28,070 research outputs found
Polarization amplitudes in decay beyond the standard model
We use a recent formalism of the weak hadronic reactions to study the helicity amplitudes in decay. This recent formalism maps the transition matrix elements at the
quark level into hadronic matrix elements, and finally writes the weak matrix
elements in terms of easy analytical formulas evaluated by means of an
elaborate angular momentum algebra. The formalism provides directly the
amplitudes for the different spin third components of the vector mesons
involved. We extend the formalism to a general case, with the operator
, that can account for different models
beyond the standard model and study in detail the reaction for the different helicities of the . The results are
shown in terms of the parameter that differs for each model. We find
that is very different for
the different components and in particular the magnitude is very sensitive to the parameter,
which makes the investigation of this magnitude a most welcome initiative to
test different models beyond the standard model.Comment: 20 pages, 6 figures, add some discussion
Helicity amplitudes in decay
We use a recent formalism of the weak hadronic reactions that maps the
transition matrix elements at the quark level into hadronic matrix elements,
evaluated with an elaborate angular momentum algebra that allows finally to
write the weak matrix elements in terms of easy analytical formulas. In
particular they appear explicitly for the different spin third components of
the vector mesons involved. We extend the formalism to a general case, with the
operator , that can accommodate
different models beyond the standard model and study in detail the reaction for the different helicities of the . The results
are shown for each amplitude in terms of the parameter that is
different for each model. We show that is very different for the different components and in
particular the magnitude is very sensitive to the
parameter, which suggest to use this magnitude to test different
models beyond the standard model. We also compare our results with the standard
model and find very similar results, and practically identical at the end point
of .Comment: 25 pages, 10 figure
, and the scalar bound state
We study the decay to based on the chiral unitary
model that generates the X(3720) resonance, and make predictions for the invariant mass distribution. From the shape of the distribution, the
existence of the resonance below threshold could be induced. We also predict
the rate of production of the X(3720) resonance to the mass
distribution with no free parameters.Comment: 9 pages, 17 figure
Observation of a cyclotron harmonic spike in microwave-induced resistances in ultraclean GaAs/AlGaAs quantum wells
We report the observation of a colossal, narrow resistance peak that arises
in ultraclean (mobility 3X10^7cm^2/Vs) GaAs/AlGaAs quantum wells (QWs) under
millimeterwave irradiation and a weak magnetic field. Such a spike is
superposed on the 2nd harmonic microwave-induced resistance oscillations (MIRO)
but having an amplitude > 300% of the MIRO, and a typical FWHM ~50 mK,
comparable with the Landau level width. Systematic studies show a correlation
between the spike and a pronounced negative magnetoresistance in these QWs,
suggesting a mechanism based on the interplay of strong scatterers and smooth
disorder. Alternatively, the spike may be interpreted as a manifestation of
quantum interference between the quadrupole resonance and the higher-order
cyclotron transition in well-separated Landau levels.Comment: 4pages, 4figure
GRB Afterglows from Anisotropic Jets
Some progenitor models of gamma-ray bursts (GRBs) (e.g., collapsars) may
produce anisotropic jets in which the energy per unit solid angle is a
power-law function of the angle (). We calculate light
curves and spectra for GRB afterglows when such jets expand either in the
interstellar medium or in the wind medium. In particular, we take into account
two kinds of wind: one () possibly from a typical red
supergiant star and another () possibly from a Wolf-Rayet
star. We find that in each type of medium, one break appears in the late-time
afterglow light curve for small but becomes weaker and smoother as
increases. When , the break seems to disappear but the afterglow decays
rapidly. Thus, one expects that the emission from expanding, highly anisotropic
jets provides a plausible explanation for some rapidly fading afteglows whose
light curves have no break. We also present good fits to the optical afterglow
light curve of GRB 991208. Finally, we argue that this burst might arise from a
highly anisotropic jet expanding in the wind () from a red
supergiant to interpret the observed radio-to-optical-band afterglow data
(spectrum and light curve).Comment: 12 pages + 10 figures, accepted by Ap
Radiative decay of the dynamically generated open and hidden charm scalar meson resonances D_{s0}^*(2317) and X(3700)
We present the formalism for the decay of dynamically generated scalar mesons
with open- or hidden-charm and give results for the decay of D^*_{s0} (2317) to
\gamma D_s^* plus that of a hidden charm scalar meson state predicted by the
theory around 3700 MeV decaying into \gamma J/\psi.Comment: Appendix adde
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