But Kane, a longtime proponent of supersymmetry, makes a more ambitious statement. In a paper posted to the physics preprint site arXiv.org on December 5, he and his collaborators work not from supersymmetry but from an even more radical overhaul of physics: string theory. (String theory is itself an extension of supersymmetry.) Their calculations predict a Higgs mass between 122 and 129 GeV. "If it's in that range it's an incredible success for connecting string theory to the real world," Kane says. He says he is confident that the upcoming LHC announcements, if they pan out as predicted, will constitute evidence for string theory. "I don't think my wife will let us bet our house, but I'll come close," he says.
That Kane and his colleagues released their paper now that the Higgs mass has been—or is about to be—restricted to a particular range, will surely lead some physicists to charge that the new study constitutes not a prediction but a "postdiction." String theory critics have long claimed that the theory has so much flexibility that one can always tweak it to make it predict just about anything.
Moreover, whether string theory can make testable predictions at all has often been the subject of debate. "The trouble is, for all we know, there might be 10,000 other ways of starting with string theory and getting the same Higgs mass, and they may differ in other respects," Lykken cautions.
And when it comes to mass predictions, consistency does not necessarily mean validation, Strassler points out. "If the Higgs turns up at 125 GeV, that would also be consistent with the Standard Model with no supersymmetric particles and no hint of string theory," Strassler says.
For all the excitement, it is still quite possible that any preliminary whiff of the Higgs will later turn out to be a statistical fluke. After all, the CMS and ATLAS detectors cannot directly catch Higgs bosons; those particles would decay into other particles immediately after being created in the LHC's proton collisions. Instead, physicists must analyze the subatomic debris from the decays and reconstruct what happened. Thousands of collisions take place every second, and many of them generate signatures similar to those of the Higgs. "The reason why we don't know whether there's a Higgs yet has mostly to do with the fact that the Higgs boson's decays look like other kinds of physics," Lykken says. "So we need to understand the other kinds of physics enough. It's not just a question of statistics."
Whether next week's announcements pan out, experts say, it is only a matter of time before a final answer is known: Once the experiments have amassed enough data, they either will find the Higgs boson and understand its properties or they will conclusively demonstrate that it does not exist. "It's just a question of when it will happen," Lykken says. "It's not going to be a maybe-yes-maybe-no kind of answer."
*Correction (12/8/11): This sentence was edited after posting. It originally misstated the mass of a proton.