# Unraveling the origin of black holes from effective spin measurements with LIGO-Virgo

## TL;DR

This paper uses LIGO-Virgo gravitational wave data to analyze the effective spin of binary black hole mergers, aiming to distinguish between primordial and astrophysical origins through statistical modeling and future event predictions.

## Contribution

It introduces a method to differentiate black hole origins by analyzing effective spin distributions and odds ratios from gravitational wave observations.

## Key findings

- Primordial black holes have a distinct effective spin distribution.
- Current data can constrain the mixture of black hole origins.
- Future detections will improve discrimination between models.

## Abstract

We investigate how to use information on the effective spin parameter of binary black hole mergers from the LIGO-Virgo gravitational wave detections to discriminate the origin of the merging black holes. We calculate the expected probability distribution function for the effective spin parameter for primordial black holes. Using LIGO-Virgo observations, we then calculate odds ratios for different models for the distribution of black holes' spin magnitude and alignment. We evaluate the posterior probability density for a possible mixture of astrophysical and primordial black holes as emerging from current data, and calculate the number of future merger events needed to discriminate different spin and alignment models at a given level of statistical significance.