Double Bangs at IceCube as a Window to the Neutrino Mass Origin

Abstract

Neutrino oscillation parameters are subject to renormalization group (RG) evolution, just like all couplings and masses of Standard Model (SM) particles. Within the SM extended with three massive neutrinos, it is well known that RG running effects in the neutrino sector are small. However, the RG running of the elements of the leptonic mixing (PMNS) matrix below the electroweak symmetry breaking scale can be enhanced in the presence of light neutrinophilic new particles. In this work, using a particular low-scale neutrino mass model as an example, and by taking into account both atmospheric and astrophysical neutrino fluxes, we show that RG running of the PMNS matrix can lead to an increased number of high-energy tau neutrino events at IceCube. This excess manifests as an increased number of spatially displaced showers called ``double bangs". We find that the number of double bangs induced by new physics through RG effects can be comparable to that arising from SM interactions of astrophysical tau neutrinos.

Figures (3)

• Figure 1: The RG evolution of the $Y_N$ (left panel) and the corresponding short-baseline neutrino transition probabilities (right panel) are shown for two benchmark points in the model (solid and dotted). The $\times$ symbols in the right panel represent the NuTeV constraints on $P_{\mu e}$, $P_{\mu \tau}$, and $P_{e \tau}$Naples:1998vaAvvakumov:2002jj, and the vertical dashed and dot-dashed lines indicate the pion mass scale, and the approximate momentum transfer for neutrino scattering in NuTeV, respectively.
• Figure 1: In the left panel, we show the RG evolution of mixing angles and phases as defined in \ref{['eq:U3']}. The angle $\theta_{12}$, along with all three phases, changes significantly in the relevant $Q^2$ range, while the angles $\theta_{13}$ and $\theta_{23}$ do not, in accord with the arguments in Ref. Antusch:2005gp. In the right panel, we show the corresponding reconstructed energy spectrum of the tau-like events. The atmospheric contribution from $\nu_e$ is too small to be observed in the presented range. If one subtracts the unfilled (no running) histogram from the stacked one and integrates over energies, $\Delta N_\tau = 2.5$ from \ref{['fig:count_diff120']} is obtained.
• Figure 2: Difference in muon and tau neutrino event counts with and without RG running, based on 7.5 years of IceCube data for $\mathcal{O}(10^3)$ points in the parameter space of the model. Among these, the star ($\bigstar$) marks the benchmark point that produces the maximum enhancement of predicted double bang events, $\Delta N_\tau = 2.5$, in the presence of RG running.