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Chao-Shang Huang

Publications and source records attributed to Chao-Shang Huang.

At least 37 records · Page 2Linked to original sources

CP asymmetries in $B\to ϕK_S$ and $B\to η' K_S$ in MSSM

We study the $B\to ϕK_S$ and $B\to \ep K_S$ decays in MSSM by calculating hadronic matrix elements of operators with QCD factorization approach and including neutral Higgs boson (NHB) contributions. We calculate the Wilson coefficients of operators including the new operators which are induced by NHB penguins at LO using the MIA with double insertions. We calculate the $α_s$ order hadronic matrix elements of the new operators for $B\to ϕK_s$ and $B\to η^\prime K_s$. It is shown that the recent experimental results on the time-dependent CP asymmetries in $B\to ϕK_S$ and $B\to \ep K_S$, $S_{ϕK}$ is negative and $S_{η^{\prime} K}$ is positive, which can not be explained in SM, can be explained in MSSM if there are flavor non-diagonal squark mass matrix elements of 2nd and 3rd generations whose size satisfies all relevant constraints from known experiments ($B\to X_Sγ, B_s\to μ^+μ^-, B\to X_s μ^+μ^-, B\to X_s g, ΔM_s$, etc.). In particular, we find that one can explain the experimental results with a flavor non-diagonal mass insertion of any chirality when $α_s$ corrections of hadronic matrix elements of operators are included, in contrast with the claim in the literature. At the same time, the branching ratios for the two decays can also be in agreement with experimental measurements.

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D_s(2317) and D_s(2457) from HQET Sum Rules

Within the framework of the heavy quark effective theory, QCD sum rules are used to calculate the masses of p-wave (c-bar s) states. The results for 0^+ and 1^+ states with the angular momentum of the light component j_l=1/2 are consistent with the experimental values for D_s(2317) and D_s(2457), respectively.

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Neutral Higgs boson contributions to CP asymmetry of $B \to ΦK_S$ in MSSM

We have studied the neutral Higgs boson (NHB) contributions to the pure penguin process $B\to ϕK_S$ in MSSM with middle and large $\tanβ$ (say, $>$ 8). We show that the $α_s$ order hadronic matrix elements of NHB induced operators can make sizable effects on both the branch ratio and time dependent CP asymmetry $S_{ϕK}$. Under the all relevant experimental constraints, the Higgs mediated contributions to $S_{ϕK}$ alone can provide a significant deviation from SM and, in particular, lead to a negative $S_{ϕK}$ which is reported by BaBar and Belle.

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CP violation in $B \to ΦK_S$ in a model III 2HDM

The mixing induced time dependent CP asymmetry, direct CP asymmetry, and branching ratio in $B \to ΦK_S$ in a model III 2HDM are calculated, in particular, neutral Higgs boson contributions are included. It is shown that satisfying all the relevant experimental constraints, for time dependent CP asymmetry $S_{ϕK}$ the model III can agree with the present data, $S_{ϕk}=-0.39\pm 0.41$, within the $1σ$ error, and the direct CP asymmetry which is zero in SM can be about $ -8% \sim -20%$ in the reasonable regions of parameters.

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The Contributions of Neutral Higgs Bosons to Charmless Nonleptonic B Decays in MSSM

We investigate the contributions of neutral Higgs bosons to nonleptonic transition $b \to q \bar{s} s, q=d, s$ under the supersymmetric context. Their effects to decay width and CP violation in corresponding exclusive decays are explored. The anomalous dimension matrices of the operators which have to be incorporated to include the contributions of neutral Higgs bosons are given. We find that when tan$β$ is large (say, 50) and neutral Higgs bosons are not too heavy (say, 100 GeV), contributions of neutral Higgs penguin can dominate electroweak penguin contributions, and for some processes, they can greatly modify both decay width and CP asymmetry.

hep-ph↗

Neutrino Bilarge Mixing and Flavor Physics in the Flipped SU(5) Model

We have constructed a specific supersymmetric flipped SU(5) GUT model in which bilarge neutrino mixing is incorporated. Because the up-type and down-type quarks in the model are flipped in the representations ten and five with respect to the usual SU(5), the radiatively generated flavor mixing in squark mass matrices due to the large neutrino mixing has a pattern different from those in the conventional SU(5) and SO(10) supersymmetric GUTs. This leads to phenomenological consequences quite different from SU(5) or SO(10) supersymmetric GUT models. That is, it has almost no impact on B physics. On the contrary, the model has effects in top and charm physics as well as lepton physics. In particular, it gives promising prediction on the mass difference, $ΔM_D$, of the $D-{\bar D}$ mixing which for some ranges of the parameter space with large $\tanβ$ can be at the order of $10^9 ~\hbar ~s^{-1}$, one order of magnitude smaller than the experimental upper bound. In some regions of the parameter space $ΔM_D$ can saturate the present bound. For these ranges of parameter space, $t \to u,c+h^0$ can reach $10^{-5}-10^{-6}$ which would be observed at the LHC and future $γ-γ$ colliders.

