Search

By employing the QCD factorization approach for the exclusive B→Vγ decays, we study the exclusive decay B→K*γ in the top-quark two-Higgs-doublet model (T2HDM). Within the considered parameter space, we find the following conclusions (a) A light charged-Higgs boson with a mass about 200 GeV is clearly excluded by the date of B→K*γ decay, and this lower limit is comparable with that from the inclusive B→Xsγ decay; (b) The theoretical predictions for CP asymmetry of B→K*γ in the T2HDM is always less than 1% in size; and (c) The isospin symmetry breaking for B→K*γ decay in the SM and T2HDM considered here is around 6% in size and well consistent with the data and the general expectations.

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

We calculate the contributions to the rare decays and from one-loop -penguin diagrams in the framework of topcolor-assisted technicolor model. Within the parameter space, we find that: (a) the new contribution from technipions is less than 2% of the standard model prediction; (b) the top-pions can provide a factor of 10 to 30 enhancement to the ratios in question; (c) the topcolor-assisted technicolor model is consistent with the current experimental data.

Corrections to the branching ratio BR(B → Xsγ) from technipions and top pions appeared in technicolor models are investigated. We found that: (a) the multiscale walking technicolor model is ruled out since it is conflict with the CLEO data; (b) the topcolor-assisted technicolor model is consistent with the CLEO data of BR(B → Xsγ) for a certain range of parameters.

We study the mixing of pseudo-Goldstone bosons predicted by technicolor theory and the effects on HERA high-Q2 events. We find that: (a) there exist two scalar leptoquarks with and with for ; (b) the and can contribute the required cross section to account for the excesses of NC and CC high-Q2 events; (c) the coexistence of and may be responsible for the splitting of averaged mass of the H1 and ZEUS high-Q2 neutral current events.

Applying the perturbative QCD method, we study the process in the topcolor-assisted technicolor model (TATCM), and compare the results with those estimated in the standard model (SM). There are two mechanisms which contribute to the process. One proceeds through the short distance transition, the other through weak annihilation accompanied by a photon emission. The contribution of weak annihilation is found to be much more important than that of tlie electromagnetic penguin in the TATCM, and the branching ratio, BR , is much smaller than that in the SM.

In this paper we calculate the contributions to the FCNC rare decay from the charged technipion and in the frarnervork of technicolor theory. We find that: (a) can provide a positive but relatively small contribution to the process; (b) the contribution is large and positive for relatively light and becomes negative for ; (c) the enhancement to the ratio can be as large as a factor of 30 for and ; (d) the lower mass bound on is for , respectively

We estimate the contributions to HERA deep inelastic scattering process from the color-triplet pseudo-Goldstone bosons appeared in technicolor theory. We find that the scalar technicolor leptoquark , the lighter mixed state of charge 2/3 color-triplet pseudo-Goldstone bosons, can provide the required extra contributions to account for the excesses of both neutral and charged current events with very high Q2 at HERA simultaneously.

In this paper a chiral composite preon model with semisimple metacolor gauge group E(6)×SU(5) is constructed based on the extended MTCT composite theory. This model predicts 4 generations of quarks and leptons. At low energy region the mass degeneracy between different generation fermions can be broken partly.

We calculate the contributions to the rare B-decays, $B \to X_{s,d} \nu \bar \nu$, $B_{s,d} \to l^+l^- $ from the unit-charged technipions. Within the considered parameter space we find that: (a) the enhancements to the branching ratios in question can be as large as three orders of magnitude; (b) the ALEPH data of $B \to X_s \nu \bar \nu$ lead to strong mass bounds on $m_{p1}$ and $m_{p8}$: $m_{p8} \geq 620, 475 GeV$ for $F_Q=40GeV$ and $m_{p1}=100, 400 GeV$ respectively. (c) the CDF data of $B_s \to \mu \bar \mu$ lead to a relatively weak limit: $m_{p8} \geq 320 GeV$ for $F_Q=40GeV$ and $m_{p1}=200 GeV$.

