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Elusive Higgs Particle May No Longer Be Hiding

Scientists say they are closer to explaining how matter got its mass.

Some of the Duke physics students and faculty who hunt for the Higgs celebrate the new particle discovery at CERN. Image courtesy of Al Goshaw, Duke.
Some of the Duke physics students and faculty who hunt for the Higgs celebrate the new particle discovery at CERN. Image courtesy of Al Goshaw, Duke.

Duke scientists are among those around the world claiming victory on the hunt for the Higgs boson.

While they won't declare they've detected the Higgs itself, the physicists announced July 4 that they did discover a new particle that closely resembles the Higgs.

"I have no hesitation of calling this a discovery of a new particle, one that looks exactly like what we need for the Higgs," said Duke physicist Al Goshaw. He uses an experiment called ATLAS, to hunt for the elusive particle, one of two Higgs-hunting experiments at the Large Hadron Collider outside Geneva, Switzerland.

But like his colleagues, Goshaw is careful not to overstate the results.

Finding the particle is important to physicists because, according to their simplest explanation of nature, called the standard model, without the Higgs, the fundamental building blocks of the universe would not combine to make molecules and ordinary matter.

The standard model has been repeatedly confirmed in other experiments, but finding the Higgs particle, along with another particle discovered in 1993, really completes the model.

The new results are the first, most convincing appearance of the Higgs, which was predicted to exist in 1964. Goshaw said the "biggest surprise" to both teams was that even though they work independently, they both had an "equally strong, consistent signal. That just carried the day." The results were announced at CERN, where the LHC is housed, and also at the International Conference on High Energy Physics in Melbourne, Australia.

According to the results, the experiments, ATLAS and CMS, each produced data showing that the new Higgs-like particle had a mass of 125-126 GeV, about 134 times the mass of the proton. "There's only a one in a million chance, for each experiment, that the results are an erroneous fluctuation, a statistic that typically signifies a discovery in science," Goshaw said. The LHC results also align well with the July 2 findings announced from the US-based Tevatron particle accelerator.

Even though the Higgs is larger than a proton, it can be trapped and its signature is fleeting, appearing only once in a trillion collisions.

Despite the eruption of cheers in the LHC auditorium and "a lot of backslapping in the hallways," according to Goshaw, physicists using LHC and Tevatron have been careful not to call the new particle the Higgs particle. That's because "it remains to be seen if what has been discovered is indeed the Higgs boson of the standard model," said Mark Kruse, another Duke physicist who collaborates on the ATLAS experiment.

He explained that the physicists "just don't yet know" if this is the "one Higgs particle" that completes the standard model, or if it is one of five Higgs particles in a much more exotic description. What is "now clear" from the LHC findings is that "something new has been seen that will open up a whole new era of exploration, making this a very exciting time in particle physics," Kruse said.

Once physicists know if this is the standard model Higgs or one of many in a more complex description of nature, "we will be one step further in our quest for an understanding of what happened in the first trillionth of a second of the Universe that made it what it is today," Kruse said. He added that "if indeed we have found it, is by no means the end of the story, in fact in some sense it is only the beginning."

Professor Ashutosh Kotwal, Director of Particle Physics at Duke and ATLAS Higgs-hunter, said he thinks, as many others do, that "we have just seen the tip of the iceberg." He said he "hopes the plot thickens, and we see some unexpected behavior in the different Higgs signatures" and that "nature throws us a curve ball."

But writing more of the Higgs story and figuring out its curveballs will have to wait. The LHC is to be shutdown at the end of 2012 for a year and a half. During that time, engineers will tweak the accelerator to make it able to collide particles at nearly two times the energy at which it slams them together now. It's in 2014, at these higher energies, that physicists may begin to see other new phenomena beyond the standard model, Goshaw said.

Duke faculty and graduate students involved in the project are: Ayana Arce, Doug Benjamin, Andrea Bocci, Al Goshaw, Ashutosh Kotwal (HEP Director), Mark Kruse (Deputy Team Leader), Seog Oh (Team Leader), Geumbong Yu, Chiho Wang; Graduate Students: Benjamin Cerio, Kevin Finelli, Lei Li, Mia Liu, Chris Pollard.