From LHC sessions: First top candidates, and one experiment has had enough!

I've spent this morning in the "Early Experience and Results from LHC" sessions. They've been almost as packed as yesterday's Higgs session, and have included two interesting firsts (for me, at least).

From ATLAS, in the presentation of the first results on QCD, Quarkonia and Heavy-Flavour Physics, one of the experiment's very first top quark candidate events. I expect that many more such events are being presented by ATLAS and CMS at this very moment in the parallel session devoted to top quarks.

And from LHCf, I learned that this small experiment is the first at LHC to have finished data taking. That's right, while the big experiments are just barely getting started, the smallest experiment has already collected all the data they need and even removed their detectors from the beamline on July 20.

The LHCf speaker was quite good - unlike the big experiments, the speakers from LHCf and TOTEM don't assume that everyone in the room already knows the details of their experiment, so they spend time at the beginning of the talk explaining their physics goals and how the experiment is set up and works. As a non-specialist, this is something I really appreciate. So I learned that the goal of LHCf is to provide input to the study of ultra-high-energy cosmic rays (UHECR) created by high-energy particles colliding with Earth's atmosphere, by studying the production of similarly ultra-high-energy showers that are man-made at the LHC. I also learned that they can distinguish between the various theories that currently exist to describe such UHECRs with a relatively small amount of data from LHC collisions (compared to the ATLAS experiment, for example, around which their detector is placed).

This isn't the end of the story for LHCf; they will be back at the start of the LHC's run with 7 TeV beams, currently scheduled to start in 2013. Between now and then they will continue and refine their analysis of 450 GeV and 3.5 TeV data, and upgrade their detector to withstand the higher radiation that will come with 7 TeV beams.