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Yuan-Guo Xu

Publications and source records attributed to Yuan-Guo Xu.

23 records · Page 2Linked to original sources
arXiv2010

Reevaluating R-parity Violating Supersymmetry Effects in B_s^0-\bar{B}_s^0 Mixing

Recently, the CDF and DØ collaborations have claimed that the CP violating phase in $B_s^0-\bar{B}_s^0$ mixing is large, which is contrary to the expectations in the Standard Model. Such a large phase suggests New Physics contributions to $B_s^0-\bar{B}_s^0$ mixing. Motivated by this, we reevaluate the constraints on R-parity violating contributions, including baryon number violating couplings not considered before, to the mixing mass matrix element $M^s_{12}$ from the recent measurements of $B_s^0-\bar{B}_s^0$ mixing. We show that present data allow us to put quite strong constraints on both the magnitudes and the weak phases of the R-parity violating parameters. Some of these bounds are better than the exciting ones, and some bounds are obtained for the first time. Near future experiments at the Tevatron, the LHC and B-factories can shrink or reveal the relevant parameter spaces of R-parity violating couplings.

hep-ph↗
arXiv2010

Studying of Bs --> K(*)-pi+, K(*)-rho+ decays within supersymmetry

Recent results from CDF Collaboration favor a large CP asymmetry in $B_s\rightarrow K^-π^+$ decay, while the Standard Model prediction is very small. Moreover, the measurement of its branching ratio is lower than the Standard Model prediction based on the QCD factorization. We compute the gluino-mediated supersymmetry contributions to $B_{s}\to K^{(*)-}π^{+}$,$K^{(*)-}ρ^{+}$ decays in the frame of the mass insertion method, and find that for $\frac{m^2_{\tilde{g}}}{m^2_{\tilde{q}}}\leq2$, the theoretical predictions including the LR and RL mass insertion contributions are compatible with the measurements of $B_s\to K^-π^+$ decay and $B^0-\bar{B}^0$ mixing within $2σ$ ranges. Using the constrained LR and RL mass insertion parameter spaces, we explore the supersymmetry mass insertion effects on the branching ratios, the direct CP asymmetries and the polarization fractions in $B_{s}\to K^{*-}π^+, K^{-}ρ^+, K^{*-}ρ^+$ decays. We find the constrained LR and RL insertions can provide sizable contributions to the branching ratios of $B_{s}\to K^{*-}π^{+}$,$K^{(*)-}ρ^{+}$ as well as the direct CP asymmetry and the longitudinal polarization of $B_{s}\to K^{*-}ρ^{+}$ decay without conflict with all related data within $2σ$ ranges. Near future experiments at Fermi Lab and CERN LHC-b can test our predictions and shrink/reveal the mass insertion parameter spaces.

hep-ph↗
arXiv2009

B_s\to K^{(*)-}K^{(*)+}, K^{(*)-}π^{+}, K^{(*)-}ρ^{+} decays in R-parity violating supersymmetry

With the first measurements of the branching ratios and the direct CP asymmetries of $B_s\to K^{-}K^{+}$, $K^{-}π^{+}$ decays by the CDF collaboration, we constrain the relevant parameter space of the Minimal Supersymmetric Standard Model with R-parity violation. Using the constrained R-parity violating couplings, we further examine their possible effects in $B_{s}\to K^{-*}π^{+}$, $K^{(*)-}ρ^{+}$ and $K^{(*)\pm}K^{(*)\mp}$ decays. We find that some branching ratios and CP asymmetries are very sensitive to the R-parity violating couplings. The direct longitudinal CP asymmetries of tree-dominated process $B_s\to K^{*-}ρ^{+}$ could be enlarged to $\sim 70%$ and the longitudinal polarizations of $B_s\to K^{*-}K^{*+}$, $K^{*-}ρ^{+}$ decays could be suppressed very much by the squark exchange couplings. Near future experiments at CERN LHC can test these predictions and shrink/reveal the parameter spaces of RPV SUSY.

hep-ph↗
arXiv2007

The rare decays $B^+_u\toπ^+\ell^+\ell^-$, $ρ^+\ell^+\ell^-$ and $B^0_d\to \ell^+\ell^-$ in the R-parity violating supersymmetry

We study the rare decays $B^{+}_u\to π^{+}\ell^{+}\ell^{-}$, $ρ^{+}\ell^{+}\ell^{-}$ and $B^{0}_d \to \ell^{+} \ell^{-}(\ell=e,μ)$ in the R-parity violating supersymmetric standard model. From the latest upper limits of $\mathcal{B}(B^+_u\toπ^+\ell^+\ell^-)$ and $\mathcal{B}(B^0_d\to\ell^+\ell^-)$, we have derived new upper bounds on the relevant R-parity violating couplings products, which are stronger than the existing ones. Using the constrained parameter space, we present the R-parity violating effects on the branching ratios and the forward-backward asymmetries of these decays. We find that $\mathcal{B}(B^0_d\to \ell^+\ell^-)$ and $\mathcal{B}(B^+_u \toρ^+\ell^+\ell^-)$ could be enhanced several orders by the R-parity violating sneutrino and squark exchanges, respectively. The R-parity violating effects on the dilepton invariant mass spectra of $B^+_u\to π^+\ell^+\ell^-$, $ρ^+\ell^+\ell^-$ and the normalized forward-backward asymmetry $\mathcal{A}_{FB}(B^+_u\toπ^+\ell^+\ell^-)$ and $\mathcal{A}_{FB}(B^+_u \toρ^+\ell^+\ell^-)$ are studied in detail. Our results could be used to probe the R-parity violating effects and will correlate with searches for the direct R-parity violating signals at the future experiments.

hep-ph↗
arXiv2006

Probe R-parity Violating Supersymmetry Effects in $B\to K^{(*)}\ell^+\ell^-$ and $B_s\to \ell^+\ell^-$ Decays

We study the decays $B\to K^{(*)}\ell^+\ell^-$ and $B_s\to \ell^+\ell^- (\ell=e,μ)$ in the minimal supersymmetric standard model with R-parity violation (RPV). From the recent measurements of their branching ratios, we have derived new upper bounds on the relevant RPV coupling products, which are stronger than the existing ones. Using the constrained parameter space, we predict the RPV effects on the forward-backward asymmetries ${\mathcal A}_{FB}(B\to K^{(*)}\ell^+\ell^-)$ and the branching ratios $ {\mathcal B}(B_s\to \ell^{+}\ell^{-}) $. Our results of the forward-backward asymmetries agree with the recent experiment data. It is also found that $\mathcal{B}(B_s\to \ell^+\ell^-)$ could be enhanced several orders by the RPV sneutrino exchange. The RPV effects on the dilepton invariant mass spectra of $B\to K^{(*)}\ell^+\ell^-$ and the normalized ${\mathcal A}_{FB}(B\to K^{(*)}\ell^+\ell^-)$ are studied in detail. Our results could be used to probe RPV effects and will correlate with searches for direct RPV signals at LHC.

hep-ph↗