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Register a new userDecay of $B^pm to tau^pm +$ missing momentum and direct measurement of the mixing parameter $U_{tau N}$
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We derive the decay widths for the leptonic decays of heavy charged pseudoscalars to massive sterile neutrinos, $M^{pm} to ell^{pm} + N$, within the frameworks involving the Standard Model and two-Higgs doublets (type II). We then apply the result to $B^pm to tau^pm +$ missing momentum of the Belle/BaBar experimental results, in order to measure directly the relevant parameter space, including the mixing parameter $U_{tau N}$.
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The hitherto unobserved purely leptonic decays B^pm -> tau^pm u and B^pm -> mu^pm u are of much interest at current and future runs of the e+e- B factories. Such decays are sensitive to charged Higgs bosons (H^pm) at the tree-level and provide essentially model independent constraints on tanbeta/m_{H^pm}. We include the large corrections to the H^pm-ub coupling induced by virtual SUSY effects and show that the bounds on tanbeta/m_{H^pm} can be significantly weakened or strengthened.
In phenomenological preparation for new measurements one searches for the carriers of quality signatures. Often, the first approach quantities may be difficult to measure or to provide sufficiently precise predictions for comparisons. Complexity of necessary details grow with precision. To achieve the goal one can not break the theory principles, and take into account effects which could be ignored earlier. Mixed approach where dominant effects are taken into account with intuitive even simplistic approach was developed. Non dominant corrections were controlled with the help of Monte Carlo simulations. Concept of Optimal Variables was successfully applied for many measurements. New techniques, like Machine Learning, offer solutions to exploit multidimensional signatures. Complementarity of these new and old approaches is studied for the example of Higgs Boson CP-parity measurements in H to tau^+tau^-, tau^pm to nu (3pi)^pm cascade decays.
We report the first measurement of the $tau$ lepton polarization in the decay ${bar B} rightarrow D^* tau^- {bar u_{tau}}$ as well as a new measurement of the ratio of the branching fractions $R(D^{*}) = mathcal{B}({bar B} rightarrow D^* tau^- {bar u_{tau}}) / mathcal{B}({bar B} rightarrow D^* ell^- {bar u_{ell}})$, where $ell^-$ denotes an electron or a muon, with the decays $tau^- rightarrow pi^- u_{tau}$ and $tau^- rightarrow rho^- u_{tau}$. We use the full data sample of $772 times 10^6$ $B{bar B}$ pairs accumulated with the Belle detector at the KEKB electron-positron collider. Our preliminary results, $R(D^*) = 0.276 pm 0.034{rm (stat.)} ^{+0.029} _{-0.026}{rm (syst.)}$ and $P_{tau} = -0.44 pm 0.47 {rm (stat.)} ^{+0.20} _{-0.17} {rm (syst.)}$, are consistent with the theoretical predictions of the Standard Model within $0.6$ standard deviation.
We report the first measurement of the $D^{ast -}$ meson polarization in the decay $B^0 to D^{*-} tau^+ u_{tau}$ using the full data sample of 772$times 10^6$ $Bbar{B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our result, $F_L^{D^ast} = 0.60 pm 0.08 ({rm stat}) pm 0.04 ({rm sys})$, where $F_L^{D^ast}$ denotes the $D^{ast-}$ meson longitudinal polarization fraction, agrees within about $1.7$ standard deviations of the standard model prediction.
Supposing only Lorentz and the gauge invariances of the Lagrangian, we derive energy and angular distributions for $tau^pm to mu^pm mu^pm mu^mp$ lepton flavor violating decay process. Using these results, we discuss methods to determine the parameters associated with the lepton flavor violating interactions.
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