
Abbas, G., Celis, A., Li, X. Q., Lu, J., & Pich, A. (2015). Flavourchanging top decays in the aligned twoHiggsdoublet model. J. High Energy Phys., 06(6), 005–26pp.
Abstract: We perform a complete oneloop computation of the twobody flavourchanging top decays t > ch and t > cV (V = gamma, Z), within the aligned twoHiggsdoublet model. We evaluate the impact of the model parameters on the associated branching ratios, taking into account constraints from flavour data and measurements of the Higgs properties. Assuming that the 125 GeV Higgs corresponds to the lightest CPeven scalar of the CPconserving aligned twoHiggsdoublet model, we find that the rates for such flavourchanging top decays lie below the expected sensitivity of the future highluminosity phase of the LHC. Measurements of the Higgs signal strength in the diphoton channel are found to play an important role in limiting the size of the t > ch decay rate when the charged scalar of the model is light.



Aebischer, J., Brivio, I., Celis, A., Evans, J. A., Jiang, Y., Kumar, J., et al. (2018). WCxf : An exchange format for Wilson coefficients beyond the Standard Model. Comput. Phys. Commun., 232, 71–83.
Abstract: We define a data exchange format for numerical values of Wilson coefficients of local operators parameterising lowenergy effects of physics beyond the Standard Model. The format facilitates interfacing modelspecific Wilson coefficient calculators, renormalisation group (RG) runners, and observable calculators. It is designed to be unambiguous (defining a nonredundant set of operators with fixed normalisation in each basis), extensible (allowing the addition of new EFTs or bases by the user), and robust (being based on industry standard file formats with parsers implemented in many programming languages). We have implemented the format for the Standard Model EFT (SMEFT) and for the weak effective theory (WET) below the electroweak scale and have added interfaces to a number of public codes dealing with SMEFT or WET. We also provide commandline utilities and a Python module for convenient manipulation of WCxf files, including translation between different bases and matching from SMEFT to WET. (C) 2018 Elsevier B.V. All rights reserved.



Boucenna, S. M., Celis, A., FuentesMartin, J., Vicente, A., & Virto, J. (2016). Phenomenology of an SU(2) x SU(2) x U(1) model with leptonflavour nonuniversality. J. High Energy Phys., 12(12), 059–43pp.
Abstract: We investigate a gauge extension of the Standard Model in light of the observed hints of lepton universality violation in b > clv and b > sl(+) l() decays at BaBar, Belle and LHCb. The model consists of an extended gauge group SU(2)(1) x SU(2)(2) x U(l)(Y) which breaks spontaneously around the TeV scale to the electroweak gauge group. Fermion mixing effects with vector like fermions give rise to potentially large new physics contributions in flavour transitions mediated by WI and Z' bosons. This model can ease tensions in B physics data while satisfying stringent bounds from flavour physics, and electroweak precision data. Possible ways to test the proposed new physics scenario with upcoming experimental measurements are discussed. Among other predictions, the ratios RM =Gamma(B > M mu(+)mu())/Gamma(B > Me(+)e()), with M = K*, phi, are found to be reduced with respect to the Standard Model expectation RM similar or equal to 1.



Boucenna, S. M., Celis, A., FuentesMartin, J., Vicente, A., & Virto, J. (2016). Nonabelian gauge extensions for Bdecay anomalies. Phys. Lett. B, 760, 214–219.
Abstract: We study the generic features of minimal gauge extensions of the Standard Model in view of recent hints of leptonflavor nonuniversality in semileptonic b > sl(+)l() and b > cl nu decays. We classify the possible models according to the symmetrybreaking pattern and the source of flavor nonuniversality. We find that in viable models the SU(2)(L) factor is embedded nontrivially in the extended gauge group, and that gauge couplings should be universal, hinting to the presence of new degrees of freedom sourcing nonuniversality. Finally, we provide an explicit model that can explain the Bdecay anomalies in a coherent way and confront it with the relevant phenomenological constraints.



Buchalla, G., Cata, O., Celis, A., Knecht, M., & Krause, C. (2018). Complete oneloop renormalization of the Higgselectroweak chiral Lagrangian. Nucl. Phys. B, 928, 93–106.
Abstract: Employing backgroundfield method and superheatkernel expansion, we compute the complete oneloop renormalization of the electroweak chiral Lagrangian with a light Higgs boson. Earlier results from purely scalar fluctuations are confirmed as a special case. We also recover the oneloop renormalization of the conventional Standard Model in the appropriate limit.



