Improved binary black hole searches through better discrimination against noise transients

Abstract

Short-duration noise transients in LIGO and Virgo detectors significantly affect the search sensitivity of compact binary coalescence (CBC) signals, especially in the high mass region. In a previous work by the authors \cite{Joshi_2021}, a $\chi^2$ statistic was proposed to distinguish them, when modeled as sine-Gaussians, from non-spinning CBCs. The present work is an extension where we demonstrate the better noise-discrimination of an improved $\chi^2$ statistic -- called the optimized sine-Gaussian $\chi^2$ -- in real LIGO data. The extension includes accounting for the initial phase of the noise transients and use of a well-informed choice of sine-Gaussian basis vectors selected to discern how CBC signals and some of the most worrisome noise-transients project differently on them~\cite{sunil_2022}. To demonstrate this improvement, we use data with blip glitches from the third observational run (O3) of LIGO-Hanford and LIGO-Livingston detectors. Blips are a type of short-duration non-Gaussian noise disturbance known to adversely affect high-mass CBC searches. For CBCs, spin-aligned binary black hole signals were simulated using the \textsc{IMRPhenomPv2} waveform and injected into real LIGO data from the same run. We show that in comparison to the sine-Gaussian $\chi^2$, the optimized sine-Gaussian $\chi^2$ improves the overall true positive rate by around 6\% in a lower-mass bin ($m_1,m_2 \in [20,40]M_{\odot}$) and by more than 3\% in a higher-mass bin ($m_1,m_2 \in [60,80]M_{\odot}$). On the other hand, we see a larger improvement -- of more than 20\% -- in both mass bins in comparison to the traditional $\chi^2$.