We prove the strong sensitivity of the gg --> H1 --> gamma.gamma cross section at the Large Hadron Collider on the explicitly CP-violating phases of the Minimal Supersymmetric Standard Model, where H1 is the lightest Supersymmetric Higgs boson.
The MSSM with explicit CP violation is studied through the di-photon decay channel of the lightest neutral Higgs boson. Through the leading one-loop order H1 --> gammar.gamma is affected by a large number of Higgs-sparticle couplings, which could be complex. Our preliminary scan over the Supersymmetric parameter space shows that more than 50% average deviations are possible, in either direction, in the corresponding branching ratio, with respect to the case of the CP-conserving MSSM. In particular, our analysis shows that in the presence of a light stop (with mass ~ 200 GeV) a CP-violating phase Arg(mu) ~ 90(deg) can render the H1 --> gamma.gamma branching ratio more than 10 times larger, for suitable combinations of the other MSSM parameters.
We study the effect of explicit CP violation in the Higgs sectors of the MSSM in the di-photon decay of the lightest CP-mixed Higgs state. Further it is shown that the gluon fusion production mechanism along with the di-photon decay enhances CP-violating effects for a large set of suitably chosen parameter values.
The Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation is studied with the help of the di-photon decay channel of the lightest neutral Higgs boson. Effects of CP violation, entering via the scalar/pseudo-scalar mixing at higher order as well as through the Higgs-sfermion-sfermion couplings at tree-level, are analyzed in the MSSM with and without light sparticles. A light stop may have a strong impact on the decay width and Branching Ratio (BR) of the decay process H_1 -> gamma gamma, whereas other light sparticles have only little influence. In some regions of the MSSM parameter space with large CP-violating phase phi_mu ~ 90 degrees a light stop can change the BR by more than 50%.
We study that a minimal supersymmetric standard model with an extra $U(1)$ gauge symmetry may accommodate the explicit CP violation at the one-loop level through radiative corrections. This model is CP conserving at the tree level and cannot realize the spontaneous CP violation for a wide parameter space at the one-loop level. In explicit CP violation scenario, we calculate the Higgs boson masses and the magnitude of the scalar-pseudoscalar mixings in this model at the one-loop level by taking into account the contributions of top quarks, bottom quarks, exotic quarks, and their superpartners. In particular, we investigate how the exotic quarks and squarks would affect the scalar-pseudoscalar mixings. It is observed that the size of the mixing between the heaviest scalar and pseudoscalar Higgs bosons is changed up to 20 % by a complex phase originated from the exotic quark sector of this model.
The possibility of a strongly first-order electroweak phase transition is established in the minimal supersymmetric standard model with an extra $U(1)$, where a nontrivial CP violating phase is introduced in its Higgs sector. We find that there is a wide region in the parameter space of the model that allows the strongly first-order electroweak phase transition. The mass of stop quark need not be smaller than the top quark mass to ensure the first-order electroweak phase transition be strong. The effect of the CP violating phase upon the strength of the phase transition is discovered. The strength of the phase transition is reduced when the size of the CP violation is increased. For a given CP violating phase, we find that the model has a larger mass for the lightest Higgs boson when it has a stronger phase transition.