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The first paper on LHC collisions?

December 2009.jpg
Figure 1 of the first of many papers

By Hamish Johnston

What surely must be the first paper reporting proton-proton collisions in the Large Hadron Collider (LHC) has appeared on the arXiv preprint server.

It’s by the ALICE collaboration — over two pages of authors from 113 institutes — and describes collisions in the ALICE detector that occured last week.

Aamodt et al describes 284 collisions that occured when both beams were at 450 GeV.

The events were used to determine something called the ‘pseudorapidity density’ of charged particles in the detector.

And what exactly is pseudorapidity? As far as I can tell, it’s a rather complicated way of expressing the angle between the momentum of a particle in the detector and the momentum of the beam.

The paper says this about these early results:

“They demonstrate that the LHC and its experiments have finally entered the phase of physics exploitation, within days of starting up the accelerator complex in November 2009.”

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