hep-ph↗

Understanding the $D^+_{sJ}(2317)$ and $D^+_{sJ}(2460)$ with Sum Rules in HQET

In the framework of heavy quark effective theory we use QCD sum rules to calculate the masses of the $\bar c s$ $(0^+, 1^+)$ and $(1^+, 2^+)$ excited states. The results are consistent with that the states $D_{sJ}(2317)$ and $D_{sJ}(2460)$ observed by BABAR and CLEO are the $0^+$ and $1^+$ states in the $j_l={1\over 2}^+$ doublet.

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CP violation in $B_{d,s} \to l^+l^-$ in the model III 2HDM

We have calculated the Wilson coefficients $C_{10}, C_{Q_i}$ (i=1,2) in the $\bar{MS}$ renormalization scheme in the model III 2HDM. Using the obtained Wilson coefficients, we have analyzed the CP violation in decays $B^0_q\to l^+l^-$ (q=d,s) in the model. The CP asymmetry, $A_{CP}$, depends on the parameters of models and $A_{CP}$ in $B_d\to l^+l^-$ can be as large as 40% and 35% for $l=τ$ and $l=μ$ respectively. It can reach 4% for $B^0_s$ decays. Because in SM CP violation is smaller than or equal to O($10^{-3}$) which is unobservably small, an observation of CP asymmetry in the decays $B^0_q \to l^+l^- (q=d,s)$ would unambiguously signal the existence of new physics.

hep-ph↗

B_s -> mu^+ mu^- and B -> X_s mu^+ mu^- in MSSM

Pure leptonic and semileptonic rare B decays, $B_s \to μ^+ μ^-$ and $B \to X_s μ^+ μ^-$ in the minimal supersymmetric Standard Model (MSSM), in particular, gluino and neutralino contributions to the decays, are discussed under Br($B \to X_s γ$) and other experimental constraints . The general scalar quark mass matrices as the new sources of flavor violation are considered. We present Wilson coefficients of $bs$ transitions from $γ$, $Z$, and neutral Higgs boson penguin diagrams by using vertex mixing method to deal with scalar down-type quark flavor changing and also give their expressions in MIA to show different sources of enhancements. We find that under the experimental constraints, with large mixing of left-handed and right-handed sbottom, $C^{(\prime)}_{10}$ can be enhanced by 10% compared with SM, in two cases, heavy gluino and fine-tuning between $δ^{dLL}_{23}$($δ^{dRR}_{23}$) and $δ^{dLR}_{23}$($δ^{dRL}_{23}$) terms in $C^{(\prime)}_7$. Particularly, $C_{10}$ and $C_{10}^{\prime}$ can reach a 20% enhancement in some regions of parameters under experimental constraints. When CP-odd Higgs $A^0$ is not too heavy ($\sim 250$GeV), and $\tanβ$ is large ($\sim 40$), neutral Higgs boson penguins with gluino and down-type squark in the loop can significantly contribute to the $bs$ transition and the contributions can compete with those due to the chargino and up-type squark loop.

hep-ph↗

B\to πϕin SM and MSSM

We investigate the pure penguin decays $B\to πϕ$ in the Standard Model(SM) and in the Constrained Minimal Supersymmetric Standard Model (CMSSM) using the QCD factorization approach and consider the Sudakov effects in the twist-3 contribution. We find ${\rm Br}(B^-\to π^-ϕ) = (1.95-5.70)\times 10^{-9}$ in SM and $(1.1-2.4)\times 10^{-8}$ in CMSSM with large $\tanβ$ which is about one order of magnitude larger than that in SM.

hep-ph↗

CP violation in $B_{d,s}\to l^+l^-$

CP violation in rare leptonic B decays are analyzed in the standard model (SM) and models beyond SM (supersymmetric models and two Higgs doublet models).

hep-ph↗

Search for new physics in $B_{d,s}\to l^+l^-$

An overview of recent theoretical developments in rare leptonic B decays is given. New physics effects on branching ratio and CP violation in the decays are analyzed in models beyond SM (supersymmetric models and two Higgs doublet models).

