Jung, M., Li, X. Q., & Pich, A. (2012). Exclusive radiative B-meson decays within the aligned two-Higgs-doublet model. J. High Energy Phys., 10(10), 063–33pp.
Abstract: In the aligned two-Higgs-doublet model, the alignment of Yukawa matrices in flavour space guarantees the absence of tree-level flavour-changing neutral currents, while allowing at the same time for new sources of CP violation, implying potentially large effects in many low-energy processes. In this work we study the constraints from exclusive radiative B -> V gamma decays, where V denotes a light vector meson. The current experimental data on the CP-averaged branching ratios and the direct CP and isospin asymmetries are analyzed. It is found that, while the branching ratios and direct CP asymmetries do not constrain the parameter space much further compared to the inclusive B -> X-s,X-d gamma decays, complementary constraints can be obtained from the isospin asymmetries Delta(K*gamma) and Delta(rho gamma). In addition, correlations between the various observables in exclusive B -> V gamma and inclusive B -> X-s,X-d gamma decays are investigated in detail, and predictions are made for several so far unmeasured observables.
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Celis, A., Jung, M., Li, X. Q., & Pich, A. (2013). Sensitivity to charged scalars in B -> D-(*)tau nu(tau) and B -> tau nu(tau) decays. J. High Energy Phys., 01(1), 054–27pp.
Abstract: We analyze the recent experimental evidence for an excess of tau-lepton production in several exclusive semileptonic B-meson decays in the context of two-Higgs-doublet models. These decay modes are sensitive to the exchange of charged scalars and constrain strongly their Yukawa interactions. While the usual Type-II scenario cannot accommodate the recent BaBar data, this is possible within more general models in which the charged-scalar couplings to up-type quarks are not as suppressed. Both the B -> D-(*)tau nu(tau) and the B -> tau nu(tau) data can be fitted within the framework of the Aligned Two-Higgs-Doublet Model, but the resulting parameter ranges are in conflict with the constraints from leptonic charm decays. This could indicate a departure from the family universality of the Yukawa couplings, beyond their characteristic fermion mass dependence. We discuss several new observables that are sensitive to a hypothetical charged-scalar contribution, demonstrating that they are well suited to distinguish between different scenarios of new physics in the scalar sector, and also between this group and models with different Dirac structures; their experimental study would therefore shed light on the relevance of scalar exchanges in semileptonic b -> c tau(-)(nu) over bar (tau) transitions.
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Campanario, F., Czyz, H., Gluza, J., Gunia, M., Riemann, T., Rodrigo, G., et al. (2014). Complete QED NLO contributions to the reaction e(+)e(-) -> mu(+)mu(-)gamma and their implementation in the event generator PHOKHARA. J. High Energy Phys., 02(2), 114–27pp.
Abstract: KLOE and Babar have an observed discrepancy of 2% to 5% in the invariant pion pair production cross section. These measurements are based on approximate NLO mu(+)mu(-)gamma cross section predictions of the Monte Carlo event generator PHOKHARA7.0. In this article, the complete NLO radiative corrections to mu(+)mu(-)gamma production are calculated and implemented in the Monte Carlo event generator PHOKHARA9.0. Numerical reliability is guaranteed by two independent approaches to the real and the virtual corrections. The novel features include the contribution of pentagon diagrams in the virtual corrections, which form a gauge-invariant set when combined with their box diagram partners. They may contribute to certain distributions at the percent level. Also the real emission was complemented with two-photon final state emission contributions not included in the generator PHOKHARA7.0. We demonstrate that the numerical influence reaches, for realistic charge-averaged experimental setups, not more than 0.1% at KLOE and 0.3% at BaBar energies. As a result, we exclude the approximations in earlier versions of PHOKHARA as origin of the observed experimental discrepancy.
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Della Morte, M., Dooling, S., Heitger, J., Hesse, D., & Simma, H. (2014). Matching of heavy-light flavour currents between HQET at order 1/m and QCD: I. Strategy and tree-level study. J. High Energy Phys., 05(5), 060–31pp.
Abstract: We present a strategy how to match the full set of components of the heavy-light axial and vector currents in Heavy Quark Effective Theory (HQET), up to and including 1/m (h) -corrections, to QCD. While the ultimate goal is to apply these matching conditions non-perturbatively, in this study we first have implemented them at tree-level, in order to find good choices of the matching observables with small contributions. They can later be employed in the non-perturbative matching procedure which is a crucial part of precision HQET computations of semileptonic decay form factors in lattice QCD.
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Li, X. Q., Lu, J., & Pich, A. (2014). Bs,d(0) -> l(+)l(-) decays in the aligned two-Higgs-doublet model. J. High Energy Phys., 06(6), 022–39pp.
Abstract: The rare decays B-s,d(0) -> l(+)l(-) are analyzed within the general framework of the aligned two-Higgs doublet model. We present a complete one-loop calculation of the relevant short-distance Wilson coefficients, giving a detailed technical summary of our results and comparing them with previous calculations performed in particular limits or approximations. We investigate the impact of various model parameters on the branching ratios and study the phenomenological constraints imposed by present data.
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