WELL, they’ve found it. Possibly. Maybe. Pinning down physicists about whether they have actually discovered the Higgs boson is almost as hard as tracking down the elusive subatomic beast itself. Leon Lederman, a leading researcher in the field, once dubbed it the “goddamn” particle, because it has proved so hard to isolate. That name was changed by a sniffy editor to the “God” particle, and a legend was born. Headline writers loved it. Physicists loved the publicity. CERN, the world’s biggest particle-physics laboratory, and the centre of the hunt for the Higgs, used that publicity to help keep the money flowing.
And this week it may all have paid off. On December 13th two of the researchers at CERN’s headquarters in Geneva announced to a breathless world something that looks encouragingly Higgsy.
The Standard Model (see table) includes familiar particles such as electrons and photons, and esoteric ones like the W and Z bosons, which carry something called the weak nuclear force. Most bosons are messenger particles that cement the others, known as fermions, together. They do so via electromagnetism and the weak and strong nuclear forces. The purpose of the Higgs boson, however, is different. It is to inculcate mass into those particles which weigh something. Without it, or something like it, some of the Standard Model’s particles that actually do have mass (particularly the W and Z bosons) would be predicted to be massless. Without it, in other words, the Standard Model would not work.
The announcement, by Fabiola Gianotti and Guido Tonelli—the heads, respectively, of two experiments at CERN known as ATLAS and CMS—was that both of their machines have seen phenomena which look like traces of the Higgs. They are traces, rather than actual bosons, because no Higgs will ever be seen directly. The best that can be hoped for are patterns of breakdown particles from Higgses that are, themselves, the results of head-on collisions between protons travelling in opposite directions around CERN’s giant accelerator, the Large Hadron Collider (LHC). Heavy objects like Higgs bosons can break down in several different ways, but each of these ways is predictable. Both ATLAS and CMS have seen a number of these predicted patterns often enough to pique interest, but not (yet) often enough to constitute proof that they came from Higgses, rather than being random fluctuations in the background of non-Higgs decays.
The crucial point, and the reason for the excitement, is that both ATLAS and CMS (which are located in different parts of the ring-shaped accelerator tunnel of the LHC) have come up with the same results. Both indicate that, if what they have seen really are Higgses, then the boson has a mass of about 125 giga-electron-volts (GeV), in the esoteric units which are used to measure how heavy subatomic particles are. That coincidence bolsters the suggestion that this is the real thing, rather than a few chance fluctuations.
src – economist