266 research outputs found
Recent Development of QCD Factorization for B-> M1 M2
After briefly introducing the framework of QCD factorization for B-> M1 M2 in
the language of the Soft-Collinear Effective Theory, we firstly address the
recent efforts on higher-order radiative corrections in QCD factorization. Then
we discuss some phenomenologies in B-> V V within the framework of QCD
factorization.Comment: 4 pages. Invited plenary talk given at the 4th International
Conference on Flavor Physics, Sep.24-Sep.28, 2007, Beijing
Broken S_3 Flavor Symmetry of Leptons and Quarks: Mass Spectra and Flavor Mixing Patterns
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_nu), 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_nu 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 theta_13 or
three quark flavor mixing angles.Comment: 13 pages, no figures; discussions about CP violation added,
references updated, to appear in Phys. Lett.
Goldstone Modes and Clebsch-Gordan Coefficients
We solve explicitly the Goldstone modes in spontaneously symmetry breaking
models with supersymmetry. We find that, when more than one fields or
representations contribute to the symmetry breaking, there exist identities
among the Clebsch-Gordan coefficients which can be used as consistent checks on
the calculations.Comment: 13 page
Exclusive Decays to Charmonium and a Light Meson at Next-to-Leading Order Accuracy
In this paper the next-to-leading order (NLO) corrections to meson
exclusive decays to S-wave charmonia and light pseudoscalar or vector mesons,
i.e. , , , and , are performed within non-relativistic (NR)
QCD approach. The non-factorizable contribution is included, which is absent in
traditional naive factorization (NF). And the theoretical uncertainties for
their branching ratios are reduced compared with that of direct tree level
calculation. Numerical results show that NLO QCD corrections markedly enhance
the branching ratio with a K factor of 1.75 for and 1.31 for . In order to
investigate the asymptotic behavior, the analytic form is obtained in the heavy
quark limit, i.e. . We note that annihilation topologies
contribute trivia in this limit, and the corrections at leading order in expansion come from form factors and hard spectator interactions. At
last, some related phenomenologies are also discussed.Comment: 20 pages, 7 figures and 5 table
- β¦