Measurement of the mean excitation energy of liquid argon

TL;DR

This paper measures the mean excitation energy of liquid argon to improve energy estimations in neutrino experiments, providing a recommended value that differs from previous standards.

Contribution

The study presents a new measurement of liquid argon's mean excitation energy using proton range data and synthesizes various data sources for a refined estimate.

Findings

Measured I-value as 199$^{+4}_{-5}$ eV using proton range data.

Recommended I-value for liquid argon as 198 $b1$ 4 eV, higher than previous standards.

Provides a more accurate parameter for neutrino energy estimation in simulations.

Abstract

The mean excitation energy (I-value) of liquid argon is a critical input for energy estimation in neutrino oscillation experiments. It is measured to be 199$^{+4}_{-5}$eV using the range of 402.2 MeV protons from the Fermilab Linac. This compares to the author's recent evaluation of (197 $\pm$ 7) eV based on a combination of an oscillator strength distribution analysis, gaseous argon range measurements, sparse stopping power data on solid argon, and an extrapolation of data on the effect of phase from other substances. Using all sources of information, we recommend a value of (198 $\pm$ 4) eV for liquid argon, which is significantly higher than 188 eV, from ICRU-37's gaseous argon evaluation, commonly used in Monte Carlo codes such as Geant4.