 The LHC produces a billion collisions per second. That gives the particles produced by any one collision less than a billionth of a second to clear the tunnel and pass into the detectors. But with particles traveling near the speed of light and the radius of the tube being just over 3 centimeters, they are all clear in 10 to the minus 10 seconds. A lot of hundreds of billions of particles created by a few seconds worth of collisions, only a few are massive enough to be interesting. But massive particles, like the Higgs boson itself, will decay into lighter particles so rapidly that they never reach the detectors. We cannot see them directly, but we can detect the lighter particles created by their decay. We can then deduce the originating particles by their decay signatures, just like we did in the cloud chambers on mountaintops. On July 4th, 2012, 45 years after Peter Higgs proposed its existence, CERN announced that one of these interesting particles created in a 2011 collision turned out to fit the decay signature or the Higgs boson. There's a Higgs boson decay into two photons event recorded by Atlas in 2016 that illustrates the decay mode for Higgs found in the 2011 event. Orange lines show the trajectories of charged particles as they passed through the inner tracking systems. The green and blue cones show jets of particles produced in the collision. The green boxes show the energy deposits in the electromagnetic calorimeter. The yellow boxes show the energy deposits in the hadronic calorimeter. The longer the box, the greater the energy deposited. The extremely long green boxes out of the bottom represent the energy deposited by the two photons created by the Higgs boson decay. According to the standard model of particle physics, there are several ways for a Higgs particle to form and to decay through W, Z, and quark particles. Here is a two-photon one. It's rare but easily identified when it happens. As two colliding protons approach each other, they overlap. Then two highly energetic gluons collide, creating a virtual top quark and anti-top quark pair. This is called gluon-gluon fusion. These unstable quarks quickly decay into a Higgs boson. The Higgs boson in turn decays into a virtual top quark and anti-top quark that quickly decay into two high energy photons. It is the photons that were detected by Atlas.