9,639 research outputs found
Microscopic 8-quark study of the antikaon nucleon nucleon systems
We study the possibility to bind eight quarks in a molecular hadronic system
composed of two nucleons and an antikaon, with the quantum numbers of a
hexaquark flavour, in particular with strangeness -1, isospin 1/2, parity -,
baryonic number 2 and two possible spins, 0 or 1. These exotic hadrons are
motivated by the deuteron, a proton-neutron boundstate, and by the model of the
Lambda(1405) as an antikaon proton boundstate. We discuss the possible
production of this hadron in the experiments which are presently investigating
hot topics like the Theta+ pentaquark or the K- deeply bound in nuclei. The K-
N interactions and the coupling to other channels are computed microscopically
from a confining and chiral invariant quark model resulting in local plus
separable Gaussian potentials. The N N interactions used here are the state of
the art Nijmegen potentials. The binding energy and the decay rate of the K- N
and K- N N systems are computed with configuration space variational methods.
The only systems that bind with our microscopic interaction are the K- N in the
I=0 channel and the K- N N in the S=0 channel.Comment: 5 pages, 5 figures (1 new and 2 updated), more detailed study of
binding with a small parameter increase, and an algebraic correction,
submitted to Physical Review
Production of the pentaquark in scattering
We study and processes
for both of the positive and negative parities of the . Employing
the effective chiral Lagrangians for the and interactions, we
calculate differential cross sections as well as total cross sections for the
and reactions. The total
cross sections for the positive-parity turn out to be approximately
ten times larger than those for the negative parity in the range of
the CM energy . The results are
rather sensitive to the mechanism of exchanges in the -- channel.Comment: 9 pages and 11 figure
Evidence for the two pole structure of the Lambda(1405) resonance
The K^- p --> pi^0 pi^0 Sigma^0 reaction is studied within a chiral unitary
model. The distribution of pi^0 Sigma^0 states forming the Lambda(1405) shows,
in agreement with a recent experiment, a peak at 1420 MeV and a relatively
narrow width of Gamma = 38 MeV. The mechanism for the reaction is largely
dominated by the emission of a pi^0 prior to the K^- p interaction leading to
the Lambda(1405). This ensures the coupling of the Lambda(1405) to the K^- p
channel, thus maximizing the contribution of the second state found in chiral
unitary theories, which is narrow and of higher energy than the nominal
Lambda(1405). This is unlike the pi^- p --> K^0 \pi Sigma reaction, which gives
more weight to the pole at lower energy and with a larger width. The data of
these two experiments, together with the present theoretical analysis, provides
a firm evidence of the two pole structure of the Lambda(1405).Comment: 4 pages, 6 figure
The role of the resonance in the reaction
We investigate the photo-production in the reaction within the effective Lagrangian method near
threshold. In addition to the "background" contributions from the contact,
channel exchange, and channel nucleon pole terms, which were
already considered in previous works, the contribution from the nucleon
resonance (spin-parity ) is also considered. We show
that the inclusion of the nucleon resonance leads to a fairly good
description of the new LEPS differential cross section data, and that these
measurements can be used to determine some of the properties of this latter
resonance. However, serious discrepancies appear when the predictions of the
model are compared to the photon-beam asymmetry also measured by the LEPS
Collaboration.Comment: 9 pages,6 figures, 1 tabl
K*-couplings for the antidecuplet excitation
We estimate the coupling of the K* vector meson to the N-->Theta+ transition
employing unitary symmetry, vector meson dominance, and results from the GRAAL
Collaboration for eta photoproduction off the neutron. Our small numerical
value for the coupling constant is consistent with the non-observation of the
Theta+ in recent CLAS searches for its photoproduction. We also estimate the
K*-coupling for the N-->Sigma* excitation, with Sigma* being the Sigma-like
antidecuplet partner of the Theta+-baryon.Comment: 9 pages, 1 figure. Minor changes in text and abstract, references
added; version to appear in Phys. Rev.
Micropropagation of rose cultivar ‘Pareo’
A protocol was developed for micropropagation of rose cv. ‘Pareo’. Nodal segments were surface sterilized with 0.1% solution of mercuric chloride for 10 min and these disinfected explants were inoculated aseptically on culture medium. The, axillary shoots were regenerated from nodal explants on agar-gelled Murashige and Skoog medium supplemented with 1.5 mg/l BAP. In vitro rooting was obtained when shoot clusters were cultured on half strength Murashige and Skoog medium supplemented with 1.0 mg/l IBA. The rooted plantlets were acclimatized successfully in the field.Key words: Micropropagation, nodal segments, rose
Instantaneous ionization rate as a functional derivative
We describe an approach defining instantaneous ionization rate (IIR) as a
functional derivative of the total ionization probability. The definition is
based on physical quantities which are directly measurable, such as the total
ionization probability and the waveform of the pulse. The definition is,
therefore, unambiguous and does not suffer from gauge non-invariance. We
compute IIR by solving numerically the time-dependent Schrodinger equation for
the hydrogen atom in a strong laser field. We find that the IIR lags behind the
electric field, but this lag is entirely due to the long tail effect of the
Coulomb field. In agreement with the previous results using attoclock
methodology, therefore, the IIR we define does not show measurable delay in
strong field tunnel ionization
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