Searching for New Physics
Last week I attended the annual LBNL ATLAS physics group meeting. On the final day some interesting comments were made about the strategy for searching for new physics at ATLAS and with the LHC in general. Here’s a brief summary to the best of my memory…
1. Measure the Standard Model
To find new physics you have to know what you are seeing in your detector. To this end the particles from the Standard Model (W and Z bosons, photons, electrons, etc.) must be well measured. That is to say when you see a photon in the calorimeter you must be confident it is indeed a photon! The best way to do this is measure the Standard Model cross-sections – and who knows while doing so you might see something unexpected! Of course you probably won’t but this relates to the next point…
2. Don’t just set limits
The rate at which the LHC is collecting data means a limit on a particular model can be superceded pretty quickly. In fact the winter conference results on the full 2010 dataset will quickly be overtaken by the initial summer results on 2011 data; however as the LHC energy is extremely likely to be changing (caveat: this decision hasn’t been made yet) a Standard Model cross-section measurement on 2010 data will stand the test of time. Setting limits in a model independent way which also makes a useful Standard Model measurement is preferential. The exception to this rule is the Standard Model Higgs on which limits are well defined and motivated.
3. What to do when new physics is found
The first thing to do when new physics is found is to characterise it. This is not a trivial task and will represent significant work at the LHC if new effects are observed. Another key thing on the discovery of new physics is not to continue looking for alternative exotic models. The new physics is only likely to take one form!