From Fermilab: “Frontier Science Result: CMS – ‘Is it the Higgs boson?’ “

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Fermilab Campus

Friday, Jan. 11, 2013
Don Lincoln

“On July 4, 2012, the CMS and ATLAS experiments announced the discovery of a new particle with a mass of 125 GeV. This particle was widely heralded in the press as the Higgs boson, but both experiments very carefully didn’t make that claim. Instead, both experiments used the language “a particle consistent with being a Higgs boson.”

One possible signature of a Higgs boson from a simulated collision between two protons. It decays almost immediately into two jets of hadrons and two electrons, visible as lines. (Wikipedia)

So why were the experiments so cagey in their announcement?

So what do we know? Well, evidence suggested that the discovered boson decayed into pairs of fermions (bottom quarks and tau leptons, both with spin 1/2) and pairs of bosons (W and Z bosons and photons, with spin 1). From this simple observation, we can infer that the newly discovered particle was electrically neutral (a prediction of Higgs theory) and was a boson (another successful prediction). In addition, using what we know about the spin of the decay products and combining that with the rules of quantum mechanics, we also know from the particle’s decay into bosons that the spin of the parent had to be 0 or 2.

A spin 0 particle would support the Higgs hypothesis, while a spin 2 particle, not being predicted, might be even more interesting. On the other hand, the universe might be malicious, and the July 2012 announcement could be referring to not only one, but maybe two particles, with spins of 0 or 2 and with masses close enough to each other that we thought we were seeing just one particle when we might actually have been seeing two….”

Now it is getting really deep and intense, so see Don’s full article here.

Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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