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 Higgs boson, for those who have not been paying attention to the minutiae of particle physics over the past few years, is a theoretical construct dreamed up in 1964 by a British researcher, Peter Higgs (pictured above), and five other, less famous individuals. It is the last unobserved piece of the Standard Model, the most convincing explanation available for the way the universe works in all of its aspects except gravity (which is dealt with by the general theory of relativity).

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. It also bolsters physicists' hopes for the future. The Standard Model, though it has stood the test of time, is held together by a number of mathematical kludges. Most of these would go away, and a far more elegant view of the world would emerge, if each of the particles in it had one or more heavier (and as-yet undiscovered) partner particles. The masses of these undiscovered partners, though, are related to the mass of the Higgs. The bigger it is, the bigger they are. And if they are too big, the LHC will not be able to find them, even in principle. Fortunately for the future of physics in general, and the LHC in particular, a Higgs of 125GeV is light enough for some of these particles to be found by the machine near Geneva.

Wake up, little Susy

This model of a world of heavy partner particles that shadows the familiar one built up by the Standard Model is called Supersymmetry, and testing it was the real purpose of building the LHC. The search for the Higgs is a search for closure on the old physical world. Susy, as Supersymmetry is known to aficionados, is the new. The particular superness of the symmetry which it proposes is that every known fermion is partnered with one or more hypothetical bosons, and every known boson with one or more fermions. These partnerships cancel out the kludges and leave a mathematically purer outcome. For this reason, Susy is top of the “what comes next” list in most physicists' minds.

It might also answer a question that has puzzled physicists since the 1930s. This is: why do galaxies, which seem to rotate too fast for their own gravity to keep them in one piece, not fly apart? The answer always given is “dark matter”—something that has a gravitational field, but does not interact much via the three forces of the Standard Model. But that is simply to label it, not to explain it. No such particle is known, but Susy predicts some, and as they are the lightest of its predictions, they should (if they exist) be within the LHC's range. If, that is, what Dr Gianotti and Dr Tonelli hope that they have seen is real.

It might not be. As Rolf-Dieter Heuer, CERN's boss, once quipped, physicists know everything about the Higgs apart from whether it exists. Technically, that is still true. Despite their having analysed some 380 trillion collisions between protons since the LHC got cracking in earnest in 2010, CERN's researchers have yet to see signs of the Higgs in an individual experiment that meet their exacting standard of having only one chance in 3.5m of being a fluke. The actual number at the moment is more like one in 2,000. But that does not take account of the coincidence between the results of the separate experiments. And more data are being crunched all the time, so it should not be long before the result is either confirmed or disproved.

If it is disproved there will, after all the brouhaha, no doubt be a period of chagrin. And then the search will resume, for there are still unexplored places out there where Dr Higgs's prediction could be hiding. After a 47-year-long search, physicists would not give the hunt up that lightly.