## We Have The Higgs!!!

What a tiring yet exciting night for the physics community. After fifty years of searching for the elusive Higgs boson and completion of the Standard Model of particle physics, the two teams at the Large Hadron Collider announced that they had in fact discovered the Higgs. It is fairly certain now that they team leaders (and probably the theorists who developed the model) will be getting a Nobel Prize for this discovery very soon.

As I just wrote a review of the Higgs
mechanism yesterday, I won't repeat it here. However I will provide
some information on the discovery itself.

First off, it is a 5 sigma signal.
Without going into a full review of statistics, that simply means
that it is a very confident discovery. A 1-sigma signal means that
you are about 84% certain of the result, or in other words if you
repeated the experiment six times, one of them would give a false
positive. A 2-sigma signal is about 97.5% certain that the discovery
is real, and a 3-sigma is 99.9% certain. This is a 5-sigma signal,
which is only wrong one time in 3.5 million experiments, or is
99.99998% certain!

The manner in which it was discovered
is also interesting. The Higgs leaves no real effect on the
detectors, and it decays away far too quickly to ever be seen
directly anyway. But the basic Higgs model has very well defined
probabilities for being produced in high energy collisions and well
understood decay rates to other particles that can be detected. So
the LHC collided billions and billions of protons together, and then
the teams counted how many of these collisions produced each type of
detectable particle. We can easily calculate how many and what type
of particles are produced without a Higgs and with a Higgs. When the
collisions were analyzed, it showed the predicted rates for a Higgs
model.

Second, when the Higgs (or any
particle) is produced and decays with a certain combination of energy
and momentum (specifically when the mass, energy, and momentum
satisfy E^2 – p^2 c^2 = m^2 c^4), the process becomes far more
efficient and the number of detectable particles is increased. So by
analyzing the energies of the particles, and looking for peaks in
their energy distribution, the mass of the Higgs can be determined.

The LHC found the Higgs to have a mass
of 125GeV (which happens to be almost where I was guessing it to be
in my dissertation :) ). For comparison, a single hydrogen atom
weighs about 1GeV and 125GeV is roughly the weight on a single atom
of Iodine or Xenon. Except the Higgs particle is many orders of
magnitude smaller than these atoms, and it has no internal structure
(or at least none that is known yet)

So after fifty years of searching and
countless hours and dollars spent on experiments, the Higgs has
finally been found. The Standard Model of particle physics is now
complete. Now we start exploring new frontiers of physics....