Field of Science

Higgs at the Tevatron

posted by @ulaulaman about #higgs #physics #tevatron
This is the week of the Higgs. Indeed, wednesday, at CERN, ATLAS and CMS announced the results of the elaboration of the data collected in the first part of 2012... and a lot of journalists write about the probable discover of the Higgs boson. Indeed the two collaborations are disegned in order to discover the boson related to the mechanism that provides the mass to the other particles. Waiting for the conference, today CDF and DZero, the two collaborations of Tevatron, publicize in two conferences the first elaboration of the complete set of data about Higgs research. Their result was summarize by the following plot:
In the image there is the combination of the final results from the two collaborations. The two experiments combined detecte an excess in signals around 125 GeV with a 2.5 sigma. It is not the discover of the Higgs boson, but it could be a good clue for the existence of the boson. So I don't know if ATLAS and CMS will confirm or update this result in their next conferences, but in every case I must remmber to the readers that with a mass of 125 GeV we have need of physics beyond Standard Model, because the only SM is not sufficient to explain our universe. In order to explain better, I reprint here some considerations that I just published for the previous Higgs day:
In 2009 Ellis et al.(1) 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:
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 (...).
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.(1) tested the region around 128.6 GeV for Higgs mass (and this is the case following ATLAS and CMS results, and today Tevatron results), they write:
It should be noted that the 'unstable' region is not necessary incampatible with our existence (...)
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(1):
I woul conclude the post with this quotation by Sergio Bertolucci, CERN Director for Research and Computing (via CERN press release):
We now have more than double the data we had last year that should be enough to see whether the trends we were seeing in the 2011 data are still there, or whether they've gone away. It's a very exciting time.

Read also: FermiLab press release | A 2.5 Sigma Higgs Signal From The Tevatron! by Tommaso Dorigo (that he is the source of the first image).
(1) Ellis, J., Espinosa, J., Giudice, G., Hoecker, A., & Riotto, A. (2009). The probable fate of the Standard Model Physics Letters B, 679 (4), 369-375 DOI: 10.1016/j.physletb.2009.07.054 (arXiv).

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