11323590
Charmless two-body B decays: A global analysis with QCD factorization
In this paper, we perform a global analysis of $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PP}$ and $\mathrm{PV}$ decays with the QCD factorization approach. It is encouraging to observe that the predictions of QCD factorization are in good agreement with experiment. The best fit $\ensuremath{\gamma}$ is around $79\ifmmode^\circ\else\textdegree\fi{}.$ The penguin-diagram--to--tree-diagram ratio $|{P}_{\ensuremath{\pi}\ensuremath{\pi}}{/T}_{\ensuremath{\pi}\ensuremath{\pi}}|$ of ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays is preferred to be larger than $0.3.$ We also show the confidence levels for some interesting channels: ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0},$ ${K}^{+}{K}^{\ensuremath{-}},$ and ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\pi}}^{+},\ensuremath{\omega}{K}^{+}.$ For $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\pi}{K}^{*}$ decays, they are expected to have smaller branching ratios with more precise measurements.
119387058
Nonleptonic charmless 2-body B decays in the perturbative QCD approach
With the generalized factorization approximation, we calculate the branching ratios and $\mathrm{CP}$ asymmetries in B meson decays into two charmless pseudoscalar mesons. We give a new estimation of the matrix elements of $(S+P)(S\ensuremath{-}P)$ current products with the perturbative QCD method instead of the equation of motion. We find that our results are comparatively smaller than those in the literature.
119210077
Refactorizing NRQCD short-distance coefficients in exclusive quarkonium production
In a typical exclusive quarkonium production process, when the center-of-mass energy, is much greater than the heavy quark mass in, large kinematic logarithms of s/m(2) will unavoidably arise at each order of perturbative expansion in the short-distance coefficients of the nonrelativistic QCD (NRQCD) factorization formalism, which may potentially harm the perturbative expansion. This symptom reflects that the hard regime in NRQCD factorization is too coarse and should be further factorized. We suggest that this regime can be further separated into "hard" and "collinear" degrees of freedom, so that the familiar light-cone approach can be employed to reproduce the NRQCD matching coefficients at the zeroth order of m(2)/s and order by order in alpha(s). Taking two simple processes, exclusive eta(b)+ gamma production in e(+)e(-) annihilation and Higgs boson radiative decay into gamma, as examples, we illustrate how the leading logarithms of s/m(2) in the NRQCD matching coefficients are identified and summed to all orders in alpha(s) with the aid of Brodsky-Lepage evolution equation. (C) 2009 Elsevier B.V. All rights reserved.
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.
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.
54838095
Holographic photon production with magnetic field in anisotropic plasmas
A bstractWe investigate the thermal photon production from constant magnetic field in a strongly coupled and anisotropic plasma via the gauge/gravity duality. The dual geometry with pressure anisotropy is generated from the axion-dilaton gravity action introduced by Mateos and Trancancelli and the magnetic field is coupled to fundamental matters(quarks) through the D3/D7 embeddings. We find that the photon spectra with different quark mass are enhanced at large frequency when the photons are emitted parallel to the anisotropic direction with larger pressure or perpendicular to the magnetic field. However, in the opposite conditions for the emitted directions, the spectra approximately saturate isotropic results in the absence of magnetic field. On the other hand, a resonance emerges at moderate frequency for the photon spectrum with heavy quarks when the photons move perpendicular to the magnetic field. The resonance is more robust when the photons are polarized along the magnetic field. On the contrary, in the presence of pressure anisotropy, the resonance will be suppressed. There exist competing effects of magnetic field and pressure anisotropy on meson melting in the strongly coupled super Yang-Mills plasma, while we argue that the suppression led by anisotropy may not be applied to the quark gluon plasma.