No abstract

We reemphasize the strong dependence of the branching ratios B(K + → π + ν ν) and B(K L → π 0 ν ν) on |V cb | that is stronger than in rare B decays, in particular for K L → π 0 ν ν. Thereby the persistent tension between inclusive and exclusive determinations of |V cb | weakens the power of these theoretically clean decays in the search for new physics (NP). We demonstrate how this uncertainty can be practically removed by considering within the SM suitable ratios of the two branching ratios between each other and with other observables like the branching ratios forWe use as basic CKM parameters V us , |V cb | and the angles β and γ in the unitarity triangle (UT) with the latter two determined through the measurements of tree-level B decays. This avoids the use of the problematic |V ub |. A ratio involving B(K + → π + ν ν) and B(B s → µ + µ − ) while being |V cb |-independent exhibits sizable dependence on the angle γ. It should be of interest for several experimental groups in the coming years. We point out that the |V cb |-independent ratio of B(B + → K + ν ν) and B(B s → µ + µ − ) from Belle II and LHCb signals a 1.8σ tension with its SM value. As a complementary test of the Standard Model we propose to extract |V cb | from different observables as a function of β and γ. We illustrate this with ε K , ∆M d and ∆M s finding tensions between these three determinations of |V cb | within the SM. We point out that from ∆M s and S ψK S alone one finds |V cb | = 41.7(6) × 10 −3 and |V ub | = 3.64(12) × 10 −3 . We stress the importance of a precise measurement of γ.

In this paper we present the complete one-loop matching conditions, up to dimension-six operators of the Standard Model effective field theory, resulting by integrating out the two scalar leptoquarks S 1 ∼ (3, 1) 1 3 and S 3 ∼ (3, 3) 1 3 . This allows a phenomenological study of low-energy constraints on this model at one-loop accuracy, which will be the focus of a subsequent work. Furthermore, it provides a rich comparison for functional and computational methods for one-loop matching, that are being developed. As a corollary result, we derive a complete set of dimension-six operators independent under integration by parts, but not under equations of motions, called Green's basis, as well as the complete reduction formulae from this set to the Warsaw basis.

We perform a complete study of the low-energy phenomenology of S1 and S3 leptoquarks, aimed at addressing the observed deviations in B-meson decays and the muon magnetic dipole moment. Leptoquark contributions to observables are computed at one-loop accuracy in an effective field theory approach, using the recently published complete one-loop matching of these leptoquarks to the Standard Model effective field theory. We present several scenarios, discussing in each case the preferred parameter space and the most relevant observables.

Finding better ways to prove the Standard Model Effective Field Theory is a very important direction of research. This paper focuses on measurements of Electroweak triple gauge couplings, paying special attention on the regime of validity of the Effective Field Theory (EFT). In this regard, one of our goals is to find measurements leading to a large increase of the interference between the SM amplitude and the contribution of irrelevant operators in the EFT. We propose two such distributions that will lead to a better accuracy. Improvements compared to the traditional methods as well as LHC high luminosity prospects are discussed.