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Simulate proton smashing with updated LHC@home

Help find the Higgs! CERN has updated its LHC@home software, allowing …

Particle physics may be all about finding the unknown, but to do that we need a really strong grip on the known. If the Higgs boson is out there, it's just one of a large collection of particles that can spray the photons and leptons that are picked up by detectors. Figuring out whether there's a hint of the Higgs (or something even more exotic) in these collisions requires us to account for everything else that just looks like the Higgs. Subtract all that background noise and (hopefully) that leaves real signal for everyone to get excited about.

This simple description glosses over what's actually a hideous computational problem. Given two protons colliding at a specific energy, the Standard Model predicts that all sorts of things might pop into existence briefly, with the energy of the collision distributed among them. Because their hardware is different, each of the detectors at the LHC would register the results in different ways. Figuring out what this background of known events looks like requires the averaging of as many typical Standard Model events as we can model.

That's where distributed computing can come in. Each of these events can be modeled independently, making the problem embarrassingly parallel, so the folks at CERN have decided that home computer users should be able to get in on the action. As a result, CERN put together  LHC@home, which has recently been given a number of updates.

Although the software uses the standard BOINC client, it's still not for the faint of heart. CERN does its scientific computing in a customized Linux environment, and its staff has decided that it's best to replicate that environment rather than trying to ensure that their software produces valid results on different operating systems and hardware. As such, LHC@home requires that users install VirtualBox, which lets the CERN environment run in a virtual machine on any of the major platforms. That's a hassle, but at least it lets users host CERN's Linux distribution "without risking the integrity of your machine."

Once installed, the software runs simulations of Standard Model physics that produce virtual collisions and predicts what they'll end up looking like in the LHC's different detectors. These simulations will go into establishing the Standard Model backgrounds that are essential to identifying when something unusual happens. This background is the dashed "Expected" line in graphs such as the one below.

The average Standard Model background is the dashed line here. The actual data differs from it at several locations on the energy spectrum.

We tried to get the system running on a computer here in the Ars virtual office, but the BOINC system indicated it was not accepting any new accounts at the moment (this seems to be a temporary hold). For those who want a taste of the LHC in the meantime, you can follow the progress of the machine using the same interface that many of the detectors' control rooms use. If you'd just like to check in on the progress of the work, the ATLAS detector provides a convenient readout of the amount of data it has obtained. Less than a week after clearing two inverse femtobarns, the detector is nearly a quarter of the way through a third.

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