No Arabic abstract
In models with an extended Higgs sector there exists an alignment limit, in which the lightest CP-even Higgs boson mimics the Standard Model Higgs. The alignment limit is commonly associated with the decoupling limit, where all non-standard scalars are significantly heavier than the $Z$ boson. However, alignment can occur irrespective of the mass scale of the rest of the Higgs sector. In this work we discuss the general conditions that lead to alignment without decoupling, therefore allowing for the existence of additional non-standard Higgs bosons at the weak scale. The values of $tanbeta$ for which this happens are derived in terms of the effective Higgs quartic couplings in general two-Higgs-doublet models as well as in supersymmetric theories, including the MSSM and the NMSSM. Moreover, we study the information encoded in the variations of the SM Higgs-fermion couplings to explore regions in the $m_A - tanbeta$ parameter space.
We present an update of the branching ratios for Higgs-boson decays in the Standard Model. We list results for all relevant branching ratios together with corresponding uncertainties resulting from input parameters and missing higher-order corrections. As sources of parametric uncertainties we include the masses of the charm, bottom, and top quarks as well as the QCD coupling constant. We compare our results with other predictions in the literature.
One way to probe new physics beyond standard model is to check the correlation among higher dimension operators in effective field theory. We examine the strong correlation between the processes of $pprightarrow tHq$ and $pprightarrow tq$ which both depend on the same three operators. The correlation indicates that, according to the data of $pprightarrow tq$, $sigma_{tHq}=big[106.8 pm 64.8big]~{rm fb}$ which is far below the current upper limit $sigma_{tHq}leq 900~{rm fb}$.
We present results from a state-of-the-art fit of electroweak precision observables and Higgs-boson signal-strength measurements performed using 7 and 8 TeV data from the Large Hadron Collider. Based on the HEPfit package, our study updates the traditional fit of electroweak precision observables and extends it to include Higgs-boson measurements. As a result we obtain constraints on new physics corrections to both electroweak observables and Higgs-boson couplings. We present the projected accuracy of the fit taking into account the expected sensitivities at future colliders.
The high-energy scattering of massive electroweak bosons, known as vector boson scattering (VBS), is a sensitive probe of new physics. VBS signatures will be thoroughly and systematically investigated at the LHC with the large data samples available and those that will be collected in the near future. Searches for deviations from Standard Model (SM) expectations in VBS facilitate tests of the Electroweak Symmetry Breaking (EWSB) mechanism. Current state-of-the-art tools and theory developments, together with the latest experimental results, and the studies foreseen for the near future are summarized. A review of the existing Beyond the SM (BSM) models that could be tested with such studies as well as data analysis strategies to understand the interplay between models and the effective field theory paradigm for interpreting experimental results are discussed. This document is a summary of the EU COST network VBScan workshop on the sensitivity of VBS processes for BSM frameworks that took place December 4-5, 2019 at the LIP facilities in Lisbon, Portugal. In this manuscript we outline the scope of the workshop, summarize the different contributions from theory and experiment, and discuss the relevant findings.
A recent preliminary investigation based on Durguts report at the American Physical Society site shows a structure at $18.4~ {rm GeV}$ exists in the invariant mass distribution of $Upsilon l^+l^- ~ (l = e,, mu)$ at the LHC center-of-mass energy of $7$ and $8~ {rm TeV}$. Its appearance attracts attention of theorists and experimentalists of high energy physics, because it might be a Higgs-like boson of $18.4~ {rm GeV}$ which would serve as a signal of the new physics beyond the Standard Model. We have carried out computations on the corresponding quantities (production and decay rates) based on quantum field theory and compared the results with experimental data. Our numerical results do not support the assertion that the $18.4~ {rm GeV}$ peak corresponds to a neutral $0^{++}$ boson which decays into $Upsilon l^+l^-$. Much further works (both experimental and theoretical) are badly needed.