2,044 research outputs found
Study of tau- --> V P- nu(tau) in the framework of resonance chiral theory
In this paper we study two kinds of tau decays: (a) tau- --> (rho pi-,omega
pi-, phi pi-, K*0 K-) nu(tau), which belong to Delta S=0 processes and (b)
Delta S = 1 processes, like tau- --> (rho K-, omega K-, phi K-, \bar{K*0} pi-)
nu(tau), in the framework of resonance chiral theory. We fit the tau- --> omega
pi- nu(tau) spectral function and the invariant mass distribution of omega K in
the process of tau- --> omega K- nu(tau) to get the values of unknown resonance
couplings. Then we make a prediction for branching ratios of all channels.Comment: Published version; References added. 20 pages, 3 figures, 2 table
as a source of background on the Lepton Flavour Violating decay
We calculate the decay of in the framework of
Resonance Chiral Theory (). By demanding the high energy constraints
from QCD on the related form factors, we could predict the various physical
observables of without any free parameter. Our
results show that for a realistic cut on the photon energy (around MeV)
this mode gives a branching ratio of roughly that should have already
been detected at the heavy-flavour factories. Another interesting subject we
have studied based on our calculation of the decay
is the experimental background estimation of the
lepton flavour violation process . We point out that
although the description of radiation that PHOTOS provides -which has been used
by BaBar and Belle collaborations to estimate this source of background- is in
excellent agreement with the theoretical expectations in the low energy region
in decay, this is not the case in the high
energy region, precisely where it is easier that this decay mimics the process
.Comment: 6 pages, 7 figures. Contribution to the Proceedings of the TAU10
Conference held in Manchester, 13-17 September 2010. To be published in Nucl.
Phys. Proc. Supp
Pi pi scattering lengths at O(p^6) revisited
This article completes a former work where part of the O(p^6) low-energy
constants entering in the pi pi scattering were estimated. Some resonance
contributions were missed in former calculations and slight differences
appeared with respect to our outcome. Here, we provide the full results for all
the contributing O(p^6) couplings. We also perform a reanalysis of the hadronic
inputs used for the estimation (resonance masses, widths...). Their reliability
was checked together with the impact of the input uncertainties on the
determinations of the chiral couplings and the scattering lengths a^I_J. Our
outcome is found in agreement with former works though with slightly larger
errors. However, the effect in the final values of the a^I_J is negligible
after combining them with the other uncertainties. Based on this consistency,
we conclude that the previous scattering length determinations seem to be
rather solid and reliable, with the cO(p^6) low-energy constants quite under
control. Nevertheless, the uncertainties found in the present work point out
the limitation on further improvements unless the precision of the O(p^6)
couplings is properly increased.Comment: 19 pages. Improved treatment of the a0 decay width and update of the
numerical outcomes. Final version published in Phys. Rev. D
(10.1103/PhysRevD.79.096006
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