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Closing in on the Higgs boson
Posted: 27 July 2010

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Scientists working at the US Department of Energy's Fermilab DZero and CDF projects have together narrowed down the mass range of the elusive Higgs boson particle.

The Higgs boson is currently just a theoretical particle, proposed by British physicist Peter Higgs as a solution to one of the most basic – but as yet unsolved – puzzles in particle physics: why some particles possess mass and others do not. Finding the Higgs could help scientists finally understand dark matter, which itself is only inferred from its gravitational effect, which in turn results from the dark matter possessing mass.

The latest results for the search for the elusive Higgs boson particle exclude a mass for the Higgs of between 158 and 175 GeV/c2 with 95 percent probability. Image: Fermilab.

Thanks to experiments conducted by both the Large Hadron Collider at CERN and the Tevatron Collider at Fermilab in the US, tracking down this "most-wanted" particle is getting closer and closer. The new Fermilab results, which required analysis of some 500,000 billion proton-antiproton collisions that the two experiments have studied since 2001, rule out a quarter of the mass range previously thought possible for the Higgs.

“Our latest result is based on about twice as much data as a year and a half ago,” says Stefan Soeldner-Rembold of the University of Manchester, who leads the international DZero Experiment. “As we continue to collect and analyse data, the experiments will either exclude the Standard Model Higgs boson in the entire allowed mass range or we’ll go on to see first hints of its existence. There is less and less room for the Higgs boson to hide now.”

The CDF detector is the height of a three-story house and records the characteristics of the debris from the high-energy proton-antiproton collisions, information that can be used to shed light on the existence of the Higgs particle. Image: Fermilab.

The Tevatron operates by accelerating beams of protons and antiprotons in opposite directions around a circular, four mile-long track at nearly the speed of light. At the two detectors (CDF – the Collider Detector at Fermilab, and DZero, named for its location in the ring) the beams collide and the debris detected by the experiments. CDF and DZero monitor each particle's flight path, energy, momentum and electric charge to help scientists identify the types of particles created by the collisions, and to see if any new particles have been created.

STFC’s Director of Science Programmes, Professor John Womersley, who also formerly led the DZero experiment for several years, comments: “There are important pieces missing in our understanding of the basic building blocks of the Universe and these results are an important step in learning how our Universe works and why it exists. STFC is proud to support the UK scientists who are playing such a strong role this area of research at this key time.”

The results were announced at the International Conference on High Energy Physics (ICHEP) in Paris, yesterday.