iSGTW Feature - Tevatron Higgs update August 08

Feature - Tevatron brings Higgs one step closer

The Tevatron at Fermilab in Batavia, Illinois, U.S..
Image courtesy of Fermilab.

On June 4 we reported that teams from CDF and DZero at Fermilab, aided by processing power from the Open Science Grid, had jointly amassed enough data at that time to state with 90% certainty that the Higgs boson, the particle that could help explain dark matter, dark energy and why particles have mass, does not have the expected mass of 160 GeV/c2. This hot topic in particle physics is getting hotter. Here we give an update.

Scientists from the CDF and DZero collaborations at the Tevatron at Fermilab presented results which for the first time exclude, with 95% probability, a mass for the Higgs of 170 GeV/c2. This value lies near the middle of the possible mass range for the particle established by earlier experiments.

"These results mean that the Tevatron experiments are very much in the game for finding the Higgs," said Pier Oddone, director of Fermilab.

Combining results from the two collider experiments effectively doubles the data available for analysis by experimenters and allows each experimental group to cross check and confirm the other's results. The Open Science Grid continues to be instrumental in enabling this analysis. In the near future, the Fermilab experimenters expect to test more and more of the available mass range for the Higgs.

The top image shows the potential range for finding the Higgs and the now excluded regions, expressed in mass units of GeV/c2, representing energy over the speed of light squared, from the equation E=mc2.

The bottom image (click for complete graph) shows results announced at the conference. They exclude a mass for the Higgs of 170 GeV/c2 with 95% probability. CL refers to "confidence level"; σ refers to a standard deviation, which indicates the spread of values in a data set around the mean.

Images courtesy of Fermilab.

Currently, Fermilab's plans call for the Tevatron experiments to continue operating through 2010. In that time, both groups expect to double their analysis data sets, improving their chances to observe the Higgs.

"The Fermilab collider program is running at full speed," said Dennis Kovar, associate director of the Office of Science for High Energy Physics at the U.S. Department of Energy.

Scientists expect operations to begin at the Large Hadron Collider at CERN, in Europe, this fall. Observation of the Higgs is also a key goal for LHC experiments.

The new Higgs results are among the approximately 150 results that the two experiments presented at the International Conference on High Energy Physics in Philadelphia held July 29-August 5. Virtually all the results relied on simulations done on OSG; simulations are used for comparison purposes to better understand the real data. OSG produced about 200 million, or 30% of DZero's simulated events between August 2007 and July 2008, for a weekly average of just under 4 million. CDF ran over a billion simulated events, or 170 Terabytes, through OSG resources in roughly the same period, averaging 23 million events (3.5 TB) per week.

"The discovery of the Higgs boson would answer one of the big questions in physics today," said Joseph Dehmer, director of the Division of Physics for the National Science Foundation. "We have not heard the last from the Tevatron experiments."

-Fermilab Office of Communication and Anne Heavey, iSGTW

Funding for the CDF and DZero experiments comes from DOE's Office of Science, the National Science Foundation, and a number of international funding agencies.

Read the full press release.