In one of the last updates before the Large Hadron Collider (LHC) shuts down until 2015, CERN has announced that its observation of the Higgs boson (or a particle that is Higgs-like) is now approaching 7 sigma certainty.
5 sigma — 99.9999% certainty, or more correctly a 0.00001% chance that you have made a faulty observation — is the threshold for an observation to be labeled a scientific discovery. CERN crossed the 5 sigma threshold this summer. At 7 sigma, both the CMS and ATLAS teams are reporting that there’s only a 0.0000000001% chance that they haven’t found a Higgs-like particle.
Over the last few months you may have noticed the use of the phrase “Higgs-like,” rather than “Higgs boson.” This is because CERN and the scientific community can’t be certain that they’ve actually found the Higgs boson — all they know is that they’ve found a particle, with a mass of around 125 GeV, that behaves as predicted by the Standard Modelof particle physics. With its discovery now completely and utterly confirmed, further analysis (due in 2013) will now focus on the particle’s spin, and other properties. Eventually, perhaps after upgrades are completed and the LHC turns back on in 2015, the particle will be officially announced as the Higgs boson (or not, which would be much more interesting).
In other news, CERN says that it has observed the decay of the Bs meson (strange B meson) into two muons. Apparently this is one of the rarest processes ever observed in particle physics, which means it’s a good chance that it could lead to new science.
If you’ve paid any attention to physics or physical science research in the past few years, you’ve heard about the Large Hadron Collider (LHC), the world’s largest and highest-energy particle accelerator. The LHC was built partially with the hopes of finding the elusive Higgs boson, a theorized but undiscovered particle which, if found, would sew up nicely our understanding of the relationship between mass and energy.
The Higgs boson is the only particle left in our understanding of particle physics (called the Standard Model) that we haven’t discovered. We think it exists — there’s math that postulates it does — it simply has never been observed. This is why it’s called the “God Particle,” because it’s the particle that would explain the difference between objects with mass and objects that have only energy — objects with form and objects without.
If we do find it, we’ll know that we have the right idea about how particles acquire mass — as in, how photons, riding on beams of light, have no mass at all, while the W and Z bosons (two particles that govern the “weak force,” one of the fundamental forces that keep atoms together) have the masses that they do, and why other subatomic particles have the weights that they have.
Faced with the mystery, English physicist Peter Higgs set out to understand how exactly energy in the universe became mass — how particles, with their wave-like characteristics, acquired mass and interacted with other particles around them. He theorized of a field, one that made up the lattice of the entire universe, that’s responsible for the mass of objects, specifically particles. The Higgs boson would be a density of that field, or an observable indication that it exists.
So why are physicists around the world eagerly searching for the Higgs? The field itself, aside from being the explanation for why everything in the universe has mass, is also one of the final pieces of the puzzle we call the Standard Model of physics.
It neatly ties together elements of quantum mechanics and electromagnetism, and would be an integral part of the material world that we all live in. Plus, it may even interact with other particles we have yet to discover, like the ones that may make up dark matter.
The trouble is we won’t know if the field exists unless we find the Higgs boson, or some indication that there’s a mechanism that allows particles to acquire mass. This is precisely what the latest generation of particle accelerators like the LHC and the Tevatron are trying to solve.
Even today, the search is on. Every so often there are reports that someone’s found something at LHC or Tevatron, or that a discovery has been made, all of which are quickly tamped down by the researchers there, mostly because it doesn’t count until it’s been reviewed, analyzed, and documented properly. In modern physics, there are very few “eureka!” moments, and a lot of plodding through data and calculations for years. In fact, even as the search for the Higgs continues, there are other physicists working on theories that would explain the same phenomenon without the need for the Higgs boson or the Higgs field at all — if it doesn’t exist, science will just march on to the next set of likely theories.
To that end, it may be years before physicists can confidently say there is a Higgs boson, a Higgs Field, or that we understand the mechanism by which the particles that make up everything around us in the universe actually have mass, as opposed to just being formless energy.