In this paper, we study the upper bounds on the mass insertion parameters $(��^{q}_{AB})_{ij}$ 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 $\left (��^{u,d}_{AB})_{3j,i3}$. Some regions allowed by the data of $Br(B \to X_s ��) $ are excluded by the requirement of a SM-like $C_{7��}(m_b)$ imposed by the data of $Br(B \to X_s l^+ l^-)$., 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

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

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 $B \to V ��$ ($V=K^*, ��$), 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 $B \to X_s ��$ 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 $��_{0-}^{exp} (K^*��) = (3.9 \pm 4.8)%$, but still can not be excluded if we take the large errors into account; (d) the CP asymmetry $\acp(B \to ����)$ 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 $��(����)$ is less than 10% in the region of $��= [ 40 \sim 70]^\circ$ preferred by the global fit result, but can be as large as 20 to 40% in the regions of $��\leq 10^\circ$ and $��\geq 120^\circ$. The SM and model III-B predictions for $��(����)$ are opposite in sign for small or large values of the CKM angles; (f) the U-spin symmetry breaking $��U(K^*,��)$ in the SM and the general two-Higgs-doublet models is generally small in size: $\sim 10^{-7}$., Revtex, 38 pages with 14 eps figures, minor corrections

Within the framework of the Top-color-assisted Technicolor (TC2) model, we calculate the new physics contributions to the branching ratios $\calb(B_{s,d} \to ����)$ and CP violating asymmetries $\rcpm(B_{s,d} \to ����)$ in the QCD factorization based on the heavy-quark limit $m_b \gg ��_{QCD}$. Using the considered parameter space, we find that (a) for both $B_s\to ����$ and $B_d \to ����$ decays, the new physics contribution can provide a factor of two to six enhancement to their branching ratios, (b) for the $B_s \to ����$ decay, its direct CP violation is very small in both the SM and TC2 model, and (c) the CP violating asymmetry $\rcpm(B_d \to ����)$ 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., 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 $B\to X_{s} ��\bar��$ 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 $\calb(B\to X_s ��\bar��)$ and can saturate the experimental bound on $\calb(B \to X_s ��\bar��)$ in some regions of the parameter space; (b) besides the CLEO data of $B \to X_s ��$, the ALEPH upper limit on $\calb (B \to X_s ��\bar��)$ also lead to further constraint on the size of the Yukawa coupling $��_{tt}$: $��_{tt}< 6.4$ for $��_{bb}=2.7$ and $\mhp=200$ GeV., 10 pages, 3 figures in eps and 1 in ps, Latex file

In this paper we try to extract the CKM angle $��$ from the new "mixed" system of $B^+ \to ��^+ K^0$ and $B_d^0 \to ��^0 K^0$ decays. We also made an update for the constraints on the angle $��$ 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 $��$ from the measurement of $R$ is therefore not as promising as before, but some bounds on $��$ can still be read off from $r-��$ plane if $r$ could be fixed by using an additional input; (b) the measured $R_1$ implies a limit on the strong phase $��_1$; (c) due to the contribution from the color allowed electroweak penguin, the minimal value of $R_1$ can be larger than unit. For $��_1=0.2$ and $R_1=1.2$, the range of $65^\circ \leq ��\leq 115^\circ$ will be excluded, such bounds on $��$ are interesting and complimentary to the limits from global fit; (d) the dependences of extraction of $��$ on the variation of parameters $��_1$, $��$, $r_1$ and strong phases are also studied., 22 pages, Latex file, 12 EPS figures. two typos are corrected. To be published in Phys. Rev. D

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, 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 $B\to ��^+ ��^-, K^- ��^+$ and $K^0 ��^+$ lead to a strong constraint on the form factor $F_0^{B��}(0)$: $F_0^{B��}(0)=0.24 \pm 0.03$; (b) the new physics enhancements to the penguin-dominated $B \to K ��$ 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., 9 pages, Latex file, to be published in Phys. Rev. D

