What will scientists do if they fail to find the Higgs boson?
Largely unnoticed at the weekend, the Large Hadron Collider (LHC), the world's most powerful particle accelerator, ended one hell of a run. Since March, protons had been whizzing more-or-less continuously around the collider's 27-kilometre ring, located at CERN, Europe's premier high-energy laboratory on the French–Swiss border near Geneva. At four points around the ring, protons collide at near-light-speed. The energies released are high enough to briefly create heavy particles, and physicists have been hoping for one above all others — the Higgs.
The Higgs boson is a missing bolt in the standard model of particle physics. In popular parlance, it is known as the particle that gives all other particles mass. However, physicists like the Higgs (and its associated field) because the particle provides an elegant way to combine electromagnetism with the weak nuclear force. Such a step would create a single electroweak theory that is stronger than its two parts. It would also consolidate the four known forces into three — bringing researchers closer to an ultimate theory of everything. There are good reasons to hope that the Higgs is there, but nothing in nature requires it. Already in August, physicists saw one possible signal sink from view.
With the end of this year's run, the two largest detectors at the LHC have each collected six inverse femtobarns (about 42×1013 collisions worth) of data. Crucially, that is enough to tell whether the Higgs takes the form that physicists believe it must for it to give mass and unify forces.
In other words, if the Higgs does not exist, then the world will probably be told so within weeks. (Or at least that scientists are 95% sure that it does not exist.)
A Higgs no-show would certainly create a public-relations headache for CERN, for the field of high-energy physics and possibly for science itself. For better or worse, the boson is popularly referred to as the ‘God particle'. Scientists forced to admit that they have seen no sign of it would no doubt face the wrath of non-believers — the kind that asks where decades of hard graft and taxpayers' billions have gone.
In September, CERN's council discussed a report on ‘The scientific significance of the possible exclusion of the SM Higgs boson in the mass range 114–600 GeV and how it should be best communicated'. The public version of the document, available online, emphasizes that the failure to find the Higgs would be just as exciting as a discovery. Privately, discussions are under way on whether the lab should announce that a negative result ‘excludes' the Higgs, which sounds final, or merely ‘disfavours' it — as 95% leaves a bit of wriggle room.
Spin aside, scientists are unlikely to panic. If the predicted Higgs is not there, they will stick to their plans and collect additional data in next year's run. If that does not turn up a signal, then they will have to wait for more than a year for the LHC to undergo an upgrade that will allow it to run at twice its current energy. At these higher energies, the standard model becomes much less predictable, and researchers will either find something new, or they will greatly improve their understanding of the existing theory. The collisions that happen in the LHC are complex, as is the analysis, and this extra effort could take years.
If high-energy physicists eventually find something new, then the field may flourish. If they only refine the existing models, it may eventually fade. Regardless, the LHC does what experiment must: it puts a good hypothesis to the test.
About this article
Cite this article
Collision course. Nature 479, 6 (2011). https://doi.org/10.1038/479006a
Archives of Pharmacal Research (2015)