Synopsis: Narrowing the Range of Possibilities

Particle discoveries attract the most attention, but determining where not to look can be just as important.

On 4 July 2012, two experimental collaborations at the Large Hadron Collider, ATLAS and CMS, reported the discovery of a new particle that appears to be the Higgs boson, though further measurements will be needed for confirmation. In Physical Review D, the ATLAS collaboration presents the techniques that were used in their experiments, as well as an analysis of all their data collected in 2011, which allowed them to exclude wide ranges of possible mass values for the Higgs boson.

The existence of the Higgs boson is a crucial test of the electroweak symmetry breaking mechanism of the standard model of particle physics (see 13 March 2012 Viewpoint), but its mass can only be determined experimentally. The rate at which high-energy proton-proton collisions will produce the Higgs boson and the rate of its decay to various other elementary particles are known for a given Higgs mass. However, other processes can produce the same final particles; this is referred to as background.

In 2011, the ATLAS collaboration searched for the Higgs boson in the mass range of 110600 giga-electron-volts (GeV) in several decay channels, including decay to a pair of photons and decay to four leptons via a pair of Z bosons. By comparing their data with the expected background, the team was able to exclude wide mass ranges in which the Higgs boson could lie, leaving only two small windows between about 116 and 130 GeV. Furthermore, around a mass of 126 GeV, their data show hints of a new particle compatible with being a Higgs boson at the 3σ level. – Urs Heller


Features

More Features »

Announcements

More Announcements »

Subject Areas

Particles and Fields

Previous Synopsis

Materials Science

Doing a Crack Job on Aluminum

Read More »

Next Synopsis

Related Articles

Viewpoint: Spinning Black Holes May Grow Hair
Gravitation

Viewpoint: Spinning Black Holes May Grow Hair

A spinning black hole may lose up to 9% of its mass by spontaneously growing “hair” in the form of excitations of a hypothetical particle field with a tiny mass. Read More »

Synopsis: Proton Loses Weight
Particles and Fields

Synopsis: Proton Loses Weight

The most precise measurement to date of the proton mass finds a value that is 3 standard deviations lower than previous estimates. Read More »

Viewpoint: Scattering Experiments Tease Out the Strong Force
Particles and Fields

Viewpoint: Scattering Experiments Tease Out the Strong Force

The scattering of protons from a carbon isotope can be used to test models of the strong force. Read More »

More Articles