hep-ph↗

$(g-2)_μ$ and CP Asymmetries in $B^0_{d,s} \to l^+ l^-$ and $b \to s γ$ in SUSY models

We show that with a good fit to the muon $g-2$ constraint, the CP asymmetry can be as large as 25% (15%) for $B^0_d \to τ^+ τ^-$ ($B^0_d \to μ^+ μ^-$) in SUGRA models with nonuniversal gaugino masses and MSSM. If tau events indentified at B factories the CP asymmetry in $B^0_d \to τ^+τ^-$ can be a powerful probe on physics beyond SM. An interesting case is that new physics gives a prediction on the branching ratio which is still in the uncertain region of the SM prediction. The CP asymmetry for $B^0_d \to l^+ l^-$ in this case can still reach 20%. So it is powerful to shed light on physics beyond SM while the CP asymmetry of $b \to s γ$ in this case can only reach 2% at most which is too small to draw a definite conclusion on new physics effects at B factories.

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Rare decay $B\to X_sl^+l^-$ in a CP spontaneously broken two Higgs doublet model

The Higgs boson mass spectrum and couplings of neutral Higgs bosons to fermions are worked out i n a CP spontaneously broken two Higgs doublet model in the large tan$β$ case. The differential branching ratio, forward-backward asymmetry, CP asymmetry and lepton polarization for $B\to X_s l^+ l^-$ are computed. It is shown that effects of neutral Higgs bosons are quite significant when $\tanβ$ is large. Especially, the CP violating normal polarization $P_N$ can be as large as several percents.

hep-ph↗

N=2 6-dimensional Supersymmetric $E_6$ Breaking

We study the $N=2$ supersymmetric $E_6$ models on the 6-dimensional space-time where the supersymmetry and gauge symmetry can be broken by the discrete symmetry. On the space-time $M^4\times S^1/(Z_2\times Z_2') \times S^1/(Z_2\times Z_2')$, for the zero modes, we obtain the 4-dimensional $N=1$ supersymmetric models with gauge groups $SU(3)\times SU(2) \times SU(2) \times U(1)^2$, $SU(4)\times SU(2) \times SU(2) \times U(1)$, and $SU(3)\times SU(2) \times U(1)^3$ with one extra pair of Higgs doublets from the vector multiplet. In addition, considering that the extra space manifold is the annulus $A^2$ and disc $D^2$, we list all the constraints on constructing the 4-dimensional $N=1$ supersymmetric $SU(3)\times SU(2) \times U(1)^3$ models for the zero modes, and give the simplest model with $Z_9$ symmetry. We also comment on the extra gauge symmetry breaking and its generalization.

hep-th↗

Sudakov effects in BBNS approach

The end-point singularity is an unsolved problem in BBNS approach. Incorporating the partonic transverse momentum and the Sudakov form factor, this problem can be solved model-independently. We discuss the Sudakov effects in BBNS approach. The BBNS approach is compared with the modified PQCD approach. The main idea of Sudakov form factor is briefly discussed. Our conclusion is that the twist-3 contribution for the hard spectator scattering is numerically not important in $B\to ππ$ decays, compared with the twist-2 contribution.

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Heavy quark polarizations of $e^+e^-\to q \bar q h$ in the general two Higgs doublet model

The polarizations of the heavy quark ($q=t$ or $b$) in the process $e^+e^- \to q \bar q h$ have been calculated in the general two Higgs doublet model. The CP violating normal polarization of the top quark can reach 8%, and $2 \sim 3%$ for the bottom quark, while it is zero in the standard model. The longitudinal and transverse polarizations of the bottom quark can be significantly different from those in SM and consequently could aslo be used as the probe of the new physics.

hep-ph↗

Non-Universal Gaugino Masses in Supersymmetric SO(10)

We consider SUSY SO(10) models in which SUSY breaking occurs via an F-term which does not transform as an SO(10) singlet. This results in non-universal GUT-scale gaugino masses leading to a different pattern of sparticle masses from what is expected in the minimal supergravity model (mSUGRA). We study three breaking chains of SO(10) down to the standard model through SU(4)$\timesSU(2)\times$SU(2), SU(2)$\times$SO(7) and `flipped' SU(5) achieved by the representations 54 and 210 which appear in the symmetric product of two SO(10) adjoints. We examine the phenomenological implications of the different boundary conditions corresponding to the different breaking chains and present the sparticle spectrum.

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