Dark Matter Detection with Bound Nuclear Targets: The Poisson Phonon Tail

Area of Science:

• * Particle Physics and Astrophysics
• * Condensed Matter Physics
• * Detector Physics

Background:

• * Dark matter (DM) interactions with nuclei can cause elastic nuclear recoil or single-phonon excitation.
• * An intermediate scattering regime with multiphonon excitations emerges when DM momentum matches nuclear momentum spread.
• * Understanding these interactions is crucial for developing sensitive dark matter detectors.

Purpose of the Study:

• * To investigate the physics of dark matter scattering in solid-state systems, focusing on multiphonon excitations.
• * To determine the potential for enhanced dark matter detection sensitivity using multiphonon signals.
• * To explore the implications for detecting sub-GeV dark matter and probing cosmological DM production.

Main Methods:

• * A simplified model of a single nucleus in a harmonic potential was used to analyze scattering dynamics.
• * Calculations focused on energy deposition, phonon occupation number, and energy spread in the multiphonon regime.
• * Electronic excitations and dark photon models were employed to connect multiphonon signals to other detection channels.

Main Results:

• * The mean energy deposited in multiphonon scattering equals the elastic scattering value.
• * Phonon occupation follows a Poisson distribution, leading to an energy spread of ΔE=qsqrt[ω_{0}/(2m_{N})].
• * Multiphonon signals can increase sensitivity to sub-GeV dark matter, even above single-phonon energy thresholds.

Conclusions:

• * Low-threshold calorimetric detectors can exploit multiphonon signals for enhanced sub-GeV dark matter sensitivity.
• * Multiphonon signals are expected to accompany ionization signals from DM-electron scattering and the Migdal effect.
• * These signals can probe key experimental milestones for dark matter produced via thermal freeze-out.