It was a great success of this sector of physics, and it justifies the investment spent to construct the LHC. All is well, then. We are paving the way to new triumphs. We expect new particles and the appearance of dark matter in our detectors... Or don't we ?
Here the phantom makes its appearance. There is a subtly unsettling scenario. The mass of the Higgs particle has a peculiar value. About 125 GeV (a bit more than 130 times the proton mass). If combined with the top quark mass, the heaviest-known particle (about 173 GeV), it determines a point in a strange diagram where the stability of the Universe is studied. The diagram predicts if the Universe's fate will be determined by accelerated expansion, which (very) slowly but unstoppably will extinguish every light (and then we are in a stable Universe) or it will undergo a brisk change (the fall in the vacuum!) at a given instant (presumably very far away) of its future evolution -and then the Universe is meta-stable. A unstable Universe is instead not foreseen, since in that case you would not be reading this article, nor would I exist to write it.
In the current theoretical framewher the appearance of the Universe through the mysterious and (for the time being) scientifically unfathomable Big Bang has been follwed by a incredibly rapid transition called inflation, which gave rise to the object of minuscule but understandable dimensions (centimeters) whose evolution can be predicted by us. Our accelerators, LHC first of all, allow us in fact to reach energies, and thus temperatures, which existed then and consequently to produce the same fundamental particles that such a infernal forge was capable of manifesting.
So here's the quandary. Can the Higgs mass fit in a coherent theory that allows that very value, without the intervention of any other particle at any mass scale up to the Planck mass ? At the Planck mass our science (I hope only temporarily) stops, because gravity becomes the master and we are yet incapable of combine it with quantum mechanics.
Or, this insertion does not exist, and then surely other particles such as supersymmetric ones will appear at the LHC or in our underground detectors such as those of Gran Sasso, under the guise of dark matter.
In short, must physicists of the first (few) decades get ready to cross a desert, or a tropical forest of particles ? Has high-energy physics arrived with the Higgs to the swan song, or to the dawn of a new beginning ?
In this question lies the big theme of anthropic principle. We can explain the Universe as a set of physical constants that descend from a primary law that adjusts all of them starting from a simple first principle. This is the Universe, the one and only. Will we see it slowly fading in the great darkness and cold caused by Dark Energy ?
The extraordinary circumstance that observes the mass of the higgs boson combined with the top quark mass making possible to bring the Standard Model validity up to the Planck mass could instead be a strong sign in favor of the multiverse. The existence, that is, of a immense number of universes (again something that does not stand possible comparisons... 10 followed by 500 zeroes) in each of which physical constants are different. If this were the case, we are in the right one for our own existence, and there remains little to ask ourselves about.
What to do ? Well, in the meantime we measure well the Higgs and top quark masses. Then we continue to search for new particles at the LHC and in underground labs. When LHC will start again in 2015, and will take data at its nominal energy of 14 TeV for a sufficient period of time, we will be able to make more insightful our analysis we have been doing, and understand better the messages that Nature is sensing us. We will be kind of ghostbusters!