Studying the Properties of Soft Kaons in the LDMX ECal

Abstract

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 $\theta < 60^\circ$ 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.