is improved by a factor ∼ 20 up to an horizon of D ∼ 75 kpc.

Expanding Core-Collapse Supernova Search Horizon of Neutrino Detectors

“…We reanalysed simulated KamLAND background + injections of 65 kpc from [1] and we obtained more recovered injections (without adding any more noise) with our 2-parameter method. The comparison between the two methods is in figure 2: the green area is the standard 1-parameter search (m-only) while the red area is the improvement for our 2-parameter method (m, ξ) where both areas pass the threshold in imitation frequency 2 of ≤ 1/100 years following the SNEWS [5] criteria.…”

“…In this formula P (k) represents the probability that a cluster of multiplicity k is produced by the background. Based on [1], we also characterised each cluster by its duration, i.e. the time elapsing from the first to the last event in the cluster.…”

“…[duration] . The results of [1] showed that by performing a new additional cut in ξ, it is possible to disentangle further the simulated astrophysical signals from background.…”

“…The black solid line in the figure represents the normalised probability for background clusters to have a specific value of ξ so that, where k in this case is a possible multiplicity value. In [1], it has been observed that the background curve has a probability density function (PDF) of 4-parameter Gamma distribution with some p-value of the fit. However, in order to be more generic, we will not use any distribution fit and we rely on the interpolation of the simulated background.…”

“…Several astrophysical sources are expected to give rise to impulsive bursts of low-energy neutrinos [1] such as core-collapse supernovae (CCSNe) [2], failed supernovae (failed-SNe) [3], as well as the hypothetical quark novae (QNe) [4]. All these sources have a common signature, which is an impulsive neutrino emission with a total emitted energy of the order of 10 53 ergs, average neutrino energy of ∼ 10 MeV and a short duration of the order of 10 seconds (∼ 0.5 seconds for the failed-SNe).…”