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Tuesday, July 10, 2012

La fiducia che la scoperta del bosone di Higgs sia confermata è circa pari alla probababilità che esca testa 20 volte di fila nel lancio di una moneta.

Brian Greene Reacts to Today’s CERN Announcement | World Science Festival

Earlier this morning, CERN made a much-anticipated announcement about its progress in finding the elusive Higgs particle. Below, Brian Greene explains the significance of the news. • More information and a video of the CERN announcement here Here’s a summary of today’s announcement: The Large Hadron Collider (a 17-mile-long circular tunnel in which protons are sent whizzing around in opposite directions at just shy of light-speed, and directed into head-on collisions) has two mammoth detectors called ATLAS and CMS (each of which captures and analyzes particulate debris created by the proton–proton collisions). Two independent (and highly competitive) research teams, involving thousands of scientists, using each of these detectors have seen moderately convincing evidence that the elusive Higgs particle has been created in some of the proton–proton collisions.
This is a challenging experiment as the detectors can’t see the Higgs particle directly—it is a short-lived particle that quickly falls apart (decays)—but, rather, they infer its presence by seeing its decay products. (Watch here, as physicist and ATLAS researcher Monica Dunford explains this process of inferring new possible particles during the World Science Festival.) In particular, the equations show that when a Higgs particle decays, some fraction of the time two photons (particles of light) are produced. The researchers sift through a maelstrom of debris for these photons, but even then they need to ensure that the photons weren’t produced by some other, more mundane process.  This painstaking work, aided by sophisticated computer analysis, now shows evidence of a Higgs particle that weighs about 126 times as much as a proton.
The researchers’ confidence in this result, while fairly strong, does not yet rise to the level at which a definitive discovery is claimed (there’s roughly a chance of a few in a thousand that the data is a statistical fluke, sort of like the chance of getting 8 to 9 heads in a row when you flip a coin; the protocol for claiming a definitive discovery is more like 1 in a million, similar to getting heads about 20 times in a row). But within the next few months, or surely within the next year, the teams should know whether or not they’ve found the Higgs particle.

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