Search

In the framework of topcolor-assisted technicolor(TC2) model, there exist tree-level flavor-changing (FC) couplings which can result in the loop-level FC coupling $tcg$. Such $tcg$ coupling can contribute significant clues at the forthcoming Large Hadron Collider (LHC) experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving $tcg$ coupling at the Tevatron and LHC: $pp(p\bar{p})\to t\bar{q}(q=u,d,s),tg$. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling $tcg$. On the other hand, these processes can also provide some valuable information of the coupling $tcg$ with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model., Comment: 15 pages, 10 figures

In this paper, we study the upper bounds on the mass insertion parameters $(\delta^{q}_{AB})_{ij}$ in the minimal supersymmetric standard model (MSSM). We found that the information from the measured branching ratio of $B \to X_s l^+ l^-$ decay can help us to improve the upper bounds on the mass insertions parameters $\left (\delta^{u,d}_{AB})_{3j,i3}$. Some regions allowed by the data of $Br(B \to X_s \gamma) $ are excluded by the requirement of a SM-like $C_{7\gamma}(m_b)$ imposed by the data of $Br(B \to X_s l^+ l^-)$., Comment: 16 pages, 5 eps figure files, typos removed

By choosing two typical input parameter points in the minimal supergravity (mSUGRA) model and using the QCD factorization (QCDF) approach, we studied the supersymmetric effects to the CP violation of the two-body charmless hadronic $B$ meson decays. We found that though the SUSY contributions can give large corrections to the CP asymmetries for some decay channels, they could not be distinguished experimentally from the SM values because of the large theoretical errors dominated by calculating the annihilation contributions in the QCDF approach., Comment: 7 pages, shortened for submiting to Phys. Rev. D as brief report

By employing the QCD factorization approach for the exclusive $B \to V \gamma$ decays, we calculated the new physics contributions to the branching ratios, CP asymmetries, isospin and U-spin symmetry breaking of $B \to K^*\gamma$ and $B \to \rho \gamma$ decays, induced by the charged Higgs penguin diagrams appeared in the top-quark two-Higgs-doublet model(T2HDM). Within the considered parameter space, we found that (a) a charged-Higgs boson with a mass larger than 300 GeV are always allowed by the date of $B \to V \gamma$ decay, and such lower limit on $\mhp$ are comparable with those obtained from the inclusive $B \to X_s \gamma$ decay; (b) the CP asymmetry of $B \to \rho \gamma$ in the T2HDM can be as large as 10% in magnitude and has a strong dependence on the angle $\theta$ and the CKM angle $\gamma$; (c) the isospin symmetry breakings of $B \to V \gamma$ decays in the T2HDM are generally small in size: around 6% for $B \to K^* \gamma$ decay and less than 20% for $B \to \rho \gamma$ decay; and (d) the U-spin symmetry breaking $\Delta U(K^*,\rho)$ in the T2HDM is also small in size, only about 8% of the branching ratio $\calb (B \to \rho^0 \gamma)$., Comment: RevTex file, 25 pages, 12 eps figures

We calculate the branching ratios and CP-violating asymmetries for $B^0 \to \pi^0 \eta^{(\prime)}$ and $B^+\to \pi^+ \eta^{(\prime)}$ decays in the perturbative QCD (pQCD) factorization approach here. We not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The pQCD results for the CP-averaged branching ratios are $Br(B^+ \to \pi^+ \eta) \approx 4.1 \times 10^{-6}$, $Br(B^+ \to \pi^+ \eta^\prime) \approx 2.4 \times 10^{-6}$, and $Br(B^0 \to \pi^0 \eta^{(\prime)}) \approx 0.2 \times 10^{-6}$, which agree very well with the measured values or currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: $A_{CP}^{dir}(\pi^\pm \etap)\sim A_{CP}^{dir}(\pi^0 \etap)\sim -0.35 $, and $A_{CP}^{mix}(\pi^0 \etap)\sim 0.67$, but with large errors. The pQCD prediction for $A_{CP}^{dir}(\pi^\pm \eta)$ ($A_{CP}^{dir}(\pi^\pm \eta^\prime))$ has the same (opposite) sign with the primary measured values. Further improvements in both theory and experiments are needed to clarify this discrepancy., Comment: 28 pages, 8 figures, several typos corrected

