# Observation of Anti-correlation between Scintillation and Ionization for MeV Gamma-Rays in Liquid Xenon

## TL;DR

This study demonstrates a strong anti-correlation between scintillation and ionization signals in liquid xenon for MeV gamma-rays, leading to improved energy resolution by combining these signals, with potential for further enhancement.

## Contribution

It provides the first detailed measurement of anti-correlation in liquid xenon for MeV gamma-rays and shows how combining signals enhances energy resolution.

## Key findings

- Achieved 1.7% energy resolution at 662 keV with combined signals.
- Anti-correlation reduces fluctuations, improving resolution.
- Potential to reach below 1% resolution with better light collection and noise reduction.

## Abstract

A strong anti-correlation between ionization and scintillation signals produced by MeV gamma-rays in liquid xenon has been measured and used to improve the energy resolution by combining the two signals. The improvement is explained by reduced electron-ion recombination fluctuations of the combined signal compared to fluctuations of the individual signals. Simultaneous measurements of ionization and scintillation signals were carried out with Cs-137, Na-22 and Co-60 gamma rays, as a function of electric field in the liquid. A resolution of 1.7%(sigma) at 662 keV was measured at 1 kV/cm, significantly better than the resolution from either scintillation or ionization alone. A detailed analysis indicates that further improvement to less than 1%(sigma) is possible with higher light collection efficiency and lower electronic noise.