Can Baryon Acoustic Oscillations Illuminate the Parity-Violating Galaxy 4PCF?

TL;DR

This paper explores the potential of using Baryon Acoustic Oscillations in the parity-odd galaxy 4-point correlation function as a new method to detect early Universe parity violation, which could indicate physics beyond the Standard Model.

Contribution

It demonstrates how BAO features can appear in the parity-odd 4PCF and proposes a model-independent search method for future galaxy surveys.

Findings

BAO imprint can exist in the parity-odd 4PCF.

Detection of BAO in the odd 4PCF can serve as a standard ruler.

A formula relates BAO measurement precision to detection significance.

Abstract

Measurements of the galaxy 4-Point Correlation Function (4PCF) from theSloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (SDSS BOSS) have recently found strong statistical evidence for parity violation. If this signal is of genuine physical origin, it must stem from beyond-Standard Model physics, most likely during the very early Universe, prior to decoupling ($z$$\sim$$1,020$). Since the Baryon Acoustic Oscillation (BAO) features imprint at decoupling, they are expected in the parity-odd galaxy 4PCF, and so detecting them would be an additional piece of evidence that the signal is genuine. We demonstrate in a toy parity-violating model how the BAO imprint on the parity-odd 4PCF. We then outline how to perform a model-independent search for BAO in the odd 4PCF, desirable since, if the signal is real, we may not know for some time what model of e.g. inflation is producing it. If BAO are detected in the parity-odd sector, they can be used as a standard ruler as is already done in the 2PCF and 3PCF. We derive a simple formula relating the expected precision on the BAO scale to the overall parity-odd detection significance. Pursuing BAO in the odd 4PCF of future redshift surveys such as DESI, Euclid, Spherex, and Roman will be a valuable additional avenue to determine if parity violation in the distribution of galaxies is of genuine cosmological origin.