TY - JOUR

T1 - Dark Matter Detection with Bound Nuclear Targets

T2 - The Poisson Phonon Tail

AU - Kahn, Yonatan

AU - Krnjaic, Gordan

AU - Mandava, Bashi

N1 - Funding Information:
We thank Daniel Baxter, Gordon Baym, Simon Knapen, Jonathan Kozaczuk, Noah Kurinsky, and Tongyan Lin for many enlightening discussions. The work of Y. K. is supported in part by US Department of Energy Grant No. DE-SC0015655. Fermilab is operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
Publisher Copyright:
© 2021 authors. Published by the American Physical Society.

PY - 2021/8/20

Y1 - 2021/8/20

N2 - Dark matter (DM) scattering with nuclei in solid-state systems may produce elastic nuclear recoil at high energies and single-phonon excitation at low energies. When the DM momentum is comparable to the momentum spread of nuclei bound in a lattice, q0=2mNω0 where mN is the mass of the nucleus and ω0 is the optical phonon energy, an intermediate scattering regime characterized by multiphonon excitations emerges. We study a greatly simplified model of a single nucleus in a harmonic potential and show that, while the mean energy deposited for a given momentum transfer q is equal to the elastic value q2/(2mN), the phonon occupation number follows a Poisson distribution and thus the energy spread is ΔE=qω0/(2mN). This observation suggests that low-threshold calorimetric detectors may have significantly increased sensitivity to sub-GeV DM compared to the expectation from elastic scattering, even when the energy threshold is above the single-phonon energy, by exploiting the tail of the Poisson distribution for phonons above the elastic energy. We use a simple model of electronic excitations to argue that this multiphonon signal will also accompany ionization signals induced from DM-electron scattering or the Migdal effect. In well-motivated models where DM couples to a heavy, kinetically mixed dark photon, we show that these signals can probe experimental milestones for cosmological DM production via thermal freeze-out, including the thermal target for Majorana fermion DM.

AB - Dark matter (DM) scattering with nuclei in solid-state systems may produce elastic nuclear recoil at high energies and single-phonon excitation at low energies. When the DM momentum is comparable to the momentum spread of nuclei bound in a lattice, q0=2mNω0 where mN is the mass of the nucleus and ω0 is the optical phonon energy, an intermediate scattering regime characterized by multiphonon excitations emerges. We study a greatly simplified model of a single nucleus in a harmonic potential and show that, while the mean energy deposited for a given momentum transfer q is equal to the elastic value q2/(2mN), the phonon occupation number follows a Poisson distribution and thus the energy spread is ΔE=qω0/(2mN). This observation suggests that low-threshold calorimetric detectors may have significantly increased sensitivity to sub-GeV DM compared to the expectation from elastic scattering, even when the energy threshold is above the single-phonon energy, by exploiting the tail of the Poisson distribution for phonons above the elastic energy. We use a simple model of electronic excitations to argue that this multiphonon signal will also accompany ionization signals induced from DM-electron scattering or the Migdal effect. In well-motivated models where DM couples to a heavy, kinetically mixed dark photon, we show that these signals can probe experimental milestones for cosmological DM production via thermal freeze-out, including the thermal target for Majorana fermion DM.

UR - http://www.scopus.com/inward/record.url?scp=85113610104&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85113610104&partnerID=8YFLogxK

U2 - 10.1103/PhysRevLett.127.081804

DO - 10.1103/PhysRevLett.127.081804

M3 - Article

C2 - 34477403

AN - SCOPUS:85113610104

VL - 127

JO - Physical Review Letters

JF - Physical Review Letters

SN - 0031-9007

IS - 8

M1 - 081804

ER -