
Citation: Dimitrova, K.; on behalf of
the PADME Collaboration. Using
Artificial Intelligence in the
Reconstruction of Signals from the
PADME Electromagnetic Calorimeter.
Preprints 2022,6, 46. https://doi.
org/10.3390/instruments6040046
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Article
Using Artificial Intelligence in the Reconstruction of Signals from
the PADME Electromagnetic Calorimeter
Kalina Dimitrova * and on behalf of the PADME collaboration †
Faculty of Physics, Sofia University “St. Kliment Ohridski”, 5 J. Bourchier Blvd., 1164 Sofia, Bulgaria
*Correspondence: kalina@phys.uni-sofia.bg
† The PADME collaboration: A.P. Caricato, M. Martino, I. Oceano, F. Oliva, S. Spagnolo (INFN Lecce and
Salento Univ.), G. Chiodini (INFN Lecce), F. Bossi, R. De Sangro, C. Di Giulio, D. Domenici, G. Finocchiaro,
L.G. Foggetta, M. Garattini, A. Ghigo, P. Gianotti, I. Sarra, T. Spadaro, E. Spiriti, C. Taruggi, E. Vilucchi
(INFN Laboratori Nazionali di Frascati), V. Kozhuharov (Faculty of Physics, Sofia Univ. “St. Kl. Ohridski” and
INFN Laboratori Nazionali di Frascati), S. Ivanov, Sv. Ivanov, R. Simeonov (Faculty of Physics, Sofia Univ.
“St. Kl. Ohridski”), G. Georgiev (Sofia Univ. “St. Kl. Ohridski” and INRNE Bulgarian Academy of Science),
F. Ferrarotto, E. Leonardi, P. Valente, A. Variola (INFN Roma1), E. Long, G.C. Organtini, G. Piperno, M. Raggi (INFN
Roma1 and “Sapienza” Univ. Roma), S. Fiore (ENEA Frascati and INFN Roma1), V. Capirossi, F. Iazzi, F. Pinna
(Politecnico of Torino and INFN Torino), A. Frankenthal (Princeton University).
Abstract:
The PADME apparatus was built at the Frascati National Laboratory of INFN to search for a
dark photon (
A0
) produced via the process
e+e−→A0γ
. The central component of the PADME detector
is an electromagnetic calorimeter composed of 616 BGO crystals dedicated to the measurement of the
energy and position of the final state photons. The high beam particle multiplicity over a short bunch
duration requires reliable identification and measurement of overlapping signals. A regression machine-
learning-based algorithm has been developed to disentangle with high efficiency close-in-time events
and precisely reconstruct the amplitude of the hits and the time with sub-nanosecond resolution. The
performance of the algorithm and the sequence of improvements leading to the achieved results are
presented and discussed.
Keywords: dark photon; calorimetry; signal reconstruction; machine learning
1. Introduction
In recent years, the search for an explanation of the Dark Matter phenomenon has led to
the development of various hypotheses for an extension of the Standard Model, e.g., Weakly
Interacting Massive Particles (WIMPs) [
1
]. However, the non-observation of new states with
mass in the order of 100 GeV led scientists to explore other Dark Matter explanations. The
main goal of PADME (Positron Annihilation into Dark Matter Experiment) [
2
] is to search for
the dark photon
A0
, a hypothetical gauge boson connecting the dark and the visible sector.
In the case of non-vanishing interaction strength
α0
with the electrons,
A0
can be produced in
the annihilation process of beam positrons with electrons from the target:
e+e−→A0γ. (1)
Knowing the four-momenta of the beam’s positrons, the electrons at rest and the photon
produced in the process, the missing mass of the dark photon can be calculated:
M2
miss = (Pe++Pe−−Pγ)2. (2)
The positron beam provided by the DA
Φ
NE LINAC [
3
] can reach energies up to 550 MeV,
providing a limit for the missing mass of 23.7 MeV, and is composed of bunches with a 50 Hz
rate. Each bunch contains about 2
×
10
4
particles and its length can be varied with typical
values of 200–300 ns.
arXiv:2210.00811v1 [hep-ex] 3 Oct 2022