Signature of sterile species in atmospheric neutrino data at neutrino telescopes

TL;DR

This work proposes using TeV-energy atmospheric neutrinos crossing the Earth as a probe for sterile neutrinos in light of LSND/MiniBooNE tensions. By solving the full neutrino evolution in Earth's matter under 3+1 and 3+2 mass schemes, it shows that resonant matter effects can amplify active-sterile oscillations, producing distinct energy- and path-length–dependent signatures detectable by neutrino telescopes like IceCube. In the 3+1 case, nonzero θ34 can enhance both in-matter mixing angles, yielding large νμ→ντ or νμ→νs transitions depending on parameters; in 3+2, two sterile states produce two resonances with patterns that depend on mass ordering. The anticipated high-statistics TeV data could unambiguously reveal sterile signatures and distinguish between mass/mixing scenarios, offering a complementary test to short-baseline experiments and potentially resolving LSND/MiniBooNE tensions.

Abstract

The MiniBooNE results have still not been able to comprehensively rule out the oscillation interpretation of the LSND experiment. So far the so-called short baseline experiments with energy in the MeV range and baseline of few meters have been probing the existence of sterile neutrinos. We show how signatures of these extra sterile states could be obtained in TeV energy range atmospheric neutrinos travelling distances of thousands of kilometers. Atmospheric neutrinos in the TeV range would be detected by the upcoming neutrino telescopes. Of course vacuum oscillations of these neutrinos would be very small. However, we show that resonant matter effects inside the Earth could enhance these very tiny oscillations into near-maximal transitions, which should be hard to miss. We show that imprint of sterile neutrinos could be unambiguously obtained in this high energy atmospheric neutrino event sample. Not only would neutrino telescopes tell the presence of sterile neutrinos, it should also be possible for them to distinguish between the different possible mass and mixing scenarios with additional sterile states.

Figures (11)

• Figure 1: Values of $\sin^2 \theta_{24}$ at which we have maximal oscillations as a function of the distance $L$ travelled inside Earth. We have assumed $\sin^2 \theta_{14}=0$ and $\sin^2 \theta_{34}=0$ and the 3+1 mass spectrum. The dashed line shows the boundary between the mantle and core of the Earth.
• Figure 2: The survival probability $P_{\mu\mu}$ as a function of $L$ using the PREM profile for the Earth density. The different line types correspond to different fixed values of $E$ and each panel shows the results for different fixed values of $\sin^2 \theta_{24}$ given in the panels. We have assumed the 3+1 mass spectrum and taken $|\Delta m^2_{41}|=1$ eV$^2$, $\sin^2 \theta_{14}=0$ and $\sin^2 \theta_{34}=0$. The probability corresponds to neutrinos for $\Delta m^2_{41} < 0$ and to antineutrinos for $\Delta m^2_{41} > 0$.
• Figure 3: The survival probability $P_{\mu\mu}$ as a function of $L$ using the PREM profile for the Earth density. The different line types correspond to different fixed values of $|\Delta m^2_{41}|$ and each panel shows the results for different fixed values of $E$ given in the panels. We have assumed the 3+1 mass spectrum and taken $\sin^2 \theta_{24}=0.04$ eV$^2$, $\sin^2 \theta_{14}=0$ and $\sin^2 \theta_{34}=0$. The probability corresponds to neutrinos for $\Delta m^2_{41} < 0$ and to antineutrinos for $\Delta m^2_{41} > 0$.
• Figure 4: The ${\nu_{\mu}}\rightarrow {\nu_{\mu}}$ (upper left hand panel), ${\nu_{\mu}}\rightarrow {\nu_{\tau}}$ (upper right hand panel) and ${\nu_{\mu}}\rightarrow \nu_s$ (lower right hand panel) oscillation probabilities, as a function of the neutrino energy $E$ for the 3+1 mass spectrum, when the neutrinos travel a distance $L=2R_e$, where $R_e$ is the radius of the Earth. The black (dark) solid lines show the probabilities for neutrinos while the cyan (light) solid lines show the probabilities for antineutrinos. The dashed lines give the probabilities if matter effects were not taken into account and one had oscillations in vacuum. The values of the oscillation parameters taken for this figure is shown in the lower left hand panel. In particular this plot is for $\Delta m^2_{41} =1$ eV$^2$. Probabilities in matter have been obtained using the PREM profile.
• Figure 5: Same as Fig. \ref{['fig:EIH']} but for $\Delta m^2_{41} = +1$ eV$^2$.