Has the Higgs Been Discovered? Physicists Gear Up for Watershed Announcement

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Rumors are flying about a December 13 update on the search for the long-sought Higgs boson at Europe's Large Hadron Collider
By Davide Castelvecchi | December 8, 2011 |


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The talks were announced last week; true to form, the particle physics rumor mill shifted into high gear, and by the weekend multiple anonymous sources had leaked consistent information, according to several bloggers, including Peter Woit, Lubos Motl and Philip Gibbs. Both experiments are said to have seen evidence of the long-sought Higgs, pointing to a particle mass of around 125 billion electron volts, or 125 GeV. (125 billion electron volts is roughly the mass of 125 hydrogen atoms.)* Such results would not constitute an ironclad discovery quite yet, being below the required "5 sigma," a measure of statistical reliability. But the two experiments are rumored to have seen signals of 2.5 sigma and 3.5 sigma, which together would give a strong hint. (Three sigmas would correspond to a one-in-370 chance of the finding being a statistical quirk, although in particle physics experiments it is not uncommon for 3-sigma results to vanish.)

Previous rounds of data analysis from the LHC as well as from its U.S. predecessor, Fermilab's Tevatron, had narrowed the Higgs mass range down to somewhere between 115 and 140 GeV. But the new announcement would constitute the first time that both LHC experiments had made a precise and consistent estimate of the mass.

Even before the data are out, theoretical physicists around the world are working out the possible implications. Some have pointed out that a value of 125 GeV would be good news for supersymmetry, a theory that predicts that each particle would have a heavier partner known as a superparticle (at least for particles within the framework of the Standard Model of particle physics, the currently accepted description of the subatomic world). "Most supersymmetric models put a Higgs below 140 or so," says Matt Strassler of Rutgers University. Supersymmetry has long been a favorite candidate for extending the Standard Model, because it would answer numerous open questions, beginning with the nature of dark matter, the unseen mass that keeps galaxies rotating faster than they otherwise would.


rest of article
http://www.scientificamerican.com/article.cfm?id=higgs-...