Search by the SENSEI Experiment for Millicharged Particles Produced in the NuMI Beam.

Millicharged particles appear in several extensions of the standard model, but have not yet been detected. These hypothetical particles could be produced by an intense proton beam striking a fixed target. We use data collected in 2020 by the SENSEI experiment in the MINOS cavern at the Fermi National Accelerator Laboratory to search for ultrarelativistic millicharged particles produced in collisions of protons in the NuMI beam with a fixed graphite target.

Back-Side Readout Silicon Photomultiplier.

We present a novel structure for the back-side readout silicon photomultipler (SiPM). Current SiPMs are front-illuminated structures with front-side readout, which have relatively small geometric fill factor leading to degradation in their photon detection efficiency (PDE). Back-side readout devices will provide an advantageous solution to achieve high PDE.