Speaker
Description
Current and future experiments need to know the stopping power of liquid argon for charged particles. It is used directly in calibration, to measure muon energy, and more broadly affects the simulation of all charged particles. The main parameter that controls stopping power is the mean excitation energy, or I-value. Commonly used values are $(188\pm6)$eV from ICRU-37 (1984), and $(187\pm3)$eV from ICRU-90 (2016), both evaluations for gaseous argon. We have re-evaluated existing experimental data, including range/stopping power and oscillator strength distribution measurements, taking into account phase. Further, we have performed a new proton range measurement on LAr at Fermilab. We recommend $(201\pm3)$eV, a value which shifts energy reconstruction in LAr TPCs by $\sim 0.5\%$. This shift feeds linearly into the measured value of $\Delta m^2$ and is similar to the projected DUNE sensitivity, which reaches 0.5% in 350 kt-MW-years.
| Working Group | WG 6: Detectors |
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