Abstract: In this paper, we continue to construct the low-energy effective field theories (EFTs) of the canonical seesaw models, which are natural extensions of the Standard Model (SM) to accommodate tiny but nonzero neutrino masses. Different from three right-handed neutrino singlets in the type-I seesaw model, the Higgs triplet in the type-II seesaw model participates directly in the electroweak gauge interactions, rendering the EFT construction more challenging. By integrating out the heavy Higgs triplet in the functional-integral formalism, we carry out a complete one-loop matching of the type-II seesaw model onto the so-called Standard Model Effective Field Theory (SMEFT). It turns out that 41 dimension-six operators (barring flavor structures and Hermitian conjugates) in the Warsaw basis of the SMEFT can be obtained, covering all those 31 dimension-six operators in the case of type-I seesaw model. The Wilson coefficients for 41 dimension-six operators are computed up to \(\mathcal{O}\left( M^{-2}_\Delta \right)\) with \(M^{}_\Delta\) being the mass scale of the Higgs triplet. Moreover, the branching ratios of rare radiative decays of charged leptons \(l^-_\alpha \to l^-_\beta + \gamma\) are calculated in the EFT and compared with that in the full theory in order to demonstrate the practical application and the correctness of our EFT construction.
Abstract: We discuss some theoretical aspects related to the \(B\)-anomalies, both for the neutral current and the charged current anomalies. A possible combined explanation within an EFT framework as well as an explicit simplified model featuring the \(U_1\) leptoquark are discussed. The model gives rise to predictions in other sectors that are experimentally accessible within the next few years.
Ilaria Brivio, Sally Dawson, Jorge de Blas, Gauthier Durieux, Pierre Savard, Roberto Contino, Céline Degrande, Adam Falkowski, Florian Goertz, Christophe Grojean, Fabio Maltoni, Ken Mimasu, Giuliano Panico, Francesco Riva, William Shepherd, Eleni Vryonidou, Andrea Wulzer, Cen Zhang
Abstract: The truncation of the standard-model effective field theory, its validity and the associated uncertainties have been discussed in meetings of the LHC EFT WG. Proposals were made by participants to address these issues. No consensus was reached and no formal recommendation is therefore put forward at this time. None of the proposals has been approved or validated and further work is needed to establish a prescription. This note aims at summarizing the proposals and points of debate.
Abstract: Using the functional method, one-loop matching of the type-I, -II and -III seesaw models are investigated and the results are presented in both the Green’s and the Warsaw bases. Although these models generate the same dimension-5 Weinberg operator, they could induce quite different types of dimension-6 effective operators that can be utilized for model discrimination. We also find the threshold effects from one-loop matching could be significant, which turn out to allow triggering electroweak symmetry breaking radiatively in type-II seesaw while forbid that in type-I/-III models. An analytical criterion for such radiative symmetry breaking is also derived in type-II seesaw. Finally, we investigate the indirect signatures from different types of dimension-6 operators at high-energy colliders, low-energy precision experiments and forward physics facilities for model discrimination.
Abstract: We describe a general procedure to construct the independent and complete operator bases for generic Lorentz invariant effective field theories, given any kind of gauge symmetry and field content, up to any mass dimension. By considering the operator as contact on-shell amplitude, the so-called amplitude operator correspondence, we provide a unified construction of the Lorentz and gauge and flavor structures by Young Tableau tensor. Several bases are constructed to emphasize different aspects: independence (y-basis and m-basis), repeated fields with flavors (p-basis), and conserved quantum numbers (j-basis). We also provide new algorithms for finding the m-basis by defining inner products for group factors and the p-basis by constructing the matrix representations of the Young symmetrizers from group generators. The on-shell amplitude basis gives us a systematic way to convert any operator into such basis, so that the conversions between any other operator bases can be easily done by linear algebra. All of these are implemented in a Mathematica package: ABC4EFT (Amplitude Basis Construction for Effective Field Theories).
