And there it goes again

This morning around 9:30, the Large Hadron Collider (LHC) at CERN produced the first proton collisions since the restart of the accelerator at the beginning of April, following an interruption of more than two years. These collisions occurred at an energy of 900 GeV, a modest reach for the LHC but nevertheless, a major and encouraging milestone half way into the eight-week restart program. These collisions will allow the experiments to check their calibrations and test all their event reconstruction algorithms. If all keeps going well, the first collisions at an energy of 13 TeV (fifteen times higher) will take place in the coming weeks. The accelerator should begin supplying collisions regularly to the experiments at the beginning of June. The goal will then be to deliver approximately one inverse femtobarn of data before July, that is approximately one twenty-fifth of what was accumulated during the first period of operation between 2010-2012. The experiments would then have have a chance to begin exploring new territories, just in time to bring some excitement to the major Summer conferences.

For more information, see CERN homepage

One of the events recorded by the detector ATLAS this morning. The collisions between the proton beams produced heavy and unstable particles, which almost immediately broke into fragments. The light yellow lines denote the tracks left by these fragments as they flew across the detector. The fact that all these tracks emerge from one unique collision point confirms that such collisions took place.

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