arXiv subjects

Chris Sellgren

Publications and source records attributed to Chris Sellgren.

3 recordsLinked to original sources

arXiv2025

LDMX -- The Light Dark Matter eXperiment

The Light Dark Matter eXperiment (LDMX) is an electron fixed-target experiment optimized to search for sub-GeV dark matter production through the missing momentum signature. LDMX is designed to operate in End Station A at SLAC, using an 8 GeV electron beam accelerated alongside the LCLS-II drive beam. The design of the apparatus is strongly motivated by the performance requirements of a high-rate missing momentum search and leverages detector technologies and designs from other experiments along with existing facilities at SLAC. LDMX will improve on previous results by up to three orders of magnitude, enabling broad sensitivity to dark sector scenarios including the dark matter interaction strengths motivated by freeze-out of MeV-GeV mass dark matter to the observed relic abundance. With hermetic forward coverage, LDMX also has sensitivity to visible signatures of dark sectors and provides a unique probe of electron-nuclear interactions important to interpreting data from accelerator-based neutrino experiments. This report encompasses the technical design of the LDMX Detector, its simulated performance, and the physics capabilities of the experiment.

hep-ex↗

arXiv2025

Sensitivity of an Early Dark Matter Search using the Electromagnetic Calorimeter as a Target for the Light Dark Matter eXperiment

The Light Dark Matter eXperiment (LDMX) is proposed to employ a thin tungsten target and a multi-GeV electron beam to carry out a missing momentum search for the production of dark matter candidate particles. We study the sensitivity for a complementary missing-energy-based search using the LDMX Electromagnetic Calorimeter as an active target with a focus on early running. In this context, we construct an event selection from a limited set of variables that projects sensitivity into previously-unexplored regions of light dark matter phase space -- down to an effective dark photon interaction strength $y$ of approximately $2\times10^{-13}$ ($5\times10^{-12}$) for a 1MeV (10MeV) dark matter candidate mass.

hep-ex↗

arXiv2023

Studying the Properties of Soft Kaons in the LDMX ECal

Low energy photonuclear $K^{+/-}$ events have emerged as one of the most difficult backgrounds for the LDMX detector to veto. This report discusses an extended study of the properties of soft kaons in the ECal, using a GEANT4 particle gun to combat the low statistics of these events. Simulations reveal that the most dangerous events are those in which a kaon decays before reaching a silicon detector layer. Threshold values are determined for the parameters of the most dangerous kaon events. A study of an enhanced photonuclear sample is analyzed to understand the kinematics of typical and dangerous events. A theoretical model for energy loss is incorporated for corroboration and to provide further predictions. The results of the three approaches of study are shown to provide complimentary predictions. A key result is that events with $E_k > 200$ MeV and $θ< 60^\circ$ are expected to produce a 3-hit track in at least 95\% of cases, while events on the other side of this threshold will be expected to produce fewer than 3 hits in about 40\% of all cases.

hep-ex↗