The something in the nothingness

Recent studies have shown that a vacuum, previously thought of as a state of total nothingness, is really filled with energy-hungry "virtual particles' that could interfere with high energy collision experiments.

These virtual particles spring in and out of existence until they can seize enough energy to materialise as "real' particles.

In high energy collisions at accelerator labs, some of the original beam energy can be consumed by ripping particle-antiparticle pairs out of the vacuum. Sometimes this process is the very reason for doing the experiment, but sometimes it is only a detriment.

In the Large Hadron Collider (LHC) under construction at the CERN lab in Geneva, a major source of beam losses (particles exiting from the useable beam) for heavy-ion collisions is thought to be an event where the counter-moving ions pass each other and spawn a pair of particles — an electron and positron — one of which (the positron) goes off to oblivion while the other (the electron) latches onto one of the ions.

The charged ion then behaves slightly differently as it races through the chain of powerful magnets that normally steer the particles around the accelerator. After travelling a certain distance, the modified ion will leave its fellows and smash into the beam pipe carrying the beams, heating up the pipe and surrounding magnet coils.

Accelerator physicists sought to observe this effect at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven Lab on Long Island (which uses around 6.3 TeV of energy per copper nucleus). They found a tiny splash of energy amounting to around 0.0002 W, or about what a firefly puts out.

According to CERN scientist John Jowett, this "bound-free-pair production' will be much more formidable at LHC than at RHIC. The heavier, more highly charged lead nucleus and the larger energies (574 TeV per lead nucleus) used at LHC mean the phenomenon should be some 100,000 times more prominent than the test at RHIC.

This would amount to about 25 watts, the equivalent of a reading lamp, which could be sufficient to heat the magnets in the beam pipe enough to decrease their superconductivity and interrupt the operation.