Evidence of the Higgs particle's decay in quarks

July 19, 2017, University of Freiburg
The illustration shows an event that could be the sought-after decay of the Higgs particle in quarks. Credit: ATLAS collaboration

As part of the ATLAS collaboration, the Freiburg research group led by Prof. Dr. Karl Jakobs and Dr. Christian Weiser has contributed to finding strong evidence that, among other things, the Higgs particle decays into quarks. The researchers analyzed data sets that were recorded in 2015 and 2016 with the ATLAS detector at the world's largest particle accelerator, the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland.

"The strong evidence that the Higgs particle, as predicted by theory, decays into quarks provides yet another essential piece to the puzzle about this particle," says Weiser, who leads the research activity in Freiburg. "The goal now is to prove the decay exists beyond a shadow of a doubt and, based on this knowledge, to measure the Higgs particle's properties more accurately."

As a result, measuring the decay is extremely important for the researchers in order to explain the short lifespan of the Higgs particle. Measurable deviations from standard theory's predictions could point to so-called new physics, which reaches beyond the Standard Model.

The discovery of the Higgs particle through the ATLAS and CMS experiments at the LHC accelerator in CERN in 2012 presented a milestone in physics even as the particle's existence had been predicted nearly 50 years prior to that. It is a most short-lived particle that decays into other particles nearly the moment it is produced.

The rate with which decays into various particles occur can be computed within the framework of the underlying theory. Up to now, researchers have been able to fully prove the decay into other particles - so-called W and Z bosons, photons and tau leptons. But they had not been able to observe the Higgs particle's decay into a couple of b-quarks that is expected to occur with the largest rate of around 60 percent probability. The reason is that a number of other processes exist that are hard to differentiate from the Higgs particle's decay in b-quarks and that occur at a much higher rate.

But now they have discovered new evidence: The probability that the observed signal is feigned solely by other processes is only 0.018 percent. The presentation of these findings was one of the highlights of the conference run by the European Physical Society (EPS) that was held July 5-12, 2017 in Venice, Italy.

Explore further: Probing physics beyond the Standard Model with the ATLAS Experiment

More information: press.cern/update/2017/07/lhc- … lve-deeper-precision

Related Stories

Evidence found for the Higgs boson direct decay into fermions

June 22, 2014

For the first time, researchers at CERN have found evidence for the direct decay of the Higgs boson into fermions—another strong indication that the particle discovered in 2012 behaves in the way the standard model of particle ...

Maybe it wasn't the Higgs particle after all

November 7, 2014

Last year CERN announced the finding of a new elementary particle, the Higgs particle. But maybe it wasn't the Higgs particle, maybe it just looks like it. And maybe it is not alone.

ATLAS sees Higgs boson decay to fermions

November 28, 2013

The ATLAS experiment at CERN has released preliminary results that show evidence that the Higgs boson decays to two tau particles. Taus belong to a group of subatomic particles called the fermions, which make up matter. ...

Recommended for you

Physicists build fractal shape out of electrons

November 12, 2018

In physics, it is well-known that electrons behave very differently in three dimensions, two dimensions or one dimension. These behaviours give rise to different possibilities for technological applications and electronic ...

Atomic parity violation research reaches new milestone

November 12, 2018

A reflection always reproduces objects as a complete mirror image, rather than just its individual parts or individual parts in a completely different orientation. It's all or nothing, the mirror can't reflect just a little. ...

Innovative experimental scheme can create mirror molecules

November 12, 2018

Exploring the mystery of molecular handedness in nature, scientists have proposed a new experimental scheme to create custom-made mirror molecules for analysis. The technique can make ordinary molecules spin so fast that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.