The Multi-Messenger Astroparticle Physics: the First Constraint on Light Millicharged Dark Matter via Time-Delay Analysis of GRB GW170817A
Wenxing Zhang, Junle Pei, Xin Zhang, Tianjun Li
TL;DR
The paper develops a multi-messenger astroparticle-physics framework to constrain light millicharged dark matter by exploiting the time delay between gravitational waves and gamma rays from GW170817A. It treats millicharged dark matter as a homogeneous medium that modifies photon propagation through forward Compton scattering, with the refractive index given by $n = 1 + \frac{\rho_N}{4 m \omega^2} \mathcal{M}$ and $|\mathcal{M}| = 2 \epsilon^2 e^2$, leading to a time delay $\Delta t = \frac{L}{4 m \omega^2} \sum_i \mathcal{M}_i$. Using the observed delay $\Delta t \approx 1.7$ s and two timing scenarios, the authors derive upper bounds on the millicharge parameter $\epsilon$, finding $\epsilon_{\max} \approx 15.86 \left(\frac{m}{1 \text{ eV}}\right) \left(\frac{0.4 \text{ GeV}/\text{cm}^3}{\rho}\right)^{1/2} \left(\frac{\omega}{100 \text{ keV}}\right)$ or $\epsilon_{\max} \approx 2.26 \left(\frac{m}{1 \text{ eV}}\right) \left(\frac{0.4 \text{ GeV}/\text{cm}^3}{\rho}\right)^{1/2}$, implying $\epsilon \lesssim 10^{-14}$ for $m \lesssim 10^{-15}$ eV. The work further argues that Bose-Einstein condensate effects can be incorporated such that single-particle amplitudes map onto collective multi-particle scattering, reinforcing the robustness of the conservative bounds. Overall, the study demonstrates that multi-messenger timing of neutron-star mergers is a powerful, complementary probe of ultralight millicharged dark matter with potential improvements as more events are observed.
Abstract
The multi-messenger astroparticle physics provides a new approach to probe the new physics beyond the Standard Model. We propose to probe the light dark matter which can interact with electromagnetic interaction. To be concrete, we derive the new constraint on the millicharged dark matter from the multi-messenger observations of GW170817. In the neutron star merger event GW170817, the first detection of a gamma-ray burst (GRB) delayed by approximately 1.7 seconds relative to the gravitational wave emission was observed. Utilizing this delay, we constrain the parameter space of the millicharged dark matter within the large-scale structure of the Universe. For dark matter mass below $10^{-15}$ eV, the parameter $ε$ is constrained to be less than $10^{-14}$, representing the most stringent limits achieved to date.