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Register a new userNew Terms for the Compact Form of Electroweak Chiral Lagrangian
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The compact form of the electroweak chiral Lagrangian is a reformulation of its original form and is expressed in terms of chiral rotated electroweak gauge fields, which is crucial for relating the information of underlying theories to the coefficients of the low-energy effective Lagrangian. However the compact form obtained in previous works is not complete. In this letter we add several new chiral invariant terms to it and discuss the contributions of these terms to the original electroweak chiral Lagrangian.
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A revised and complete list of the electroweak chiral lagrangian operators up to dimension-four is provided. The connection of these operators to the $S$, $T$ and $U$ parameters and the parameters describing the triple gauge boson vertices $WWgamma$ and $WWZ$ is made, and the size of these parameters from new heavy physics is estimated using a one flavor-doublet model of heavy fermions. The coefficients of the chiral lagrangian operators are also computed in this model.
We add a nonstandard higgs into the traditional bosonic part of electroweak chiral Lagrangian, in purpose of finding out the contribution to EWCL coefficients from processes with internal line higgs particle. To construct the effective Lagrangian with higgs, we use low energy expansion scheme and write down all the independent terms conserving $SU(2)times U_Y(1)$ symmetry in the nonlinear representation which we show is equivalent to the linear representation. Then we integrate out higgs using loop expansion technique at 1-loop level, contributions from all possible terms are obtained. We find three terms, $mathcal{L}_5$, $mathcal{L}_7$, $mathcal{L}_{10}$ in EWCL are important, for which the contributions from higgs can be further expressed in terms of higgs partial decay width $Gamma_{hto ZZ}$ and $Gamma_{hto WW}$. Higg mass dependence of the coefficients in EWCL are discussed.
The Standard Model of fundamental interactions, albeit an incredibly elegant and successful theory, lacks explanations for some experimental and theoretical open questions. Interestingly, many of these problems seem to be related to the electroweak symmetry breaking sector of the theory, whose dynamical generation is still unknown. Important questions such as what is the true nature of the Higgs boson, why is its mass so light and so close to that of the electroweak gauge bosons or whether the properties of this particle are the ones predicted in the Standard Model remain unanswered. The LHC is our tool to unveil these mysteries and vector boson scattering processes are the perfect window to access them, since they are considered as the most sensitive observables to new physics in the electroweak symmetry breaking sector. In this Thesis we employ the effective electroweak chiral Lagrangian with a light Higgs, which assumes a strongly interacting electroweak symmetry breaking sector, to perform a model independent analysis of the phenomenology of vector boson scattering processes at the LHC as well as to present quantitative predictions for the sensitivity to possible beyond the Standard Model physics scenarios.
We discuss the sensitivity of the $e^+ e^- rightarrow W^+ W^-$ cross section at a future $e^+ e^-$ collider with $sqrt{s}=500$GeV to the non-decoupling effects of a techni-$rho$ like vector resonance. The non-decoupling effects are parametrized by the chiral coefficients of the electroweak chiral perturbation theory. We define renormalization scale independent chiral coefficients by subtracting the Standard Model loop contributions. We also estimate the size of the decoupling effects of the techni-$rho$ resonance by using a phenomenological Lagrangian including the vector resonance.
The meson-baryon interactions in s-wave in the strangeness S=-1 sector are studied using a chiral unitarity approach based on the next-to-leading order chiral SU(3) Lagrangian. The model is fitted to the large set of experimental data in different two-body channels. Particular attention is paid to the $Xi$ hyperon production reaction, $bar{K} N rightarrow K Xi$, where the effect of the next-to-leading order terms in the Lagrangian play a crucial role, since the cross section of this reaction at tree level is zero.
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