Scientists reveal hints of Higgs Boson from Tevatron data

7 Mar 2012

The 6.4km Tevatron accelerator at Fermi National Accelerator Laboratory in Batavia, Illinois. Tevatron typically produced about 10m proton-antiproton collisions per second. Image courtesy of

Scientists at Fermilab, the US laboratory dedicated to high-energy physics, say they may have finally pinpointed the elusive Higgs Boson particle. The scientists had been analysing the full data set from the Tevatron lab, which closed down on 30 September at Fermilab.

The scientists revealed today at the annual conference on Electroweak Interactions and Unified Theories in Italy that two independent experiments “see hints of a Higgs boson”.

‘Higgs boson may nearly be cornered’

The physicists took measurements from the CDF and DZero collaborations at the Department of Energy’s Fermi National Accelerator Laboratory. They now believe the “Higgs Boson may nearly be cornered”.

Based on the CDF and DZero collaborations, the researchers said they found excesses in their data that might be interpreted as coming from a Higgs Boson with a mass in the region of 115 to 135 GeV.

In this range, the new result has a probability of being due to a statistical fluctuation at level of significance known among scientists as 2.2 sigma. This new result also excludes the possibility of the Higgs having a mass in the range from 147 to 179 GeV, Fermilab affirmed today in a press release.

However, the physicists claim evidence of a new particle only if the probability that the data could be due to a statistical fluctuation is less than 1 in 740, or three sigmas. They said a discovery is claimed only if that probability is less than 1 in 3.5m, or five sigmas.

The three-story, 6,000-tonne CDF detector takes snapshots of the particles that emerge when protons and antiprotons collide.

The three-storey, 6,000-tonne CDF detector takes snapshots of the particles that emerge when protons and antiprotons collide

They said today this result “sits well” within the constraints set out by earlier direct and indirect measurements made by CERN’s Large Hadron Collider (LHC), the Tevatron, and other accelerators. They’ve placed the mass of the Higgs Boson within the range of 115 to 127 GeV.

Fermilab said these latest Higgs Boson findings are also consistent with the December 2011 announcement of excesses seen in that range by LHC experiments, which searched for the Higgs in different decay patterns.

“None of the hints announced so far from the Tevatron or LHC experiments, however, are strong enough to claim evidence for the Higgs boson,” it said.

Speaking today, Jim Siegrist, the US Department of Energy associate director of science for high energy physics, said the “end game is approaching in the hunt for the Higgs Boson”.

“This is an important milestone for the Tevatron experiments, and demonstrates the continuing importance of independent measurements in the quest to understand the building blocks of nature,” he added.

Dmitri Denisov, DZero co-spokesperson and physicist at Fermilab, spoke about how there is still a lot of work ahead before the scientific community can say for sure whether the Higgs Boson exists.

“Based on these exciting hints, we are working as quickly as possible to further improve our analysis methods and squeeze the last ounce out of Tevatron data,” Denisov.

Fermilab indicated today that only high-energy particle colliders such as the Tevatron and LHC can recreate the energy conditions found in the universe shortly after the Big Bang. According to the Standard Model, the theory that explains and predicts how nature’s building blocks behave and interact with each other, the Higgs Boson gives mass to other particles.

Higgs Boson strides at Tevatron and the LHC at CERN

Before it closed last September, the Tevatron was a proton/anti-proton collider, with a maximum centre of mass energy of 2 TeV. Meanwhile, the LHC is a proton/proton collider that will ultimately reach 14 TeV.

Fermilab physicists said that because the two accelerators collide different pairs of particles at different energies and produce different types of backgrounds, the search strategies are different.

Rob Roser, CDF co-spokesperson and physicist at Fermilab, said the result revealed today represents years of work from hundreds of scientists around the world.

“But we are not done yet,” he said. “Together with our LHC colleagues, we expect 2012 to be the year we know whether the Higgs exists or not, and assuming it is discovered, we will have first indications that it behaves as predicted by the Standard Model.”

Carmel Doyle was a long-time reporter with Silicon Republic