It's Official: New Particle is the Higgs – But Which Kind?
Last year’s tentative announcement of a “Higgs-like” boson (a key fundamental particle) based upon preliminary data analysis from the Large Hadron Collider’s (LHC) two massive detectors (ATLAS and CMS) has been officially confirmed, CERN scientists announced earlier today.
Despite the July, 2012 announcement of a 99% certainty (of the particle being the Higgs), the scientists working at the LHC needed a good deal more data to be absolutely sure; definitive proof of the existence of the long-sought-after particle — sometimes called the “god particle” despite scientists’ objections — would have to wait for a mountain of data collected from thousands more collision experiments conducted over the past seven months.
The new particle appears to have the tell-tale spin-parity characteristics of a real Higgs boson (that is, ‘0’ spin and positive parity), as predicted in the Standard Model (SM). The particle made its appearance at the 125 GeV (billion electron volts) energy level.
“The preliminary results with 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,” said CMS spokesperson Joe Incandela in a statement.
Questions Remain – More Than One Higgs
Once again, there remains some uncertainty as to this particle’s “true” identity. This is because, as it turns out, there is more than one type of Higgs out there — according to other theories of quantum physics. The Higgs confirmed today may actually be one of the lightest of the Higgs that are out there — coming in at 126 times the mass of a proton.
Detecting a Higgs boson is a rare event, as the Higgs only makes its appearance once in every trillion collisions or so. According to SM, the Higgs Boson — one of several bosons in SM — is associated with a field (the ‘Higgs field”) which confers mass onto some of the other particles as they emerge from this quantum field.
Never observed directly, a Higgs boson is determined by its branching fraction or ratio, that is, the sub-atomic particles that it decays into after appearing for a billionth of a second. For example, a Higgs could decay into two photons (a more common outcome; photons carry the electromagnetic force), or, two ‘W’ or ‘Z’ particles (which mediate the weak force), or, two ‘bottom’ quarks (one of which is an anti-quark), or, the “purest” Higgs signal: the decay of the Higgs into two ‘Z’ particles and then into four leptons (H -> ZZ -> llll). *
So, with some 200,000 bosons appearing per collision experiment, but with the Higgs type bosons only appearing rarely (and detected indirectly), there is yet a great deal more experimentation needed — and more data to sift through — to finally identify what type of Higgs we are dealing with. It could be the “vanilla” variety, which would support the Standard Model, or, perhaps some more exotic and fleeting form.
The Fate of the Universe Rests Upon a Single Particle’s Mass
One other note of interest here: the calculated mass of this Higgs particle (126 times the mass of a proton) backs up earlier predictions (including those made by Einstein) indicating a fundamentally unstable universe — a universe that will end in “catastrophe” billions of years hence. Confirmation of the Higgs Boson would confirm what’s known as “vacuum instability” and so may seal the fate of the cosmos to one of ultimate self-annihilation.
However, there is some recent evidence that the Standard Model may be flawed, so, perhaps the universe as we know it may ultimately persevere.
*A lepton is a type of fundamental particle in the Standard Model that does not combine with others via the ‘strong’ force (one of the four forces in Nature recognized by physicists). Examples of leptons are the electron, the muon and the tau lepton.
Read the full CERN press release.
Top Image: (proton-proton collision producing four high-energy electrons); CERN