The Higgs as a Composite Nambu-Goldstone Boson

126

187

We continue our investigation of gauge theories in which the Higgs boson arises as a pseudo-Nambu-Goldstone boson (pNGB) and top-partners arise as bound states of three hyperfermions. All models have additional pNGBs in their spectrum that should be accessible at LHC. We analyze the patterns of symmetry breaking and present all relevant couplings of the pNGBs with the gauge fields. We discuss how vacuum misalignment and a mass for the pNGBs is generated by a loop-induced potential. Finally, we paint a very broad, qualitative, picture of the kind of experimental signatures these models give rise to, setting the stage for further analysis.

Section: Jhep06(2016)107mentioning

confidence: 99%

Gauge theories of partial compositeness: scenarios for Run-II of the LHC

Ferretti

2016

126

187

“…The composite nature of the Higgs is indeed the source of an infrared-saturated contribution to the EW oblique parameters [47] that, taken on its own, sets a stringent bound on the compositeness scale of the Higgs boson and inevitably raises the amount of fine-tuning [48][49][50][51]. It is thus clear that a scenario with an acceptable amount of tuning can only be obtained if further corrections to the EW parameters are present.…”

Section: Jhep10(2013)160mentioning

confidence: 99%

Light top partners and precision physics

Grojean

Matsedonskyi

Panico

2013

170

227

We analyze the corrections to the precision EW observables in minimal composite Higgs models by using a general effective parametrization that also includes the lightest fermionic resonances. A new, possibly large, logarithmically divergent contribution to S is identified, which comes purely from the strong dynamics. It can be interpreted as a running of S induced by the non-renormalizable Higgs interactions due to the nonlinear σ-model structure. As expected, the corrections to the T parameter coming from fermion loops are finite and dominated by the contributions of the lightest composite states. The fit of the oblique parameters suggests a rather stringent lower bound on the σ-model scale f 750 GeV. The corrections to the Zb L b L vertex coming from the lowest-order operators in the effective Lagrangian are finite and somewhat correlated to the corrections to T . Large additional contributions are generated by contact interactions with 4 composite fermions. In this case a logarithmic divergence can be generated and the correlation with T is removed. We also analyze the tree-level corrections to the top couplings, which are expected to be large due to the sizable degree of compositeness of the third generation quarks. We find that for a moderate amount of tuning the deviation in V tb can be of order 5% while the distortion of the Zt L t L vertex can be 10%.

“…Interestingly, there exists a simple dispersion relation for the electromagnetic pion mass difference in QCD [63][64][65]. In particular, in that case current four point functions can be reduced to two point functions using PCAC and current algebra.…”

Section: Jhep03(2012)046mentioning

confidence: 99%

Exploring T and S parameters in Vector Meson Dominance models of strong electroweak symmetry breaking

Orgogozo

Rychkov

2012

Abstract:We revisit the electroweak precision tests for Higgsless models of strong EWSB. We use the Vector Meson Dominance approach and express S and T via couplings characterizing vector and axial spin-1 resonances of the strong sector. These couplings are constrained by the elastic unitarity and by requiring a good UV behavior of various formfactors. We pay particular attention to the one-loop contribution of resonances to T (beyond the chiral log), and to how it can improve the fit. We also make contact with the recent studies of Conformal Technicolor. We explain why the second Weinberg sum rule never converges in these models, and formulate a condition necessary for preserving the custodial symmetry in the IR.