We-Fu Chang

Electric dipole moment in the split supersymmetry models

We study an important contribution to the electric dipole moment (EDM) of the electron (or quarks) at the two-loop level due to the W-EDM in the recently proposed scenario of split supersymmetry. This contribution is independent of the Higgs mass, and it can enhance the previous estimation of the electron (neutron) EDM by 20-50% (40-90%). Our formula is new in its analytical form.

Large Two-Loop Contributions to g-2 from a Generic Pseudoscalar Boson

We calculate the dominant contributions to the muon g - 2 at the two-loop level due to a pseudoscalar boson that may exist in any exotic Higgs sector in most extensions of the standard model. The leading effect comes from diagrams of the Barr-Zee type. A sufficiently light pseudoscalar Higgs boson can give rise to contribution as large as the electroweak contribution which is measurable in the next round of g - 2 experiment. The coming improved data on muon g - 2 can put the best limit on the possible existence of a light pseudoscalar boson in physics beyond the standard model.

Additional two-loop contributions to electric dipole moments in supersymmetric theories

Abstract We calculate the two-loop contributions to the electric dipole moments of the electron and the neutron mediated by charged Higgs in a generic supersymmetric theories. The new contributions are originated from the potential CP violation in the trilinear couplings of the charged Higgs bosons to the scalar-top or the scalar-bottom quarks. These couplings did not receive stringent constraints directly. We find observable effects for a sizable portion of the parameter space related to the third generation scalar-quarks in the minimal supersymmetric standard model.

Constraints from electric dipole moments on chargino baryogenesis in the minimal supersymmetric standard model

A commonly accepted mechanism of generating baryon asymmetry in the minimal supersymmetric standard model (MSSM) depends on the CP violating relative phase between the gaugino mass and the Higgsino μ term. The direct constraint on this phase comes from the limit of electric dipole moments (EDM) of various light fermions. To avoid such a constraint, a scheme which assumes the first two generation sfermions are very heavy is usually evoked to suppress the one-loop EDM contributions. We point out that under such a scheme the most severe constraint may come from a new contribution to the electric dipole moments of the electron, the neutron or atoms via the chargino sector at the two-loop level. As a result, the allowed parameter space for baryogenesis in MSSM is severely constrained, independent of masses of the first two generation sfermions. PACS numbers: 11.30.Er,11.30.Fs, 12.60.Jv, 98.80.Cq While the Standard Model of particle physics continues to accurately describe a wide array of experimental tests many physicists suspect that the next generation of a unified field theory will be supersymmetric. This supersymmetric theory in its simplest form, MSSM[1], may help to solve many of the outstanding problems in the Standard Model. Two examples of this sort are the coupling-constant-unification problem and the observed baryon asymmetry of the universe(BAU). It is the latter of these two that will be discussed in this paper. It has been demonstrated that SM is insufficient in generating large enough BAU[2]. Particles lighter in mass but stronger in coupling are needed to make the electroweak transition more first order. Additionally, a new CP violating phase is required to generate enough BAU. It is very appealing that MSSM naturally provides a solution to both requirements[3]. The top-quark partner, stop, which is naturally lighter than the other squarks can make the transition more first order, while there are plenty of new CP violating phases at our disposal in the soft SUSY breaking sector. In particular, it was shown that the most likely scenario is to make use of the relative phase between the soft SUSY breaking gaugino mass and the μ term of the Higgsino sector[3]. In such a case, the BAU is generated through the scattering of the charginos with the bubble wall. The CP violation is provided by the chargino mixing. It turns out that in most parameter space of MSSM, a nearly maximal CP violating phase is needed to generate enough BAU. One immediate question is whether or not such a new source of CP violation is already severely experimentally constrained. It is not surprising that the most severe constraints are provided by the current experimental limits of the electric dipole moment(EDM) of the electron (de) and the neutron (dn). Fortunately the lowest order (one-loop) contributions to various EDM’s through the chargino mixing can be easily suppressed by demanding that the first two generations of sfermions to be heavier than the third one[4, 5]. For example, if one requires these sfermions to be heavier than 10 TeV, the one-loop induced EDM’s will be safely small[6]. In fact, such a scenario can even be generated naturally in a more basic scheme referred to as the more minimal SUSY model[7]. However, despite the enlarged parameter space of MSSM, thanks to all the intricate limits provided by accumulated data from various collider experiments, there is only a small region of parameters left within MSSM for such baryogenesis to work[3]. In this letter we wish to point out that even if sfermions of the first two generations are assumed to be very heavy, there are important contributions to the EDM of the electron at the two-loop level via the chargino sector that strongly constraint the chargino

Constraints on New Scalars from the LHC 125 GeV Higgs Signal

We study the implications the recent results from the LHC Higgs searches have on scalar new physics. We study the impact on both the Higgs production and decay from scalars with and without colour, and in cases where decoupling do and do not happen. We investigate possible constraints on scalar parameters from the production rate in the diphoton channel, and also the two vector boson channels. Measurements from both channels can help disentangle new physics due to colour from that due to charge, and thus reveal the nature of the new scalar states.

Effective gauge-Higgs operators analysis of new physics associated with the Higgs boson

We study the new physics(NP) related to the recent discovered 125 GeV Higgs by employing an important subset of the standard model(SM) gauge invariant dimension-six operators constructed by the the SM Higgs and gauge fields. Explicitly, we perform a model-independent study on the production and decays of the Higgs, the electric dipole moments(EDM) of the neutron and the electron, and we take into account the anomalous magnetic dipole moments of muon and electron as well. We find that, even all Higgs decay channels agree with the SM predictions, the SM theoretical uncertainties provide a lot of room to host NP associated with the 125 GeV boson. A linear relation is revealed in our numerical study that

Alternative interpretation of the Fermilab Tevatron top events

\mu_{ZZ}\simeq \mu_{WW}

Lepton flavor violation in extra dimension models

and

Minimal model of Majoronic dark radiation and dark matter

0.6 \lesssim \mu_{ZZ,WW} \lesssim 1.4

Lepton Universality, Rare Decays and Split Fermions

at 95% CL with or without the EDMs constraints. The neutron and electron EDMs severely constrain the relevant Wilson coefficients. Therefore the CP violating components in the