Protons have *collided* in the LHC

At least it looks like it from this CMS event display:

See the CMS e-commentary for hourly updates and more information.  (That’s how I know which results are public. :))

The yellow boxes are silicon strips that detected the passage of particles (most likely pions in this case) and the green lines radiating from the center are tracks reconstructed from those hits.  They’re not constrained to meet at the center: that’s an indication that these particles actually originated where the beams collide.  Beyond that, the red and blue bars show how much energy was collected in the electromagnetic calorimeter (electrons, photons, and hadrons) and the hadronic calorimeter (hadrons only), respectively.  No activity can be seen in the muon detector (red boxes).

This is all consistent with what one should expect from the collision of two protons— a strong (QCD) interaction between the quarks and gluons producing a handful of strongly-interacting hadrons, rather than photons, electrons, muons, or taus, which are insensitive to the strong force.  An electroweak interaction between the quarks and gluons, producing possible Higgs bosons or any of a number of other exciting possibilities * * * * * * * *…,  are more rare, and will require collecting and sifting through huge numbers of collisions.

The CERN twitter site says that all four experiments saw collision-like events.  It’s finally happening!

Tags: CMS, LHC, physics