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Tom Siegfried

It’s almost time to get to know the Higgs boson better

The Large Hadron Collider at CERN (inside of ATLAS detector shown) will resume particle collisions in January 2015, the start of a run that will reveal how the Higgs boson interacts with other particles to search for clues to new physics.

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COPENHAGEN — Higgs boson physicists and Doctor Who fans have something in common. They’ve met someone new and want to get to know them better.

Since Matt Smith regenerated into Peter Capaldi last year, every Whovian has been wondering about the details of the new Doctor’s personality, like how he’ll interact with Clara and his other intertemporalspatial acquaintances. It seems like it has been a long time between Doctor Who seasons.

Similarly, since the Higgs boson discovery was reported in 2012, every particle physics fan has been wondering what the details will be about how the Higgs interacts with nature’s other subatomic particles, leading to a deeper understanding of time and space. It seems like it has been a long time between data-collecting runs at the Large Hadron Collider, the European atom smasher that produced the Higgs by colliding protons together.

Happily, there’s good news in both universes. Doctor Who returns in August. Higgs fans need to wait a little longer: the Large Hadron Collider will restart collisions in January 2015, CERN director Rolf-Dieter Heuer announced June 23 at the EuroScience Open Forum conference.

It will be Easter or so, he said, before actual scientific data collection will resume. Eventually, the new LHC experimental run will attain collision energies of 14 teraelectron volts, twice the energy of the collisions that enabled discovery of the Higgs boson. But at first, the LHC will operate at 13 TeV. The powerful magnets that guide proton beams around the collider’s 27-kilometer tunnel need to be prepared for higher energy, and they can be more easily prepared for 13 TeV. After a few months or perhaps a year, the magnets should be ready to cope with the 14 TeV goal.

With the higher energies, the LHC should be able to go beyond merely identifying the Higgs, the particle famous for providing nature’s other basic particles with mass. The new LHC data should enable more precise determinations for various properties of the Higgs boson.

“At the moment we don’t know it as well as we know the other elementary particles,” Fabiola Gianotti, who works on the ATLAS experiment at the LHC, said in a news briefing.

“As it happens with a new friend, you want to know him or her better,” she said. “And so we are going to measure it in all details, to do a complete scan…. What we are going to do is to measure the way the Higgs boson interacts with the other particles.”

As Heuer pointed out, physicists have their expectations about how those interactions should be quantified. Deviations from those expectations will get scientists excited, because that would signify the discovery of unknown aspects of physics.

“It’s a door to new physics,” said Gianotti. “The problem is, where is the new physics?”

Many physicists hold high hopes that the LHC data will disclose where the new physics has been hiding, in the process answering some of the long-term outstanding questions about nature that have resisted answers by other means. Why the universe seems to be composed of vastly more matter with very little antimatter, for instance. And what the identity is of the particle that makes up dark matter, which is more abundant in the cosmos than ordinary atomic matter by something like 5-to-1.

Gianotti and Heuer both emphasized that it could still take many years to wrest nature’s secrets from the LHC’s data. The LHC’s second run, like the first, should last three years before it is shut down again for further improvements. And it will keep on going from there.

“All together, we foresee at the moment a 20 years’ additional program at the LHC,” Heuer said. If all goes as planned, that would mean the number of proton-proton collisions recorded by 2035 would total about 100 times as many as those collected so far.

“There’s a huge amount of physics to be done,” Heuer said. “Discovering the Higgs boson is easy. The work starts now.”

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