Synopsis: Higgs-like Particle in a Mirror

The particle thought to be the Higgs boson seems likely to pass an important identity check.

Physicists have been searching for the Higgs boson for nearly 50 years. In July 2012, two collaborations at the Large Hadron Collider at CERN announced the discovery of a new particle that meets the general expectations for a Higgs boson. But is this particle the final piece of the standard model, or something more exotic?

One important test is the parity of the particle: how its mirror image behaves. In a mirror, even-parity particles look the same, whereas odd-parity particles appear reversed. The standard model Higgs boson is a scalar, a spin-0 even-parity particle. But there are many models that include a spin-0 odd-parity particle known as a pseudoscalar.

For the first time, the CMS Collaboration at the LHC has placed constraints on this possibility. They study decays of the new particle to a pair of Z bosons, each of which, in turn, decays to a pair of leptons. They analyze the angular distribution of the leptons under the assumption that the new particle is spin 0, and find that the odd-parity pseudoscalar scenario is disfavored, having an effective statistical p value of only 2.4%. So all the evidence thus far is consistent with the new particle being the standard model Higgs boson. – Robert Garisto


More Announcements »

Subject Areas

Particles and Fields

Previous Synopsis

Quantum Information

Hitting Reset After a Quantum Measurement

Read More »

Related Articles

Viewpoint: Ghostly Neutrino Comes into Sharper Focus
Particles and Fields

Viewpoint: Ghostly Neutrino Comes into Sharper Focus

The first results from the NOvA experiment set new constraints on charge-parity violation in neutrinos and on the ordering of neutrino masses. Read More »

Synopsis: Explaining a 750  GeV Bump
Particles and Fields

Synopsis: Explaining a 750 GeV Bump

Theorists try to explain data from the LHC that could be hinting at the existence of new particles. Read More »

Synopsis: The Heavy Limit of Dark Matter
Particles and Fields

Synopsis: The Heavy Limit of Dark Matter

A theoretical investigation of super-heavy dark matter particles finds that their existence might be discerned in the cosmic microwave background. Read More »

More Articles