In this paper,we calculate the branching ratios and CP-violating asymmetries for $B^0 \to \rho^0 \eta^{(\prime)}$ and $B^+\to \rho^+ \etap$ decays in the perturbative QCD factorization approach. In this approach, we not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The theoretical predictions for the branching ratios are $Br(B^+ \to \rho^+ \eta^{(\prime)}) \approx 9 \times 10^{-6}$ and $Br(B^0 \to \rho^0 \eta^{(\prime)}) \approx 5 \times 10^{-8}$, which agree well with the measured values and currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: $A_{CP}^{dir}(\rho^\pm \eta)\approx -13 %$, $A_{CP}^{dir}(\rho^\pm \eta^\prime)\approx -18 %$, $A_{CP}^{dir}(\rho^0 \eta)\approx -41%$, $A_{CP}^{dir}(\rho^0 \eta^\prime)\approx -27%$, $A_{CP}^{mix}(\rho^0 \eta)\approx +25%$, and $A_{CP}^{mix}(\rho^0 \eta^\prime) \approx +11%$, which can be tested by the current or future B factory experiments., Comment: 29 pages, 9 ps figures, more phenomenological discussions added, scale dependence of computed observables are considered, typos corrected, the figures and conclusions remain unchanged

By employing the QCD factorization approach, we calculate the new physics contributions to the branching radios of the two-body charmless $ B \to PV$ and $B \to VV$ decays in the framework of the minimal supergravity (mSUGRA) model. we choose three typical sets of the mSUGRA input parameters in which the Wilson coefficient $C_{7\gamma}(m_b)$ can be either SM-like (the case A and C) or has a flipped-sign (the case B). We found numerically that (a) the SUSY contributions are always very small for both case A and C; (b) for those tree-dominated decays, the SUSY contributions in case B are also very small; (c) for those QCD penguin-dominated decay modes, the SUSY contributions in case B can be significant, and can provide an enhancement about $30% \sim 260%$ to the branching ratios of $B \to K^*(\pi,\phi,\rho)$ and $K \phi$ decays, but a reduction about $30% \sim 80%$ to $ B\to K(\rho, \omega)$ decays; and (d) the large SUSY contributions in the case B may be masked by the large theoretical errors dominated by the uncertainty from our ignorance of calculating the annihilation contributions in the QCD factorization approach., Comment: 34 pages, 8 PS figures, this is the correct version 3

By employing the QCD factorization approach, we calculate the new physics contributions to the branching radios of the two-body charmless $ B \to PP$ decays in the framework of the minimal supergravity (mSUGRA) model. Within the considered parameter space, we find that (a) the supersymmetric (SUSY) corrections to the Wilson coefficients $C_k$ ($k=3-6$) are very small and can be neglected safely, but the leading order SUSY contributions to $C_{7\gamma}(M_W)$ and $C_{8g}(M_W)$ can be rather large and even change the sign of the corresponding coefficients in the standard model; (b) the possible SUSY contributions to those penguin-dominated decays in mSUGRA model can be as large as $30-50%$; (c) for the well measured $B \to K \pi$ decays, the significant SUSY contributions play an important rule to improve the consistency of the theoretical predictions with the data; (d) for $B \to K \eta'$ decays, the theoretical predictions of the corresponding branching ratios become consistent with the data within one standard deviation after the inclusion of the large SUSY contributions in the mSUGRA model., Comment: 31 pages, Latex file, 4 ps and eps figures, minor corrections, final version to appear in Physical Review D

By employing the QCD factorization approach, we calculated the next-to-leading order new physics contributions to the branching ratios, CP asymmetries, isospin and U-spin symmetry breaking of the exclusive decays $B \to V \gamma$ ($V=K^*, \rho$), induced by the charged Higgs penguins in the general two-Higgs-doublet models. Within the considered parameter space, we found that (a) the new physics corrections to the observables are generally small in the model I and model III-A, moderate in model II, but large in model III-B; (b) from the well measured branching ratios and upper limits, a lower bound of $\mhp > 200$ GeV in model II was obtained, while the allowed range of $\mhp$ in model III-B is $ 226 \leq \mhp \leq 293 $ GeV; these bounds are comparable with those from the inclusive $B \to X_s \gamma$ decay; (c)the NLO Wilson coefficient $C_7(m_b)$ in model III-B is positive and disfavered by the measured value of isospin symmetry breaking $\Delta_{0-}^{exp} (K^*\gamma) = (3.9 \pm 4.8)%$, but still can not be excluded if we take the large errors into account; (d) the CP asymmetry $\acp(B \to \rho \gamma)$ in model III-B has an opposite sign with the one in the standard model (SM), which may be used as a good observable to distinguish the SM from model III-B; (e) the isospin symmetry breaking $\Delta(\rho\gamma)$ is less than 10% in the region of $\gamma = [ 40 \sim 70]^\circ$ preferred by the global fit result, but can be as large as 20 to 40% in the regions of $\gamma \leq 10^\circ$ and $\gamma \geq 120^\circ$. The SM and model III-B predictions for $\Delta(\rho \gamma)$ are opposite in sign for small or large values of the CKM angles; (f) the U-spin symmetry breaking $\Delta U(K^*,\rho)$ in the SM and the general two-Higgs-doublet models is generally small in size: $\sim 10^{-7}$., Comment: Revtex, 38 pages with 14 eps figures, minor corrections

