Speaker
Description
Sub-GeV dark matter (DM) which interacts with electrons can excite electrons occupying molecular orbitals in a scattering event. In particular, aromatic compounds such as benzene or xylene
have an electronic excitation energy of a few eV, making them sensitive to DM as light as a few
MeV. These compounds are often used as solvents in organic scintillators, where the de-excitation
process leads to a photon which propagates until it is absorbed and re-emitted by a dilute fuor.
The fuor photoemission is not absorbed by the bulk, but is instead detected by a photon detector
such as a photomultiplier tube. We develop the formalism for DM{electron scattering in aromatic
organic molecules, calculate the expected rate in p-xylene, and apply this calculation to an existing
measurement of the single photo-electron emission rate in a low-background EJ-301 scintillator cell.
Despite the fact that this measurement was performed in a shallow underground laboratory under
minimal overburden, the DM{electron scattering limits extracted from these data are already approaching leading constraints in the 3{100 MeV DM mass range. We discuss possible next steps
in the evolution of this direct detection technique, in which scalable organic scintillators are used
in solid or liquid crystal phases and in conjunction with semiconductor photodetectors to improve
sensitivity through directional signal information and potentially lower dark rates.
