2,153 research outputs found
VMD, the WZW Lagrangian and ChPT: The Third Mixing Angle
We show that the Hidden Local Symmetry Model, supplemented with well-known
procedures for breaking flavor SU(3) and nonet symmetry, provides all the
information contained in the standard Chiral Perturbation Theory (ChPT)
Lagrangian . This allows to rely on radiative
decays of light mesons ( and ) in order to extract
some numerical information of relevance to ChPT: a value for , a quark mass ratio of , and a negligible
departure from the Gell-Mann--Okubo mass formula. The mixing angles are
and . We also give the values of all decay constants. It is shown that
the common mixing pattern with one mixing angle is actually quite
appropriate and algebraically related to the mixing pattern
presently preferred by the ChPT community. For instance the traditional
is functionally related to the ChPT and fulfills
. The vanishing of , supported by all
data on radiative decays, gives a novel relation between mixing angles and the
violation of nonet symmetry in the pseudoscalar sector. Finally, it is shown
that the interplay of nonet symmetry breaking through U(3) \ra SU(3)
U(1) satisfies all requirements of the physics of radiative decays without any
need for additional glueballs.Comment: 31 pages, 1 figur
A Global Treatment Of VMD Physics Up To The : I. Annihilations, Anomalies And Vector Meson Partial Widths
The HLS Model, equipped with a mechanism providing the breaking of U(3)/SU(3)
symmetry and an isospin symmetry breaking leading naturally to vector meson
mixing, has been recently shown to successfully account for e^+ e^- \ra
\pi^+\pi^- cross section and for the dipion spectrum in decay. The
present study shows that the full anomalous sector of the HLS model can be
considered and is validated by the experimental data. Indeed, this extended
model provides a successful simultaneous fit to the e^+ e^- \ra \pi^+\pi^-
data together with the available data on e^+ e^- \ra \pi^0\gamma, e^+ e^-
\ra \eta\gamma and e^+ e^- \ra \pi^0 \pi^+\pi^- cross sections. It is shown
that the fit of these data sets also predicts an accurate description of the
\eta/\eta^\prime \ra \pi^+ \pi^- \gamma decays fully consistent with the
reported information on their branching fractions and spectra. Finally, one
also derives from our global fits products of widths of the form \Gamma (V \ra
f_1)\Gamma(V \ra e^+ e^-) and ratios of the form \Gamma (V \ra f_1)/\Gamma
(V \ra f_2) describing decays of vector mesons to several non--leptonic final
states.Comment: 58 pages, 10 figures Corrected a few misprints. Footnote 10 change
A Global Treatment Of VMD Physics Up To The : I. Annihilations, Anomalies And Vector Meson Partial Widths
The HLS Model, equipped with a mechanism providing the breaking of U(3)/SU(3)
symmetry and an isospin symmetry breaking leading naturally to vector meson
mixing, has been recently shown to successfully account for e^+ e^- \ra
\pi^+\pi^- cross section and for the dipion spectrum in decay. The
present study shows that the full anomalous sector of the HLS model can be
considered and is validated by the experimental data. Indeed, this extended
model provides a successful simultaneous fit to the e^+ e^- \ra \pi^+\pi^-
data together with the available data on e^+ e^- \ra \pi^0\gamma, e^+ e^-
\ra \eta\gamma and e^+ e^- \ra \pi^0 \pi^+\pi^- cross sections. It is shown
that the fit of these data sets also predicts an accurate description of the
\eta/\eta^\prime \ra \pi^+ \pi^- \gamma decays fully consistent with the
reported information on their branching fractions and spectra. Finally, one
also derives from our global fits products of widths of the form \Gamma (V \ra
f_1)\Gamma(V \ra e^+ e^-) and ratios of the form \Gamma (V \ra f_1)/\Gamma
(V \ra f_2) describing decays of vector mesons to several non--leptonic final
states.Comment: 58 pages, 10 figures Corrected a few misprints. Footnote 10 change
B decays dominated by omega-phi mixing
Recently Belle has established the 90% confidence level (CL) upper limit \b
< 9.4 \times 10^{-7} for the branching ratio for , a
process expected to be suppressed by the Okubo-Zweig-Iizuka (OZI) rule
disfavoring disconnected quark diagrams. We use information on --
mixing to establish likely lower bounds on this and related processes. We find
that the Belle result is about a factor of five above our limit, while other
decays such as and , for which
upper limits have been obtained by BaBar, could be observable with similar
improvements in data. We argue that a significant enhancement of our predicted
decay rates by rescattering is unlikely.Comment: paragraph added, submitted to Physics Letters
Can VMD improve the estimate of the muon g-2 ?