In this paper, we calculated the next-to-leading order (NLO) new physics contributions to the mass splitting $\dmd$ and the branching ratio $\brbxsga$ induced by the charged Higgs loop diagrams in the third type of two-Higgs-doublet models (model III) and draw the constraints on the free parameters of model III. For the model III under consideration, we found that (a) an upper limit $|\ltt|\leq 1.7$ is obtained from the precision data of $\dmd=0.502 \pm 0.007 ps^{-1}$, while $|\ltt| \approx 0.5$ is favored phenomenologicaly; (b) for $B \to X_s \gamma$ decay, the NLO QCD contributions tend to cancel the LO new physics contributions; (c) a light charged Higgs boson with a mass around or even less than 200 GeV is still allowed at NLO level by the measured branching ratio $\brbxsga$: numerically, $188 \leq \mh \leq 215$ GeV for $(|\ltt|,|\lbb|)=(0.5,18)$; (d) the NLO QCD contributions tend to cancel the LO contributions effectively, the lower limit on $\mh$ is consequently decreased by about 200 GeV; (e) the allowed region of $\mh$ will be shifted toward heavy mass end for a non-zero relative phase $\theta$ between the Yukawa couplings $\ltt$ and $\lbb$. The numerical results for the conventional model II are also presented for the sake of a comparison., Comment: 42 pages, 18 eps figures, Revtex, new references added

Based on the effective Hamiltonian with the generalized factorization approach, we calculate the branching ratios and CP asymmetries of $B \to VV$ decays in the Topcolor-assisted Technicolor (TC2) model. Within the considered parameter space we find that: (a) for the penguin-dominated $B \to K^{*+}\phi$ and $K^{*0}\phi$ decays, the new physics enhancements to the branching ratios are around 40%; (b) the measured branching ratios of $B \to K^{*+} \phi$ and $ K^{*0} \phi$ decays prefer the range of $3 \lesssim \nceff \lesssim 5$; (c) the SM and TC2 model predictions for the branching ratio ${\cal B}(B^+ \to \rho^+ \rho^0)$ are only about half of the Belle's measurement; and (d) for most $B \to VV$ decays, the new physics corrections on their CP asymmetries are generally small or moderate in magnitude and insensitive to the variation of $\mpcc$ and $\nceff$., Comment: 16 pages, Revtex, 4 EPS figures

In this paper, we draw constraints on the Cabibbo-Kobayashi-Maskawa (CKM) angle $\alpha$ and the strong phase $\delta$ from the experimental measurements of $\ssb$, the CP-violating asymmetries and branching ratios of $B \to \pi^+ \pi^-, \pi^+ \pi^0$ and $K^0 \pi^+$ decays. In the SM, the measured $\ssb$ leads to an upper limit on $\alpha$: $\alpha \leq 180^\circ-\beta$. Taking the weighted-average of the newest BaBar and Belle measurements of $\spp$ and $\app$ in $B^0 \to \pi^+\pi^-$ decay as the experimental input, we find the allowed range of angle $\alpha$, $76^\circ \leq \alpha \leq 135^\circ$ for $r=|P/T| =0.3 \pm 0.1 $. From the measured CP-averaged branching ratios of $B \to \pi^+ \pi^-, \pi^+ \pi^0$ and $K^0 \pi^+$ decays, we found an inequality, $\cos{\alpha} \cos{\delta} \geq 0.45$. The region of $70^\circ \leq \alpha \leq 110^\circ$ is thus excluded by applying this inequality. The combined constraints on $\alpha$ and $\delta$ are $117^\circ \leq \alpha \leq 135^\circ$ and $-160^\circ \leq \delta \leq -132^\circ$ if we take $\spp=0.49 \pm 0.27$ and $\app=0.51 \pm 0.19$ as the experimental input. The new lower limit on the angle $\alpha$ is dominated by the measured branching ratios considered in this paper, and is much stronger than those obtained before., Comment: 31 pages, Revtex, 10 PS/EPs figures, some corrections have been made, several new references added. Repot-no: BIHEP-TH-2003-7

