Fermilab Today

CERN's ATLAS and CMS experiments presented combined measurements of the Higgs boson for the first time since the particle was discovered in 2012.. Image: CERN

Three years after the announcement of the discovery of a new particle, the so-called Higgs boson, the ATLAS and CMS collaborations present for the first time combined measurements of many of its properties, at the third annual Large Hadron Collider Physics Conference (LHCP 2015). By combining their analyses of the data collected in 2011 and 2012, ATLAS and CMS draw the sharpest picture yet of this novel boson. The new results provide in particular the best precision on its production and decay and on how it interacts with other particles. All of the measured properties are in agreement with the predictions of the Standard Model and will become the reference for new analyses in the coming months, enabling the search for new physics phenomena. This follows the best measurement of the mass of the Higgs boson, published in May 2015 after a combined analysis by the two collaborations.

"The Higgs boson is a fantastic new tool to test the Standard Model of particle physics and study the Brout-Englert-Higgs mechanism that gives mass to elementary particles," said CERN Director General Rolf Heuer. "There is much benefit in combining the results of large experiments to reach the high precision needed for the next breakthrough in our field. By doing so, we achieve what for a single experiment would have meant running for at least two more years."

There are different ways to produce a Higgs boson and different ways for a Higgs boson to decay to other particles. For example, according to the Standard Model, the theory that best describes forces and particles, when a Higgs boson is produced, it should decay immediately in about 58 percent of cases into a bottom quark and a bottom antiquark. By combining their results, ATLAS and CMS determined with the best precision to date the rates of the most common decays.

From Quantum Diaries

An experimental road trip

Scientist Bo Jayatilaka assumes the driver seat in a Tesla Model S P85D as part of a two-day road trip. Photo: Sam Paakkonen

On May 31, about 50 miles from the Canadian border, an electric car struggled up steep hills, driving along at 40 miles per hour. The sun was coming up and rain was coming down. Things were looking bleak. The car, which usually plotted the route to the nearest charging station, refused to give directions.

"It didn't even say turn around and go back," said Bo Jayatilaka, who was driving the car. "It gave up and said, 'You're not going to make it.' The plot disappeared."

Rewind to a few weeks earlier: Tom Rammer, a Chicago attorney, had just won two days with a Tesla at a silent cell phone auction for the American Cancer Society. He recruited Mike Kirby, a Fermilab physicist, to figure out how to get the most out of those 48 hours.

Rammer and Kirby agreed that the answer was a road trip. Their initial plan was a one-way trip to New Orleans. Another involved driving to Phoenix and crossing the border to Mexico for a concert. Tesla politely vetoed these options. Ultimately, Rammer and Kirby decided on an 867-mile drive from Chicago to Boston. Their goal was to pick up Jayatilaka, a physicist working on the CMS experiment, and bring him back to Fermilab. To document their antics, the group hired a film crew of six to follow them on their wild voyage from the Windy City to Beantown.

—Ali Sundermier

In Brief

Breaking out the blankets at the Technical Division picnic

Julie Kurnat (right) and other picnickers listen to the announcements of the raffle winners. Photo: Tom Nicol, TD

From left: Mike Jeeninga, Brent Sylvester, Darrell Frye and Armando Barboza (all of TD) cook meat on the grill for their colleagues. Photo: Tom Nicol, TD

It's not a picnic until you spread a blanket on the grass. Sergey Antipov, Paola Buitrago, Anu Ghosh and Gerald Quiroz share a Technical Division blanket (notice the label on the blanket's front right corner). Photo: Tom Nicol, TD

Yuenian Huang, TD, was one of this year's raffle winners. He won a four-piece pliers set. Photo: Tom Nicol, TD

The Technical Division held its annual picnic at Kuhn Barn on Thursday. Raffle prizes were given away, and people enjoyed their food on custom picnic blankets, courtesy of the Technical Division.

Photo of the Day

Apple picking

Geese go apple picking in the Village. Photo: Sudeshna Ganguly, University of Illinois at Urbana-Champaign

In the News

The case for complex dark matter

From Quanta Magazine, Aug. 20, 2015

Dark matter — the unseen 80 percent of the universe's mass — doesn't emit, absorb or reflect light. Astronomers know it exists only because it interacts with our slice of the ordinary universe through gravity. Hence the hunt for this missing mass has focused on so-called WIMPs — Weakly Interacting Massive Particles — which interact with each other as infrequently as they interact with normal matter.

Physicists have reasons to look for alternatives to WIMPs. For two decades, astronomers have found less dark matter at the centers of galaxies than what WIMP models suggest they should. The discrepancy is even worse at the cores of the universe's tiny dwarf galaxies, which have few ordinary stars but lots of dark matter.