178 research outputs found
Some continuum physics results from the lattice V-A correlator
We present preliminary results on extractions of the chiral LECs L_10 and
C_87 and constraints on the excited pseudoscalar state pi(1300) and pi(1800)
decay constants obtained from an analysis of lattice data for the flavor ud
light quark V-A correlator. A comparison of the results for the correlator to
the corresponding mildly-model-dependent continuum results (based primarily on
experimental hadronic tau decay data) is also givenComment: 7 pages, 3 figures. Prepared for the Proceedings of the 30th
International Symposium on Lattice Field Theory, Cairns, Australia, June
24-29, 2012; expanded version of Reference 1
New results from the lattice on the theoretical inputs to the hadronic tau determination of V_us
Recent sum rule determinations of |V_us|, employing flavor-breaking
combinations of hadronic tau decay data, are significantly lower than either
expectations based on 3-family unitarity or determinations from K_ell3 and
Gamma[K_mu2]/Gamma[pi_mu2]. We use lattice data to investigate the
accuracy/reliability of the OPE representation of the flavor-breaking
correlator combination entering the tau decay analyses. The behavior of an
alternate correlator combination, constructed to reduce problems associated
with the slow convergence of the D = 2 OPE series, and entering an alternate
sum rule requiring both electroproduction cross-section and hadronic tau decay
data, is also investigated. Preliminary updates of both analyses, with the
lessons learned from the lattice data in mind, are also presented.Comment: 8 pages, 5 figures. Prepared for the proceedings of the 12th
International Workshop on Tau Lepton Physics, Sep. 17-21, 2012, Nagoya, Japan
and the 10th International Conference on Confinement and the Hadron Spectrum,
Oct. 6-13, 2012, Garching/Munich, German
Consequences of the BaBar e^+e^- --> pi^+pi^- Measurement for the Determination of Model-Dependent rho-omega Mixing Effects in Pi_{\rho\omega}(m_{\rho}^2) and (g-2)_mu
We update our analysis of rho-omega mixing effects in the pion form factor to
incorporate the recently published BaBar e^+e^- --> pi^+\pi^- cross-sections.
The implications for tau-decay-based Standard Model estimates of the leading
order hadronic contribution [a_\mu]_{had}^{LO}, to the anomalous magnetic
moment of the muon, and for the extraction of the off-diagonal vector meson
self-energy matrix element, Pi_{\rho\omega}(m_\rho^2), are discussed.Comment: 7 pages, 2 figure
Decay constants, light quark masses and quark mass bounds from light quark pseudoscalar sum rules
The flavor and pseudoscalar correlators are investigated using
families of finite energy sum rules (FESR's) known to be very accurately
satisfied in the isovector vector channel. It is shown that the combination of
constraints provided by the full set of these sum rules is sufficiently strong
to allow determination of both the light quark mass combinations ,
and the decay constants of the first excited pseudoscalar mesons in
these channels. The resulting masses and decay constants are also shown to
produce well-satisfied Borel transformed sum rules, thus providing non-trivial
constraints on the treatment of direct instanton effects in the FESR analysis.
The values of and obtained are in good agreement with the
values implied by recent hadronic decay analyses and the ratios obtained
from ChPT. New light quark mass bounds based on FESR's involving weight
functions which strongly suppress spectral contributions from the excited
resonance region are also presented.Comment: 28 pages, 10 figure
Isospin Breaking and -> Decay
We study decay up to including all orders of the chiral
expansion and one-loop level of mesons in formlism of chiral constituent quark
model. This G-parity forbidden decay is caused by and
electromagnetic interaction of mesons. We illustrate that in the formlism both
nonresonant contact interaction and resonance exchange contribute to
this process, and the contribution from resonance exchange is dominant.
We obtain that transition matrix element is
MeV, and
isospin breaking parameter is MeV at energy scale .Comment: Revtex file, 16 pages, four eps figur
Models of Isospin Breaking in the Pion Form Factor: Consequences for the Determination of Pi_{\rho\omega}(m_rho^2) and (g-2)_mu/2
We study the implications of several recent high-precision measurements of
the pion form factor in the region of the rho-omega interference "shoulder" for
(i) the extraction of the rho-omega mixing matrix element,
Pi_{\rho\omega}(m_rho^2), and (ii) the evaluation of the isospin-breaking (IB)
correction needed to incorporate hadronic tau decay data into the determination
of the Standard Model expectation for the leading order hadronic contribution,
[a_mu]_{had}^{LO}, to the anomalous magnetic moment of the muon, focussing, in
the latter case, on the model-dependence of the rho-omega mixing component of
the IB correction. We consider a range of different models for the broad rho
contribution to the e^+e^- --> \pi\pi amplitude, applying these models to each
experimental data set, and find that the model dependence of the rho-omega
mixing correction is significantly larger than the uncertainty induced by
experimental errors for any individual model. We also find that, for each such
model, the recent data allows one to separate rho-omega mixing and direct omega
--> \pi\pi coupling contributions to the amplitude, and hence to obtain a
reasonably precise extraction of Pi_{\rho\omega}(m_rho^2), uncontaminated by
direct omega --> \pi\pi coupling effects, for use in meson exchange model
calculations of charge symmetry breaking in NN scattering.Comment: 25 pages, 4 figures. Final published version. Main change is
inclusion of a detailed discussion of the source of differences between the
present work and M. Davier et al. (arXiv:0906.5443v3
Charmed Baryons with
The width of a recently discovered excited charmed-strange baryon, a
candidate for a state with spin 3/2, is calculated. In the absence of
configuration mixing between the ground-state (spin-1/2) charmed-strange baryon
and the spin-1/2 state lying about 95 MeV above it,
one finds and , where the tilde denotes the partial
width with kinematic factors removed. Assuming a kinematic factor for P-wave
decay of , one predicts MeV, while the channel is closed. Some
suggestions are given for detecting the , the spin-3/2 charmed
nonstrange baryon, and the , the spin-3/2 charmed doubly-strange
baryon.Comment: 11 pages, latex, 2 uuencoded figures sent separatel
Dibaryons as axially symmetric skyrmions
Dibaryons configurations are studied in the framework of the bound state
soliton model. A generalized axially symmetric ansatz is used to determine the
soliton background. We show that once the constraints imposed by the symmetries
of the lowest energy torus configuration are satisfied all spurious states are
removed from the dibaryon spectrum. In particular, we show that the lowest
allowed state in the channel carries the quantum numbers of the H
particle. We find that, within our approximations, this particle is slightly
bound in the model. We discuss, however, that vacuum effects neglected in the
present calculation are very likely to unbind the H.Comment: 24 pages, LaTeX, TAN-FNT-93-12 (it replaces old version which was
truncated
On Deusons or Deuteronlike Meson-Meson Bound States
The systematics of deuteronlike two-meson bound states, {\it deusons}, is
discussed. Previous arguments that many of the present non- states are
such states are elaborated including, in particular, the tensor potential. For
pseudoscalar states the important observation is made that the centrifugal
barrier from the P-wave can be overcome by the and terms of the
tensor potential. In the heavy meson sector one-pion exchange alone is strong
enough to form at least deuteron-like and composites
bound by approximately 50 MeV, while and states are
expected near the threshold.Comment: Invited talk at the Hadron93 International Conf. on Hadron
Spectroscopy, Como, Italy 22.-25.6. 1993. 5 pages in LATEX HU-SEFT R 1993-13
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