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'Enormous Breakthrough' Confirms Particle Discovered in 2012 was Higgs Boson

Jun 23, 2014 11:35 AM EDT

In a recent scientific breakthrough, researchers at CERN laboratory in Geneva have succeeded in finding the first evidence of the direct decay of the Higgs boson particle into fermions, a "strong indication" that the particle discovered in 2012 is indeed the Higgs boson.

Previously, the Higgs particle could only be detected through its decay into bosons. Now, these findings confirm that bosons decay to fermions - a group of particles that includes all leptons and quarks - as predicted by the Standard Model of particle physics.

"This is an enormous breakthrough," lead researcher Markus Klute, an assistant professor of physics at MIT, said in a university news release. "Now we know that particles like electrons get their mass by coupling to the Higgs field, which is really exciting."

In July 2012, scientists announced they had discovered what they thought was the Higgs boson particle following experiments at CERN, the European Organization for Nuclear Research.

Even though the new particle's properties were consistent with those predicted for the Higgs boson by the Standard Model, more evidence was needed to confirm this.

"What we are trying to do is establish whether this particle is really consistent with the Higgs boson, the particle we predict in our Standard Model, and not one of many Higgs bosons, or an imposter that looks like it but has a different origin,"Klute explained.

This new study, published in the journal Nature Physics, shows that the new particle is in line with the Standard Model. It sits in the mass-energy region of 125 to 126 gigaelectronvolts (GeV), has no spin, and it can decay into a variety of lighter particles - photons, W bosons, or Z bosons.

However, it remained uncertain whether they could also decay to fermion pairs, Klute says.

Since the Higgs particle is extremely short-lived, it cannot be detected directly, but rather only via its decay products. In order to detect fermions, the researchers were hunting for particles called tau leptons - particles that are about 3,500 times heavier than electrons - because they are much easier to spot.

The findings showed decay to tau leptons, with authors saying there was just a one in 10,000 chance that the signal they saw would have appeared without Higgs particles.

Despite the confidence in their breakthrough discovery, researchers want to be absolutely sure.

"Within the current level of precision there is still room for other models with particles that look like the Standard Model Higgs, so we need to accumulate more data to figure out if there is a deviation," they concluded.

The Large Hadron Collider is currently undergoing an upgrade, and won't begin operating again in 2015. Once it's back in business, Klute and researchers will continue with collision experiments.

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