A powerful veto for gravitational wave searches using data from Virgo's first scientific run

The use of vetoes generated from auxiliary channels suppresses most of the high amplitude noise triggers that impair gravitational wave (GW) burst and binary inspiral searches. During Virgo's first scientific run (VSR1), many of the remaining loud burst and inspiral Virgo triggers were observed with nearly equal significance in both the in-phase (ACp) and quadrature (ACq) interferometer output channels, while we expect the ACq channel to be insensitive to a GW signal. We describe a veto based on the ratio of the amplitude of the ACp and ACq signals. From studying hardware signal injections, we demonstrate that the ratio of the amplitude of coincident ACp and ACq triggers can be safely used to define a veto; we show its efficiency for the burst and binary inspiral analyses of the VRS1 data.