CECERN collider could become the world's fastest stopwatch

Heavy ion collisions at CERN should be able to produce the shortest light pulses ever created. This was demonstrated by computer simulations at the Vienna University of Technology. The pulses are so short that they cannot even be measured by today’s technological equipment. Now, a method has been proposed to create the world’s most precise stopwatch for the world’s shortest light pulses.

Phenomena taking place on very short time scales are often investigated using ultra short laser pulses. Today, pulse durations of the order of at-to seconds (one quintillionth of one second) can be created. But these records could soon be broken.

“Atomic nuclei in particle colliders like the LHC at CERN or at RHIC can create light pulses which are still a million times shorter than that”, says Andreas Ipp from TU Vienna.

In the ALICE experiment at CERN,lead nuclei are collided almost at the speed of light. The debris of the scattered nuclei together with new particles created by the power of the impact from a quark-gluon plasma, a state of matter which is so hot that even protons and neutrons melt.Their building block – quarks and gluons – can move independently without being bound to each other. This quark-gluon plasma (one septillionth of a second).

From the quark-gluon plasma created in a particle collider, light pulses can be emitted. However, conventional measurement techniques are much too slow to resolve flashes on a yoctosecond timescale. “That’s why we make use of the Hanbury Brown Twiss effect, an idea which was originally developed for astronomical measurements”, says Andreas Ipp.

In a Hanbury Brown-Twiss experiment, correlations between two different light detectors are studied. That way, the diameter of a star can be calculated very precisely.

“Instead of studying spatial distances, the effect can just as well be used for measuring time intervals”, says Peter Somkuti, who carried out many of the calculations. The computer simulations show that the yocto second pulses of the quark-gluon plasma could be resolved by a Hanbury Brown-Twiss experiment.

“It would be hard to do, but it would definitely be achievable”, says Ipp. This experiment would not require any additional expensive detectors, it could be done with the “forward calorimeter”, which is supposed to go on line at CERN in 2018. That way, it could become the world’s most accurate stopwatch.