Priority for physics
As you’ll all know by now, the LHC will restart in September. I’m well aware that we are all used to hearing dates for the LHC start-up announced at the beginning of the year and then slipping as the year goes on, and although we can never rule out further changes in the schedule, we have good reasons to be optimistic. This time, we assembled all the experts from the LHC and the experiments at the Chamonix workshop to discuss every detail. And at Chamonix, we had much more information at our disposal than we have had in the past, so we can be more confident than ever before that we’re working to a realistic schedule that everybody can buy in to.
Since the incident on 19 September, we have learned our lessons. We understand the LHC’s magnets much better now, and we know what needs to be done to operate the LHC safely and reliably through its first physics run. People have asked me how we settled on September for the first beam – why not sooner, or later? The answer is simple. There are two things on the critical path that prevent us from starting any earlier: we need to have the new quench protection system fully installed and tested before we put beam in the machine again, and the whole machine including Sector 3-4 needs to be cold. Those two things will not happen before September. Why not later, installing all the new pressure relief valves around the whole ring? Because we’re confident that we can run safely at 5 TeV per beam with the measures that we’re putting into place now. Furthermore, running at 5 TeV will allow us to learn more about the LHC, and help us to refine the consolidation steps to be taken for the next shutdown period.
Another question I’ve been asked is whether the 200 inverse picobarn target for integrated luminosity – a measure of the amount of data we’ll collect in the LHC’s first run - is sufficient for useful analyses to be made. The answer is a resounding yes. The cross-section for physics such as Higgs particle production is much higher at 5 TeV per beam than at lower energies, meaning that if there’s useful physics there, we’ll start to see signals in the LHC’s first run.
