Using b→sγb \to s\gamma to Probe Top Quark Couplings

Possible anomalous couplings of the top-quark to on-shell photons and gluons are constrained by the recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays. We find that the process \bsg\ can lead to reasonable bounds on both the anomalous electric and magnetic dipole moments of the top-quark, while essentially no limits are obtained on the corresponding chromoelectric and chromomagnetic moments, which enter the expression for the decay rate only through operator mixing.Comment: 10 pages plus 6 figures (available by request), LaTex, ANL-HEP-PR-93-3

Can b→sγb\to s\gamma Close the Supersymmetric Higgs Production Window?

We show that the present limit from CLEO on the inclusive decay $b\to s\gamma$ provides strong constraints on the parameters of the charged Higgs sector in two-Higgs-Doublet-Models. Only a slight improvement in the experimental bound will exclude the region in the Supersymmetric Higgs parameter space which is inaccessible to collider searches.Comment: 8 pages plus 3 figures (available by request), latex, ANL-HEP-PR-92-110. Substantial revision to text, results unchange

Recalculation of QCD Corrections to b→sγb \to s \gamma Decay

We give a more complete calculation of $b \to s\gamma$ decay, including leading log QCD corrections from $m_{top}$ to $M_W$ in addition to corrections from $M_{W}$ to $m_b$. We have included the full set of dimension-6 operators and corrected numerical mistakes of anomalous dimensions in a previous paper\cite{Cho}. Comparing with the calculations without QCD running from $m_{top}$ to $M_W$\cite{Mis}, the inclusive decay rate is found to be enhanced. At $m_t=150$GeV, it results in 12\% enhancement, and for $m_t=250$GeV, 15\% is found. The total QCD effect makes an enhanced factor of 4.2 at $m_t=150$GeV, and 3.2 for $m_t=250$GeV.Comment: 16 pages, 7 figures (uuencoded ps files), Changes of description. To appear in Phys. Rev.

Supersymmetric b→sγb \rightarrow s \gamma with Large Chargino Contributions

Supersymmetric (SUSY) theories are often thought to give large branching ratios for $b \rightarrow s \gamma$ from charged Higgs loops. We show that in many cases chargino loop contributions can cancel those of the Higgs, and SUSY can give $B(b \rightarrow s \gamma)$ at or below the \SM\ prediction. We show this occurs because the large stop mass splittings usually found in SUSY break a GIM mechanism suppression. These effects are strongly enhanced by large $\tan\beta$, so that $B(b \rightarrow s \gamma)$ is very sensitive to the value of $\tan\beta$, contrary to what has been claimed. We also note that the supergravity relation $B_0 = A_0-1$ is somewhat disfavored over the general case.Comment: TRI-PP-93-66. 12pp (Plain LATEX)+4 fig not incl. PostScript file of figs available (~3MB), contact Corrie Kost [email protected]. Request hardcopy or FAX of figures through [email protected]

Constraints From b→sγb \to s\gamma on the Left-Right Symmetric Model

Recent results from the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays are used to constrain the parameter space of two versions of the Left-Right Symmetric Model. In the first scenario, when the left- and right-handed Cabibbo-Kobayashi-Maskawa mixing matrices are equal, $V_L=V_R$, the radiative $B$ decay data is shown to lead to strong bounds on the $W_L-W_R$ mixing angle that are quite insensitive to either the top quark or $W_R$ mass. The second scenario examined is that of Gronau and Wakaizumi wherein $b$-quark decays proceed only via right-handed currents and $V_L$ and $V_R$ are quite distinct. For this model, the combined constraints from Tevatron $W_R$ searches, the $B$ lifetime, and radiative $B$ decays lead to a very highly restricted allowed range for the $W_L-W_R$ mixing angle.Comment: 16 pages, 9 figures(not included), LaTex, SLAC-PUB-642

Multiplicity Distributions in b→s gluonb\rightarrow s\ gluon Decays

The final states for the process $b \rightarrow s\ \gamma$ have been extensively discussed in the literature. Similarly-detailed analyses for the case $b \rightarrow s\ gluon$ have not been performed. Generally this process is searched for in 2-body decays such as ${\rm B}^0 \rightarrow {\rm K}^+ \pi^-$. We present simple arguments to suggest that most of the time the quark-level process will give rise to final states with rather high multiplicities. Comments are made about the applicability of these results to $b \rightarrow d\ gluon$ and hadronic $b\rightarrow u$ decays.Comment: 11 pages, uuencoded postscript fil

