Narrow Results

Decays of B mesons into final states containing a τ lepton are sensitive to new charged current interactions that break lepton-flavor universality. These decays have been studied only at e⁺e^- colliders, where the low-background environment and well-known initial state make it possible to observe small signals with undetectable neutrinos. In particular, the large data samples of the B factories and recent advances in techniques for full-event reconstruction have led to evidence for the decay B⁺→τ⁺ ν_τ and unambiguous observation of the decays . These results exclude large regions of the parameter space for a variety of new physics models. Furthermore, the branching fraction for has been measured to be higher than the Standard Model expectation by more than three standard deviations, making this an interesting topic for further research. This paper reviews the theoretical and experimental status of this topic, summarizing the results at this time and outlining the path for further improvements.

In two-Higgs-doublet models with exact $Z_2$ symmetry, putting $m_h\simeq 125\mathrm{\text{GeV}}$ at the alignment limit, the following limits on the heavy scalar masses are obtained from the conditions of unitarity and stability of the scalar potential: $m_H$, $m_A$, $m_{H^{+}}<1\mathrm{\text{TeV}}$ and $1/8<tan\beta <8$. The constraints from $b\to s\gamma$ and neutral meson mass differences, when superimposed on the unitarity constraints, put a tighter lower limit on $tan\beta$ depending on $m_{H^{+}}$. It has also been shown that larger values of $tan\beta$ can be allowed by introducing soft breaking term in the potential at the expense of a correlation between $m_H$ and the soft breaking parameter.

In this paper we consider some aspects of the Manohar–Wise extension of the SM with a colour-octet electroweak-doublet scalar applied to 2HDM. We present theoretical constraints on the parameters of this extension to both the SM and the 2HDM and discuss related phenomenology at LHC.

In this paper we consider some aspects of the Manohar–Wise extension of the SM with a colour-octet electroweak-doublet scalar applied to 2HDM. We present theoretical constraints on the parameters of this extension to both the SM and the 2HDM and discuss related phenomenology at LHC.