Does a particle traveling near the speed of light create an observable/measureable gravitational field around it? I know most elementary particles travel near the speed of light and have no gravitational effect, but I'm talking about a more massive particle, say, iron for instance.
As a more specific example of what I'm trying to say; if you had a particle accelerator, could you create a decent, measurable gravitational effect in the epicenter of the circle outlined by the accelerator by accelerating a very heavy element close to the speed of light?