https://doi.org/10.1140/epjc/s10052-022-11063-9
Regular Article - Experimental Physics
Measurements of the ionization efficiency of protons in methane
1
Department of Mechanical and Materials Engineering, Queen’s University, K7L 3N6, Kingston, ON, Canada
2
LPSC, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble, France
3
Department of Physics, Engineering Physics and Astronomy, Queen’s University, K7L 3N6, Kingston, ON, Canada
4
Chemistry and Chemical Engineering Department, Royal Military College of Canada, K7K 7B4, Kingston, ON, Canada
5
Department of Physics, University of Alberta, T6G 2R3, Edmonton, AB, Canada
6
IRFU, CEA, Université Paris-Saclay, 91191, Gif-sur-Yvette, France
7
SNOLAB, P3Y 1N2, Lively, ON, Canada
8
Pacific Northwest National Laboratory, 99354, Richland, WA, USA
9
School of Physics and Astronomy, University of Birmingham, B15 2TT, Birmingham, UK
10
SUBATECH, IMT-Atlantique/CNRS-IN2P3/Nantes University, 44307, Nantes, France
11
Aristotle University of Thessaloniki, Thessaloniki, Greece
Received:
25
January
2022
Accepted:
23
November
2022
Published online:
9
December
2022
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 
), 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 
, with kinetic energies in between 
and 
in 
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 
with 
and 
. In agreement with some previous works in other gas mixtures, we measured less ionization energy than predicted from SRIM simulations, the difference reaching 
at .
© The Author(s) 2022
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