136 research outputs found
Consistency tests of AMPCALCULATOR and chiral amplitudes in SU(3) Chiral Perturbation Theory: A tutorial based approach
Ampcalculator is a Mathematica based program that was made publicly available
some time ago by Unterdorfer and Ecker. It enables the user to compute several
processes at one-loop (upto ) in SU(3) chiral perturbation theory. They
include computing matrix elements and form factors for strong and non-leptonic
weak processes with at most six external states. It was used to compute some
novel processes and was tested against well-known results by the original
authors. Here we present the results of several thorough checks of the package.
Exhaustive checks performed by the original authors are not publicly available,
and hence the present effort. Some new results are obtained from the software
especially in the kaon odd-intrinsic parity non-leptonic decay sector involving
the coupling . Another illustrative set of amplitudes at tree level we
provide is in the context of -decays with several mesons including quark
mass effects, of use to the BELLE experiment. All eight meson-meson scattering
amplitudes have been checked. Kaon-Compton amplitude has been checked and a
minor error in published results has been pointed out. This exercise is a
tutorial based one, wherein several input and output notebooks are also being
made available as ancillary files on the arXiv. Some of the additional
notebooks we provide contain explicit expressions that we have used for
comparison with established results. The purpose is to encourage users to apply
the software to suit their specific needs. An automatic amplitude generator of
this type can provide error-free outputs that could be used as inputs for
further simplification, and used in varied scenarios such as applications of
chiral perturbation theory at finite temperature, density and volume. This can
also be used by students as a learning aid in low-energy hadron dynamics.Comment: 25 pages, plain latex, corresponds to version to appear in EPJA,
additional ancillary files adde
Quantum Theory contents insertion in High School curricula
A inovação científica e tecnológica do século XX foi esmagadora. Contudo, a nossa experiência docente permite-nos afirmar que as aprendizagens na escola secundária estão longe de acompanhar a evolução que se verifica na sociedade atual. No entanto, já estão a ser incluídos alguns conteúdos de Física Moderna nos currículos oficiais de vários países, parecendo evidenciar uma preocupação em atualizar a preparação dos jovens para o mundo que os rodeia. Neste artigo relatamos um estudo que fizemos acerca dos currículos de Física de alguns países, sobretudo no que diz respeito à Teoria Quântica, a grande invenção do século XX, tentando identificar os conteúdos selecionados e a maneira como estes se integram nas orientações curriculares gerais.In the XXth century, scientific and technological innovation has been overwhelming. Our teaching
profession lead us to believe that studies in High Schools do not follow the evolution of ideas that characterizes
our modern society. However, some contents of Modern Physics are already included in the official curricula
of several countries, which seem to be worried about the improvement of today’s youth training. In this paper
we report a study made about Physics’ curricula in several countries, emphasizing Quantum Theory issues, the
biggest invention of the XXth century, trying to identify the selected subjects selected and the way they fit into
general curricula orientations
tau-->eta(eta')2pi nu, 3pi nu and WZW anomaly
The effects of the anomalous contact terms are taken into account in tau to
eta(eta')2pi nu decay. tau to 3pi nu is computed. Theoretical result agrees
with data. It is the first time the anomalous vertex eta aa is tested. An a_{1}
resonance is predicted in the final state. The decay rate of tau to eta'3pi nu
is predicted.Comment: 15 pages, one latex file for the paper and one p-script file for the
figur
Isospin Violation in tau -> 3 pi nu_tau
Isospin violating signals in the tau -> 3 pi nu_tau decay mode are discussed.
For the tau -> pi^- pi^- pi^+ nu_tau decay mode, isospin violation arises from
the vector current contribution in the tau -> omega pi nu_tau decay with the
subsequent isospin violating omega decay into pi^+ pi^-. We demonstrate that
such effects may be observed in presently available data through the
measurement of the interference effects of these vector current contributions
with the dominating axial vector current, i.e. through a measurement of the
structure functions W_F,W_G,W_H and W_I. In the case of the tau -> pi^0 pi^0
pi^- nu_tau decay mode, a vector current contribution is generated by eta pi
mixing in the decay chain tau -> eta rho nu_tau -> pi^0 pi^0 pi^- nu_tau. We
find that this effect is rather small, the magnitude of the associated
interference terms being too low for present statistics.Comment: LaTex, 16 pages, 5 figures. The complete paper is also available via
anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints
Probing Lepton-number/flavour-violation in Semileptonic Tau Decays into Two Mesons
The evaluation, systematic analysis and numerical study of the semileptonic
-lepton decays with two mesons in the final state has been made in the
frame of the standard model extended by right handed neutrinos. In the
analysis, heavy-neutrino nondecoupling effects, finite quark masses, quark and
meson mixings, finite widths of vector mesons, chiral symmetry breakings in
vector-meson--pseudoscalar-meson vertices and effective
Higgs-boson--pseudoscalar-meson couplings have been included. Numerical
estimates reveal that the decays , and have branching ratios of the order
of , close to present-day experimental sensitivities.Comment: 33 pages, LaTeX, 6 Postscript figures. To appearin Phys. Rev.
Precise measurement of hadronic tau-decays with an eta meson
We have studied hadronic tau decay modes involving an eta meson using 490
fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy
e+e- collider. The following branching fractions have been measured: B(tau- ->
K- eta nu)=(1.58 +- 0.05 +- 0.09)x 10^{-4}, B(tau- -> K- pi0 eta nu)=(4.6 +-
1.1 +- 0.4)x 10^{-5}, B(tau- -> pi- pi0 eta nu)=(1.35 +- 0.03 +- 0.07)x
10^{-3}, B(tau- -> pi- KS eta nu)=(4.4 +- 0.7 +- 0.2)x 10^{-5}, and B(tau- ->
K^{*-} eta nu)=(1.34 +- 0.12 +- 0.09)x 10^{-4}. These results are substantially
more precise than previous measurements. The new measurements are compared with
theoretical calculations based on the CVC hypothesis or the chiral perturbation
theory. We also set upper limits on branching fractions for tau decays into K-
KS eta nu, pi- KS pi0 eta nu, K- eta eta nu, pi- eta eta nu and non-resonant K-
pi^0 eta nu final states.Comment: 24 pages, 7 figure
Transcription Inhibition by DRB Potentiates Recombinational Repair of UV Lesions in Mammalian Cells
Homologous recombination (HR) is intricately associated with replication, transcription and DNA repair in all organisms studied. However, the interplay between all these processes occurring simultaneously on the same DNA molecule is still poorly understood. Here, we study the interplay between transcription and HR during ultraviolet light (UV)-induced DNA damage in mammalian cells. Our results show that inhibition of transcription with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) increases the number of UV-induced DNA lesions (γH2AX, 53BP1 foci formation), which correlates with a decrease in the survival of wild type or nucleotide excision repair defective cells. Furthermore, we observe an increase in RAD51 foci formation, suggesting HR is triggered in response to an increase in UV-induced DSBs, while inhibiting transcription. Unexpectedly, we observe that DRB fails to sensitise HR defective cells to UV treatment. Thus, increased RAD51 foci formation correlates with increased cell death, suggesting the existence of a futile HR repair of UV-induced DSBs which is linked to transcription inhibition
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