Celis, A., Cirigliano, V., & Passemar, E. (2014). Lepton flavor violation in the Higgs sector and the role of hadronic taulepton decays. Phys. Rev. D, 89(1), 013008–19pp.
Abstract: It has been pointed out recently that current lowenergy constraints still allow for sizable flavorchanging decay rates of the 125 GeV boson into leptons, h > tau l (l = e, mu). In this work we discuss the role of hadronic taulepton decays in probing lepton flavor violating couplings in the Higgs sector. At low energy, the effective Higgs coupling to gluons induced by heavy quarks contributes to hadronic tau decays, establishing a direct connection with the relevant process at the LHC, pp(gg) > h > tau l. Semileptonic transitions like tau > l pi pi are sensitive to flavorchanging scalar couplings, while decays such as tau > l eta((l)) probe pseudoscalar couplings, thus providing a useful lowenergy handle to disentangle possible Higgs flavor violating signals at the LHC. As part of our analysis, we provide an appropriate description of all the relevant hadronic matrix elements needed to describe Higgs mediated tau > pi pi transitions, improving over previous treatments in the literature.



Celis, A., Cirigliano, V., & Passemar, E. (2014). Modeldiscriminating power of lepton flavor violating tau decays. Phys. Rev. D, 89(9), 095014–14pp.
Abstract: Within an effective field theory framework, we discuss the possibility to discriminate among different operators that contribute to lepton flavor violating (LFV) tau decays. Correlations among decay rates in different channels are shown to provide a basic handle to unravel the origin of LFV in these processes. More information about the underlying dynamics responsible for LFV can be gathered from differential distributions in threebody decays like tau > μpi pi or tau > 3 mu: these are considered in some detail. We incorporate in our analysis recent developments in the determination of the hadronic form factors for tau > μpi pi. Future prospects for the observation of LFV tau decays and its interpretation are also discussed.



Celis, A., FuentesMartin, J., Jung, M., & Serodio, H. (2015). Family nonuniversal Z ' models with protected flavorchanging interactions. Phys. Rev. D, 92(1), 015007–17pp.
Abstract: We define a new class of Z' models with neutral flavorchanging interactions at tree level in the downquark sector. They are related in an exact way to elements of the quark mixing matrix due to an underlying flavored U(1)' gauge symmetry, rendering these models particularly predictive. The same symmetry implies leptonflavor nonuniversal couplings, fully determined by the gauge structure of the model. Our models allow us to address presently observed deviations from the standard model and specific correlations among the new physics contributions to the Wilson coefficients C9, 10((')l) can be tested in b > sl(+)l() transitions. We furthermore predict leptonuniversality violations in Z' decays, testable at the LHC.



Celis, A., FuentesMartin, J., & Serodio, H. (2015). An invisible axion model with controlled FCNCs at tree level. Phys. Lett. B, 741, 117–123.
Abstract: We derive the necessary conditions to build a class of invisible axion models with Flavor Changing Neutral Currents at treelevel controlled by the fermion mixing matrices and present an explicit model implementation. A horizontal PecceiQuinn symmetry provides a solution to the strong CP problem via the PecceiQuinn mechanism and predicts a cold dark mater candidate, the invisible axion or familon. The smallness of active neutrino masses can be explained via a type I seesaw mechanism, providing a dynamical origin for the heavy seesaw scale. The possibility to avoid the domain wall problem stands as one of the most interesting features of the type of models considered. Experimental limits relying on the axionphoton coupling, astrophysical considerations and familon searches in rare kaon and muon decays are discussed.



Celis, A., FuentesMartin, J., & Serodio, H. (2014). A class of invisible axion models with FCNCs at tree level. J. High Energy Phys., 12(12), 167–53pp.
Abstract: We build a class of invisible axion models with treelevel Flavor Changing Neutral Currents completely controlled by the fermion mixing matrices. The scalar sector of these models contains threeHiggs doublets and a complex scalar gauge singlet, with the same fermionic content as in the Standard Model. A horizontal PecceiQuinn symmetry provides a solution to the strong CP problem and predicts the existence of a very light and weakly coupled pseudoGoldstone boson, the invisible axion or familon. A phenomenological analysis is performed taking into account familon searches in rare kaon and muon decays, astrophysical considerations and axion searches via axionphoton conversion. Drastic differences are found in the axion properties of different models due to the strong hierarchy of the CKM matrix, making some of the models considered much more constrained than others. We also obtain that a rich variety of these models avoid the domain wall problem. A possible mechanism to protect the solution to the strong CP problem against gravitational effects is also discussed.