Nonperturbative Contributions to the Inclusive Rare Decays B→XsγB\to X_s\gamma and B→Xsℓ+ℓ−B\to X_s\ell^+\ell^-

We discuss nonperturbative contributions to the inclusive rare $B$ decays $B\to X_s\gamma$ and $B\to X_s\ell^+\ell^-$. We employ an operator product expansion and the heavy quark effective theory to compute the leading corrections to the decay rate found in the free quark decay model, which is exact in the limit $m_b\to\infty$. These corrections are of relative order $1/m_b^2$, and may be parameterised in terms of two low-energy parameters. We also discuss the corrections to other observables, such as the average photon energy in $B\to X_s\gamma$ and the lepton invariant mass spectrum in $B\to X_s\ell^+\ell^-$.Comment: 25 pages, 2 figures available upon request, uses harvmac.tex, SLAC-PUB-6317, UCSD/PTH 93-23, JHU-TIPAC-930020, UTPT 93-19, CMU-HEP 93-12, DOE-ER/40682-3

Vector Dominance Effects in Weak Radiative Decays of the B Mesons

The long distance vector-meson-dominance (VMD) effects on the weak radiative decays \bb\to\rho\gamma and \bb^0\to D^{*0}\gamma are studied. For \bb\to\rho\gamma decays, the VMD contribution is $(10-20)\%$ of the short-distance penguin amplitude. The pole effect is as important as the VMD one in the decay $B^-\to\rho^-\gamma$, but it is suppressed in \bb^0\to \rho^0\gamma. The branching ratio of \bb\to\rho\gamma, estimated to be of order $10^{-6}$, strongly depends on the sign of the Wolfenstein parameter $\rho$. A measurement of any deviation of the ratio R=\Gamma(B^-\to\rho^- \gamma)/\Gamma(\bb^0\to\rho^0\gamma) away from the isospin value 2 will not only provide a probe on the long-range contribution but also fix the sign of $\rho$: $R>2$ for $\rho0$. The decay \bb^0\to D^{*0}\gamma does not receive short-distance contributions, and its branching ratio, predicted to be $0.9\times 10^{-6}$, is dominated by $W$-exchange accompanied by a photon emission.Comment: 13 pages and three figures available upon reques

Penguin-Diagram Induced B→KXϕB \rightarrow K_X\phi Decays in the Standard Model and in the Two-Higgs-Doublet Model

We systematically analyse the gluonic penguin-induced charmless decays B \ra K_X\phi($K_X$ denotes the meson state $s\bar q \;(q=u\ {\rm or}\ d)$ ), in the standard model and the two-Higgs-doublet model. These processes, being induced at one-loop level, are of great importance in measuring the virtual top quark effect in the standard model, and also in searching for the non-standard signals in the low energy region. It is shown that the QCD effect is also significant in these processes, as in the weak radiative processes B \ra X_s \gamma. We also show that the charged Higgs contribution can not provide sizable enhancements for the decays B \ra K_X\phi, in contrast to the decays B \ra K_X\gamma. It is also found that processes such as B \ra K_1(1400)\phi and B \ra K(1460)\phi have large branching fractions among B \ra K_X\phi decays.Comment: 18pages, Latex. Paper (Hayashi, Takemi et al. AUE-02-93) is replaced with reviced version Jan 1994 and aloso the title is change

A lattice study of the exclusive B→K∗γB \to K^* \gamma decay amplitude, using the Clover action at β=6.0\beta=6.0

We present the results of a numerical calculation of the $B\to K^* \gamma$ form factors. The results have been obtained by studying the relevant correlation functions at $\beta=6.0$, on an $18^3 \times 64$ lattice, using the ${\rm O(a)}$-improved fermion action, in the quenched approximation. From the study of the matrix element $$ we have obtained the form factor $T_1(0)$ which controls the exclusive decay rate. The results are compared with the recent results from CLEO. We also discuss the compatibility between the scaling laws predicted by the Heavy Quark Effective Theory (HQET) and pole dominance, by studying the mass- and $q^2$-dependence of the form factors. From our analysis, it appears that the form factors follow a mass behaviour compatible with the predictions of the HQET and that the $q^2$-dependence of $T_2$ is weaker than would be predicted by pole dominance.Comment: 17 pages, LaTeX + epsf.sty. Uuencoded, compressed, tar archive including the text and one postscript figur