7,009 research outputs found
Resonances and weak interactions in decays
We describe the -wave in decays using
a unitary model for the Final State Interactions (FSI). The three body
decay is treated as a quasi two-body process where, at the weak vertex, the D
meson decays into a resonance and a pion. The weak part of the decay amplitude
is evaluated using the effective weak Hamiltonian within the factorization
approximation.Comment: 4 pages. Contribution to the X Hadron Physics, Florianopolis-Brazil,
March 26-31, 200
K* resonance effects on direct CP violation in B -> pi pi K
Charged and neutral B decays into two charged pions and a charged or a
neutral kaon are analyzed within the QCD factorization scheme where final state
interactions before and after hadronization are included. The K*(892) and
K*(1430) resonance effects are taken into account using the presently known
pion-Kaon strange vector and scalar form factors. The weak decay amplitudes,
which are calculated at leading power in Lambda_QCD/m_b and at the
next-to-leading order in the strong coupling constant, include the hard
scattering and annihilation contributions. The end point divergences of these
weak final state interactions are controlled by two complex parameters
determined through a fit to the available effective mass and helicity angle
distribution, CP asymmetry and K*(892) branching ratio data. The predicted
K*(1430) branching ratios and the calculated direct CP violation asymmetries
are compared to the Belle and BABAR Collaboration data.Comment: Comments: 22 pages, 2 figures and 3 tables. In this new version, the
results are unchanged, but, the last paragraph of the Section "RESULTS AND
SUMMARY" (now called "RESULTS AND DISCUSSION") has been replaced by a new
Section "SUMMARY AND OUTLOOK". To appear in Physical Review
Pseudoscalar-scalar transition form factors in covariant light front dynamics
In an explicitly covariant light-front formalism, we analyze transition form
factors between pseudoscalar and scalar mesons. Application is performed in
case of the transition in the full available transfer momentum
range .Comment: 4 pages, 4 figures. Talk given at the XXXIII International Conference
on High Energy Physics, ICHEP06, Moscow, 26 July-02 Augus
Form factors in B->f0(980) and D->f0(980) transitions from dispersion relations
Within the dispersion relation approach we give the double spectral
representation for space-like and time-like B-> f_0(980) and D-> f_0(980)
transition form factors in the full q^2 range. The spectral densities, being
the input of the dispersion relations, are obtained from a triangle diagram in
the relativistic quark model.Comment: Talk given at MESON 2006, Krakow, 9-13 June 200
Scalar meson properties from D-meson decays
Decay amplitudes of D(D_s)->f0(980)X, X=pi, K, are compared to experimental
branching ratios with the aim of singling out the poorly known D->f0(980)
transition form factor in these amplitudes. Since the other elements of the
amplitudes are either calculable in an effective QCD theory using operator
product expansion or are known from experiment (e.g. the pion and kaon decay
constants), we can take advantage of these reactions to constrain the
transition form factors obtained in relativistic quark models. In these models,
the f0(980) wavefunction requires an unknown size parameter for both its
non-strange ubar u(dbar d) and strange sbar s components, which we fit to the
D(D_s) decay data.Comment: Talk given at the Few Body 18 conference in Santos, Brazil. 4 pages,
to be published in Nuclear Physics
Structure of the solar photosphere studied from the radiation hydrodynamics code ANTARES
The ANTARES radiation hydrodynamics code is capable of simulating the solar
granulation in detail unequaled by direct observation. We introduce a
state-of-the-art numerical tool to the solar physics community and demonstrate
its applicability to model the solar granulation. The code is based on the
weighted essentially non-oscillatory finite volume method and by its
implementation of local mesh refinement is also capable of simulating turbulent
fluids. While the ANTARES code already provides promising insights into
small-scale dynamical processes occurring in the quiet-Sun photosphere, it will
soon be capable of modeling the latter in the scope of radiation
magnetohydrodynamics. In this first preliminary study we focus on the vertical
photospheric stratification by examining a 3-D model photosphere with an
evolution time much larger than the dynamical timescales of the solar
