Resonant Scattering of Boosted Dark Matter

TL;DR

The paper develops a GENIE-based simulation of boosted dark matter scattering off nucleons via resonant baryon excitations, a channel that can contribute over $30\%$ of the rate at certain boosts. It derives a resonant cross section in terms of leptonic and hadronic currents and helicity amplitudes, including a Breit–Wigner treatment, and provides implementation into GENIE with resonant scattering enabled by default. Two BD M scenarios with a heavy vector mediator $Z'$—the Two Component Model and Dark Matter Rain—are studied under both isospin-conserving and maximally isospin-violating couplings to quantify enhancements in experimental sensitivity. Phenomenological studies for DUNE, Hyper-Kamiokande, JUNO, and Super-K demonstrate improved reach when resonant scattering is included, and the work outlines plans for public GENIE integration and future extensions to other mediator structures.

Abstract

We develop a simulation within GENIE of the excitation of baryonic resonances by boosted dark matter. This work completes the simulation of all scattering modes for dark matter entering a detector at relativistic speeds. At some boosts, resonant scattering can contribute over 30% to the scattering rate. This channel offers a potentially powerful probe of the isospin structure of dark matter interactions via the relative prominence of the isospin-changing $Δ$ resonance. We study the estimated sensitivity of large volume detectors such as DUNE, Hyper-Kamiokande, and JUNO to all dark matter scattering modes and demonstrate the expected improvement in sensitivity when resonant scattering is included.

Figures (8)

• Figure 1: The Feynman diagram for (a) scalar dark matter and (b) fermionic dark matter undergoing resonant scattering off a nucleon $\mathcal{N}$. A baryonic excitation $\mathcal{N}^*$ is produced. Where, $Z^\prime$ is the gauge boson that mediates the interaction.
• Figure 2: The fractional effect of $SU(2)$ charge alignment to the contribution of resonant scattering in the proton cross-section of $\sigma_{\chi p}$ in terms of the boost factor $\gamma$. Solid lines represent the maximal isospin symmetry breaking model while dashed lines are the isospin symmetry conserving model. The left plot shows the two mass points considered in the DM Rain model, while the right plot represents the various mass points taken for the two-component DM model.
• Figure 3: Angular (a) and energy (b) distribution for the reconstructed outgoing particles of scattering in the fermionic Dark Matter Rain model at DUNE for $m_{\chi}=1$GeV and $\gamma=4$. The angle $\theta$ is measured with respect to the vertical. The blue distribution shows the BDM signal excluding the contribution from resonant scattering. The red curve shows the signal after including resonant scattering. Both BDM curves use the maximally isospin violating model. The shaded gray region shows the atmospheric neutrino background. The normalization is arbitrary and, for the signal, depends on the particular couplings chosen.
• Figure 4: Expected $5\sigma$$g_{Z^\prime}^4$ sensitivity at DUNE, Super-Kamiokande, Hyper-Kamiokande, and JUNO in the Dark Matter Rain model for masses $m_\chi = 100~{\rm MeV}$ (left) and $m_\chi= 1~{\rm GeV}$ (right). The solid lines indicate the constraints including resonant scattering in the simulation. The dashed lines representing the solution without resonant scattering contributions.
• Figure 5: Percentage of resonant scattering contribution to the signal strength in the Dark Matter Rain model across various detectors for $m_\chi = 100~{\rm MeV}$ (left) and $m_\chi = 1~{\rm GeV}$ (right).