A pre-print of a conference paper from eleven months ago analyzes the extent to which the available data on the CKM matrix element values rules out beyond the Standard Model Physics.(adsbygoogle = window.adsbygoogle || []).push({});

It finds that in the most rigid model dependent analysis, that new physics are excluded up to a characteristic energy scale of about 500,000 TeV. There is no practical way that a human designed experiment could reach these energy scales from an engineering perspective. These are energy scales that haven't existed anywhere in the Universe since the early moments of the Big Bang.

If the assumptions of the model are relaxed, new physics are still excluded up to a characteristic energy scale of 114 TeV. This would take an accelerator on the order of ten times as powerful as the LHC or more to test.

To allow for new physics at a characteristic energy scale of 11 TeV which is the highest that there is a realistic chance that could be discovered at the LHC, one would have to abandon assumptions that are almost certainly correct based upon the available experimental evidence.

These limits are much more strict than the energy scale limitations established by direct searches for new particles at the LHC.

So, if this analysis of correct, the likelihood that we can experimentally observe any new physics that could tweak the parameters of the CKM matrix is dim indeed. But, how credible is this analysis? What loopholes remain for "relatively" low energy new beyond the Standard Model physics?

The paper is:

Unitarity Triangle Analysis in the Standard Model and Beyond

Cristiano Alpigiani, Adrian Bevan, Marcella Bona, Marco Ciuchini, Denis Derkach, Enrico Franco, Vittorio Lubicz, Guido Martinelli, Fabrizio Parodi,Maurizio Pierini, Luca Silvestrini, Viola Sordini, Achille Stocchi, Cecilia Tarantino, Vincenzo Vagnoni

(Submitted on 26 Oct 2017 (v1), last revised 27 Oct 2017 (this version, v2))

The pertinent language from the conclusion of the paper is as follows: Flavour physics represents a unique test bench for the Standard Model (SM). New analyses performed at the LHC experiments are now providing unprecedented insights into CKM metrology and new evidences for rare decays. The CKM picture can provide very precise SM predictions through global analyses. We present here the results of the latest global SM analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice QCD and phenomenological calculations. In addition, the Unitarity Triangle (UT) analysis can be used to constrain the parameter space in possible new physics (NP) scenarios. We update here also the UT analysis beyond the SM by the UTfit collaboration. All of the available experimental and theoretical information on ΔF=2 processes is reinterpreted including a model-independent NP parametrisation. We determine the allowed NP contributions in the kaon, D, B_{d}, and B_{s}sectors and, in various NP scenarios, we translate them into bounds for the NP scale as a function of NP couplings.

In the case of the general NP scenario, left plot in Fig. 6 shows the case of arbitrary NP flavour structures (|Fi | ∼ 1) with arbitrary phase and Li = 1 corresponding to strongly-interacting and/or tree-level NP. The overall constraint on the NP scale comes from the kaon sector (Im C 4 K in Fig. 6) and it is translated into Λgen > 5.0 · 105 TeV. As we are considering arbitrary NP flavour structures, the constraints on the NP scale are very tight due to the absence of the CKM or any flavour suppression.

In the NMFV case, the strongest bound is again obtained from the kaon sector (Im C 4 K in right plot in Fig. 6) and it translates into the weaker lower limit ΛNMFV > 114 TeV. In this latter case and in the current scenario, the Bs system also provides quite stringent constraints.

In conclusion, a loop suppression is needed in all scenarios to obtain NP scales that can be reached at the LHC. For NMFV models, an αW loop suppression might not be sufficient, since the resulting NP scale is still of the order of 11 TeV. The general model is out of reach even for αW (or stronger) loop suppression. Finally, the reader should keep in mind the possibility of accidental cancellations among the contribution of different operators, that might weaken the bounds we obtained.

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# I How credible are CKM matrix limits on new physics?

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