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In 1964, British physicist Peter Higgs postulated that mass came from elementary particles, namely from a special kind of boson, or the Higgs boson. This particle was thought to exist shortly after the Big Bang – more specifically, at the time when particles gained mass.
The Higgs is predicted by the Standard Model, a chart that describes how elementary particles and the four universal forces (electromagnetic, weak nuclear force, strong nuclear force, and gravity) behave and interact with one another. If the Higgs boson’s existence were to be confirmed, not only would the mysterious particle complete the Model, but it would also fix any inconsistencies.
In December 2011, particle physicists at the Large Hadron Collider (LHC) at CERN (Conseil Européen pour la Recherche Nucléaire, or the European Council for Nuclear Research) noticed unexpected energy fluctuations in the data during their experiment. These fluctuations were thought to have been caused by the Higgs boson decaying. (When particles decay, the emit energy).
There were doubts about the Higgs causing the fluctuations; since then, the LHC, Tevatron, and other particle accelerator laboratories around the have collaborated to search for the Higgs boson, hoping to find correlations of spikes of energy in the graphs.
Last Friday, Tevatron became successful. Its CDF and DZero experiments, working separately, found similar spikes, but the energy was much greater. Previously, particle physicists have hypothesized the Higgs boson to have mass ranging from 115 to 135 gigaelectronvolts (GeV). However, this recent energy excess indicates that the Higgs may have a mass of 147 to 179 GeV instead. Nevertheless, the fluctuations were there, and the LHC and other particle accelerator laboratories have noted them too.
“We are not done yet,” Rob Roser, CDF co-spokesperson and physicist at Fermilab, insists in Fermilab’s press release. “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.”
To actually detect the Higgs boson is difficult. The particle decays quick enough for instruments not to catch their being. Furthermore, instead of decaying into only one or two particles, it decays into sets of particles, all of which are different each time. In order to make things a little simpler, Tevatron and the LHC will be using different methods to hunt for the Higgs.
The LHC, which is an underground circular collider, will smash protons together while using maximum mass energy of 14 GeV. Meanwhile, Tevatron, a synchrotron (a type of circular particle accelerator in which a particle beam travels, guided by a magnetic field), will smash protons and antiprotons together at maximum mass energy of 2 GeV and look for sets of bottom quarks – a type of quark – into which the Higgs boson may decay.
According to Fermilab, ultimately “[d]iscovering the Higgs boson relies on observing a statistically significant excess of the particles into which the Higgs decays and those particles must have corresponding kinematic properties that allow for the mass of the Higgs to be reconstructed.” With the two laboratories experimenting simultaneously, yet with dissimilar methods, particle physicists hope to come across more and better evidence.
“One picture may show a child that is blocked from the other’s view by a tree,” explains Gregorio Bernardi, DZero co-spokesperson at the Nuclear Physics Laboratory of the High Energies (LPNHE) in Paris.
“Both pictures may show the child but only one can resolve the child’s features. You need to combine both viewpoints to get a true picture of who is in the park. At this point both pictures are fuzzy and we think maybe they show someone in the park. Eventually the LHC with future data samples will be able to give us a sharp picture of what is there. The Tevatron by further improving its analyses will also sharpen the picture which is emerging today.”
Like the LHC, Tevatron aims to study the fundamental building blocks of the universe and relationship between matter and energy by trying to create the conditions that existed at the time of the Big Bang. Fermilab receives financial support from the United States’ Department of Energy.