granulation and of particular large horizontal extent corresponding to on the solar surface to smooth out horizontal spatial
inhomogeneities separately for up- and downflows. The highly resolved Cartesian
grid thereby covers of the upper convection zone and the
adjacent photosphere. Correlation analysis, both local and two-point, provides
a suitable means to probe the photospheric structure and thereby to identify
several layers of characteristic dynamics: The thermal convection zone is found
to reach some ten kilometers above the solar surface, while convectively
overshooting gas penetrates even higher into the low photosphere. An wide transition layer separates the convective from the
oscillatory layers in the higher photosphere.Comment: Accepted for publication in Astrophysics and Space Science; 18 pages,
12 figures, 2 tables; typos correcte
Scalar resonances in a unitary -wave model for
We propose a model for decays following
experimental results which indicate that the two-pion interaction in the
-wave is dominated by the scalar resonances and
. The weak decay amplitude for , where is a
resonance that subsequently decays into , is constructed in a
factorization approach. In the -wave, we implement the strong decay by means of a scalar form factor. This provides a unitary
description of the pion-pion interaction in the entire kinematically allowed
mass range from threshold to about 3 GeV. In order to
reproduce the experimental Dalitz plot for \Dppp, we include contributions
beyond the -wave. For the -wave, dominated by the , we use a
Breit-Wigner description. Higher waves are accounted for by using the usual
isobar prescription for the and . The major
achievement is a good reproduction of the experimental
distribution, and of the partial as well as the total \Dppp branching ratios.
Our values are generally smaller than the experimental ones. We discuss this
shortcoming and, as a byproduct, we predict a value for the poorly known transition form factor at .Comment: 23 pages, 2 figures. Two new equations. The value for the strength of
the contribution of the scalar form factor now agrees with other results in
the literature. Main results unchanged. Version to appear in Phys. Rev.
Mesoscopic motion of atomic ions in magnetic fields
We introduce a semiclassical model for moving highly excited atomic ions in a
magnetic field which allows us to describe the mixing of the Landau orbitals of
the center of mass in terms of the electronic excitation and magnetic field.
The extent of quantum energy flow in the ion is investigated and a crossover
from localization to delocalization with increasing center of mass energy is
detected. It turns out that our model of the moving ion in a magnetic field is
closely connected to models for transport in disordered finite-size wires.Comment: 4 pages, 2 figures, subm. to Phys.Rev.A, Rap.Co
The Scalar Meson f0(980) in Heavy-Meson Decays
A phenomenological analysis of the scalar meson f0(980) is performed that
relies on the quasi-two body decays D and Ds -> f0(980)P, with P=pi, K. The
two-body branching ratios are deduced from experimental data on D or Ds -> pi
pi pi, K Kbar pi and from the f0(980) -> pi+ pi- and f0(980) -> K+ K- branching
fractions. Within a covariant quark model, the scalar form factors F0(q2) for
the transitions D and Ds -> f0(980) are computed. The weak D decay amplitudes,
in which these form factors enter, are obtained in the naive factorization
approach assuming a quark-antiquark state for the scalar and pseudoscalar
mesons. They allow to extract information on the f0(980) wave function in terms
of u-ubar, d-dbar and s-sbar pairs as well as on the mixing angle between the
strange and non-strange components. The weak transition form factors are
modeled by the one-loop triangular diagram using two different relativistic
approaches: covariant light-front dynamics and dispersion relations. We use the
information found on the f0(980) structure to evaluate the scalar and vector
form factors in the transitions D and Ds -> f0(980), as well as to make
predictions for B and Bs -> f0(980), for the entire kinematically allowed
momentum range of q2.Comment: 45 pages, 9 figures and 9 tables. The use of dispersion relations to
calculate the weak transition form factors is better justified. A more
extensive discussion on the strange and non-strange flavor content mixing is
introduced. Results unchanged. Version to appear in Phys. Rev.
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