Flores-Tlalpa, A., Lopez Castro, G., & Roig, P. (2016). Five-body leptonic decays of muon and tau lepton. J. High Energy Phys., 04(4), 185–21pp.
Abstract: We study the five-body decays u(-) -> e(-)e(+)e(-)nu u (nu) over bar (e) and tau(-) -> l(-)l'+l'-nu(tau)(nu) over bar (l) for l, l' = e, u within the Standard Model (SM) and in a general effective field theory description of the weak interactions at low energies. We compute the branching ratios and compare our results with two previous – mutually discrepan – SM calculations. By assuming a general structure for the weak currents we derive the expressions for the energy and angular distributions of the three charged leptons when the decaying lepton is polarized, which will be useful in precise tests of the weak charged current at Belle II. In these decays, leptonic T-odd correlations in triple products of spin and momenta – which may signal time reversal violation in the leptonic sector – are suppressed by the tiny neutrino masses. Therefore, a measurement of such T-violating observables would be associated to neutrinoless lepton flavor violating (LFV) decays, where this effect is not extremely suppressed. We also study the backgrounds that the SM five-lepton lepton decays constitute to searches of LFV L- -> ? l(-)l'+l'(-) decays. Searches at high values of the invariant mass of the l'(+)l'(-) pair look the most convenient way to overcome the background.
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Bonilla, C., Nebot, M., Valle, J. W. F., & Srivastava, R. (2016). Flavor physics scenario for the 750 GeV diphoton anomaly. Phys. Rev. D, 93(7), 073009–5pp.
Abstract: A simple variant of a realistic flavor symmetry scheme for fermion masses and mixings provides a possible interpretation of the diphoton anomaly as an electroweak singlet “flavon.” The existence of TeV scale vectorlike T-quarks required to provide adequate values for Cabibbo-Kobayashi-Maskawa (CKM) parameters can also naturally account for the diphoton anomaly. Correlations between V-ub and V-cb with the vectorlike T-quark mass can be predicted. Should the diphoton anomaly survive in a future run, our proposed interpretation can also be tested in upcoming B and LHC studies.
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Botella, F. J., Branco, G. C., Nebot, M., & Rebelo, M. N. (2016). Flavour-changing Higgs couplings in a class of two Higgs doublet models. Eur. Phys. J. C, 76(3), 161–17pp.
Abstract: We analyse various flavour-changing processes like t -> hu, hc, h -> t e, tau μas well as hadronic decays h -> bs, bd, in the framework of a class of two Higgs doublet models where there are flavour-changing neutral scalar currents at tree level. These models have the remarkable feature of having these flavour-violating couplings entirely determined by the CKM and PMNS matrices as well as tan beta. The flavour structure of these scalar currents results from a symmetry of the Lagrangian and therefore it is natural and stable under the renormalisation group. We show that in some of the models the rates of the above flavour-changing processes can reach the discovery level at the LHC at 13 TeV even taking into account the stringent bounds on low energy processes, in particular μ-> e gamma.
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Yamagata-Sekihara, J., Garcia-Recio, C., Nieves, J., Salcedo, L. L., & Tolos, L. (2016). Formation spectra of charmed meson-nucleus systems using an antiproton beam. Phys. Lett. B, 754, 26–32.
Abstract: We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson-nucleon interactions and the properties of the charmed mesons in the nuclear medium. The (D) over bar mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the (D) over barN pair. Employing an effective model for the (D) over barN and DN interactions and solving the Klein-Gordon equation for (D) over bar and D in finite nuclei, we find that the D0-11B system has 1s and 2p mesic nuclear states and that the D0-11B system binds in a 1s state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the [(D) over bar B--11] and [D-0-B-11] mesic nuclei for an antiproton beam on a C-12 target. Our results suggest that it is possible to observe the 2p D- mesic nuclear state with an appropriate experimental setup.
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Sborlini, G. F. R., Driencourt-Mangin, F., Hernandez-Pinto, R. J., & Rodrigo, G. (2016). Four-dimensional unsubtraction from the loop-tree duality. J. High Energy Phys., 08(8), 160–42pp.
Abstract: We present a new algorithm to construct a purely four dimensional representation of higher-order perturbative corrections to physical cross-sections at next-to-leading order (NLO). The algorithm is based on the loop-tree duality (LTD), and it is implemented by introducing a suitable mapping between the external and loop momenta of the virtual scattering amplitudes, and the external momenta of the real emission corrections. In this way, the sum over degenerate infrared states is performed at integrand level and the cancellation of infrared divergences occurs locally without introducing subtraction counter-terms to deal with soft and final-state collinear singularities. The dual representation of ultraviolet counter-terms is also discussed in detail, in particular for self-energy contributions. The method is first illustrated with the scalar three-point function, before proceeding with the calculation of the physical cross-section for gamma* -> q (q) over bar (g), and its generalisation to multi-leg processes. The extension to next-to-next-to-leading order (NNLO) is briefly commented.
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