Within the framework of the Top-color-assisted Technicolor (TC2) model, we calculate the new physics contributions to the branching ratios $\calb(B_{s,d} \to \gamma \gamma)$ and CP violating asymmetries $\rcpm(B_{s,d} \to \gamma \gamma)$ in the QCD factorization based on the heavy-quark limit $m_b \gg \Lambda_{QCD}$. Using the considered parameter space, we find that (a) for both $B_s\to \gamma \gamma$ and $B_d \to \gamma \gamma$ decays, the new physics contribution can provide a factor of two to six enhancement to their branching ratios, (b) for the $B_s \to \gamma \gamma$ decay, its direct CP violation is very small in both the SM and TC2 model, and (c) the CP violating asymmetry $\rcpm(B_d \to \gamma \gamma)$ is around the ten percent level in both the SM and TC2 model, but the sign of CP asymmetry in the TC2 model is different from that in the SM., Comment: 23 pages, Revtex, 9 PS/EPs figures, minor corrections, final version to appear in Phys.Rev. D

In this paper, we calculated the new physics contribution to theoretically very clean rare decay $B\to X_{s} \nu \bar{\nu}$ in the general two-Higgs-doublet model (model III). Within the considered parameter space, we found that (a) the new physics contribution can provide one to two orders of enhancement to the branching ratio $\calb(B\to X_s \nu \bar{\nu})$ and can saturate the experimental bound on $\calb(B \to X_s \nu \bar{\nu})$ in some regions of the parameter space; (b) besides the CLEO data of $B \to X_s \gamma$, the ALEPH upper limit on $\calb (B \to X_s \nu \bar{\nu})$ also lead to further constraint on the size of the Yukawa coupling $\lambda_{tt}$: $\lambda_{tt}< 6.4$ for $\lambda_{bb}=2.7$ and $\mhp=200$ GeV., Comment: 10 pages, 3 figures in eps and 1 in ps, Latex file

In this paper, we study and try to find the constraint on the CKM angle alpha from the experimental measurements of CP violation in B_d^0 --> pi^+ pi^- decay, as reported very recently by BaBar and Belle Collaborations. After considering uncertainties of the data and the ratio r of penguin over tree amplitude, we found that strong constraint on both the CKM angle alpha and the strong phase delta can be obtained from the measured CP asymmetries S_{pi pi} and A_{pi pi}: (a) the ranges of 87 degrees <= alpha <= 131 degrees and 36 degrees <= delta <= 144 degrees are allowed by 1 sigma of the averaged data for r = 0.31; (b) for Belle's result alone, the limits on alpha and delta are 104 degrees <= alpha <= 139 degrees and 42 degrees <= delta <= 138 degrees for 0.32 <= r <= 0.41; and (c) the angle alpha larger than 90 degrees is preferred., Comment: Revtex, 17 pages with 6 ps/eps figure files, new Babar data Reported at ICHEP 2002 considered

In this paper, we reexamine the new physics contributions to seven well measured $B \to PP$ decays in the standard model (SM) and the general two-Higgs-doublet model (model III) and compare the theoretical predictions with the new data. Within the considered parameter space we found that: (a) the measurements of the branching ratios for $B\to \pi^+ \pi^-, K^- \pi^+$ and $K^0 \pi^+$ lead to a strong constraint on the form factor $F_0^{B\pi}(0)$: $F_0^{B\pi}(0)=0.24 \pm 0.03$; (b) the new physics enhancements to the penguin-dominated $B \to K \pi$ and $K \etap$ decays are significant in size, $\sim (40-65)%$ $w.r.t$ the SM predictions, and play an important role in restoring the consistency between the data and the theory., Comment: 9 pages, Latex file, to be published in Phys. Rev. D