Abstract: This course on Feynman integrals starts from the basics, requiring only knowledge from special relativity and undergraduate mathematics. Topics from quantum field theory and advanced mathematics are introduced as they are needed. The course covers modern developments in the field of Feynman integrals. Topics included in this course are: Representations of Feynman integrals, integration-by-parts, differential equations, intersection theory, multiple polylogarithms, Gelfand-Kapranov-Zelevinsky systems, coactions and symbols, cluster algebras, elliptic Feynman integrals, motives associated to Feynman integrals.
Abstract: The Standard Model Effective Field Theory (SMEFT) is a universal way of parametrizing New Physics (NP) manifesting as new heavy particle interactions with the Standard Model (SM) degrees of freedom, that respect the SM gauged symmetries. Higher order terms in the NP interactions possibly lead to sizable effects, mandatory for meaningful phenomenological studies, such as contributions to neutral meson mixing, which typically pushes the scale of NP to energy scales much beyond the reach of direct searches in colliders. I discuss the leading-order renormalization of double-insertions of dimension-6 four-fermion operators that change quark flavor by one unit (i.e., \(|\Delta F| = 1\)), (\(F = \)strange-, charm-, or bottom-flavor) by dimension-8 operators relevant to meson mixing (i.e., \(|\Delta F| = 2\)) in SMEFT, and consider the phenomenological implications of contributions proportional to large Yukawas. Given the underlying interest of SMEFT to encode full-fledged models at low energies, this work stresses the need to consider dimension-8 operators in phenomenological applications of dimension-6 operators of SMEFT.
January 20, 12:10: Seminar at the Theoretical Physics Department, UNIZAR (Zaragoza, Spain).
January 27: Seminar at IFT, UAM (Madrid, Spain). Link to video
Both talks have the title “Using Machine Learning techniques in phenomenological studies in flavour physics”, and the following abstract:
In the recent years, a series of measurements in the observables \(R_{K^{(*)}}\) and \(R_{D^{(*)}}\) concerning the semileptonic decays of the (B) mesons have shown hints of violations of Lepton Flavour Universality (LFU). An updated model-independent analysis of New Physics violating LFU, by using the Standard Model Effective Field Theory (SMEFT) Lagrangian with semileptonic dimension six operators at \(\Lambda = 1\,\mathrm{TeV}\) is presented. We perform a global fit, in order to assess the impact of the New Physics in a broad range of observables including \(B\)-physics, electroweak precision test, Higgs physics and nuclear \(\beta\) decays. We discuss the relevance of the mixing in the first generation for the observables with heavier lepton flavours. We use for the first time in this context a Montecarlo analysis of the likelihood function to extract the confidence intervals and correlations between observables. Our results show that a suitable strategy is to use a Gradient Boosting predictor as a proxy of the real likelihood function, and to analyze the SHAP values as a measure of the impact of each parameter of SMEFT Lagrangian in the fit.
The slides will be available at my repo, in their corresponding branches: Unizar and IFT.
Abstract: Positivity bounds of higher derivative operators are derived from analyticity, causality and unitarity in effective field theory. We show that the positivity bounds can be derived from the non-negativity of relative entropy between a theory with and without interactions between heavy and light degrees of freedom. We prove that the interactions increase thermodynamic entropy at fixed energy and charge, which implies the extremality relations of a wide class of black holes exhibiting Weak-Gravity-Conjecture-like behavior. As the entropy constraint is a consequence of Hermiticity of Hamiltonian operator, any UV theory violating the entropy constraint would not respect the second law of the thermodynamics.
Abstract: We investigate matching conditions and threshold corrections between full and effective theories based on the type I seesaw mechanism. In general, using an intuitive Feynman diagrammatical approach, we compute the amplitudes before and after integrating out heavy right-handed neutrinos at the matching scale. In particular, we derive the one-loop matching conditions between the full and the effective theories. The matching conditions of the parameters are influenced by one-loop corrections to the corresponding vertices as well as wave function corrections for the Higgs and the lepton fields. Our results are comparable to earlier results based on a functional approach.
Keep going!Keep going ×2!Give me more!Thank you, thank youFar too kind!Never gonna give me up?Never gonna let me down?Turn around and desert me!You're an addict!Son of a clapper!No wayGo back to work!This is getting out of handUnbelievablePREPOSTEROUSI N S A N I T YFEED ME A STRAY CAT
