The fifth lecture (given before the momentous announcement on the 4th of July that the Higgs appeared to be found) was on the hunt for the Higgs Boson given by Dr Jonathon Hays from Imperial College. Dr Hays works on CMS at the LHC looking for the Higgs amongst other things (www.cms.cern.ch).
There is no real evidence for string theory. The standard model is the best description of what constitutes matter but there are a few pieces missing such as gravity and dark matter. The Higgs is believed to be why some sub-atomic particles have mass. Energy/mass and momentum must always be conserved so this can be seen by looking for mc^2 plus electron and positron trajectories. You need to measure something that depends on mass. Examples of conservation:
Energy, momentum and mass need to be measured.
There are massive problems if the Higgs can’t be found. The mass of the Z boson would be zero.
How the Higgs Boson is believed to be produced: Two protons collide at very high energies. Theory tells us how often the Higgs should be produced. Unfortunately the Higgs is very short lived and decays. Predictions about production and decay inform searches for the Higgs Boson. Different signals need to be looked for. Increased chance of finding something + more evidence (multiple measurements) tells us what we have actually have found. Evidence for the Higgs is seeing two Z bosons or two photons or two W bosons appearing.
H –> γγ (gamma, gamma) Collect collisions and look for two high energy photons.
As we now know the Higgs has appeared to be discovered. We can now explain mass (although finding nothing would have been even more exciting). Questions that need to be answered: Why does the Higgs decay happen? Why must the Higgs interact? Why does the Higgs disappear and produce other particles? The tevatron wasn’t sensitive enough to detect the Higgs.