3,891 research outputs found

### Mixing of pseudoscalar mesons and isospin symmetry breaking

Mixing of the pseudoscalar mesons is discussed in the quark-flavor basis with
the hypothesis that the basis decay constants follow the pattern of particle
state mixing. The divergences of the axial vector currents which embody the
axial vector anomaly, combined with this hypothesis provide a calculational
scheme for the parameters describing the mixing of the pion, eta and eta'
mesons. Phenomenological applications of this mixing scheme are presented with
particular interest focussed on isospin symmetry breaking in QCD estimated as
eta and eta' admixtures to the pion. In contrast to previous work a possible
difference in the basis decay constants f_u and f_d is considered and
consequences of this potentially large effect on the strength of isospin
symmetry breaking is discussed.Comment: 10 pages, (using LATEX with w-ijmpa.sty), invited talk presented at
MESON 2004, 8th Intern. Workshop on Meson Production, Properties and
Interaction

### The study of $B\to J/\Psi \eta^{(\prime)}$ decays and determination of $\eta-\eta^{\prime}$ mixing angle

We study $B\to J/\Psi \eta^{(\prime)}$ decays and suggest two methods to
determine the $\eta-\eta^{\prime}$ mixing angle. We calculate not only the
factorizable contribution in QCD facorization scheme but also the
nonfactorizable hard spectator corrections in pQCD approach. We get the
branching ratio of $B\to J/\Psi \eta$ which is consistent with recent
experimental data and predict the branching ratio of $B\to J/\Psi
\eta^{\prime}$ to be $7.59\times 10^{-6}$. Two methods for determining
$\eta-\eta^{\prime}$ mixing angle are suggested in this paper. For the first
method, we get the $\eta-\eta^{\prime}$ mixing angle to be about
$-13.1^{\circ}$, which is in consistency with others in the literature. The
second method depends on less parameters so can be used to determine the
$\eta-\eta^{\prime}$ mixing angle with better accuracy but needs, as an input,
the branching ratio for $B\to J/\Psi \eta^{\prime}$which should be measured in
the near future.Comment: 16pages,4figure

### See-Saw Masses for Quarks and Leptons in SU(5)

We build on a recent paper by Grinstein, Redi and Villadoro, where a see-saw
like mechanism for quark masses was derived in the context of spontaneously
broken gauged flavour symmetries. The see-saw mechanism is induced by heavy
Dirac fermions which are added to the Standard Model spectrum in order to
render the flavour symmetries anomaly-free. In this letter we report on the
embedding of these fermions into multiplets of an SU(5) grand unified theory
and discuss a number of interesting consequences.Comment: 15 pages, 4 figures (v3: outline restructured, modified mechanism to
cancel anomalies

### Mixing and Decay Constants of Pseudoscalar Mesons: The Sequel

We present further tests and applications of the new eta-eta' mixing scheme
recently proposed by us. The particle states are decomposed into orthonormal
basis vectors in a light-cone Fock representation. Because of flavor symmetry
breaking the mixing of the decay constants can be identical to the mixing of
particle states at most for a specific choice of this basis. Theoretical and
phenomenological considerations show that the quark flavor basis has this
property and allows, therefore, for a reduction of the number of mixing
parameters. A detailed comparison with other mixing schemes is also presented.Comment: 9 page

### Role of "Intrinsic Charm" in Semi-Leptonic B-Meson Decays

We discuss the role of so-called "intrinsic-charm" operators in semi-leptonic
B-meson decays, which appear first at order 1/m_b^3 in the heavy quark
expansion. We show by explicit calculation that -- at scales mu <= m_c -- the
contributions from "intrinsic-charm" effects can be absorbed into
short-distance coefficient functions multiplying, for instance, the Darwin
term. Then, the only remnant of "intrinsic charm" are logarithms of the form
ln(m_c^2/m_b^2), which can be resummed by using renormalization-group
techniques. As long as the dynamics at the charm-quark scale is perturbative,
alpha_s(m_c) << 1, this implies that no additional non-perturbative matrix
elements aside from the Darwin and the spin-orbit term have to be introduced at
order 1/m_b^3. Hence, no sources for additional hadronic uncertainties have to
be taken into account. Similar arguments may be made for higher orders in the
1/m_b expansion.Comment: 14 pages, 1 figure, uses slashed.sty, slight modifications to match
published versio

### Light-cone sum rules: A SCET-based formulation

We describe the construction of light-cone sum rules (LCSRs) for exclusive
$B$-meson decays into light energetic hadrons from correlation functions within
soft-collinear effective theory (SCET). As an example, we consider the SCET sum
rule for the $B \to \pi$ transition form factor at large recoil, including
radiative corrections from hard-collinear loop diagrams at first order in the
strong coupling constant.Comment: LaTex, 4 pages, 2 eps figures. Talk given at QCD05, 12th
International QCD Conference, 4-9th July 2005, Montpellier, Franc

### Supersymmetric contributions to B --> K pi in the view of recent experimental result

Supersymmetric contributions to the branching ratios and CP asymmetries of
B--> K pi decays are analyzed in the view of recent experimental measurements.
We show that supersymmetry can still provide a natural solution to the apparent
discrepancy between theses results and the standard model expectations. We
emphasize that chargino contributions may enhance the electroweak penguin
effects that can resolve to the B--> K pi puzzle. We also point out that a
non-universal $A$-terms is an essential requirement for this solution.Comment: 9 pages, 2 figure

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