Wai-Yee Keung

New Two-Loop Contribution to Electric Dipole Moments in Supersymmetric Theories

We calculate a new type of two-loop contribution to the electric dipole moments of the electron and neutron in supersymmetric theories. The new contributions are originated from the potential CP violation in the trilinear couplings of the Higgs bosons to the scalar-top or the scalar-bottom quarks. These couplings did not receive stringent constraints directly. The electric dipole moments are induced through a mechanism analogous to that due to Barr and Zee [Phys.thinspthinspRev.thinspthinspLett.thinspthinsp{bold 65}, 21 (1990)]. 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 which cannot be excluded by earlier considerations. {copyright} {ital 1999} {ital The American Physical Society }

Collider Signals of Unparticle Physics

Phenomenology of the notion of an unparticle U, recently perceived by Georgi, to describe a scale invariant sector with a nontrivial infrared fixed point at a higher energy scale is explored in details. Behaving like a collection of d(U) (the scale dimension of the unparticle operator O(U)) invisible massless particles, this unparticle can be unveiled by measurements of various energy distributions for the processes Z-->f f U and e- e+-->gammaU at e- e+ colliders, as well as monojet production at hadron colliders. We also study the propagator effects of the unparticle through the Drell-Yan tree-level process and the one-loop muon anomaly.

PAMELA and dark matter

Assuming that the positron excess in PAMELA satellite data is a consequence of annihilations of cold dark matter, we consider from a model-independent perspective if the data show a preference for the spin of dark matter, and find that they do not. We then perform a general analysis of annihilations into two-body states to determine what weighted combination of channels best describes the data.

Top quark forward–backward asymmetry

Abstract The recent forward–backward asymmetry recorded by the CDF Collaboration for the top and anti-top quark pair production indicates more than 2 σ deviation from the Standard Model prediction, while its total production cross section remains consistent. We propose a W ′ boson that couples to down and top quarks. We identify the parameter space that can give rise a large enough forward–backward asymmetry without producing too many top and anti-top quark pairs. Other models presented previously in the literature that can produce such effects are also briefly discussed.

Two loop contributions of flavor changing neutral Higgs bosons to mu ---> e gamma

The two-loop mechanism of Bjorken and Weinberg is used to constrain flavor-changing neutral Higgs bosons. We calculate the complete set of two-loop diagrams for the rare decay [mu][r arrow][ital e]+[gamma] induced by such neutral Higgs bosons, for arbitrary Higgs boson and top quark masses. The analytic result is used to set limits on Higgs boson masses for some recent models with a specific ansatz about the flavor-changing couplings. For example, in the Cheng-Sher scenario of multi-Higgs-doublet models, all neutral Higgs bosons possess flavor-changing ([ital f][sub [ital i]][leftrightarrow][ital f][sub [ital j]]) couplings proportional to [radical][ital m][sub [ital i]m[ital j]] . We find that the present limit on [mu][r arrow][ital e][gamma] implies that, in such a scheme, these neutral Higgs bosons should be heavier than 200 GeV.

Electromagnetic properties of dark matter: Dipole moments and charge form factor

Abstract A neutral dark matter particle may possess an electric dipole moment (EDM) or a magnetic dipole moment (MDM), so that its scattering with nuclei is governed by electromagnetic interactions. If the moments are associated with relevant operators of dimension-5, they may be detectable in direct search experiments. We calculate complete expressions of the scattering cross sections and the recoil energy spectra for dark matter with these attributes. We also provide useful formulae pertinent to dark matter that interacts via an electric charge form factor (CFF) which is related to the charge radius defined by an effective dimension-6 operator. We show that a 7 GeV dark matter particle with an EDM, MDM or CFF easily reproduces the CoGeNT excess while remaining consistent with null searches.

On ψ and ϒ production via gluons

Abstract Present data on ψ production by real and virtual photons are well described by the photon-gluon fusion model. In this framework, the energy dependence of the photoproduction cross section directly determines the x -dependence of the gluon distribution in nucleons at mass scale m ψ 2 . The analogous processes for ψ production in pp collisions are quark-antiquark and gluon-gluon fusion; here the energy dependence of d σ /d y ( y =0) again determines the x -dependence of the gluon distribution at the same mass scale. Similar considerations apply to ϒ production. In all cases we find the x -dependence agrees with the form (1 − x ) 5 / x suggested by naive power counting. The normalization of the photon-gluon and gluon-gluon processes apparently differs, however; possible reasons are discussed.

Split supersymmetry, stable gluino, and gluinonium

In the scenario recently proposed by Arkani-Hamed and Dimopoulos, the supersymmetric scalar particles are all very heavy, at least of the order of

Total width of 125 GeV Higgs boson.

{10}^{9}\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}

Electric dipole moment in the split supersymmetry models

but the gauginos, Higgsinos, and one of the neutral Higgs bosons remain under a TeV. The most distinct signature is the metastable gluino. However, the detection of metastable gluino depends crucially on the spectrum of hadrons that it fragments into. Instead, here we propose another unambiguous signature by forming the gluino-gluino bound state, gluinonium, which will then annihilate into