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Measurements of the ionization efficiency of protons in methane
Ist Teil von
The European physical journal. C, Particles and fields, 2022-12, Vol.82 (12), p.1114-10, Article 1114
Ort / Verlag
Berlin/Heidelberg: Springer Berlin Heidelberg
Erscheinungsjahr
2022
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
The amount of energy released by a nuclear recoil ionizing the atoms of the active volume of detection appears “quenched” compared to an electron of the same kinetic energy. This different behavior in ionization between electrons and nuclei is described by the Ionization Quenching Factor (IQF) and it plays a crucial role in direct dark matter searches. For low kinetic energies (below
50
keV
), IQF measurements deviate significantly from common models used for theoretical predictions and simulations. We report measurements of the IQF for proton, an appropriate target for searches of Dark Matter candidates with a mass of approximately
1
GeV
, with kinetic energies in between
2
keV
and
13
keV
in
100
mbar
of methane. We used the Comimac facility in order to produce the motion of nuclei and electrons of controlled kinetic energy in the active volume, and a NEWS-G SPC to measure the deposited energy. The Comimac electrons are used as a reference to calibrate the detector with 7 energy points. A detailed study of systematic effects led to the final results well fitted by
IQF
(
E
K
)
=
E
K
α
/
(
β
+
E
K
α
)
with
α
=
0.70
±
0.08
and
β
=
1.32
±
0.17
. In agreement with some previous works in other gas mixtures, we measured less ionization energy than predicted from SRIM simulations, the difference reaching
33
%
at
2
keV
.