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New Evidence Surfaces In Favor Of Higgs Boson Discovery

June 24, 2014
Image Caption: Event recorded with the CMS detector in 2012 at a proton-proton centre of mass energy of 8 TeV. The event shows characteristics expected from the decay of the SM Higgs boson to a pair of photons (dashed yellow lines and green towers). The event could also be due to known standard model background processes. Credit: CERN 2012/CMS Collaboration

John P. Millis, Ph.D. for redOrbit.com – Your Universe Online

Nearly two years ago the physics community was abuzz with news that researchers at the LHC had found evidence of the Higgs Boson, the long sought particle that could finally explain where all particles in the Universe get their mass. However, this initial finding was only the beginning.

The data only revealed that the team had found a Higgs-like particle, one that exhibited the expected behavior predicted by theorists. But additional work would need to be done to confirm that this was, in fact, the smoking gun. Now, scientists have found new data that supports the initial findings.

“In July 2012, we knew we had discovered some sort of boson, and it looked a lot like it was a Higgs boson,” reports Paul Padley, a professor of physics and astronomy at Rice University, and co-author of the new study. “To firmly establish it’s the Standard Model Higgs boson, there are a number of checks we have to do. This paper represents one of these fundamental checks.”

While the LHC is shut down to upgrade the accelerator – eventually allowing it to operate at even higher energies – scientists working on the project are continuing to sift through the massive amount of data accumulated through 2012. According to Padley, “[it’s] like doing the analysis at a crime scene, when they look to see which gun fired the bullets. As we find more evidence, it looks more like a Standard Model Higgs boson. This paper is important because it really establishes that it’s decaying to fermions.”

Fermions are a class of particle that includes fundamental particles such as quarks and leptons. Since the Higgs Boson cannot be observed directly, the scientists look for traces of these fermions streaming through the detector from the decay of the Higgs. Then by analyzing the paths of the fermions, physicists can find where the Higgs particle emerged in the particle interaction.

“We’re able to connect the dots to see these tracks,” says Karl Ecklund, an assistant professor of physics and astronomy at Rice University. “For the Higgs studies, particularly in the case of the fermions, we’re looking for Higgs-to-bottom quarks and Higgs-to-tau (antitau) pairs. Taus are heavy versions of the electron.”

Over the next couple of years, physicists will continue to pore over the data already accumulated, looking for new evidence of the Higgs. But in the summer of 2015, the LHC will resume data acquisition, and researchers are hopeful that even more opportunities for Higgs detections will be possible.

“It’s going to be focused on new things that could appear at higher energies,” Ecklund said. “One definite target will be seeing more Higgs bosons, which should tell us a lot more about their properties. The main excitement is going to be that because the energy is higher, we could produce the Higgs in association with other particles.”

Also, according to Ecklund, top quarks “should actually have the strongest coupling to the Higgs because the top quark and the Higgs combined make a fairly heavy thing to produce. We’re interested in understanding how the top quark fits into the Standard Model and whether, since it’s so heavy, it could have a special role in relating to the Higgs. Maybe there are hints of new physics that aren’t in the Standard Model. We know the standard model is incomplete.”

Of course, the Higgs is not the end of the story, in fact it is only the beginning. There are still many open questions in the world of particle physics; questions that physicists hope the Higgs particle can shed some light on.

“The first step is to measure with great precision the properties of the Higgs boson we’ve discovered, and then use it as a tool for further discovery. We’re trying to probe questions about the universe and dark matter. In fact, there was a big study of the priorities in particle physics, and the No. 1 priority for the entire field is to study the properties of this boson and use it as a tool for discovery. This represents a step down that path,” says Padley.

A paper on this research is published in the journal Nature Physics.


Source: John P. Millis, Ph.D. for redOrbit.com - Your Universe Online



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