MiniBooNE low energy excess. Backgrounds are shown in the stacked histogram and come from electron neutrino events, which are electron-like, and also misidentified muon neutrino events, which are photon-like.

The MiniBooNE experiment performed a short baseline search for the muon neutrino to electron neutrino oscillation signature suggested by the LSND experiment. MiniBooNE observed an unexpected excess of neutrino interactions producing final state electrons or photons at lower energies, hence called low energy excess (LEE). Proposed explanations for the source of these events predict either a background events (from photon) or neutrino event (from electron), but MiniBooNE cannot discriminate between these two possibilities.

If in fact the anomalous MiniBooNE events signal true electrons, explanations from theorists suggest a beyond the Standard Model interpretation. One model proposed a new type of “sterile” neutrino.

MicroBooNE’s main goal is to understand the source of the MiniBooNE excess. With a novel particle detector, a liquid argon time projection chamber (LArTPC), MicroBooNE can provide excellent electron/photon discrimination thus will help understand the source of the low energy excess.

How the single-phase LArTPC reads charge signals

However, it is extremely challenging to remove cosmic backgrounds in LArTPC detector operating near-surface like MicroBooNE, due to a long drift-time. Traditional 2D imaging reconstruction paradigms suffers from this cosmic-rays, resulting in signal event selection inefficiency.

Wire-Cell 3D reconstruction of electron neutrino

Wire-Cell is a novel 3D tomographic imaging reconstruction algorithm, capitalize all information from the TPC 2D wires and reconstruct 3D cell image of ionization electrons. The Wire-Cell reconstructs the image in topology-agnostic way, hence it works very well in inclusive selection. Deep learning technique is also used to enhance the accuracy of the primary neutrino vertex identification.

Wire-Cell’s rejection of comsic-ray background

I’m collaborating with BNL EDG group, co-leading a team to use this Wire-Cell algorithm to perform electron neutrino selection and LEE analysis to test MiniBooNE anomaly. Recently, our work in rejecting cosmic-ray backgrounds with this Wire-Cell reconstruction demonstrated a great performance in selecting neutrinos. You can find this work in a long paper and a short letter. We have now 3D patter recognition tool in hands, based on the previous work of cosmic rejection technique, which enables us to perform a particle identification with outstanding efficiency. We are very close to release our first LEE analysis with the Wire-Cell, so stay tuned!