At the March 14, 2013 Rencontres de Moriond conference in La Thuile, Italy, CERN physicists confirmed the new fundamental particle discovered in the Large Hadron Collider is a Higgs boson. Ever cautious, CERN labeled the findings “preliminary new results.” The existence of still heavier Higgs bosons remains an open question.
A Higgs Boson
In July of last year, CERN scientists announced they had found a new “Higgs-like” particle. Now, after analysis of 2.5 times more data, physicists from the ATLAS and CMS teams are confident the new boson — at a mass of around 126 GeV (gigaelectron volts) — is indeed a Higgs.
In the latest Geneva press release, CMS spokesperson Joe Incandela said:
“ . . . the full 2012 data set are magnificent and to me it is clear that we are dealing with a Higgs boson, though we still have a long way to go to know what kind of Higgs boson it is.”
The venerated Standard Model of particle physics predicts the existence of a single Higgs boson, although it does not specify its mass. Yet to be substantiated theories such as supersymmetry predict multiple Higgs bosons. To search for additional Higgs particles, CERN is upgrading its Large Hadron Collider to run at twice its current energy by 2015.
Higgs: Spin and Parity
Why do CERN physicists feel they have seen evidence of a Higgs boson? The Higgs is an unstable particle which lives for the tiniest fraction of a second. It then transforms or decays into lighter particles. The angles at which these lighter particles scatter tell physicists the spin and parity of the original particle. The data indicates a spin of zero and positive parity — just the characteristics of a Higgs boson predicted by the Standard Model. Other data support the Higgs findings as well.
According to ATLAS spokesperson Dave Charlton:
“The beautiful new results . . . point to the new particle having the spin-parity of a Higgs boson as in the Standard Model.”
To get an idea of what spin is, imagine a skater spinning on ice. Like all rotating objects, her body possesses angular momentum. This is a product of her mass, how fast she is spinning, and how much her body is spread out. When she pulls her arms in, she spins faster. Why? Because her body mass is now concentrated in a smaller space. She must spin faster to keep her angular momentum the same. This is the Law of Conservation of Angular Momentum at work.