Upper Limits from Counting Experiments with Multiple Pipelines

TL;DR

This paper extends classical upper limit calculations for counting experiments to multiple, potentially correlated measurements, providing a method to combine data from various procedures to set more stringent upper limits, exemplified in gravitational-wave burst searches.

Contribution

It introduces a generalized framework for combining multiple counts from different procedures in counting experiments, optimizing the rank ordering for stronger upper limits.

Findings

Proposes a new ordering method matched to measurement sensitivity.

Demonstrates improved upper limits in gravitational-wave burst searches.

Provides a unified approach for multiple counting experiments.

Abstract

In counting experiments, one can set an upper limit on the rate of a Poisson process based on a count of the number of events observed due to the process. In some experiments, one makes several counts of the number of events, using different instruments, different event detection algorithms, or observations over multiple time intervals. We demonstrate how to generalize the classical frequentist upper limit calculation to the case where multiple counts of events are made over one or more time intervals using several (not necessarily independent) procedures. We show how different choices of the rank ordering of possible outcomes in the space of counts correspond to applying different levels of significance to the various measurements. We propose an ordering that is matched to the sensitivity of the different measurement procedures and show that in typical cases it gives stronger upper limits than other choices. As an example, we show how this method can be applied to searches for gravitational-wave bursts, where multiple burst-detection algorithms analyse the same data set, and demonstrate how a single combined upper limit can be set on the gravitational-wave burst rate.