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Recently there has been interest in the correlation between R(D * ) and the branching ratio (BR) of B − c → τν in models with a charged scalar H ± . Any enhancement of R(D * ) by H ± alone (in order to agree with current data) also enhances BR(B − c → τν), for which there has been no direct search at hadron colliders. We show that LEP data taken at the Z peak requires BR(B − c → τν) 10%, and this constraint is significantly stronger than the recent constraint BR(B − c → τν) 30% from considering the lifetime of B c . In order to respect this new constraint, any explanation of the R(D) and R(D * ) anomaly in terms of H ± alone would require the future measurements of R(D * ) to be even closer to the Standard Model prediction. A stronger limit on BR(B − c → τν) (or its first measurement) would be obtained if the L3 collaboration used all its data taken at the Z peak. * Electronic address: a.g.akeroyd@soton.ac.uk † Electronic address:

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We study the influence of a charged-Higgs on the excess of branching fraction ratio,, in a generic twoHiggs-doublet model. In order to investigate the lepton polarization, the detailed decay amplitudes with lepton helicity are given. When the charged-Higgs is used to resolve excesses, it is found that two independent Yukawa couplings are needed to explain the R D and R D * anomalies. We show that when

In this study, we investigate muon g − 2, R K ( * ) , and R D ( * ) anomalies in a specific model with one doublet, one triplet, and one singlet scalar leptoquark (LQ). When the strict limits from the ℓ ′ → ℓγ, ∆B = 2, B s → µ + µ − , and B + → K + νν processes are considered, it is difficult to use one scalar LQ to explain all of the anomalies due to the strong correlations among the constraints and observables. After ignoring the constraints and small couplings, the muon g −2 can be explained by the doublet LQ alone due to the m t enhancement, whereas the measured and unexpected smaller R K ( * ) requires the combined effects of the doublet and triplet LQs, and the R D and R D * excesses depend on the singlet LQ through scalar-and tensor-type interactions.

Publisher's Note: Forward-backward asymmetry of the top quark in diquark models [Phys. Rev. D 82, 034034 (2010)]

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We study the lepton flavor violation (LFV) in tau decays in the framework of the supersymmetric seesaw mechanism with nonholomorphic terms for the lepton sector at a large tan. In particular, we analyze two new decay modes ! 'f 0 980 and ! 'K K ÿ arising from the scalar boson exchanges contrast to ! ' 0 from the pseudoscalar ones. We find that the decay branching ratios of the two new modes could be not only as large as the current upper limits of O10 ÿ7 , but also larger than those of ! ' 0 . Experimental searches for the two modes are important for the LFV induced by the scalarmediated mechanism. In addition, we show that the decay branching ratios of ! ' ÿ are related to those of ! ' and ! 'f 0 980. In the standard model (SM), since the neutrinos are regarded as massless particles, the processes associated with lepton flavors are always conserved. Inspired by the discoveries of nonzero neutrino masses [1,2], it has been studied enormously how to generate the neutrino masses which are less than a few eV. By supplementing with singlet right-handed Majorana neutrinos with masses M R required to be around the scale of unified theory, it is found that the seesaw mechanism is one of the natural ways [3] to obtain the small neutrino masses. Accordingly, in non-SUSY models, it is easy to understand that the effects of the lepton flavor violation (LFV) are suppressed by 1=M R . However, in models with SUSY, due to the nondiagonal neutrino mass matrix, the flavor conservation in the slepton sector at the unified scale will be violated at the M R scale via renormalization [4 -6]. The flavor violating effects could propagate to the electroweak scale so that instead of 1=M R , the suppression of the LFV could be 1=M SUSY with M SUSY