In this paper we try to extract the CKM angle $\gamma$ from the new "mixed" system of $B^+ \to \pi^+ K^0$ and $B_d^0 \to \pi^0 K^0$ decays. We also made an update for the constraints on the angle $\gamma$ from the observables $R$ and $A_0$. In the parametrization, the SU(2) isospin symmetry of strong interactions has been applied. We found the following results: (a) the measured value of $R$ is now very close to unit, the bound on the angle $\gamma$ from the measurement of $R$ is therefore not as promising as before, but some bounds on $\gamma$ can still be read off from $r-\gamma$ plane if $r$ could be fixed by using an additional input; (b) the measured $R_1$ implies a limit on the strong phase $\Delta_1$; (c) due to the contribution from the color allowed electroweak penguin, the minimal value of $R_1$ can be larger than unit. For $\epsilon_1=0.2$ and $R_1=1.2$, the range of $65^\circ \leq \gamma \leq 115^\circ$ will be excluded, such bounds on $\gamma$ are interesting and complimentary to the limits from global fit; (d) the dependences of extraction of $\gamma$ on the variation of parameters $\epsilon_1$, $\rho$, $r_1$ and strong phases are also studied., Comment: 22 pages, Latex file, 12 EPS figures. two typos are corrected. To be published in Phys. Rev. D

Using the low energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to $B \to \pi^+ \pi^-, K \pi$ and $K \etap$ in the Topcolor-assisted-Technicolor(TC2) model, and compare the results with the available data. By using $F_0^{{\rm B\pi}}(0)=0.20\pm 0.04$ preferred by the CLEO data of $B \to \pi^+ \pi^-$ decay, we find that the new physics enhancements to $B \to K \etap$ decays are significant in size, $\sim 50%$ with respect to the standard model predictions, insensitive to the variations of input parameters and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large $B\to K \etap$ decay rates., Comment: Latex file, 16 pages with 2 eps figures. Accepted for publication in Mod.Phys.Lett. A

Based on the low-energy effective Hamiltonian, we calculate the new physics corrections to the branching ratio and the differential distributions of the rare decay $B \to X_s \gamma \gamma$ induced by the new gluonic and electroweak charged-Higgs penguin diagrams in the general two-Higgs-doublet model with the restriction $\lambda_{ij}^{U,D}=0$ for $i\neq j$. Within the considered parameter space, we see the following: (a) the standard model predictions of ${\cal B}(B \to X_s \gamma \gamma)$ and $A_{FB}$ have a moderate $m_s$ dependence; (b) in model III, the prediction of the branching ratio ${\cal B}(B \to X_s \gamma \gamma)$ ranges from one third to three times of the standard model prediction, but is highly correlated with that of ${\cal}(B \to X_s \gamma)$; (c) the new physics enhancement to the branching ratio ${\cal B}(B \to X_s \gamma \gamma)$ in model II can be as large as $(30-50)%$; (d) the contribution from 1PR diagrams is dominant and hence four normalized differential distributions are insensitive to the variation of scale $\mu$ and possible new physics corrections; (e) due to the smallness of its decay rate and the long-distance background, the $B \to X_s \gamma \gamma$ decay is not a better process in detecting new physics than the $B \to X_s \gamma$ decay., Comment: Latex file, 27 pages with 17 ps and eps figures. Accepted for publication in Phys.Rev. D

we calculate the new physics contributions to seven measured decays $B \to \pi^+ \pi^-, K \pi$ and $ K \etap$ in the general two-Higgs-doublet model (Model III). Within the considered parameter space, we find that: (a) the CLEO/BaBar measurement of $B\to \pi^+ \pi^-$ decay prefers a small $F_0^{B\pi}(0)$: $F_0^{B\pi}(0)=0.25 \pm 0.03$; (b) the new physics enhancements to the penguin-dominated $B \to K\pi$ and $B\to K \etap$ decays are significant in size, $\sim (40-70)%$ $w.r.t$ the standard model predictions; and (c) the new physics enhancements can boost the branching ratios ${\cal B}(B \to K^+ \etap)$ and ${\cal B}(B \to K^0 \etap)$ to be consistent with the data within one standard deviation, and hence lead to a simple and plausible new physics interpretation for the $\etap K$ puzzle., Comment: 19 pages, Latex file, 6 EPS figures. Small corrections

