When anything is cooled the molecules shake less violently. They contract, right? And when the sea is warmed it expands, right? So why is it that when you put a bottle of water in the freezer, there is less room in the bottle? As though the water has expanded?
By Celia Elliott
April 5, 2010
Physics undergraduate Matthew Feickert has been awarded a Universities Research Association (URA) Visiting Scholar Award for Summer 2010. He will be in residence at Fermi National Accelerator Laboratory (FNAL), where he will work under the direction of Assistant Professor of Physics Mark S. Neubauer on an analysis of proton-antiproton collision data collected using the CDF detector.
Their project, "A search for WZ and WW resonances (including Higgs) in the lvqq final state," involves a new analysis of CDF data that has applicability to Neubauer's work on the ATLAS experiment at the Large Hadron Collider (LHC) in in the pursuit of an understanding of the origin of electroweak symmetry breaking. The most sensitive search for a Higgs boson with a mass near the W boson pair production threshold of 165 GeV/c2 involves decay of the Higgs to a pair of W bosons, where each W decays to a charged lepton and a neutrino. (See "Higgs mass constrained by new analysis", a news story on a recent search for the Higgs boson in this "fully-leptonic" decay mode.)
It is more than six times more likely for one of the W bosons to decay to a quark-antiquark pair leading to two high-energy jets than it is to decay to a charged lepton and a neutrino, leading to an overall higher Higgs decay rate in the semi-leptonic decay channel. The drawback to the semi-leptonic decay channel is that it has larger background, compared with the fully leptonic decay channel for a Higgs mass at or below 165 GeV/c2. However, the background decreases very rapidly with increasing energy, such that the larger overall decay rate present in the semileptonic decay channel becomes important to the search for a Higgs boson with mass above the W boson pair threshold. The sensitivity to a high-mass Higgs boson will soon become dominated by the LHC experiments CMS and ATLAS.
Universities Research Association, Inc. is a consortium of 87 leading research universities; the not-for-profit corporation was founded in 1965 for management and operation of research facilities in the national interest. With the University of Chicago, it operates FNAL in Batavia, Illinois.
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