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Register a new userApproaching robust EFT limits for CP-violation in the Higgs sector
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Constraining CP-violating interactions in effective field theory (EFT) of dimension six faces two challenges. Firstly, degeneracies in the multi-dimensional space of Wilson coefficients have to be lifted. Secondly, quadratic contributions of CP-odd dimension six operators are difficult to disentangle from squared contributions of CP-even dimension six operators and from linear contributions of dimension eight operators. Both of these problems are present when new sources of CP-violation are present in the interactions between the Higgs boson and heavy strongly-interacting fermions. We show that degeneracies in the Wilson coefficients can be removed by combining measurements of Higgs-plus-two-jet production via gluon fusion with measurements of top-pair associated Higgs production. In addition, we demonstrate that the sensitivity of the analysis can be improved by exploiting the top-quark threshold in the gluon fusion process. Finally, we substantiate a perturbative argument about the validity of EFT by comparing the quadratic and linear contributions from CP-odd dimension six operators and use this to show explicitly that high statistics measurements at future colliders enable the extraction of perturbatively robust constraints on the associated Wilson coefficients.
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We discuss the prospects - within several models - for the observation of CP-violation (CPV) in top decays and production. The outlook looks best for t -> bW at the LHC (MSSM CPV), t -> b tau u_tau at TeV3, LHC and NLC (H^+ CPV), p p-bar -> t b-bar + X at TeV3 (MSSM CPV), p p -> t t-bar + X at the LHC (MSSM CPV and neutral Higgs CPV) and for e^+ e^- -> t t-bar h, t t-bar Z, where h is the lowest mass neutral Higgs boson, at an NLC with energy geq 1 TeV (neutral Higgs CPV).
The violation of CP symmetry is one of Sakharovs conditions for the matter-antimatter asymmetry of the Universe. Currently known sources of CP violation in the quark and neutrino sectors are insufficient to account for this. Is CP also violated in the Higgs sector? Could the SM-like Higgs boson be a mixture of even and odd CP states of an extended Higgs sector? With what precision could such effects be measured at future electron-positron colliders? These questions will be discussed in the light of the latest and ongoing studies at ILC.
CP-violation in the Higgs sector remains a possible source of the baryon asymmetry of the universe. Recent differential measurements of signed angular distributions in Higgs boson production provide a general experimental probe of the CP structure of Higgs boson interactions. We interpret these measurements using the Standard Model Effective Field Theory and show that they do not distinguish the various CP-violating operators that couple the Higgs and gauge fields. However, the constraints can be sharpened by measuring additional CP-sensitive observables and exploiting phase-space-dependent effects. Using these observables, we demonstrate that perturbatively meaningful constraints on CP-violating operators can be obtained at the LHC with luminosities of ${cal{O}}$(100/fb). Our results provide a roadmap to a global Higgs boson coupling analysis that includes CP-violating effects.
The Higgs boson discovered at the LHC opened a new chapter for particle physics. Its properties need to be studied in detail to distinguish a purely standard model (SM) Higgs boson from one of many scalars in an enlarged Higgs sector. The CMS collaboration has reported a possible lepton flavor violating (LFV) signal $htomutau$, which if confirmed, implies that the Higgs sector is larger than in the SM. New physics responsible for this type of decay may, in general, also introduce other observable effects such as charge-parity (CP) violation in $hto tautau$. We study two types of models that single out the third generation and can induce large $h to mutau$ rates with different consequences for CP violation in $h to tau tau$. Predictions for the size of the CP violating couplings require knowledge of the lepton Yukawa matrices and we discuss this in the context of two different textures considering all existing constraints.
In this paper, we study the CP violating processes in a general two-Higgs-doublet model (2HDM) with tree-level flavor changing neutral currents. In this model, sizable Yukawa couplings involving top and charm quarks are still allowed by the collider and flavor experiments, while the other couplings are strongly constrained experimentally. The sizable couplings, in general, have imaginary parts and could largely contribute to the CP violating observables concerned with the $B$ and $K$ mesons. In particular, the contribution may be so large that it affects the direct CP violating $K$ meson decay, where the discrepancy between the experimental result and the Standard Model prediction is reported. We discuss how well the anomaly is resolved in the 2HDM, based on study of the other flavor observables. We also propose the way to test our 2HDM at the LHC.
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