## Friday, March 03, 2006

### Collider physics

Yesterday Nima explained the essence of the LHC olympics, including some basics of collider physics for those of us who have never heard an official introduction to it.

The previous blog article about the LHC olympics is here.

He explained that the LHC will start to collide next summer. After some time like one year, they will shut it down for several months, trying to increase the luminosity.

Most events are boring forward scattering blah blah blah, and we are usually interested in rare, special events with a lot of transverse energy which typically correspond to new physics. The LHC will be a TeV machine to produce colored particles - gluinos and squarks are the most typical new examples - and a TeV machine to product new particles such as Z' bosons as resonances in the s-channel. For new non-resonant un-colored particles, the LHC will only be a multi-100-GeV machine: the difference in the LHC capacity to produce these two groups of particles is a factor of seven in energy. With Reagan's SSC, the difference would only be a factor of three.

At the LHC olympics, you obtain a black box which is composed of many lines. Each line has 8 or 9 entries describing the four-momentum of a particle and its identity. An event is encoded in several lines, and a typical black box has 50,000 events or so and it is up to you what quantities you decide to draw in order to find out the secret Lagrangian. If you open Jesse Thaler's website, you will find, among other things, a section dedicated to the LHC olympics, starting with a description of the Harvard box. A subpage contains Chameleon software for Mathematica, a very user-friendly and logical piece of software engineering by Natalia Toro and Philip Schuster.

There have been arguments whether the experimenters would (and should) give the theorists the data in a format that is sufficiently similar to the format of the LHC olympics. Instead, the experimenters will try to generate their plots themselves, attempting to discover the new particles without any help of theorists. But their efforts can get stuck and we will see what happens.

I had to leave the talk before it ended to teach the renormalization group.