Measurement of Parity-Violating Modes of the Dark Energy Spectroscopic Instrument (DESI) Year 1 Luminous Red Galaxies' 4-Point Correlation Function

TL;DR

This paper presents the first measurement of the parity-violating 4-point correlation function in galaxy data, finding a significant auto-correlation signal but no corresponding cross-correlation, raising questions about the origin of the PV signal.

Contribution

It introduces the first measurement of the PV 4PCF in DESI Year 1 LRG data and compares auto and cross analyses, revealing a significant auto signal without a corresponding cross detection.

Findings

Significant auto PV 4PCF signal detected at 4-10σ

No PV signal detected in cross-correlation analysis

Discrepancy between auto and cross measurements raises questions

Abstract

Here we report the first measurement of the parity-violating (PV) 4-Point Correlation Function (4PCF) of the Dark Energy Spectroscopic Instrument's Year 1 Luminous Red Galaxy (DESI Y1 LRG) sample, motivated by the potential detection of the PV 4PCF in the Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (SDSS BOSS) galaxies. In our auto-correlation ("auto") analysis, we find a statistically significant excess of the PV signal compared to mocks without any PV, at 4-10$\sigma$ depending on details of the analysis. This could arise either from genuine PV or from an underestimation of the variance in the mocks; it is unlikely to arise, at the signal level, from a systematic. We then cross-correlate ("cross") the putative PV signal between different, independent patches of sky, and there find no detection of parity violation. The two measurements are in significant tension: while the cross has somewhat larger error bars than the auto, this is not sufficient to explain the discrepancy. We thus present the current work as an intriguing addition to the PV work on BOSS and as motivation for exploring further the relationship between the auto and cross PV 4PCF analyses.