118456126
Broken S3 flavor symmetry of leptons and quarks: Mass spectra and flavor mixing patterns
Abstract We apply the discrete S 3 flavor symmetry to both lepton and quark sectors of the Standard Model extended by introducing one Higgs triplet and realizing the type-II seesaw mechanism for finite neutrino masses. The resultant mass matrices of charged leptons ( M l ), neutrinos ( M ν ), up-type quarks ( M u ) and down-type quarks ( M d ) have a universal form consisting of two terms: one is proportional to the identity matrix I and the other is proportional to the democracy matrix D . We argue that the textures of M l , M u and M d are dominated by the D term, while that of M ν is dominated by the I term. This hypothesis implies a near mass degeneracy of three neutrinos and can naturally explain why the mass matrices of charged fermions are strongly hierarchical, why the quark mixing matrix is close to I and why the lepton mixing matrix contains two large angles. We discuss a rather simple perturbation ansatz to break the S 3 symmetry and obtain more realistic mass spectra of leptons and quarks as well as their flavor mixing patterns. We stress that the I term, which used to be ignored from M l , M u and M d , is actually important because it can significantly modify the smallest lepton flavor mixing angle θ 13 or three quark flavor mixing angles.
15449960
QCD Factorization For B Decays To Two Light Pseudoscalars Including Chirally Enhanced Corrections
Since b quark mass is not asymptotically large, chirally enhanced corrections which arise from twist-3 wave functions may be important in B decays. We thus evaluate the hadronic matrix elements with the emitted meson described by leading twist and twist-3 distribution amplitudes $\Phi_p(x)$. After summing over the four "vertex correction" diagrams, we obtain the results with infrared finiteness which shows that chirally enhanced corrections arise from $\Phi_p(x)$ can be consistently included in QCD factorization. We also briefly discuss the contributions from "hard spectator" diagrams.
14205678
Phenomenological analysis of B -> PP decays with QCD factorization
In this paper, we study nonleptonic charmless B decays to two light pseudoscalar mesons within the frame of QCD factorization, including the contributions from the chirally enhanced power corrections and weak annihilation. Predictions for the CP-averaged branching ratios and CP-violating asymmetries are given. Within the reasonable range of the parameters, we find that our predictions for the branching ratios of B-->PP are consistent with the present experimental data. But because of the logarithmic divergences at the end points in the hard spectator scatterings and weak annihilation, there are still large uncertainties in these predictions.
119112269
Probing W+W−γ production and anomalous quartic gauge boson couplings at the CERN LHC
A bstractTriple gauge boson associated production at the LHC serves as an interesting channel to test the robustness of the Standard Model. Any deviation from its SM prediction may indicate possible existence of relevant new physics, e.g., anomalous quartic gauge boson couplings. In this paper, a Monte-Carlo feasibility study of measuring W+W−γ production with pure leptonic decays and probing anomalous quartic gauge-boson (e.g., WWγγ) couplings, is presented in detail for the first time, with parton shower and detector simulation effects taken into account. Our results show that at the $ \sqrt{s}=14 $ TeV LHC with an integrated luminosity of 100 (30) fb−1, one can reach a significance of 9 (5) σ to observe the SM W+W−γ production, and can constrain at the 95% C.L. the anomalous WWγγ coupling parameters, e.g., $ a{{{_{0,c}^W}} \left/ {{{\varLambda^2}}} \right.} $ (see ref. [16] for their definitions), at 1 × 10−5 GeV−2 level, respectively.