ANNIE Phase II Reconstruction Techniques

Abstract: The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a 26-ton Gd-doped water Cherenkov detector installed in the Booster Neutrino Beam at Fermilab. The experiment has two complementary goals: (1) perform the first measurement of the neutron yield from $\nu_{\mu}$ interactions as a function of Q$^2$ in order to constrain neutrino-nucleus interaction theoretical models, and (2) demonstrate the power of new fast-timing, position-sensitive detectors by making the first deployment of Large Area Picosecond PhotoDetectors (LAPPDs) in a physics experiment. In Phase I, ANNIE successfully performed neutron background measurements. To realise the Phase II measurements the ANNIE collaboration has developed several reconstruction techniques using the arrival time and position of the Cherenkov photons in the detector photomultipliers (PMTs) and LAPPDs. A maximum-likelihood fit is used to reconstruct the neutrino interaction vertex and direction. Machine and Deep Learning techniques are used for the muon and neutrino energy reconstruction. We present the results of ANNIE reconstruction techniques and the improvement we can get in resolution with the use of LAPPDs.