Unknown particle ‘near match’ for Higgs

RICE (US) — Physicists have announced the observation of a never-before-seen particle, which may turn out to be the Higgs boson or something new and equally important.

The search for the Higgs particle is at the heart of the most expensive science project in history—CERN’s $6 billion Large Hadron Collider (LHC).


In the announcement, LHC officials in Geneva, Switzerland, stopped short of declaring a victory in the Higgs search, saying instead that they have found a new particle with properties that make it a likely match for the supermassive Higgs particle.

“To use an analogy from CSI: We’ve found a body, but we need to wait for the DNA results to declare it the Higgs,” says Rice University particle physicist Paul Padley, a co-investigator on the LHC Compact Muon Solenoid (CMS) experiment.

“We’re not calling this the Higgs for the same reason the police don’t guess about the identity of a body. It’s our responsibility to be sure.”

The search for the Higgs particle marks a historic turning point in physics: The particle is the final unobserved piece of a puzzle called the Standard Model (SM), a model which jibes with every particle physics experiment ever performed. The Higgs, a type of particle known as a boson (pronounced “BOH-sahn”), is one of the linchpins of the SM.

“In our current understanding, all of the fundamental particles of nature get their mass through the Higgs mechanism,” says Frank Geurts, assistant professor of physics and astronomy and a co-investigator on the CMS experiment.

“So, if we don’t find the Higgs particle—if that’s not there—then we seriously have to rethink why we exist at all.”

Padley says the search for the Higgs at LHC is one of the greatest endeavors in human history. “There are multiple experiments at LHC, and on the CMS experiment alone there are more than 3,000 scientists from 179 institutions in 41 countries. The experiment recreates conditions that existed in the first billionth of a second after the Big Bang.”

Geurts, Padley, and assistant professor Karl Ecklund, who have each devoted many years to the search for the Higgs boson, say the only prospect more exciting than finding the long-anticipated Higgs is finding something completely unexpected.

“When I was a physics undergraduate, we were taught that the expansion of the universe was slowing,” Padley says. “Whether or not the universe would one day collapse upon itself was an open question, and the Hubble Space Telescope was launched, in part, to answer that question.

“What the Hubble found was utterly shocking,” Padley says. “The Hubble found the universe was expanding faster and faster every second. It was completely new and totally unexpected knowledge, and that is exactly the sort of unpredictable discovery we expect to find with the LHC once it ramps up to full power.”

Rice physicists played a key role developing some of the electronic systems that sort CMS data in real time and select what to keep for future analysis. That’s no simple task because the CMS experiment produces 40 terabytes of data—enough to fill more than 8,500 DVD discs—each second. And a single run of the machine can last for weeks or even months.

Rice researchers also contributed to the CMS pixel detector, which is like a 66-megapixel camera that snaps a photo 40 million times per second. Located just 4 centimeters from the head-on proton collisions in the LHC, the pixel detector records the trajectories of hundreds of particles that are produced in the collisions, and it helps sort through the debris of the collisions so that CMS physicists can reconstruct which particles are produced in any given collision.

They also helped build and maintain some of the electronics that mine collision data in real time and flag collisions, which are often referred to as “events,” that should be saved for future analysis. These stored events provided the data that scientists needed to confirm today’s announcement about the likely candidate for the Higgs particle.

“The science unveiled today could not have happened without Rice’s hardware and software as well as hundreds of other critical components that were conceived and created at universities and national laboratories the world over,” says Ecklund.

In addition to Padley, Geurts, and Ecklund, Rice Department of Physics and Astronomy faculty co-investigators at LHC include Professor Jay Roberts and , Assistant Professor Wei Li.

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