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Kim, C. S., Lopez-Castro, G., Tostado, S. L., & Vicente, A. (2017). Remarks on the Standard Model predictions for R(D) and R(D*). Phys. Rev. D, 95(1), 013003–7pp.
Abstract: Semileptonic b -> c transitions, and in particular the ratios R(D-(*())) = Gamma(B -> D-(*())tau nu)/Gamma(B -> D-(*())l nu), can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by the BABAR, Belle, and LHCb collaborations and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that R(D) might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In contrast, the Standard Model prediction for R(D*) is found to be more robust, because possible pollutions from B* contributions turn out to be negligibly small; this indicates that R(D) is a promising observable for searches of new physics.
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Escribano, P., Martin Lozano, V., & Vicente, A. (2023). Scotogenic explanation for the 95 GeV excesses. Phys. Rev. D, 108(11), 115001–13pp.
Abstract: Several hints of the presence of a new state at about 95 GeV have been observed recently. The CMS and ATLAS Collaborations have reported excesses in the diphoton channel at about this diphoton invariant mass with local statistical significances of 2.9 sigma and 1.7 sigma, respectively. Furthermore, a 2 sigma excess in the bb over bar final state was also observed at LEP, again pointing at a similar mass value. We interpret these intriguing hints of new physics in a variant of the Scotogenic model, an economical scenario that induces Majorana neutrino masses at the loop level and includes a viable dark matter candidate. We show that our model can explain the 95 GeV excesses while respecting the relevant collider, Higgs, and electroweak precision bounds and discuss other phenomenological features of our scenario.
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Vicente, A. (2018). Anomalies in b -> s transitions and dark matter. Adv. High. Energy Phys., 2018, 3905848–11pp.
Abstract: Since 2013, the LHCb collaboration has reported on the measurement of several observables associated with b -> s transitions, finding various deviations from their predicted values in the Standard Model. These include a set of deviations in branching ratios and angular observables, as well as in the observables R-k and R-k*, specially built to test the possible violation of Lepton Flavor Universality. Even though these tantalizing hints are not conclusive yet, the b -> s* anomalies have gained considerable attention in the flavor community. Here we review new physics models that address these anomalies and explore their possible connection to the dark matter of the Universe. After discussing some of the ideas introduced in these works and classifying the proposed models, two selected examples are presented in detail in order to illustrate the potential interplay between these two areas of current particle physics.
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Aristizabal Sierra, D., Herrero-Garcia, J., Restrepo, D., & Vicente, A. (2016). Diboson anomaly: Heavy Higgs resonance and QCD vectorlike exotics. Phys. Rev. D, 93(1), 015012–12pp.
Abstract: The ATLAS Collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8-2.2 TeV. In light of these results, we argue that such a signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I two Higgs doublet model. We demonstrate that in the presence of colored vectorlike fermions, its gluon fusion production cross section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. Our findings show that barring the color triplet case, any QCD “exotic” representation can fit the ATLAS result in fairly large portions of the parameter space. We have found that if the diboson excess is confirmed and this mechanism is indeed responsible for it, then the LHC Run-2 should find (i) a CP-odd scalar with mass below similar to 2.3 TeV, (ii) new colored states with masses below similar to 2 TeV, (iii) no statistically significant diboson events in the W(+/-)Z channel, (iv) events in the triboson channels W(+/-)W(-/+)Z and ZZZ with invariant mass amounting to the mass of the CP-odd scalar.
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Vicente, A. (2019). Higgs Lepton Flavor Violating Decays in Two Higgs Doublet Models. Front. Physics, 7, 174–13pp.
Abstract: The discovery of a non-zero rate for a lepton flavor violating decay mode of the Higgs boson would definitely be an indication of New Physics. We review the prospects for such signal in Two Higgs Doublet Models, in particular for Higgs boson decays into tau μfinal states. We will show that this scenario contains all the necessary ingredients to provide large flavor violating rates and still be compatible with the stringent limits from direct searches and low-energy flavor experiments.
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