Energy, vertex, and time response of a LiquidO detector with an opaque-scintillator target to Compton-tagged electrons
Abstract
LiquidO detectors confine scintillation light near its point of production by stochastic scattering in an opaque medium and collect it with a lattice of wavelength-shifting (WLS) fibers. The elementary signal of such a detector is the point-like sub-MeV energy deposition, yet the response to that signal at the center of the detector volume has not been measured against an event-by-event ground truth. To close this gap, we couple BPULSE, a 4-liter prototype LiquidO detector, to a Compton-coincidence calibration setup that selects electron recoils of known energy on a constrained beam axis. The prototype is a 160 mm cube of opaque scintillator with 64 WLS fibers in alternating orthogonal layers at a 20 mm pitch, read out by silicon photomultipliers. Compton scatters of collimated gamma-ray beams from 137Cs and 60Co sources are tagged by a NaI(Tl) spectrometer. For 373.4 keV electrons, tagged from 90∘ scatters of the 137Cs beam, the detector collects 19.04 ± 0.07 photoelectrons (p.e.). Across four operating points, the two sources at two scattering angles, it responds linearly at 48.3 ± 1.5 p.e./MeV. The energy resolution of (23.4 ± 0.4)% matches the Poisson statistics of the detected photoelectrons. Collection at both fiber ends and larger sensors would raise the light yield of this target to an estimated 108-124 p.e./MeV. Center-of-mass reconstruction locates each recoil to the width of the delivered 20 mm beam spot, which bounds the intrinsic localization of the detector from above. The arrival time response sets a lower bound of 1.5 ns on the single-scatter start time at the observed ≈ 19 p.e. light level. This single-scatter response is the building block for reconstructing multi-site events. It constrains the light collection, confinement, and timing models on which reconstruction in future LiquidO detectors will rest.
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BibTeX
@misc{collaboration2026energy,
title = {{Energy, vertex, and time response of a LiquidO detector with an opaque-scintillator target to Compton-tagged electrons}},
author = {LiquidO Collaboration and S. Katz and J. T. Moffatt and G. Wendel and D. F. Cowen and I. Jovanovic and S. Schoppmann and A. S. Wilhelm and J. Apilluelo and L. Asquith and N. P. Barradas and J. L. Beney and M. Berberan e Santos and X. de la Bernardie and T. J. C. Bezerra and M. Bongrand and C. Bourgeois and D. Breton and J. Busto and A. Cabrera and A. Cadiou and E. Calvo and M. de Carlos Generowicz and B. J. Cattermole and E. Chauveau and M. Chen and P. Chimenti and S. Kr. Das and S. Dusini and A. Earle and M. Felizardo and C. Frigerio Martins and J. Galán and J. A. García and A. Gibson-Foster and C. Girard-Carillo and J. J. Gómez-Cadenas and W. C. Griffith and K. Groomes and M. Guitière and F. Haddad and J. Hartnell and A. Holin and I. G. Irastorza and W. Keck and A. Kling and L. Koch and J. F. Le Du and F. Lefevre and P. Loaiza and J. A. Lock and T. Lux and G. Luzón and J. Maalmi and J. P. Malhado and F. Mantovani and J. G. Marques and C. Marquet and M. Martínez and D. Navas-Nicolás},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18849},
eprint = {2610.18849},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18849},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Energy, vertex, and time response of a LiquidO detector with an opaque-scintillator target to Compton-tagged electrons
AU - LiquidO Collaboration
AU - S. Katz
AU - J. T. Moffatt
AU - G. Wendel
AU - D. F. Cowen
AU - I. Jovanovic
AU - S. Schoppmann
AU - A. S. Wilhelm
AU - J. Apilluelo
AU - L. Asquith
AU - N. P. Barradas
AU - J. L. Beney
AU - M. Berberan e Santos
AU - X. de la Bernardie
AU - T. J. C. Bezerra
AU - M. Bongrand
AU - C. Bourgeois
AU - D. Breton
AU - J. Busto
AU - A. Cabrera
AU - A. Cadiou
AU - E. Calvo
AU - M. de Carlos Generowicz
AU - B. J. Cattermole
AU - E. Chauveau
AU - M. Chen
AU - P. Chimenti
AU - S. Kr. Das
AU - S. Dusini
AU - A. Earle
AU - M. Felizardo
AU - C. Frigerio Martins
AU - J. Galán
AU - J. A. García
AU - A. Gibson-Foster
AU - C. Girard-Carillo
AU - J. J. Gómez-Cadenas
AU - W. C. Griffith
AU - K. Groomes
AU - M. Guitière
AU - F. Haddad
AU - J. Hartnell
AU - A. Holin
AU - I. G. Irastorza
AU - W. Keck
AU - A. Kling
AU - L. Koch
AU - J. F. Le Du
AU - F. Lefevre
AU - P. Loaiza
AU - J. A. Lock
AU - T. Lux
AU - G. Luzón
AU - J. Maalmi
AU - J. P. Malhado
AU - F. Mantovani
AU - J. G. Marques
AU - C. Marquet
AU - M. Martínez
AU - D. Navas-Nicolás
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18849
UR - https://arxiv.org/abs/2610.18849
AB - LiquidO detectors confine scintillation light near its point of production by stochastic scattering in an opaque medium and collect it with a lattice of wavelength-shifting (WLS) fibers. The elementary signal of such a detector is the point-like sub-MeV energy deposition, yet the response to that signal at the center of the detector volume has not been measured against an event-by-event ground truth. To close this gap, we couple BPULSE, a 4-liter prototype LiquidO detector, to a Compton-coincidence calibration setup that selects electron recoils of known energy on a constrained beam axis. The prototype is a 160 mm cube of opaque scintillator with 64 WLS fibers in alternating orthogonal layers at a 20 mm pitch, read out by silicon photomultipliers. Compton scatters of collimated gamma-ray beams from ^137Cs and ^60Co sources are tagged by a NaI(Tl) spectrometer. For 373.4 keV electrons, tagged from 90^∘ scatters of the ^137Cs beam, the detector collects 19.04 ± 0.07 photoelectrons (p.e.). Across four operating points, the two sources at two scattering angles, it responds linearly at 48.3 ± 1.5 p.e./MeV. The energy resolution of (23.4 ± 0.4)% matches the Poisson statistics of the detected photoelectrons. Collection at both fiber ends and larger sensors would raise the light yield of this target to an estimated 108-124 p.e./MeV. Center-of-mass reconstruction locates each recoil to the width of the delivered 20 mm beam spot, which bounds the intrinsic localization of the detector from above. The arrival time response sets a lower bound of 1.5 ns on the single-scatter start time at the observed ≈ 19 p.e. light level. This single-scatter response is the building block for reconstructing multi-site events. It constrains the light collection, confinement, and timing models on which reconstruction in future LiquidO detectors will rest.
ER -