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Register a new userA no-go theorem for non-standard explanations of the $tauto K_Spi u_tau$ CP asymmetry
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The CP asymmetry in $tauto K_Spi u_tau$, as measured by the BaBar collaboration, differs from the Standard Model prediction by $2.8sigma$. Most non-standard interactions do not allow for the required strong phase needed to produce a non-vanishing CP asymmetry, leaving only new tensor interactions as a possible mechanism. We demonstrate that, contrary to previous assumptions in the literature, the crucial interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watsons final-state-interaction theorem. Furthermore, we find that the strength of the relevant CP-violating tensor interaction is strongly constrained by bounds from the neutron electric dipole moment and $D$-$bar{D}$ mixing. These observations together imply that it is extremely difficult to explain the current $tauto K_Spi u_tau$ measurement in terms of physics beyond the Standard Model originating in the ultraviolet.
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In this work, we proceed to study the $CP$ asymmetry in the angular distributions of $tauto K_Spi u_tau$ decays within a general effective field theory framework including four-fermion operators up to dimension-six. It is found that, besides the commonly considered scalar-vector interference, the tensor-scalar interference can also produce a nonzero $CP$ asymmetry in the angular distributions, in the presence of complex couplings. Using the dispersive representations of the $Kpi$ form factors as inputs, and taking into account the detector efficiencies of the Belle measurement, we firstly update our previous SM predictions for the $CP$ asymmetries in the same four $Kpi$ invariant-mass bins as set by the Belle collaboration. Bounds on the effective couplings of the nonstandard scalar and tensor interactions are then obtained under the combined constraints from the $CP$ asymmetries measured in the four bins and the branching ratio of $tau^-to K_Spi^- u_tau$ decay, with the numerical results given respectively by $mathrm{Im}[hat{epsilon}_S]=-0.008pm0.027$ and $mathrm{Im}[hat{epsilon}_T]=0.03pm0.12$, at the renormalization scale $mu=2~mathrm{GeV}$ in the $mathrm{overline{MS}}$ scheme. Using these best-fit values, we also find that the distributions of the $CP$ asymmetries can deviate significantly from the SM prediction in almost the whole $Kpi$ invariant-mass regions. The current bounds are still plagued by large experimental uncertainties, but will be improved with more precise measurements from the Belle II experiment as well as the proposed Tera-Z and STCF facilities.
In a combined study of the decay spectra of $tau^-to K_Spi^- u_tau$ and $tau^-to K^-eta u_tau$ decays within a dispersive representation of the required form factors, we illustrate how the $K^*(1410)$ resonance parameters, defined through the pole position in the complex plane, can be extracted with improved precision as compared to previous studies. While we obtain a substantial improvement in the mass, the uncertainty in the width is only slightly reduced, with the findings $M_{K^{*prime}}=1304 pm 17,$MeV and $Gamma_{K^{*prime}} = 171 pm 62,$MeV. Further constraints on the width could result from updated analyses of the $Kpi$ and/or $Keta$ spectra using the full Belle-I data sample. Prospects for Belle-II are also discussed. As the $K^-pi^0$ vector form factor enters the description of the decay $tau^-to K^-eta u_tau$, we are in a position to investigate isospin violations in its parameters like the form factor slopes. In this respect also making available the spectrum of the transition $tau^-to K^-pi^0 u_tau$ would be extremely useful, as it would allow to study those isospin violations with much higher precision.
A general framework for studying compactifications in supergravity and string theories was introduced by Candelas, Horowitz, Strominger and Witten. This was further generalised to take into account the warp factor by de Wit, Smit and Hari Dass. Though the prime focus of the latter was to find solutions with nontrivial warp factors (shown not to exist under a variety of circumstances), it was shown there that de Sitter compactifications are generically disfavoured. In this note we place these results in the context of a revived interest in de Sitter spacetimes .
There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders.
We introduce fully SGUTs, SUSY grand unified theories that, upon symmetry breaking through the Higgs mechanism, decompose into a visible sector and an extra sector where the dynamics of the extra sector gauge group is responsible for SUSY breaking. Fully SGUTs thus have the important feature that all gauge groups of the visible sector and the extra sector unify into a simple gauge group at the SGUT scale, therefore generalizing the successful MSSM gauge coupling unification to all the gauge couplings of the theory. By focusing on the ISS SUSY-breaking mechanism in the extra sector, we show that it is impossible to reproduce the MSSM matter content when there exists a metastable ISS SUSY-breaking state.
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