J. de Blas, M. Ciuchini, E. Franco, A. Goncalves, S. Mishima, M. Pierini, L. Reina, L. Silvestrini

Abstract: We perform a global fit of electroweak data within the Standard Model, using state-of-the art experimental and theoretical results, including a determination of the electromagnetic coupling at the electroweak scale based on recent lattice calculations. In addition to the posteriors for all parameters and observables obtained from the global fit, we present indirect determinations for all parameters and predictions for all observables. Furthermore, we present full predictions, obtained using only the experimental information on Standard Model parameters, and a fully indirect determination of Standard Model parameters using only experimental information on electroweak data. Finally, we discuss in detail the compatibility of experimental data with the Standard Model and find a global p-value of 0.5.

Peter Adshead, Kaloian D. Lozanov

Abstract: We study fermions derivatively coupled to axion-like or pseudoscalar fields, and show that the axial vector current of the fermions is not conserved in the limit where the fermion is massless. This violation of the classical chiral symmetry is due to the background axion field. We compute the contributions to this anomalous Ward identity due to the pseudoscalar field alone, which arise in Minkowski space, as well as the effects due to interaction with an external gravitational field. In all cases, these interactions induce terms in the axion effective action that can be removed by the addition of local counterterms. We perform our computations both perturbatively using Feynman graphs, as well as by studying the transformation properties of the path integral measure. Using the heat kernel method, we include the effects of gravity as well as gauge fields, and compute the anomaly. Finally, we verify our relation by considering derivatively coupled fermions during pseudoscalar-driven inflation and computing the divergence of the axial current in de Sitter spacetime.

Avital Dery, Mitrajyoti Ghosh

Abstract: We analyze the New Physics sensitivity of a recently proposed method to measure the CP-violating \({\cal B}(K_S\to\mu^+\mu^-)_{\ell=0}\) decay rate using \(K_S - K_L\) interference. We present our findings both in a model-independent EFT approach as well as within several simple NP scenarios. We discuss the relation with associated observables, most notably \({\cal B}(K_L\to\pi^0\nu\bar\nu)\). We find that simple NP models can significantly enhance \({\cal B}(K_S\to\mu^+\mu^-)_{\ell=0}\), making this mode a very promising probe of physics beyond the standard model in the kaon sector.

Vincenzo Cirigliano, David Díaz-Calderón, Adam Falkowski, Martín González-Alonso, Antonio Rodríguez-Sánchez

Abstract: Hadronic \(\tau\) decays are studied as probe of new physics. We determine the dependence of several inclusive and exclusive \(\tau\) observables on the Wilson coefficients of the low-energy effective theory describing charged-current interactions between light quarks and leptons. The analysis includes both strange and non-strange decay channels. The main result is the likelihood function for the Wilson coefficients in the tau sector, based on the up-to-date experimental measurements and state-of-the-art theoretical techniques. The likelihood can be readily combined with inputs from other low-energy precision observables. We discuss a combination with nuclear beta, baryon, pion, and kaon decay data. In particular, we provide a comprehensive and model-independent description of the new physics hints in the combined dataset, which are known under the name of the Cabibbo anomaly.

Aleksandr Azatov, Diptimoy Ghosh, Amartya Harsh Singh

Abstract: A major task in phenomenology today is constraining the parameter space of SMEFT and constructing models of fundamental physics that the SM derives from. To this effect, we report an exhaustive list of sum rules for 4-fermion operators of dimension 6, connecting low energy Wilson coefficients to cross-sections in the UV. Unlike their dimension 8 counterparts which are amenable to a positivity bound, the discussion here is more involved due to the weaker convergence and indefinite signs of the dispersion integrals. We illustrate this by providing examples with weakly coupled UV completions leading to opposite signs of the Wilson coefficients for both convergent and non-convergent dispersion integrals. We further decompose dispersion integrals under weak isospin and color groups which lead to a tighter relation between IR measurements and UV models. These sum rules can become an effective tool for constructing consistent UV completions for SMEFT following the prospective measurement of these Wilson coefficients.

Jérémie Quevillon, Christopher Smith, Pham Ngoc Hoa Vuong

Abstract: In this paper, we discuss the construction of Effective Field Theories (EFTs) in which a chiral fermion, charged under both gauge and global symmetries, is integrated out. Inspired by typical axion models, these symmetries can be spontaneously broken, and the global ones might also be anomalous. In this context, particular emphasis is laid on the derivative couplings of the Goldstone bosons to the fermions, as these lead to severe divergences and ambiguities when building the EFT. We show how to precisely solve these difficulties within the path integral formalism, by adapting the anomalous Ward identities to the EFT context. Our results are very generic, and when applied to axion models, they reproduce the non-intuitive couplings between the massive SM gauge fields and the axion. Altogether, this provides an efficient formalism, paving the way for a systematic and consistent methodology to build entire EFTs involving anomalous symmetries, as required for axion or ALP searches.

Quentin Bonnefoy, Emanuele Gendy, Christophe Grojean, Joshua T. Ruderman

Abstract: As SMEFT is a framework of growing importance to analyze high-energy data, understanding its parameter space is crucial. The latter is commonly split into CP-even and CP-odd parts, but this classification is obscured by the fact that CP violation is actually a collective effect that is best captured by considering flavor-invariant combinations of Lagrangian parameters. First we show that fermion rephasing invariance imposes that several coefficients associated to dimension-six operators can never interfere with operators of dimension \(\leq4\) and thus cannot appear in any physical observable at \({\cal O}\left(1/\Lambda^2\right)\). For those that can, instead, we establish a one-to-one correspondence with CP-odd flavor invariants, all linear with respect to SMEFT coefficients. We explicitly present complete lists of such linear CP-odd invariants, and carefully examine their relationship to CP breaking throughout the parameter space of coefficients of dimension \(\leq 4\). Requiring that these invariants all vanish, together with the Jarlskog invariant, the strong-CP phase, and the 6 CP-violating dimension-6 bosonic operators, provides \(699(+1+1+6)\) conditions for CP conservation to hold in any observable at leading order, \({\cal O}\left(1/\Lambda^2\right)\).