Measurement of Milli-Charged Particles with a running electromagnetic coupling constant at IceCube

TL;DR

This work investigates a two-component dark matter scenario in which TeV-scale heavy DM φ captured by Earth decays to relativistic milli-charged particles χ with energy $E_χ\sim m_φ/2$, detectable at IceCube via deep inelastic scattering as χ interacts with ice nuclei through a running electromagnetic coupling from a massless hidden photon with kinetic mixing $ε$. The authors model MCP production, propagation through the Earth (with interaction length $L_e^χ$) and detection, incorporating the running coupling $α(Q^2)=α_0/(1-Δα(Q^2))$ and a DIS cross section $σ_{χN}≈ε^2 σ^γ_{eN}$. Using 10 years of IceCube data and Feldman–Crousins limits, they derive upper bounds on the MCP flux and exclude a new region in the $m_{χ}$–$ε$ plane, specifically $4\text{ GeV}<m_{χ}<100\text{ GeV}$ and $5.51×10^{-2}<ε<0.612$, with detectable signals around $\mathcal{O}(\text{TeV})$ for $5.65×10^{-5}\lesssim ε^2\lesssim1.295×10^{-3}$ and $τ_φ=10^{18}$ s. The results depend strongly on the heavy DM lifetime, with the MCP flux scaling as $Φ_{MCP}\propto 1/τ_φ$, and cosmological constraints remaining satisfied given the small MCP relic abundance.

Abstract

It is postulated that heavy dark matter $φ$ with a mass on the order of TeV, once captured by the Earth, can decay into relativistic milli-charged particles (MCPs). These MCPs are potentially detectable at the IceCube neutrino telescope. In this study, MCPs are modeled within the massless hidden photon framework, where they interact with nuclei via a running electromagnetic coupling constant, thereby enabling the prediction of their expected event rates and fluxes at IceCube. The expected number of background neutrino events at IceCube has also been evaluated. Under the assumption that no signal events are observed over a 10-year period at IceCube, upper limits on the MCP flux have been derived at the 90\% confidence level. The results suggest that MCPs originating from the Earth's core could be directly detected at IceCube at energies around $\mathcal{O}(1\ \text{TeV})$ for a fractional charge-squared range of $5.65\times10^{-5} \lesssim ε^2 \lesssim 1.295\times10^{-3}$. Furthermore, with 10 years of IceCube data, a new region in the $m_{\text{MCP}}$-$ε$ parameter space--specifically, $4\ \text{GeV} < m_{\text{MCP}} < 100\ \text{GeV}$ and $5.51\times10^{-2} < ε< 0.612$--has been excluded.

Figures (9)

• Figure 1: Schematic of MCPs produced from decay of heavy DM particles captured in the Earth's core, which then traverse the Earth and ice to become detectable by the detector like IceCube neutrino telescope
• Figure 2: The capture rates of $\phi$'s. This figure shows these rates at which $\phi$'s are captured to the interior of the Earth, for a scattering cross section of $\sigma_{\phi N}=10^{-44}$ cm$^2$.
• Figure 3: The MCP interaction lengths with the Earth were computed when $\epsilon^2$ = $5.65\times10^{-5}$(red solid line), $4\times10^{-4}$(blue dash line) and $1.295\times10^{-3}$(magenta dot line), respectively.
• Figure 4: Distributions of expected MCPs with $\tau_{\phi}$ = $10^{18}$ s and $\epsilon^2=5.65\times10^{-5}$, $4\times10^{-4}$, $1.295\times10^{-3}$ and astrophysical and atmospheric neutrinos. Their energy bins are 100 GeV.
• Figure 5: With the different $\epsilon^2$ (= $5.65\times10^{-5}$, $4\times10^{-4}$ and $1.295\times10^{-3}$) and $\tau_{\phi}$ = $10^{18}$, the numbers of expected MCPs were evaluated assuming 10 years of IceCube data, respectively. The evaluation of numbers of expected neutrinos was performed by integrating over the region caused by one standard energy and median angular uncertainties.