Geometric model of particles: a didactical approach

About ten years ago Giovanni Guido proposed me a new model to describe particles. Under certain aspects it remembers to me a string model: simplifying as much as possible, Giovanni's model supposes the presence of small quantum oscillators connected to each other by lines that run along a space-time lattice; these lines form geometric figures, golden triangles to be precise, which constitute the geometric structure of particles, elementary and otherwise. I have never had the opportunity to actively work on the model: the commitments in outreach with INAF have always been somehow a priority due to the type of contract that, in some way, pushes me to give priority to these aspects. However, despite everything, we have used his vision to describe a universe that is in a certain sense cyclical that you can find in the following two articles: The Universe at Lattice-Fields and Variational Principle in an Expanding Universe.
Working on Guido's particle model, however, has always been a worry of mine, so a couple of years ago I proposed to him to try to develop a didactic formulation of the model that could be used to bring elementary particles not only to university, but also to high school. From that idea, although my contributions to the writing were minimal, a triptych of articles came out, of which you can find the links below, and which received a particular review that made me very happy:

The Authors propose a didactic model representative of the particles described of the Standard Model. In this approach, particles result to be geometric forms corresponding to geometric structures of coupled quantum oscillators. An in-depth phenomenology of particles surfaces and this seems fully compatible with that of the Standard Model. Consequently, it is possible to calculate the mass of Higgs's Boson and the mass of the pair "muon and muonic neutrino" in "geometrical" sense. Via this geometric approach, it seems also possible to solve crucial aspects of the Standard Model. as the neutrinos’ oscillations and the intrinsic chirality of the neutrino and antineutrino. The paper is very interesting and deserves immediate publication in JHEPGC.

I don't consider the work finished and indeed I would like to be able to bring these ideas into practice in schools. For now I'm happy to share this happiness here on the blog.

The Geometric Model of Particles: An Original Didactic about Standard Model -> The Quarks | Nucleons and K-Mesons | Leptons and Bosons

Hints of physics behind standard model?

The LHCb collaboration is studying the decay of mesons $B$ in order to find some violations in standard model rules. In particular LHCb has measured a particular ratio, named $R (D^*)$, between two decay modes of $\overline{B}^0$ and they find a violation from the standard model prediction that is compatible with other similar measures:

In the SM all charged leptons, such as taus ($\tau$) or muons ($\mu$), interact in an identical fashion (or, in physicists' language, have the same "couplings"). This property is called "lepton universality". However, differences in mass between the leptons must be accounted for, and affect decays involving these particles. The $\tau$ lepton is much heavier than the $\mu$ lepton and therefore the SM prediction for the ratio $R(D^*)$ is substantially smaller than 1. This ratio is considered to be precisely calculable thanks to the cancellation of uncertainties associated with the $B$ to $D^*$ meson transition.

from press release | read also LHC signal hints at cracks in physics' standard model

But there is another hint of new physics. At the end of July Nature Physics published a new paper from the LHCb collaboration about the possible existence of a new particle:

The LHCb collaboration published in Nature Physics a paper based on run 1 data which reports the determination of the parameter $|V_{ub}|$ describing the transition of a $b$ quark to a $u$ quark. This measurement was made by studying a particular decay of the $\Lambda_b^0$ baryon. Other measurements of $|V_{ub}|$ by previous experiments had returned two sets of inconsistent results, depending on which method was used to determine the parameter. Theorists had suggested that this discrepancy could be explained by the presence a new particle contributing to the decay process, which affected the result differently, depending on the measurement method. Today's result from LHCb removes the need for this new particle, while the puzzle of why the original sets of measurements do not agree persists.

from press release | read also: From generation to generation

where $|V_{ub}|$ is connected to the Cabibbo-Kobayashi-Maskawa matrix.

The B mesons and the new physics

posted by @ulaulaman via @LHCbExperiment #newphysics #Bmesons #LHC #CERN #particlephysics

The search about B mesons decays has a great importance in physics for the possible clues of new physics that could be discovered. So theoretical phisicists have developed some new observables in order to test this possibility. LHCb produced new results about these new parameters, in particular the so called $P_5'$.

According to Joaquim Matias from Universitat Autonoma de Barcelona and colleagues the deviation in $P_5'$ and small discrepancies in the other angular observables for this decay, follow a pattern. In a recent paper the authors claim that a global analysis of the LHCb data, together with previous measurements, show a deviation of $4.5 \sigma$ with respect to Standard Model expectations, which can be explained with the same mechanism. This demands further investigation, in particular to re-evaluate all the sources of theoretical uncertainty, and to understand the effects of correlations between the experimental measurements.

