Constraints onCP-violating gauge-Higgs operators

Abstract

We consider the most general set of SU (2) × U (1) invariant CP-violating operators of dimension six, which contribute to V V h interactions (V = W, Z, γ). Our aim is to constrain any CP-violating new physics above the electroweak scale via the effective couplings that arise when such physics is integrated out. For this purpose, we use, in turn, electroweak precision data, global fits of Higgs data at the Large Hadron Collider and the electric dipole moments of the neutron and the electron. We thus impose constraints mainly on two-parameter and three-parameter spaces. We find that the constraints from the electroweak precision data are the weakest. Among the existing Higgs search channels, considerable constraints come from the diphoton signal strength. We note that potential contribution to h → γZ may in principle be a useful constraining factor, but it can be utilized only in the high energy run. The contributions to electric dipole moments mostly lead to the strongest constraints, though somewhat fine-tuned combinations of more than one parameter with large magnitudes are allowed. We also discuss constraints on gauge boson trilinear couplings which depend on the parameters of the CP-violating operators .Although the discovery of "a Higgs-like boson" at the Large Hadron Collider (LHC) has been a refreshing development [1,2], there is no clear signal yet for physics beyond the standard model (SM). It is therefore natural that physicists are trying to wring the last drop out of the Higgs sector itself, in attempts to read fingerprints of new physics.One approach is to examine all available data in terms of specific new models, such as supersymmetry or just additional Higgs doublets. In the other approach, one can take a model-independent stance, parametrize possible modifications of the interaction terms of the Higgs with pairs of SM particles, and examine them in the light of the available data. Such modifications can again be of two types. In the first category, they are just multiplicative modifications of the coupling strengths, the Lorentz structures remaining the same as in the SM. Constraints on such modifications have already been derived from the available Higgs data [3][4][5][6][7]. In the second class, one considers additional operators with new Lorentz structures satisfying all symmetries of the SM [8][9][10][11][12][13][14][15]. Gauge invariance of such operators in their original forms may be expected, since they are obtained by integrating out new physics that is just above the reach of the present round of experiments. Sets of such higher-dimensional operators contributing to the effective coupling of the Higgs to, say a pair of electroweak vector bosons have been studied extensively. Here it makes sense to include only SU (2) × U (1) invariant operators in one's list to start with, because the yet unknown new physics lies at least a little above the electroweak symmetry breaking scale. A host of such gauge invariant higher-dimensional operators have been, and are being, analyzed with considerable...

DistinguishingCP-odd couplings of the Higgs boson to weak boson pairs

“…However, for the constraints coming from EDM measurements, one finds that EDMs have an explicit cut-off dependence other than the one coming via the parametersf i/Λ 2 . This dependence coming from loop contributions is logarithmic in nature [65]. However, all five of these CP-violating operators are not independent, and are related by the following constraint equations, which arise from using the SM equations of motion: 1…”

“…In [65] we derived limits on the parameters of the CP-odd operators using the collider data (from LEP and LHC) and measurements of electron and neutron EDMs. These limits were obtained taking mainly two parameters (2P) and three parameters (3P) nonzero at a time.…”

“…The set of CP-violating gauge-Higgs operators of dimension-6 that we have considered in our analysis [65] is listed below :…”

“…Coefficients of the latter are subject to rather strong constraints from the limits on the electric dipole moments (EDM) of the neutron and the electron and also from the upper bounds on Hg EDM [63,64], in addition to global fits of collider data (including those from the LHC) that constrain the CP-even operators as well. Arguably a detailed study of these constraints on the CP-violating operators was presented in the reference [65]. It is, however, possible to generalize the study even further.…”

Probing $$\textit{CP}$$-violating Higgs and gauge-boson couplings in the Standard Model effective field theory

“…Most studies, however, assume that the new physics contributions to the Higgs-boson couplings feature a C P-even structure, in particular when existing constraints on the effective operators are evaluated [5][6][7][8][9][10][11][12]. In comparison, the investigation of the effects of the C P-odd Higgs-boson effective operators has been relatively sparse [13][14][15][16][17][18][19], although some experimental analyses are available, e.g. [20,21].…”