Nav: Home

Direct coupling of the Higgs boson to the top quark observed

June 04, 2018

On 4 July 2012, two of the experiments at the CERN's Large Hadron Collider (LHC), ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact-Muon-Solenoid), reported independently the discovery of the Higgs boson. The discovery confirmed the existence of the last missing elementary particle of the Standard Model, half a century after the Higgs boson was predicted theoretically. At the same time the discovery marked also the beginning of an experimental programme aimed to determine the properties of the newly discovered particle. Now, the CMS collaboration achieved an important milestone in that programme.

Higgs boson and top quark-antiquark pair produced

In the Standard Model, the Higgs boson can couple to the particles of matter called fermions, with a coupling strength proportional to the fermion mass. While associated decay processes have been observed, the decay into top quarks, the heaviest known fermions, is kinematically impossible. Therefore, alternative routes for directly probing the coupling of the Higgs boson to the top quark are needed. One is through the production of a Higgs boson and a top quark-antiquark pair. This is the production mechanism that has now been observed for the first time, and in doing so, the CMS collaboration accomplished one of the primary objectives of the Higgs physics programme.

New techniques speed up data extraction

The extraction of these events from the LHC data is challenging as there are many mundane type of events that can mimic them. Identifying these events requires measurements from all CMS subdetectors, which makes the reconstruction quite complex. The team of Prof. Florencia Canelli of the Department of Physics at the University of Zurich developed, in collaboration with the CMS group of the ETH, sophisticated techniques that allowed CMS to increase the sensitivity to these events. As consequence, this milestone has been passed considerably earlier than expected. «The development of these techniques also open the possibility of increasing the sensitivity in many other areas of research at the LHC», says Canelli, who is also co-leading the physics group that studies top quarks.

Search for physics beyond the Standard Model

The present achievement is a case in point. With the observation of the coupling between the two heaviest elementary particles of the Standard Model, the LHC physics programme to characterize and more fully understand the Higgs boson has taken an important step. While the strength of the measured coupling is consistent with the Standard Model expectation, the precision of the measurement still leaves room for contributions from new physics. «In the coming years, much more data will be collected and the precision will be improved, in order to see if the Higgs boson reveals the presence of physics beyond the Standard Model», adds Florencia Canelli.

University of Zurich

Related Higgs Boson Articles:

Electrically charged higgs versus physicists: 1-0 until break
The last missing particle of the Standard Model, the Higgs boson, was discovered in 2012 in the experiments at the Large Hadron Collider.
On the trail of the Higgs Boson
In a quest to understand the production mechanisms for the Higgs Boson, Silvia Biondi from the National Institute of Nuclear Physics, Bologna, Italy investigated the traces of a rare process, called ttH, in which the Higgs Boson is produced in association with a pair of elementary particles referred to as top quarks.
New finding of particle physics may help to explain the absence of antimatter
With the help of computer simulations, particle physics researchers may be able to explain why there is more matter than antimatter in the Universe.
NYU Physicists develop new techniques to enhance data analysis for large hadron collider
NYU physicists have created new techniques that deploy machine learning as a means to significantly improve data analysis for the Large Hadron Collider (LHC), the world's most powerful particle accelerator.
SMU physicist explains the latest Higgs boson announcement in layman's terms
The discovery of the Higgs boson transforming as it decays into bottom quarks is a big step forward in the quest to understand how the Higgs particle enables fundamental particles to acquire mass.
Higgs particle's favorite 'daughter' comes home
In a finding that caps years of exploration into the tiny particle known as the Higgs boson, researchers have traced the fifth and most prominent way that the particle decays into other particles.
Researchers detect Higgs boson coupling with top quark
Detection of Higgs-top quark interaction at LHC by CMS and Atlas international collaborations, with Brazilian researchers participating, confirms theoretical predictions of Standard Model of particle physics.
Study provides insight into the physics of the Higgs particle
Physicists at the University of Bonn have succeeded in putting a superconducting gas into an exotic state.
USTC contributes to LHC experiment discovery on Higgs Boson
Research team from University and Science and Technology of China contributed much to the results of the ATLAS and CMS experiments at the Large Hadron Collider (LHC).
Photon loss won't hurt in quantum sampling, USTC researchers find
Research group of University of Science and Technology of China and Shanghai Institute of Microsystem and Information Technology carried out an experiment which brings a demonstration of quantum supremacy closer to reality.
More Higgs Boson News and Higgs Boson Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at