David Bowser-Chao

Phase effect of a general two-Higgs-doublet model in b{r_arrow}s{gamma}

In a general two-Higgs-doublet model (2HDM), without the {ital ad hoc} discrete symmetries to prevent tree-level flavor-changing-neutral currents, an extra phase angle in the charged-Higgs-fermion coupling is allowed. We show that the charged-Higgs amplitude interferes destructively or constructively with the standard model amplitude for b{r_arrow}s{gamma} depending crucially on this phase angle. The popular models I and II are special cases of our analysis. As a result of this phase angle the severe constraint on the charged-Higgs-boson mass imposed by the inclusive rate of b{r_arrow}s{gamma} from CLEO can be relaxed. We also examine the effects of this phase angle on the neutron electric dipole moment. Furthermore, we also discuss other constraints on the charged-Higgs-fermion couplings coming from measurements of B{sup 0}{minus}{bar B}{sup 0} mixing, {rho}{sub 0}, and R{sub b}. {copyright} {ital 1999} {ital The American Physical Society}

Electron Electric Dipole Moment from CP Violation in the Charged Higgs Sector

The leading contributions to the electron (or muon) electric dipole moment due to CP violation in the charged Higgs sector are at the two{endash}loop level. A careful model-independent analysis of the heavy fermion contribution is provided. We also consider some specific scenarios to demonstrate how charged Higgs sector CP violation can naturally give rise to large electric dipole moments. Numerical results show that the electron electric dipole moment in such models can lie at the experimentally accessible level. {copyright} {ital 1997} {ital The American Physical Society}

Higgs-photon associated production at hadron colliders

We present cross sections for the reactions p{bar p}{r_arrow}H{gamma} and pp{r_arrow}H{gamma} arising from the subprocess q{bar q}{r_arrow}H{gamma}. The calculation includes the complete one-loop contribution from all light quarks as well as the tree contributions from the light quarks and c and b quarks. These are the main sources of Higgs-photon associated production at hadron colliders. At Fermilab Tevatron energies, the cross section is typically between 0.1thinspfb and 1.0thinspfb for 80thinspGeV{le}m{sub H}{le}160thinspGeV, while at CERN LHC energies it exceeds about 2.0thinspfb over the same range of m{sub H}. While substantial, these cross sections are not large enough to produce a signal which is discernable above the backgrounds from q{bar q}{r_arrow}b{bar b}{gamma} and gg{r_arrow}b{bar b}{gamma}. {copyright} {ital 1998} {ital The American Physical Society}

LEPTO-MESONS, LEPTOQUARKONIUM AND THE QCD POTENTIAL

Abstract We consider bound states of heavy leptoquark-antiquark pairs (lepto-mesons) as well as leptoquark-antileptoquark pairs (leptoquarkonium). Unlike the situation for top quarks, leptoquarks (if they exist) may live long enough for these hadrons to form. We study the spectra and decay widths of these states in the context of a nonrelativistic potential model which matches the recently calculated two-loop QCD potential at short distances to a successful phenomenological quarkonium potential at intermediate distances. We also compute the expected number of events for these states at future colliders.

SIMPLE CHARGED HIGGS MODEL OF SOFT OR SPONTANEOUS CP VIOLATION WITHOUT FLAVOR CHANGING NEUTRAL CURRENTS

We propose a model of softly or spontaneously broken CP symmetry in which the CP -violating mechanism originates from the charged Higgs sector naturally. The mechanism not only accounts for the measured value of the CP -violating parameter {epsilon} but also accommodates the current limits on {epsilon}{sup {prime}}/{epsilon} . The model naturally prevents tree-level flavor changing neutral currents and the strong CP problem. Electric dipole moments vanish to one (or more) loops. Surprisingly similar to the Kobayashi-Maskawa model, our model is of milliweak character but with seemingly superweak phenomenology. {copyright} {ital 1998} {ital The American Physical Society}

CP violation and scalar lepton flavor oscillation

Lepton flavor violation can be induced in supersymmetry by the mixing of two or more of the leptonic scalar partners, {tilde l}{r_arrow}{tilde l}{sup {prime}}, where {tilde l},{tilde l}{sup {prime}}={tilde e},{tilde {mu}},{tilde {tau}}. Krashnikov and Arkani-Hamed {ital et al.} pointed out that this effect may be observable at the Next Linear Collider, through slepton pair production with subsequent lepton-flavor-violating (LFV) decays. If the slepton mixing involves all three generations, CP violation from the Cabibbo-Kobayashi-Maskawa phase could lead to asymmetries between the observed LFV decays {tilde l}{r_arrow}{tilde l}{sup {prime}} and {bar {tilde l}}{r_arrow}{bar {tilde l}}{sup {prime}}. We lay down the formalism and give simple expressions for the CP-violating asymmetry in the transition probabilities, and consider possible signals at future colliders. {copyright} {ital 1997} {ital The American Physical Society}

Radiative Higgs Boson Decays H -> f fbar gamma

Higgs boson radiative decays of the form

Higgs-boson–photon production at [Formula presented] colliders

H\rightarrow f\bar{f}\gamma

Probing anomalous Higgs coupling through μ+μ−→Hγ

are calculated in the Standard Model using the complete one-loop expressions for the decay amplitudes. Contributions to the radiative width from leptons and light quarks are given. We also present

Resonant bound state production at e−e− colliders

e\bar{e}