Based on the low-energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to branching ratios and CP-violating asymmetries of the charmless hadronic decays $B_s \to h_1 h_2$ in the standard model and the general two-Higgs doublet models (models I, II, and III). Within the considered paramter space, we find the following. (a) In models I and II, the new physics corrections are always small in size and will be masked by other larger known theoretical uncertainties. (b) In model III, the new physics corrections to the branching ratios of those QCD penguin-dominated decays $\ov B_s \to K^0\etapp, K^+ K^{-*}, etc.$, are large in size and insensitive to the variations of $\mhp$ and $\nceff$. For tree- or electroweak penguin-dominated decay modes, however, the new physics corrections are very small in size. (c) For $\ov B_s \to K^+ K^{-*}$ and other seven decay modes, the branching ratios are at the level of $(1-3)\times 10^{-5}$ and will be measurable at the future hadron colliders with large $b$ production. (d) Among the studied thirty nine $B_s$ meson decay modes, seven of them can have a CP-violating asymmetry ${\cal A}_{CP}$ larger than 20% in magnitude. The new physics corrections are small or moderate in magnitude. (e) Because of its large and $\nceff$ stable branching ratio and CP violating asymmetry, the decay $\ov B_s \to K^+ K^{-*}$ seems to be the "best" channel to find CP violation of $B_s$ system through studies of two-body charmless decays of $B_s$ meson., Comment: 39 pages, Revtex, 9 eps figures, final version accepted for publication in Phys.Rev. D

Based on the low energy effective Hamiltonian with generalized factorization, we calculate the new physics contributions to the branching ratios and CP-violating asymmetries of the two-body charmless hadronic decays $B \to PP, PV$ from the new strong and electroweak penguin diagrams in the TC2 model. The top-pion penguins dominate the new physics corrections, and both new gluonic and electroweak penguins contribute effectively to most decay modes. For tree-dominated decay modes $B \to \pi \pi, \rho \pi, etc,$ the new physics corrections are less than 10%. For decays $B \to K^{(*)} \pi$, $K^{(*)} \eta$, $etc$, the new physics enhancements can be rather large (from $- 70%$ to $\sim 200%$) and are insensitive to the variations of $N_c^{eff}$, $k^2$, $\eta$ and $m_{\tilde{\pi}}$ within the reasonable ranges. For decays $B^0 \to \phi \pi$, $\phi \eta^{(')}$, $K^* \bar{K}^0$ and $\rho^+ K^0$, $\delta {\cal B}$ is strongly $N_c^{eff}-$dependent: varying from -90% to $\sim 1680%$ in the range of $N_c^{eff}=2-\infty$. The new physics corrections to the CP-violating asymmetries ${\cal A}_{CP}$ vary greatly for different B decay channels. For five measured CP asymmetries of $B \to K \pi, K \eta', \omega \pi$ decays, $\delta {\cal A}_{CP}$ is only about 20% and will be masked by large theoretical uncertainties. The new physics enhancements to interesting $B \to K \eta'$ decays are significant in size ($\sim 50%$), insensitive to the variations of input parameters and hence lead to a plausible interpretation for the unexpectedly large $B \to K \eta'$ decay rates. The TC2 model predictions for branching ratios and CP-violating asymmteries of all fifty seven $B \to PP, PV$ decay modes are consistent with the available data within one or two standard deviations., Comment: Latex file, 56 pages with 11 ps and eps figures. to be published in Eur.Phys.J. C

Based on the low-energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to the branching ratios of the two-body charmless hadronic decays of $B_u$ and $B_d$ mesons induced by the new gluonic and electroweak charged-Higgs penguin diagrams in the general two-Higgs doublet models (models I, II and III). Within the considered parameter space, we find that: (a) the new physics effects from new gluonic penguin diagrams strongly dominate over those from the new $\gamma$- and $Z^0$- penguin diagrams; (b) in models I and II, new physics contributions to most studied B meson decay channels are rather small in size: from -15% to 20%; (c) in model III, however, the new physics enhancements to the penguin-dominated decay modes can be significant, $\sim (30 -200)%$, and therefore are measurable in forthcoming high precision B experiments; (d) the new physics enhancements to ratios ${\cal B}(B \to K \etap)$ are significant in model III, $\sim (35 -70)%$, and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large $B \to K \etap $ decay rates; (e) the theoretical predictions for ${\cal B}(B \to K^+ \pi)$ and ${\cal B}(B \to K^0 \pi^+)$ in model III are still consistent with the data within $2\sigma$ errors; (f) the significant new physics enhancements to the branching ratios of $B \to K^0 \pi^0, K^* \eta, K^{*+} \pi^-, K^+ \phi, K^{*0} \omega, K^{*+} \phi$ and $K^{*0} \phi$ decays are helpful to improve the agreement between the data and the theoretical predictions; (g) the theoretical predictions of ${\cal B}(B \to PP, PV, VV)$ in the 2HDM's are generally consistent with experimental measurements and upper limits ($90% C.L.$), Comment: 55 pages, Latex file, 17 PS and EPS figures. With minor corrections, final version to be published in Phys.Rev. D. Repot-no: PKU-TH-2000-45