We show that a VMD based theoretical input allows for a significantly
improved accuracy for the hadronic vacuum polarization of the photon which
contributes to the theoretical estimate of the muon g-2. We also show that the
only experimental piece of information in the decay which cannot be
accounted for is the accepted value for {\rm Br}(\tau \ra \pi \pi \nu_\tau),
while the spectum lineshape is in agreement with expectations from
annihilations.Comment: 6 pages, 1 figure Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
Pseudoscalar Meson Mixing in Effective Field Theory
We show that for any effective field theory of colorless meson fields, the
mixing schemes of particle states and decay constants are not only related but
also determined exclusively by the kinetic and mass Lagrangian densities. In
the general case, these are bilinear in terms of the intrinsic fields and
involve non-diagonal kinetic and mass matrices. By applying three consecutive
steps this Lagrangian can be reduced into the standard quadratic form in terms
of the physical fields. These steps are : (i) the diagonalization of the
kinetic matrix, (ii) rescaling of the fields, and (iii) the diagonalization of
the mass matrix. In case, where the dimensions of the non-diagonal kinetic and
mass sub-matrices are respectively, and , this procedure
leads to mixing schemes which involve angles and
field rescaling parameters. This observation holds true irrespective with the
type of particle interactions presumed. The commonly used mixing schemes,
correspond to a proper choice of the kinetic and mass matrices, and are derived
as special cases. In particular, - mixing, requires one angle, if
and only if, the kinetic term with the intrinsic fields has a quadratic form.Comment: REVTeX, 6 page
The Ideal Mixing Departure in Vector Meson Physics
In this work we study the departure for the ideal mixing angle
in the frame of the Nambu-Jona-Lasinio model. We have shown that in that
context, the flavour symmetry breaking is unable to produce the shifting in the
mixing angle. We introduce a nonet symmetry breaking in the neutral vector
sector to regulate the non-strange content of the meson. The phenomenon
is well reproduced by our proposal.Comment: 12 pages incl. 1 figur
A Global Treatment Of VMD Physics Up To The phi: II. tau Decay and Hadronic Contributions To g-2
Relying on the Hidden Local Symmetry (HLS) model equipped with a mechanism
breaking the U(3)/SU(3)/SU(2) symmetries and generating a dynamical vector
meson mixing, it has been shown that a global fit successfully describes the
cross sections for the e+ e- -> pi+ pi-, e+ e- -> (pi0/eta) gamma and e+ e- ->
pi0 pi+ pi- annihilation channels. One extends this global fit in order to
include also the dipion spectra from the tau decay, taking into account all
reported information on their statistical and systematic errors. A model
accounting for lineshape distortions of the rho+- spectrum relative to rho0 is
also examined when analyzing the tau data behavior within the global fit
framework. One shows that a successful account for e+ e- annihilation data and
tau spectra can be simultaneously reached. Then, issues related with
non--perturbative hadronic contributions to the muon g-2 are examined in
details. It is shown that all e+ e- data considered together allow for improved
and motivated estimates for the a_mu(pi+ pi-), the pi+ pi- loop contribution to
the muon g-2; for instance, integrated between 0.630 and 0.958 GeV, we find
a_mu(pi+ pi-)= 359.62 +- 1.62 (in units of 10^{-10}), a 40% improvement of the
current uncertainty. The effects of the various tau samples in the context of a
global fit procedure leads to conclude that different lineshape distortions are
revealed by the ALEPH, BELLE and CLEO data samples. Relying on global fits to
the data quoted above, one also provides motivated estimates of the pi+ pi-,
pi0 gamma, eta gamma and pi0 pi+ pi- contributions to a_mu up to 1 GeV with the
smallest possible uncertainties. These estimates are based on various global
fit configurations, each yielding a good probability.Comment: 43 pages, scope enlarged, model extended, same conclusions. Accepted
for publication in EPJ-
Reconstruction and Particle Identification for a DIRC System
We study the reconstruction and particle identification (PID) problem for
Ring Imaging devices providing a good knowledge of the direction of the
Cerenkov photons, as the DIRC system, on which we specialize. We advocate first
the use of the stereographic projection as a tool allowing a suitable
representation of the photon data, as it allows to represent the Cerenkov cone
always as a circle. We set up an algorithm able to perform reliably a fit of
circle arcs of small angular opening, by minimising a true Chi2 expression. The
system we develop for PID relies on this algorithm and on a procedure able to
remove background photons with a high efficiency. We thus show that, even when
the background is large, it is possible to perform an efficient PID by means of
a fit algorithm which finally provides all the circle parameters; these are
connected with the charged track direction and its Cerenkov angle. It is shown
that background effects can be dealt without spoiling significantly the
reconstruction probability distributions.Comment: 67 pages, 23 figure
Anomalous Decays: The Triangle and Box Anomalies
We examine the decay modes \eta/\etp\ra \pi^+ \pi^- \gamma within the
context of the Hidden Local Symmetry (HLS) Model. Using numerical information
derived in previous fits to and decay modes in isolation
and the lineshape determined in a previous fit to the pion form factor,
we show that all aspects of these decays can be predicted with fair accuracy.
Freeing some parameters does not improve the picture. This is interpreted as a
strong evidence in favor of the box anomaly in the \eta/\etp decays, which
occurs at precisely the level expected. We also construct the set of equations
defining the amplitudes for \eta/\etp\ra \pi^+ \pi^- \gamma and \eta/\etp
\ra \ggam at the chiral limit, as predicted from the anomalous HLS Lagrangian
appropriately broken. This provides a set of four equations depending on only
one parameter, instead of three for the traditional set. This is also shown to
match the (two--angle, two--decay--constant) \eta-\etp mixing scheme recently
proposed and is also fairly well fulfilled by the data. The information
returned from fits also matches expectations from previously published fits to
the decay modes in isolation.Comment: 47 page
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