458 research outputs found
Axial Transition Form Factors and Pion Decay of Baryon Resonances
The pion decay constants of the lowest orbitally excited states of the
nucleon and the along with the corresponding axial transition
form factors are calculated with Poincar\'e covariant constituent-quark models
with instant, point and front forms of relativistic kinematics. The model wave
functions are chosen such that the calculated electromagnetic and axial form
factors of the nucleon represent the empirical values in all three forms of
kinematics, when calculated with single-constituent currents. The pion decay
widths calculated with the three forms of kinematics are smaller than the
empirical values. Front and instant form kinematics provide a similar
description, with a slight preference for front form, while the point form
values are significantly smaller in the case of the lowest positive parity
resonances.Comment: 18 pages, 5 figures. Slightly revised, accepted in Phys. Rev.
Sea-quark effects in the pion charge form factor
It is shown that the data on the pion charge form factor admit the
possibility for a substantial sea-quark components in the pion wave function.
If the charge form factor is calculated with instant form kinematics in a
constituent quark model that is extended to include explicit
components in the pion wave function, that component will give the dominant
contribution to the calculated charge form factor at large values of
momentum transfer. The present experimental values can be described well
with component admixtures of up to 50%. The sensitivity of the
calculated charge form factor to whether one of the quarks or one of
the antiquarks is taken to be in the P-state is small.Comment: 14 page
The role of components in the N(1440) resonance
The role of 5-quark components in the pion and electromagnetic decays and
transition form factors of the N(1440) is explored. The
components, where the 4-quark subsystem has the flavor-spin symmetries
and , which are expected to have
the lowest energy of all configurations, are considered in detail
with a nonrelativistic quark model. The matrix elements between the 5-quark
components of the N(1440) and the nucleon, , play a
minor role in these decays, while the transition matrix elements and that involve quark antiquark annihilation are very
significant. Both for the electromagnetic and strong decay the change from the
valence quark model value is dominated by the confinement triggered
annihilation transitions. In the case of pion decay the calculated decay width
is enhanced substantially both by the direct and also by the
confinement triggered transitions. Agreement with the
empirical value for the pion decay width may be reached with a 30%
component in the N(1440).Comment: 23 pages revte
The role of components in the nucleon and the N(1440) resonance
The role of components in the nucleon and the N(1440) resonance is
studied by explicit coupling of the lowest positive parity state
to the components in the harmonic oscillator quark model. The lowest
energy component, where the 4-quark subsystem has the flavor-spin
symmetry , is close in energy to the lowest positive
parity excitation of the nucleon in the quark model. The confining
interaction leads to a strong mixing of the system and the
positive parity excited state of the system. This result is in line with
the phenomenological indications for a two-component structure of the N(1440)
resonance. The presence of substantial components in the N(1440) can
bring about a reconciliation of the constituent quark model with the large
empirical decay width of the N(1440).Comment: Accepted for publication in Nucl. Phys.
Five-quark components in decay
Five-quark components in the are shown to
contribute significantly to decay through
quark-antiquark annihilation transitions. These involve the overlap between the
and components and may be triggered by the confining
interaction between the quarks. With a 10% admixture of five-quark
components in the the decay width can be larger by factors 2 - 3
over that calculated in the quark model with 3 valence quarks, depending on the
details of the confining interaction. The effect of transitions between the
components themselves on the calculated decay width is however
small. The large contribution of the quark-antiquark annihilation transitions
thus may compensate the underprediction of the width of the by
the valence quark model, once the contains
components with 10% probability.Comment: accepted versio
Bound States of Heavy Flavor Hyperons
Several realistic phenomenological nucleon-nucleon interaction models are
employed to investigate the possibility of bound deuteron-like states of such
heavy flavor hyperons and nucleons, for which the interaction between the light
flavor quark components is expected to be the most significant interaction. The
results indicate that deuteron-like bound states are likely to form between
nucleons and the and charm hyperons as well as between
hyperons and double-charm hyperons. Bound states between two
hyperons are also likely. In the case of beauty hyperons the corresponding
states are likely to be deeply bound.Comment: 25 pages, 3 figures. Accepted Nucl. Phys.
Tingkat Perubahan Kesejahteraan Ekonomi Keluarga Buruh Migran
Gondanglegi sub district is occupying the first position as the largest supplier of migrant workers in the area of ​​South Malang in 2014. This research focuses on Panggungrejo Village as the object of research. A village with area of ​​203 km2, population of 1,877 people consisting of 866 men and 1,011 women. This village pervades 12 RTs, and this research took 2 RTs namely RT 5 and 6, with 5 respondents. These five respondents are representatives of various migrant workers. Some represent their wives as migrant workers, husbands and children. This study uses the theory of social mobility; a change, shift, increase or decrease of the status and role of its members. Welfare indicators used are economic, educational, social and health. The result of the research shows that there is a change of the respondents\u27 life level in terms of economic, social, educational and even health compared to prior becoming migrant worker, although the rate of change is not too significant
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