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 $B \to X_s ����$ induced by the new gluonic and electroweak charged-Higgs penguin diagrams in the general two-Higgs-doublet model with the restriction $��_{ij}^{U,D}=0$ for $i\neq j$. Within the considered parameter space, we see the following: (a) the standard model predictions of ${\cal B}(B \to X_s ����)$ and $A_{FB}$ have a moderate $m_s$ dependence; (b) in model III, the prediction of the branching ratio ${\cal B}(B \to X_s ����)$ ranges from one third to three times of the standard model prediction, but is highly correlated with that of ${\cal}(B \to X_s ��)$; (c) the new physics enhancement to the branching ratio ${\cal B}(B \to X_s ����)$ 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 $��$ and possible new physics corrections; (e) due to the smallness of its decay rate and the long-distance background, the $B \to X_s ����$ decay is not a better process in detecting new physics than the $B \to X_s ��$ decay., Latex file, 27 pages with 17 ps and eps figures. 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 $B \to ����, ����, etc,$ the new physics corrections are less than 10%. For decays $B \to K^{(*)} ��$, $K^{(*)} ��$, $etc$, the new physics enhancements can be rather large (from $- 70%$ to $\sim 200%$) and are insensitive to the variations of $N_c^{eff}$, $k^2$, $��$ and $m_{\tilde��}$ within the reasonable ranges. For decays $B^0 \to ����$, $����^{(')}$, $K^* \bar{K}^0$ and $��^+ K^0$, $��{\cal B}$ 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 $B \to K ��, K ��', ����$ decays, $��{\cal A}_{CP}$ is only about 20% and will be masked by large theoretical uncertainties. The new physics enhancements to interesting $B \to K ��'$ 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 $B \to K ��'$ 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., Latex file, 56 pages with 11 ps and eps figures. to be published in Eur.Phys.J. C

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

The new contributions to the charmless B decay $B \to X_{s}��^{\prime}$ 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: $Br(B \to X_{s}��^{\prime}) \sim 7\times 10^{-4}$ 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., Latex file, 7 pages with two EPS figures

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 $b\rightarrow s��$ 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., 11 pages, Latex, no macros, 3 figures, hard copy is available upon request. to appear in Z. Phys. C

Applying the perturbative QCD ( PQCD ) method, we study the decay $B_c\rightarrow D_s^*��$ 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 $B_c\rightarrow D_s^*��$, 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 ( $b\rightarrow s��$ ). 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., 16 pages, Latex, no macros, 1 figure(in Latex), hard copy is available upon request. to appear in Phys. Rev. D

Applying the perturbative QCD (PQCD), we study the process $B_c\rightarrow D_s^*��$ in the technicolor with a massless scalar doublet model (TCMLSM) recently presented by C. D. Carone and H. Georgi; and compare the results with that estimated in the standard model (SM). There are two mechanisms which contribute to the $B_c\rightarrow D_s^* ��$ process. One proceeds through the short distance $b\rightarrow s ��$ transition, the other through weak annihilation accompanied by a photon emission. In the SM, these two processes are found to contribute with the same order of magnitude. In the TCMLSM, the modification of $B_c\rightarrow D_s^*��$ from $��_p$ (the physical pions in this model) is small for the allowed mass of $��_p$., 16 pages, Latex, no macros, 3 figures(in Latex), hard copy is available upon request. to appear in Z. Phys. C

In this paper we calculate the contributions to the branching ratio of $B\to X_s ��$ from the charged Pseudo-Goldstone bosons appeared in one generation Technicolor model. The current $CLEO$ experimental results can eliminate large part of the parameter space in the $m(P^\pm) - m(P_8^\pm)$ plane, and specifically, one can put a strong lower bound on the masses of color octet charged PGBs $P_8^\pm$: $m(P^{\pm}_8) > 400\;GeV$ at $90\%C.L$ for free $m(P^{\pm})$., 9 pages, 3 figures(uuencoded), Minor changes(Type error), to appear in Phys. Rev. D