8/7/2012
Fermilab’s CDF and DZero collaborations at the now retired Tevatron collider did not discover the standard model Higgs boson, but their collective contribution to the Higgs boson search was nevertheless an important one.
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Fermilab’s CDF and DZero collaborations at the now retired Tevatron collider did not discover the standard model Higgs boson, but their collective contribution to the Higgs boson search was nevertheless an important one.
The report was eclipsed by the bigger announcement on July 4 from CERN of a Higgs-like boson discovery at the Large Hadron Collider (LHC). The ATLAS and CMS collaborations independently published their respective data analyses on August 1, with computations from a network of supercomputing centers around the globe, reaffirming the discovery.
ATLAS collaborators now report the observance of a Higgs-like particle with a 5.9-sigma signal, based on analyses of five decay channels using 2011 data and three decay channels (including the W-boson pair decay mode) using 2012 data. CMS collaborators report observance of the same particle with a 5-sigma signal, based on analyses of five decay channels using data from 2011 and 2012.
But the Tevatron’s ultimate contribution to the Higgs search is not a small one: the CDF and DZero collaborations observe the Higgs-like subatomic particle through a decay channel—to bottom quark and antiquark—that was not observed by ATLAS or CMS.
University of Illinois theoretical physicist Scott Willenbrock said, “The Tevatron did play a useful role in finding this particular decay channel of the Higgs-like particle. This has not been seen at LHC because of backgrounds—things that mimic the signal you are looking for.
“At the Tevatron, because the machine is not as energetic as the LHC, the backgrounds are smaller. For this particular decay channel, the Tevatron actually had an advantage.”
In 1994, Willenbrock and his collaborators were the first to propose that the particle could potentially be seen at Tevatron by looking for its decay to a bottom quark and antiquark. In their paper, “Higgs bosons at the Fermilab Tevatron” in Physical Review D, v 49, 3154 (1994), Willenbrock and his co-authors, Alan Stange and William Marciano, asserted that the observation of the Higgs in this decay mode is strong evidence that it really is the Higgs particle.
“At the time we wrote the paper, no one was thinking about looking for the Higgs boson at the Tevatron; everyone was focused on the LHC. This paper was the contrarion—it said, ‘Hey, we have a chance.’ People paid attention to it and it was one of the things that motivated people to push Fermilab’s Tevatron to its limit,” said Willenbrock.
Fermilab’s Tevatron near Batvia, Illinois, went out of commission on September 30, 2011. In its 24 years of proton-antiproton collision experiments, the Tevatron made many discoveries, most notably, the top quark in 1995. The Tevatron’s observation of the Higgs-like boson is no small part of its great legacy.
Co-authors of the Tevatron joint paper at the Department of Physics at Illinois include Steven Errede, Mark Neubauer, and Kevin Pitts; Post Doctoral Research Associates Viviana Cavaliere, Heather Gerberich and Olga Norniella; and graduate students Ben Carls (graduated March 2012), Keith Matera, Ed Rogers (graduated December 2010), and Greg Thompson (graduated June 2011).
Other Physics Illinois students who have worked on the CDF collaboration include graduate student Benjamin Esham, undergraduate student Stephanie Brandt, and REU external undergraduate students Andrew Kerr and Benjamin Stickel.
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Contact: Scott S. Willenbrock, Department of Physics, 217/333-4392 .
Writer: Siv Schwink, Department of Physics, 217/552-5671.
Illustration courtesy of CERN.
If you have any questions about the College of Engineering, or other story ideas, contact Rick Kubetz, editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-7716.