Gluon Fusion: A Probe of Higgs Sector CP Violation

We demonstrate that CP violation in the Higgs sector, \eg\ of a multi-doublet model, can be directly probed using gluon-gluon collisions at the SSC. % requires phyzzx.tex macro packageComment: UCD-93-

Probing Top-Quark Couplings at Polarized NLC

The energy spectrum of the lepton(s) in e^+e^- --> tt-bar --> l^{+-} ...../l^+l^-..... at next linear colliders (NLC) is studied for arbitrary longitudinal beam polarizations as a possible test of new physics in top-quark couplings. The most general non-standard couplings for gamma-tt-bar, Ztt-bar and Wtb vertices are considered. Expected precision of the non-standard-parameter determination is estimated applying the optimal-observable procedure.Comment: Final version, To appear in Phys. Rev.

CP-Violation in Bosonic Sector of SM with two Higgs Doublets

We investigate CP-violation effects in the bosonic sector of the Standard Model (SM) with two Higgs doublets. First we calculate the mass eigenstates of the physical neutral Higgses for small but nonzero CP-violation parameter $\xi_{\ast}$, and then a ``forward-backward'' asymmetry ${\cal A}_{fb}$ for the decay $H \to W^+W^-Z$ that would be a signal of CP-violation. Although the effects are in general small (${\cal A}_{fb} = \Gamma_{fb}/\Gamma \sim {\cal O}(10^{-3})$), ${\cal A}_{fb}$ turns out to be a rather clean signal of CP-violation, since neither the CP-conserving final state interactions nor the direct production background events contribute to $\Gamma_{fb}$. The process is a counterexample to the widespread belief that CP-violation processes must involve fermions. The CKM-type CP-violation effects that could in principle also contribute to ${\cal A}_{fb}$ are negligible. The nonzero ${\cal A}_{fb}$ could possibly be detected at some later stage in future colliders such as LHC or SSC.Comment: 11 pages (standard LaTeX), 3 figures (available from the author), DO-TH 93-1

Direct CP Violation in Angular Distribution of B→J/ψK∗B\to J/\psi K^{*} Decays

We show that the study of certain observables in the angular distribution in $B\to J/\psi K^*$ provide clear test for CP vioaltion beyond the Standard Model. These observables vanish in SM, but in models beyond SM some of them can be large enough to be measured at B factories.Comment: 7 pages, Revte

Prospects for Direct CP Violaton in Exclusive and Inclusive Charmless B decays

Within the Standard Model, CP rate asymmetries for $B\to K^-\pi^{+,0}$ could reach 10%. With strong final state phases, they could go up to 20--30%, even for $\bar K^0\pi^-$ mode which would have opposite sign. We can account for $K^-\pi^{+}$, $\bar K^0\pi^-$ and $\phi K$ rate data with new physics enhanced color dipole coupling and destructive interference. Asymmetries could reach 40--60% for $K\pi$ and $\phi K$ modes and are all of the same sign. We are unable to account for $K^-\pi^0$ rate. Our inclusive study supports our exclusive results.Comment: Minor changes, correct a small bug in Fig. 1(b). Version to appear in Phys. Rev. Let

Final-State-Interaction Simulation of T-Violation in the Top-Quark Semileptonic Decay

The standard electroweak final-state interaction induces a false T-odd correlation in the top-quark semileptonic decay. The correlation parameter is calculated in the standard model and found to be considerably larger than those that could be produced by genuine T-violation effects in a large class of theoretical models.Comment: 14 pages, 1 diagram (not included

Enhanced b→sgb\to sg Decay, Inclusive η′\eta^\prime Production, and the Gluon Anomaly

The experimental hint of large $B\to \eta^\prime + X_s$ is linked to the $b\to s$ penguins via the gluon anomaly. Using running $\alpha_s$ in the $\eta^\prime$-$g$-$g$ coupling, the standard $b\to sg^*$ penguin alone seems insufficient, calling for the need of dipole $b\to sg$ at 10% level from new physics, which could also resolve the ${\cal B}_{s.l.}$ and charm counting problems. The intereference of standard and new physics contributions may result in direct CP asymmetries at 10% level, which could be observed soon at B Factories.Comment: 12 pages, revtex, 3 figs. (version to appear in Phys. Rev. Lett.

Optimal Spin Basis in Polarized Photon Linear Colliders

We analyze the spin correlations of the top quark pairs produced at Photon Linear Colliders. We employ the circular polarized photon beams and general spin basis for the top quark pair. We consider general spin bases to find a strong spin correlation between produced top quark and anti-top quark. We show the cross-section in these bases and discuss the characteristics of results.Comment: RevTeX, 16 pages, 6 figures, psfig.sty and here.sty are require

R-parity violation and uses of the rare decay sneutrino-->gamma+gamma in hadron and photon colliders

We consider implications of the loop process sneutrino -> gamma gamma in the MSSM with R-parity violation for future experiments, where the sneutrino is produced as the only supersymmetric particle. We present a scenario for the R-parity violating couplings, where this clean decay, although rare with Br(sneutrino -> gamma gamma) ~ 10^{-6}, may be useful for sneutrino detection over a range of sneutrino masses at the LHC. Furthermore, the new sneutrino-gamma-gamma effective coupling may induce detectable sneutrino resonant production in gamma gamma collisions, over a considerably wide mass range. We compare sneutrino -> gamma gamma, gg throughout the paper with the analogous yet quantitatively very different, Higgs -> gamma gamma, gg decays and comment on the loop processes sneutrino -> WW, ZZ.Comment: 19 pages using REVTEX, 3 figures embadded in the text using epsfi

Improving constraints on tan(beta)/m_H using B \to D tau \bar{nu}

We study the q^2 dependence of the exclusive decay mode B \to D tau \bar{nu} in type II two Higgs doublet models and show that this mode may be used to put stringent bounds on tan(beta)/m_H. There are currently rather large theoretical uncertainties in the q^2 distribution, but these may be significantly reduced by future measurements of the analogous distribution for B \to D(e,mu)\bar{nu}. We estimate that this reduction in the theoretical uncertainties would eventually (i.e., with sufficient data) allow one to push the upper bound on tan(beta)/m_H down to about 0.06 GeV^{-1}. This would represent an improvement on the current bound by about a factor of 7. We then apply the method of optimized observables which allows us to estimate the reach of an experiment with a given number of events. We thus find that an experiment with, for example, 10^3 events could set a 2\sigma upper bound on tan(beta)/m_H of 0.07 GeV^{-1} or could differentiate at the 4.6\sigma level between a 2HDM with tan(beta)/m_H = 0.1 GeV^{-1} and the SM.Comment: 19 pages, Late