Has LHC observed "the" Higgs boson or do we have to deal with something more exotic? After the seminar held on July the 4th at Cern, many online newspapers have published titles reporting the "discovery" of the Higgs boson, better the "god particle", but there are questions whether it is or not the Higgs boson or if we are dealing with a more exotic particle belonging to an unknown physics.
In my view, one of the most important result is that the particle is a scalar boson, observed for the first time. Moreover, the two values of the mass as measured by ATLAS and CMS detectors are very close and their data “seem to be consistent” with the Higgs boson mass as “required” by the standard model.
It is natural that before reaching a final conclusion scientists will need to run a series of experiments to study in detail the properties of this boson and clarify its identity. To use a comparison, we can say that physicists are a like the police who are hunting a wanted man (Higgs boson) for which they have the identikit only. Although we saw him (the results of the experiments) and his features are very similar to the identikit, today the situation (the data) does not allow us to be certain about his real identity: in our example, could it be a double?
The difficulty of the identification of this new particle is related to the fact that the Higgs boson cannot directly be observed. The Higgs boson is created in the collisions of protons and it decays in a split second into various components. Now, according to the theory of particles, we expect that the decay process takes place in different ways and that the decay rates depend on the mass the Higgs boson assumes. Another problem is that the mass of the Higgs boson is not uniquely determined by the theory but today we can say that we have an approximate value, between 125 and126 GeV, which will become more precise as physicists will collect more data.
Peter Higgs, who attended the seminar at CERN, said, with a veil of shyness and a few tears to the eyes, always without losing the sense of British humor: "I am very happy that all this happens while I am still alive". Now the question is: if it is not the Higgs boson, what this new particle is?
The current idea is based on the hypothesis of a"messenger-like" particle coming from a new physics beyond the standard model. Also, physicists talk about supersymmetric particles and therefore this new particle could be a supersymmetric Higgs boson. However, with the current data it is absolutely impossible to say and for this reason physicists will need to face a series of calculations. First of all, in addition to the mass, it will be necessary to measure the spin of the particle, its intrinsic angular momentum or, more simply, the "rotation" of the particle. The standard model Higgs boson provides a zero value. The measure of this and other parameters will be crucial to verify if they are, or not, within the framework provided by the standard model. However, to accomplish these measures it certainly will take months if not years.
Assuming that this particle is confirmed to be the Higgs boson, the next step is to go into unexplored regions in terms of energy. In fact, scientists are convinced that above a certain value of energy there must be something new, in short, a new physics beyond the standard model: for example, supersymmetry is an extension.
Supersymmetry, which provides the existence of so-called supersymmetric particles, not yet observed, could explain why do exist two different kind of particles, fermions and bosons. LHC has performed just to hunt down these superparticles the lightest of which is believed to be the ideal candidate to form the dark matter.