In the framework of general two-Higgs-doublet models, we calculate the branching ratios of various inclusive charmless b decays by using the low energy effective Hamiltonian including next-to-leading order QCD corrections, and examine the current status and the new physics effects on the determination of the charm multiplicity $n_c$ and semileptonic branching ratio $B_{SL}$. Within the considered parameter space, the enhancement to the ratio $BR(b \to s g)$ due to the charged-Higgs penguins can be as large as a factor of 8 (3) in the model III (II), while the ratio $BR(b \to no charm)$ can be increased from the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II). Consequently, the value of $B_{SL}$ and $n_c$ can be decreased simultaneously in the model III. The central value of $B_{SL}$ will be lowered slightly by about 0.003, but the ratio $n_c$ can be reduced significantly from the theoretical prediction of $n_c= 1.28 \pm 0.05$ in the SM to $n_c= 1.23 \pm 0.05$, $1.18 \pm 0.05$ for $m_{H^+}=200, 100$ GeV, respectively. We find that the predicted $n_c$ and the measured $n_c$ now agree within roughly one standard deviation after taking into account the effects of gluonic charged Higgs penguins in the model III with a relatively light charged Higgs boson., Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be published in Phys.Rev.D

The new contributions to the charmless B decay $B \to X_{s}\eta^{\prime}$ from the unit-charged technipions $P^{\pm}$ and $P^{\pm}_{8}$ are estimated. The technipions can provide a large enhancement to the inclusive branching ratio: $Br(B \to X_{s}\eta^{\prime}) \sim 7\times 10^{-4}$ for $m_{p1}=100GeV$ and $m_{p8}=250 \sim 350 GeV$ when the effect of QCD gluon anomaly is also taken into account. The new physics effect is essential to interpret the CLEO data., Comment: Latex file, 7 pages with two EPS figures

We calculate the enhancements to the inclusive charmless decays of b quark, $b \to s g, s q\bar{q}, sgg$, from gluon penguin diagrams induced by the charged and neutral Higgs bosons $(H^{\pm}, h^0, H^0$, and A^0) in the Two-Higgs-Doublet Model with flavor-changing couplings. Within the considered parameter space, the new contributions from charged Higgs boson are dominant. After including the new contributions, the branching ratio $BR(b \to sg)$ (q^2 =0) can be increased form $\sim 0.2%$ in the standard model to 4.4% and 2.6% in the two-Higgs-doublet model for $m_{H^+}=100$ and 200 GeV, respectively. The new contribution to the decay mode $b \to s q \bar{q}$ with q=(u,d,s) is, however, numerically small and peaked at the lower q^2 region. The new contribution to $b \to s gg$ can also be neglected., Comment: Latex file, 14 pages with 6 PS or EPS figures. corrected some typos, added new references

We calculate the new contributions to the rare decays $K^+ \to \pi^+ \nu \bar \nu$, $K_L \to \pi^0 \nu \bar \nu$ and $K_L \to \mu^+ \mu^-$ from new $Z^0$-penguin and box diagrams induced by the unit-charged scalars $(\tilde{\pi}^\pm, \tilde{H}^\pm, \pi_1^\pm, \pi_8^\pm)$ appeared in the Topcolor-assisted technicolor (TC2) models. We find that: (a) the unit-charged top-pion $\tilde{\pi}^\pm$ and b-pion $\tilde{H}^\pm$ can provide large contributions to the rare K-decays if they are relatively light; (b) the size of mixing elements $D_{L,R}^{ij}$ ($i \neq j$) is strongly constrained by the data of $B^0$ meson mixing: $|a_R^{ts}|, |a_R^{td}| < 0.01$ for $a_L^{td}=a_L^{ts}=1/2$ and $m_{\tilde{H}^0}\leq 600GeV$; (c) the enhancements to the branching ratios of rare K-decays from new scalars can be as large as one order of magnitude; (d) there is a strong cancellation between the short- and long-distance dispersive part of the decay $K_L \to \mu^+ \mu^-$, the constraint on the new short-distance part from this decay mode is thus not strong; (e) the typical TC2 model under study is generally consistent with the available rare K-decay data., Comment: Latex file, 27 pages and 10 ps and eps figures, to be published in Eur.Phys. J. C