(via LHCb)

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The image shows the distribution of the $P_5'$ observable as a function of the $\mu^+ \mu^-$ invariant mass squared $q^2$. The black data points are compared with the Standard Model prediction.

First evidence of photon polarisation in a quark transition

posted by @ulaulaman via @LHCbExperiment #newPhysics #StandardModel #LHC #CERN

There are a lot of model about physics beyond standard model, and the experimental work is concentrate to search signals to select the new models for the future. LHCb has recently released a press release about the transition of a b-quark to an s-quark with the emission of a photon. This transition

is considered a very important process to investigate possible manifestation of new physics. This decay process is forbidden in the first approximation in the Standard Model (SM) of particle physics and moreover in the second-order processes that govern the process in the SM the emitted photon is expected to be strongly polarised. Therefore it is very sensitive to new physics effects arising from the exchange of new heavy particles in electroweak penguin diagrams (see 14 June 2013 news). Indeed, several models of new physics predict that the emitted photon should be less polarised than in the SM. Up to now different experiments have measured the decay rate of this process, ruling out significant deviations of the rate from the SM prediction and strongly reducing the allowed parameter space of new physics models. The photon polarisation was, however, never previously observed.

I think that this is a really intriguing news for a particle physics point of view.

Waiting the superluminal neutrinos (if they exist!)

It seems that Opera experiment observed some superluminal neutrinos.
First of all we must see the scientific data: at 4pm on 23rd september (Geneva time) we can connect to the Cern seminar (also on webcast), but probably a preprint will be puiblished on arXiv in the next hours. In every case I think that it's very important say some worlds about the news.
There's a lot of comments about the question, and some people say that special relativity and also standard model will be falsified by the results if they will be confirmed. Instead I think that we simply speak about an extension of standard model, and there're no really consequence about special relativity.
First of all we must remember that special relativity and standard model are first of all electromagnetic theories, where the boson is the photon and the speed of light is important for the photon and for the em interaction. And neutrinos don't interact with electromagnetic field, and the results is simply the confirmation of this situation!
At the other hand the results, if confirmed, say us simply that neutrinos are the most elusive particles in the universe: in this case they escape from the control of special relativity, which would not be the correct theory to describe them at highest energy. In the same way, we must modify standard model in order to include these new superneutrinos. In this last case the changes will be at the high orders of the theory: we must remember that, if the effect it's really important at the energy of standard model, the theory would never have been tested with a high degree of accuracy.
Another hypothesis is that the introduction of superluminal neutrinos in model standard could resolve some mathematical problems of the model, or explain some physical question (like the matter-antimatter asymmetry, for example). But we can continue playing with the assumptions: the superneutrinos could be the trace of a new fifth interaction between neutrinos and dark matter. This hypothesis is included in some dark matter theories: so model standard and special relativity could be remain unmodified.
In every case, if the results will be confirmed, the first step for model standard theorists is propose changes at the highest orders of the theory. And for the future search an extension of the theory.

Thanks to Marco Delmastro, Tommaso Dorigo, Peppe Liberti, Annarita Ruberto for sharing the news.

A circle around Higgs boson

After the post about D0 abstracts, I return to write about Higgs boson after the last Fermilab's press release about the mass limit of Higgs boson. Combinig data from D0 and CDF, Tevatron's limits are 114-137 GeV/c². The results was presented last week in Grenoble at the EPS High-Energy Physics conference, that it will finish on the 27th July.
During the same conference also LHC's experiments presented their first results, analyzed in about one month! And the conclusion seems un-huppy for Tevatron: the Fermilab's particle accelerator has only one chance to find Higgs boson before LHC. Why? We can simply see the following plots presented by ATLAS and CMS (via Résonaances, Tommaso Dorigo):

The two european experiments presented only a little region around 115 GeV/c², the Tevatron's region, to 140 GeV/c². The data from this region are probably analized and published before the end of the year, so we must wait only some months to know if Tevatron could found Higgs or not⁽¹⁾.
Tomasso examined in details some CMS preprint in which they are studied a lot of Higgs production channels, and also Philip Gibbs write a great summary about LHC presentations, who realize a great conclusion plot: