The track-length extension fitting algorithm for energy measurement of interacting particles in liquid argon TPCs and its performance with ProtoDUNE-SP data Abed Abud, Adam García Gámez, Diego Nicolás Arnaldos, Francisco Javier Sánchez Castillo, Alejandro Sánchez Lucas, Patricia Vázquez Ramos, Alicia Zamorano García, Bruno DUNE Collaboration, / Neutrino detectors Pattern recognition Cluster finding Calibration and fitting methods This work was supported by CNPq, FAPERJ, FAPEG and FAPESP, Brazil; CFI, IPP and NSERC, Canada; CERN; MŠMT, Czech Republic; ERDF, Horizon Europe, MSCA and NextGenerationEU, European Union; CNRS/IN2P3 and CEA, France; INFN, Italy; FCT, Portugal; NRF, South Korea; Generalitat Valenciana, Junta de Andalucıa-FEDER, MICINN, and Xunta de Galicia, Spain; SERI and SNSF, Switzerland; TÜBİTAK, Turkey; The Royal Society and UKRI/STFC, United Kingdom; DOE and NSF, United States of America. This paper introduces a novel track-length extension fitting algorithm for measuring the kinetic energies of inelastically interacting particles in liquid argon time projection chambers (LArTPCs). The algorithm finds the most probable offset in track length for a track-like object by comparing the measured ionization density as a function of position with a theoretical prediction of the energy loss as a function of the energy, including models of electron recombination and detector response. The algorithm can be used to measure the energies of particles that interact before they stop, such as charged pions that are absorbed by argon nuclei. The algorithm's energy measurement resolutions and fractional biases are presented as functions of particle kinetic energy and number of track hits using samples of stopping secondary charged pions in data collected by the ProtoDUNE-SP detector, and also in a detailed simulation. Additional studies describe the impact of the dE/dx model on energy measurement performance. The method described in this paper to characterize the energy measurement performance can be repeated in any LArTPC experiment using stopping secondary charged pions. 2025-06-24T10:42:49Z 2025-06-24T10:42:49Z 2025-02-25 journal article A. Abed Abud et al (2025) JINST 20 P02021 [DOI: 10.1088/1748-0221/20/02/P02021] https://hdl.handle.net/10481/104816 10.1088/1748-0221/20/02/P02021 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional IOP Publishing