We calculate the one-loop $Z^0$-penguin contributions to the rare K-decays, $K^+ \to \pi^+ \nu \bar \nu$, $K_L \to \pi^0 \nu \bar \nu$ and $K_L \to \mu^+ \mu^-$, from the unit-charged technipions $\pi_1$ and $\pi_8$ in the framework of the Multiscale Walking Technicolor Model. We find that: (a) the $\pi_1$ and $\pi_8$ can provide one to two orders enhancements to the branching ratios of the rare K-decays; (b) by comparing the experimental data of $Br(K^+ \to \pi^+ \nu \bar \nu)$ with the theoretical prediction one finds the lower mass bounds, $m_{p8} \geq 249 GeV$ for $F_Q=40GeV$ and $m_{p1}=100 GeV$; (c) by comparing the experimental data of $Br(K_L \to \mu^+ \mu^-)$ with the theoretical predictions one finds the lower bounds on $m_{p1}$ and $m_{p8}$, $m_{p1} \geq 210 GeV$ if only the contribution from $\pi_1$ is taken into account, and $m_{p8} \geq 580 GeV$ for $m_{p1}=210 GeV$, assuming $F_Q=40GeV$; (d) the assumed ranges of the masses $m_{p1}$ and $m_{p8}$ in the Multiscale Walking Technicolor Model are excluded by the rare K-decay data., Comment: Latex file, 24 pages with 14 ps and eps figures

In this paper we pursue a consistent leptoquark interpretation for HERA anomalies in the framework of Technicolor. We find that: (a) one F=0 scalar Technicolor leptoquark $P_3^{'}$ with a mass of 200 GeV can provide the required contributions to account for the excess of both neutral and charged current events with high-$Q^2$ at HERA; (b) the current data still allow the coexistence of $ P_3^{'}$ with m(P_3^{'})= 200 GeV$ and $P_3^0$ with $m(P_3^0)=225 GeV$, they could contribute effectively to $e^+p$ collision process and may be responsible for the apparent splitting of average mass of H1 and ZEUS NC events with high-$Q^2$., Comment: 26 pages, Latex, no macros, two PS figures and 1 embedded latex figure

We calculate one-loop corrections to the single-top-quark production via $q\overline{q}' \to t\overline b$ at the Fermilab Tevatron from the Pseudo-Goldstone bosons ( PGBs ) in the framework of one generation technicolor model. The maximum correction to the total cross section for the single-top-quark production is found to reach -2.4% relative to the tree-level cross section, which may be observable at a high-luminosity Tevatron., Comment: 11 pages, Latex, no macros, 2 figures(one in Latex), hard copy of another figure is available upon request

Correction to the $b\rightarrow s\gamma$ branching ratio in the multiscale walking technicolor model (MWTCM) is examined. For the original MWTCM, the correction is too large to explain the recent CLEO data. We show that if topcolor is further introduced, the branching ratio in the topcolor assisted MWTCM can be in agreement with the CLEO data for a certain range of the parameters., Comment: 11 pages, Latex, no macros, 3 figures, hard copy is available upon request. to appear in Z. Phys. C

Assuming that the actual values of $m_t$ and the data set ($\Gamma_b$, $\Gamma_h$, $\Gamma_Z$, $R_b$, $R_c$, $R_l$) are within their $1-\sigma$ errors as reported by CDF, D0 and by LEP Collaborations, the parameter $\Delta^{new}_b$ which measures the nonoblique corrections on the $Zb\overline{b}$ vertex from new physics can be determined experimentally. According to the precision data one can obtain updated constraints on the parameters $\xi$ and the masses of the charged PGBs., Comment: 10 pages, Latex, no macros, no figures, hard copy is available upon request. to appear in Commun.Theor.Phys

Applying the perturbative QCD ( PQCD ) method, we study the decay $B_c\rightarrow D_s^*\gamma$ in the standard model and multiscale walking technicolor model. In the SM, we find that the contribution of weak annihilation is more important than that of the electromagnetic penguin. The presence of Pseudo-Goldstone-Bosons in the MWTCM leads to a large enhancement in the rate of $B_c\rightarrow D_s^*\gamma$, but this model is in conflict with the branching ratio of $Z\rightarrow b\overline b$ ( $R_b$ ) and the CLEO data on the branching ratio BR ( $b\rightarrow s\gamma$ ). If topcolor is further introduced, the calculated results in the topcolor assisted MWTCM can be suppressed and be in agreement with the CLEO data for a certain range of the parameters., Comment: 16 pages, Latex, no macros, 1 figure(in Latex), hard copy is available upon request. to appear in Phys. Rev. D