Higgs particle heavier than ever?



Today in Mumbai (India), at the Lepton-Photon 2011 Conference, talks announcing new results from LHC were held. Data taking claimed almost doubling of data since July Conference in Grenoble. The results were striking and somewhat unexpected. In order to have an idea you should read this CERN press release and the general mood of people at CERN on the Guardian. What happened can be summarized in a few words: all the signals in the expected mass range for the Higgs particle just weakened and, as clearly pointed out by Tommaso Dorigo in his blog (see here), the possible signal at around 140 GeV should be dead and buried already. What remains after these announcements is a signal at around 120 GeV that also has lose its grip lowering confidence. For your considerations I would like to show you the main graphs from ATLAS and CMS

Aleandro Nisati, an Italian researcher at INFN and ATLAS Physics Coordinator, is claiming that no signal above 2.1 sigma is seen in the mass range between 110-600 GeV, in his talk. The remain at around 120 GeV is expected to be clarified in the next months with increasing data. My view is that this is already borderline with respect to Standard Model expectations and could prove to be a fluke as well. So, what could one conclude from a scenario like this? Perspectives are open to a lot of new exciting physics. It is important to stress that these results do not exclude at all the existence of Higgs particle but they seem to make its mass even more heavier. This scenario agrees quite well with a view of a strongly coupled Higgs boson as I have already pointed out in several posts and the most recent one. This in turn will entail a proof of existence for supersymmetry (see here).

I think that this situation is the most exciting one for a lot of reasons. We, the theoreticians, should start to take our pencil and paper again and turn back at study while people at CERN keep on performing their excellent work enlightening us.

Marco Frasca (2010). Mass generation and supersymmetry arXiv arXiv: 1007.5275v2

It was twenty years ago today . . .



With these beautiful words starts a recollection paper by the founder of arXiv, Paul Ginsparg. This is worth the reading as this history spans a number of years exactly overlapping the computer revolution that definitely changed our lives. What Paul also changed through these new information tools was the way researchers should approach scientific communication. It is a revolution that is not stopped yet and all the journals I submit my papers have a link to arXiv for direct uploading of the preprint. This change has had also a great impact on the way these same journals should present to authors, readers and referees as well at their website.

For my readers I would like just to point out how relevant was all this for our community with the Grisha Perelman’s case. I think all of you are well aware that Perelman never published his papers on a journal: You can find both of them on arXiv. Those preprints paid as much as a Fields medal and a Millenium prize. Not bad I should say for a couple of unpublished papers. Indeed, it is common matter to have a paper largely discussed well before its publication and often a preprint becomes a case in the community without not even seeing the light of a publication. It is quite common for us doing research to console colleagues complaining about the harsh peer-review procedure by saying that today exists arXiv and that is enough to make your work widely known.

I was a submitter since 1994, almost at the very start, and I wish that the line of successes of this idea will never end.

Finally, to prove how useful is arXiv for our community, I would like to point out to you, for your summer readings a couple of papers. The first one is this from R. Aouane, V. Bornyakov, E.-M. Ilgenfritz, V. Mitrjushkin, M. Müller-Preussker, A. Sternbeck. My readers should know that these researchers always do a fine work and get important results on their lattice computations. The same happens here where they study the gluon and ghost propagators at finite temperature in the Landau gauge. Their conclusion about Gribov copies is really striking, comforting my general view on this matter (see here), that Gribov copies are not essential not even when one rises the temperature. Besides, they discuss the question of a proper order parameter to identify the phase transition that we know exists in this case.

The next paper is authored by Tereza Mendes, Axel Maas and Stefan Olejnik (see here). The idea in this work is to consider a gauge, the \lambda-gauge, with a free parameter interpolating between different gauges to see the smoothness of the transition and the way of change of the propagators. They reach a volume of 70^4 but Tereza told me that the errors are too large yet for a neat comparison with smaller volumes. In any case, this is a route to be pursued and I am curious about the way the interpolated propagator behaves at the deep infrared with larger lattices.

Discussions on Higgs identification are well alive yet ( you can see here). take a look and enjoy!

Paul Ginsparg (2011). It was twenty years ago today … arXiv arXiv: 1108.2700v1

R. Aouane, V. Bornyakov, E. -M. Ilgenfritz, V. Mitrjushkin, M. Müller-Preussker, & A. Sternbeck (2011). Landau gauge gluon and ghost propagators at finite temperature from
quenched lattice QCD arXiv arXiv: 1108.1735v1

Axel Maas, Tereza Mendes, & Stefan Olejnik (2011). Yang-Mills Theory in lambda-Gauges arXiv arXiv: 1108.2621v1

Soverato beach


It is some days that I am not posting here but there is a very good reason: I am on vacation at Satriano, very near Soverato. These are wonderful places in Italy, in the southern region of Calabria. For your pleasure I post here a couple of photos of the moon on the sea at the Soverato beach. Similar pictures but somewhat different colors.

What’s going on with Higgs particle?



The aftermath of the EPS Conference is quite exciting on a side. Higgs hunting points to an unexpected direction even if some residuals of an old expectation are still there. I just want to show you the graphs of this conference from Tevatron and LHC

From these it is very clear that the excluded range of mass is become significantly large restricting the possibilities to the intervals of a mass around 140 GeV or to a massive Higgs implying a strongly coupled theory. The evidence for a 140 GeV Higgs particle is yet small, about two sigmas, and we cannot exclude that this is a fluke but, to support this clue, it appears both at Tevatron and LHC. A small peak at around 250 GeV is seen only by ATLAS and could disappear in the future.

What I would like to emphasize here is that the possibility of a strongly coupled Higgs is well alive and this can have deep implications for the model and physics at large. There are several reasons for this. First of all, a strongly coupled Higgs field implies supersymmetry (see here). This result is inescapable and some breaking pattern of supersymmetry must be devised to get the right mass spectrum of the Standard Model. But this is already old and well-acquired matter. The most important point is that there will be a completely new way to approach quantum field theory. So far, quantum field theory has been managed just using weak perturbation theory but a strongly coupled Higgs would mean that we will also have to devise a perturbative technique the other way round, i.e. with a coupling increasingly large.

So, I will keep on support this view of a heavy Higgs as, being a theoretical physicist, consequences will be devastating and largely more exciting of any other possibility. We will be eager to see the improvement in the next months from the measurement datasets. Certainly, on 2012 all the curtains will be definitely down.

Marco Frasca (2010). Mass generation and supersymmetry arXiv arXiv: 1007.5275v2


Get every new post delivered to your Inbox.

Join 61 other followers

%d bloggers like this: