Photon Detector Calibration and Beam Event Energy Reconstruction with the Photon Detection System in the ProtoDUNE-VD Detector at CERN

ProtoDUNE-VD is the first large-scale prototype for the Vertical Drift configuration of the Deep Underground Neutrino Experiment (DUNE) far detector installed at CERN's Neutrino Platform. During the summer of 2025, both calibration and test beam data were collected. The H2 Very Low Energy (H2-VLE) beam line beamline at the CERN Neutrino Platform can deliver particles (electrons, protons, pions, muons, and kaons) with energies ranging from sub-GeV to a few GeV. A series of beamline instruments provide particle identification via Cherenkov response and time-of-flight measurements. In this work, we use various calibration techniques of the photon detection system, enabling accurate reconstruction of beam particle energy in addition to improved particle identification.