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Physik-Institut Group of Laura Baudis

Measurement of the W-value in liquid xenon

On September 16th 2021, our measurement of the mean electronic excitation energy in liquid xenon, commonly known as the W-value, was posted on arXiv.

This value relates the energy deposition of a particle interaction in liquid xenon with the number of released scintillation and ionisation quanta and thus, determines the absolute microscopic energy scale of a liquid xenon detector. We obtained a value of (11.5 +0.2 -0.3) eV in our Xurich II TPC at UZH based on keV-scale calibration data with 37Ar and 83mKr and single electron events. This value is well-compatible with a measurement in EXO-200 from 2020 but lower than the commonly used value of (13.7+-0.2) eV measured by E. Dahl in 2009. On the right we show a schematic of the so-called Doke plot that visualises the measurement principle.

UPDATE (December 2nd): The article is now published in the European Physical Journal C: Eur. Phys. J. C 81, 1060 (2021). We thank our referees for the great input and feedback.