Standard Model predictions for rare K and B decays without new physics infection.

The Standard Model (SM) does not contain by definition any new physics (NP) contributions to any observable but contains four CKM parameters which are not predicted by this model. We point out that if these four parameters are determined in a global fit which includes processes that are infected by NP and therefore by sources outside the SM, the resulting so-called SM contributions to rare decay branching ratios cannot be considered as SM contributions to the latter. On the other hand SM predictions, that are from the CKM dependence, can be obtained for suitable ratios of the and rare decay branching ratios to , and , all calculated within the SM.

in the Standard Model at the Dawn of the 2020s.

We reanalyse the ratio in the Standard Model (SM) using most recent hadronic matrix elements from the RBC-UKQCD collaboration in combination with most important NNLO QCD corrections to electroweak penguin contributions and the isospin-breaking corrections. We illustrate the importance of the latter by using their latest estimate from chiral perturbation theory (ChPT) based on the approximation for lowest-lying mesons and a very recent estimate in the scheme that takes into account the contribution of . We find and , respectively.

Final state interactions in [Formula: see text] decays: [Formula: see text] rule vs. [Formula: see text].

Dispersive effects from strong [Formula: see text] rescattering in the final state interaction (FSI) of weak [Formula: see text] decays are revisited with the goal to have a global view on their importance for the [Formula: see text] rule and the ratio [Formula: see text] in the standard model (SM). We point out that this goal cannot be reached within a pure effective (meson) field approach like chiral perturbation theory in which the dominant current-current operators governing the [Formula: see text] rule and the dominant density-density (four-quark) operators governing [Formula: see text] cannot be disentangled from each other. But in the context of a dual QCD approach, which includes both long-distance dynamics and the UV completion, that is, QCD at short-distance scales, such a distinction is possible.

Universal Unitarity Triangle 2016 and the tension between [Formula: see text] and [Formula: see text] in CMFV models.

Motivated by the recently improved results from the Fermilab Lattice and MILC Collaborations on the hadronic matrix elements entering [Formula: see text] in [Formula: see text]-[Formula: see text] mixing, we determine the universal unitarity triangle (UUT) in models with constrained minimal flavour violation (CMFV). Of particular importance are the very precise determinations of the ratio [Formula: see text] and of the angle [Formula: see text]. They follow in this framework from the experimental values of [Formula: see text] and of the CP-asymmetry [Formula: see text].

Quark flavour observables in the Littlest Higgs model with T-parity after LHC Run 1.

The Littlest Higgs model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. The latter originate in the interactions of ordinary quarks and leptons with heavy mirror quarks and leptons that are mediated by new heavy gauge bosons. Also a heavy fermionic top partner is present in this model which communicates with the SM fermions by means of standard [Formula: see text] and [Formula: see text] gauge bosons.

Towards the identification of new physics through quark flavour violating processes.

We outline a systematic strategy that should help in this decade to identify new physics (NP) beyond the standard model (SM) by means of quark flavour violating processes, and thereby extend the picture of short distance physics down to scales as short as 10(-20) m and even shorter distance scales corresponding to energies of 100 TeV. Rather than using all of the possible flavour-violating observables that will be measured in the coming years at the LHC, SuperKEKB and in Kaon physics dedicated experiments at CERN, J-PARC and Fermilab, we concentrate on those observables that are theoretically clean and very sensitive to NP. Assuming that the data on the selected observables will be very precise, we stress the importance of correlations between these observables as well as of future precise calculations of non-perturbative parameters by means of lattice QCD simulations with dynamical fermions.

[Formula: see text] rule, [Formula: see text] and [Formula: see text] in [Formula: see text] and [Formula: see text] models with FCNC quark couplings.

The experimental value for the isospin amplitude [Formula: see text] in [Formula: see text] decays has been successfully explained within the standard model (SM), both within the large [Formula: see text] approach to QCD and by QCD lattice calculations. On the other hand within the large [Formula: see text] approach the value of [Formula: see text] is by at least [Formula: see text] below the data. While this deficit could be the result of theoretical uncertainties in this approach and could be removed by future precise QCD lattice calculations, it cannot be excluded that the missing piece in [Formula: see text] comes from new physics (NP).

Rare decay K+ --> pi+ nunu at the next-to-next-to-leading order in QCD.

We calculate the charm quark contribution to the rare decay Kappa(+)--> pi(+) nunu in the next-to-next-to-leading order of QCD. This new contribution reduces the theoretical uncertainty in the relevant parameter Pc from +/-10.1% down to +/-2.

B-->pipi, new physics in B-->piK, and implications for rare K and B decays.

The measured B-->pipi,piK branching ratios (BRs) exhibit puzzling patterns. We point out that the B-->pipi hierarchy can be nicely accommodated in the standard model (SM) through nonfactorizable hadronic interference effects, whereas the B-->piK system may indicate new physics (NP) in the electroweak (EW) penguin sector. Using the B-->pipi data and the SU(3) flavor symmetry, we fix the hadronic B-->piK parameters and show that any currently observed feature of the B-->piK system can be easily explained through enhanced EW penguin diagrams with a large CP-violating NP phase.