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Physicists study Higgs boson

Lesley Stevenson | Wednesday, March 20, 2013

Researchers from a global collaboration, including Notre Dame faculty and students, presented findings further characterizing the recently-documented Higgs boson on Thursday in La Thuile, Italy.

Physics professor Colin Jessop, one of the researchers, called the findings “the biggest discovery of particle physics for the past 50 years.”

“We can say with some surety now that the particle that we observed is the Higgs boson, or what some people call the ‘God particle,'” Jessop said.

The Higgs boson is a particle created in the high-impact, high-energy collision of protons at CERN’s Large Hadron Collider (LHC) in Geneva, Switzerland. CERN is the European Organization for Nuclear Research.

Jessop said all objects gain their property of mass through interaction with the Higgs field.

“If you create enough energy to interact with this field, you’ll make what’s called a Higgs boson, a particle that is kind of the smoking gun that there’s a Higgs field there,” Jessop said.

Jessop said researchers now can confirm that the experimental particle’s basic characteristics, including spin and parity, match those of the theoretical Higgs boson.

“In the last six months, we’ve been taking two-and-a-half times more data since July,” he said. ” and the results that we presented [in Italy] were evidence that the particle we discovered behaves exactly as we thought it was going to.” Jessop said the team confirmed the experimental Higgs boson interacts with fermions, the essential components of matter, the way it theoretically should. Until now, Jessop said researchers had not observed interactions between the Higgs boson and fermions.

“It’s supposed to interact with everything – that’s how it gives mass,” he said. “So, if there were a set of particles it didn’t interact with, then it wouldn’t have been the Higgs boson we thought it was. … We showed that the Higgs boson interacts with all the particles we thought it should.” Jessop said the findings support evidence scientists in the(Compact Muon Solenoi) Collaboration,nwhich includeg the Notre Dame team, gathered last year that suggesg the existence of the Higgs boson

“We started seeing the hints of this about a year ago at this time,” Jessop said. “we started to see some evidence, but not conclusive.”Then the signals got stronger and stronger, and in July we had a big announcement that we had observed something that looked like a Higgs boson, but we weren’t absolutely sure.”
Jessop said building accelerators able to supplh enough energy for the proton collision has been the keynobstacle to finding the Higgs boson.

“We’ve been looking to try to make one of these Higgs bosons by putting more and more energy into it … but we haven’t been able, as it turns out, to get to sufficient energy until just recently.” Jessop said.  Notre Dame sends postdoctoral researchers and graduate students to the LHC for a hands-on experience, Jessop said.

“All the people who do the hard work really are the young people, the graduate students and the [post-doctorate studentss,” he said.
Postdoctoral research associatr Jeff Kolb said he and graduate students Nil Valls and Doug Berry spent time living in Europe, not just writing computer codes to analyze data, but alsokworking on the experiment’s equipment.

In order to be listed as an author, Kolb said students must word for a year on something other than data analysis, among other requirements.

Valls said looking for evidence of the Higgs boson was the chief difficulty in analyzing the 20 petabytes (the equivalent of 20 million gigabytes) of data per year.scientists produce at the LHC.

“It’s like looking for a needle in a haystack,” Valls said. “Writing code is inevitable, for grad students at least, because that is the best way to sort of look for those needles.”

Jessop said Higgs research continues despite the temporary halt of collisions at the LHC to allow upgrades meant to double the energy of the accelerator. Data collections will resume in 2016 and continue througo 2020, he said. the Notre Dame team will continue working to improve the Higgs detector for the program’s second phase from 2023 to 2035.

“At the new energy there is a good possibility of further new discoveries in addition to continuing to study the Higgs in detail,” Jessop said. …We’ve had a giant success, but for us it’s kind of a beginning.”