### Higgs day

I've just write on my italian blog that:
There will be no dramatic announcement, but only new and more stringent limits on the Higgs mass(1)
and the conclusion of the today Higgs' event confirms that impression. Indeed Fabiola Gianotti and Giulio Tonani, respectively spokespersons of ATLAS and CMS, during their CERN's seminars presented the new limits about Higgs mass, and in the combination of the data presented in the official press release (the combination dued by the two experiments will arrive only after the publication of the papers) we can read the new limits: from 124 to 126 GeV.
After the two seminars I discussed via e-mail with Salvatore Fazio, who send me the following two plots about the preliminary results from ATLAS and CMS
and the superposition of the two previous plots:
It was not without a well justified enthusiasm that today CERN shared with the world its latest results on the hunt of the Higgs boson. Although these preliminary results are very promising, I'd join the CERN researchers in inviting to handle them with prudence. Acutally, if one superimposes the plots released by the two Collaborations, ATLAS and CMS, it becomes evident that where one experiment (ATLAS) sees an excess of 2.7 sigma above the expected Standard Model value, the other one sees only 1.5 sigma, but sees 2 sigma where the first one see almost nothing. A combination of the results from the two independent experiments is still well compatible with a statistical fluctuation. Nevertheless the data from the ATLAS Collaboration give a grate hope that Higgs boson may be caught around that energy values. To claim or not the "discovery" we have to wait until more data will be collected. At the rate of data taking, I believe that the answer can be known before the end of next year (perhaps even before the world comes to an end on Dec. 2012).
I also think, like Salvo, that in one (or two) year we could have the first step in the ultimate solution of the Higgs quest, and we'll be in an interesting scenario. Indeed in 2009 Ellis et al.(5) try to describe the fate of the standard model following connected to the possible mass of the Higgs boson. They tested the following scenarios: blow-up, collapse, metastable, survival(2). The parameter to distinguish these scenarios is the stability of the electroweak vacuum and if we look the following plot from Ellis et al. paper we see that an Higgs with a mass in the today range not only save the Standard Model, but also open the way to a physics beyond the SM(3):
This seems the most probable solution(4). I must remember to all readers that the standard model is the best verfied theory in physics

Some Gianotti's slides:
Some Tonelli's slides:

(1) non ci sarà alcun annuncio clamoroso, ma solo dei nuovi e più stringenti limiti sulla massa dell'Higgs
(2) If we set the Planck scale $M_P \sim 2 \times 10^{18} GeV$, if Higgs mass is large enough, the Higgs self-coupling could be in a non-pertubative region, and so new physics must be exist in order to prevent the Higgs self-coulpling from blowing up (blow-up scenario).
But if Higgs mass is small enough the electroweak vacuum could became instable and collapse in another vacuum, and it must be exist new physics to prevent this event.
In the metastability region,
(...) the electroweak vacuum has a lifetime longer than the age of the Universe for decay via either zero-temperature quantum fluctuations (...) or thermal fluctuations (...).
(3) In the stability region the SM will survive, but it could be the possibility that it not is the only quantum model for the universe. Indeed, when Ellis et al.(4) tested the region around 128.6 GeV for Higgs mass (and this is the case following ATLAS and CMS results), they write:
It should be noted that the 'unstable' region is not necessary incampatible with our existence (...)