Search for Light Neutral Bosons in The TREK/E36 Experiment at J-PARC

Abstract

The Standard Model (SM) represents our best description of the subatomic world and has been very successful in explaining how elementary particles interact under the influence of the fundamental forces. Despite its far reaching success in describing the building blocks of matter, the SM is still incomplete; falling short to explain dark matter, baryogenesis, neutrino masses and much more. The E36 experiment conducted at J-PARC in Japan, allows for sensitivity to search for light U(1) gauge bosons, in the muonic K + decay channel. Such U(1) bosons could be associated with dark matter or explain established muon-related anomalies such as the muon g − 2 value, and perhaps the proton radius puzzle. A realistic simulation study was employed for these rare searches in a mass range of 20 MeV to 100 MeV. Preliminary results of the upper limits for the A’ branching ratio Br(A’) extracted at 95% CL, will be presented.

Search for Light Neutral Bosons in the TREK/E36 Experiment at J-PARC

“…Specifically the µ + is tracked in the magnet gap and the e + e − form clusters in the CsI(Tl) calorimeter, and an invariant mass m ee distribution was reconstructed from the clusters. A Geant4 Monte Carlo was used to generate and reconstruct A ′ mass M A ′ , whose reconstructed widths, corresponding to 2σ, were used as the search window in the m ee spectrum, shown in Figure 4 [18]. This analysis considered masses in the range of 20-110 MeV/c 2 , in incremental step-sizes of 5 MeV/c 2 .…”