Downward-going tau neutrinos as a new prospect of detecting dark matter

Abstract

Dark matter trapped in the Sun produces a flux of all flavors of neutrinos, which then reach the Earth after propagating out of the Sun and oscillating from the production point to the detector. The typical signal which is looked at refers to the muon neutrino component and consists of a flux of up-going muons in a neutrino detector, the major source of background being atmospheric neutrinos. We propose instead a novel signature, namely the possibility of looking at the tau neutrino component of the dark matter signal, which is almost background-free in the downward-going direction, since the tau neutrino amount in atmospheric neutrinos is negligible and in the down-going baseline atmospheric muon-neutrinos have no time to sizably oscillate. We analyze the prospects of studying the downward-going tau neutrinos from dark matter annihilation (or decay) in the Sun in Cherenkov detectors, by looking at hadronic showers produced in the charged-current tau neutrino interactions and subsequent tau decay. We discuss the various sources of background (namely the small tau neutrino component in atmospheric neutrinos, both from direct production and from oscillations; tau neutrinos from solar corona interactions; the galactic tau neutrino component) as well as sources of background due to misidentification of electron and muon events. We find that the downward-going tau neutrinos signal has potentially very good prospects for Mton scale Cherenkov detectors, the main limitation being the level of misidentification of non-tau events, which need to be kept at level of percent. Several tens of events per year (depending on the dark matter mass and annihilation/decay channel) are potentially collectible with a Mton scale detector, and a 5 σ significance discovery is potentially reachable for dark matter masses in the range from 20 to 300 GeV with a few years of exposure on a Mton detector.

The Hyperbolic Asymptotics of Elliptic Hypergeometric Integrals Arising in Supersymmetric Gauge Theory

“…The β → 0 limit shrinks S 1 β , hence leaving us with the dimensionally reduced theory on S 3 b . This reduction has been noticed quantitatively in some special cases [1,18,22,24,32,45]. However, the mathematical results of [2,3] clarify that the reduction works in the nice way encountered in [1,18,22,24,32,45] -and so the above intuitive physical picture is correct -only when V eff is minimized just at x = 0; this condition was satisfied in all the examples studied rigorously by Rains [35] as well.…”

Tau neutrinos from ultracompact dark matter minihalos and constraints on the primordial curvature perturbations

“…Compared with the muon and electron neutrino the atmospheric background of the tau neutrino (ν τ ) is small especially in the direction of cosθ Z > 0, where θ Z is the zenith angle. In particular, for cosθ Z 0.5, the atmospheric tau neutrino fluxes are 3 orders smaller than the atmospheric muon and electron neutrino background [13]. For cosθ Z 0.7, the atmospheric tau neutrino fluxes are even smaller than that from solar corona interaction and galactic neutrino flux [13].…”

“…In particular, for cosθ Z 0.5, the atmospheric tau neutrino fluxes are 3 orders smaller than the atmospheric muon and electron neutrino background [13]. For cosθ Z 0.7, the atmospheric tau neutrino fluxes are even smaller than that from solar corona interaction and galactic neutrino flux [13]. Although the cascade effects of the tau neutrino make detection difficult, with the development of detection and a statistical method the detection of the tau neutrino has become possible [17][18][19].…”

“…The main way of using the neutrinos to research the properties of dark matter particle is through the observations and studies on muon neutrinos (ν µ ) [8, [10][11][12]. The main flaw of observations on ν µ is the large atmospheric background, which is caused by the interactions between the cosmic rays and atoms within atmosphere [13,14]. For electron neutrinos, ν e , the atmospheric background is also large and the cascade effects make the detection of ν e very difficult [15,16].…”

Solar WIMPs unravelled: Experiments, astrophysical uncertainties, and interactive tools

“…A reliable tau neutrino identification could also post a discovery potential for solar WIMP search, as these are background free in down-going events. Various papers have discussed this possibility [96], however the smaller cross-section as well as the experimental challenge to reliable identify tau events makes this a very difficult undertaking. Large detectors with Liquid Argon Time Projection Chambers could offer a possibility to tag tau events with a relatively small background [97].…”