38,175 research outputs found
Baryon states with open beauty in the extended local hidden gauge approach
In this paper we examine the interaction of \bar B N, \bar B \Delta, \bar B^*
N and \bar B^* \Delta states, together with their coupled channels, using a
mapping from the light meson sector. The assumption that the heavy quarks act
as spectators at the quark level automatically leads us to the results of the
heavy quark spin symmetry for pion exchange and reproduces the results of the
Weinberg Tomozawa term, coming from light vector exchanges in the extended
local hidden gauge approach. With this dynamics we look for states dynamically
generated from the interaction and find two states with nearly zero width,
which we associate to the \Lambda_b(5912) and \Lambda_b(5920) states. The
states couple mostly to \bar B^* N, which are degenerate with the Weinberg
Tomozawa interaction. The difference of masses between these two states, with
J=1/2, 3/2 respectively, is due to pion exchange connecting these states to
intermediate \bar B N states. In addition to these two \Lambda_b states, we
find three more states with I=0, one of them nearly degenerate in two states of
J=1/2,3/2. Furthermore we also find eight more states in , two of them
degenerate in J=1/2, 3/2, and other two degenerate in J=1/2, 3/2, 5/2.Comment: 26 pages, 9 figures, 24 table
and cross sections
Inspired by the recent findings of the two states in the
mass spectrum at LHCb, we investigate the elastic and inelastic cross sections
of the , , and channels within the
constraints from heavy quark spin and flavour symmetry. The () bound states predicted in earlier
works should be accessible in elastic and/or inelastic processes of the and/or ( and/or ) interactions.Comment: Minor correction
Heavy quark spin symmetric molecular states from and other coupled channels in the light of the recent LHCb pentaquarks
We consider the states, together with and other coupled channels, and take an interaction consistent with heavy
quark spin symmetry, with the dynamical input obtained from an extension of the
local hidden gauge approach. By fitting only one parameter to the recent three
pentaquark states reported by the LHCb collaboration, we can reproduce the
three of them in base to the mass and the width, providing for them the quantum
numbers and approximate molecular structure as ,
, and , and isospin
. We find another state around 4374 MeV, of
structure, for which indications appear in the experimental spectrum. Two other
near degenerate states of and nature are also found around 4520 MeV, which although less clear,
are not incompatible with the observed spectrum. In addition, a state at the same energy appears, which however does not couple
to in wave, and hence it is not expected to show up in the LHCb
experiment.Comment: 8 page
Description of as a system with the fixed center approximation
We study the system with an aim to describe the
resonance. The chiral unitary approach has achieved success in a description of
systems of the light hadron sector. With this method, the system in
the isospin sector , is found to be a dominant component of the resonance. Therefore, by regarding the system as a cluster,
the resonance, we evaluate the system applying the
fixed center approximation to the Faddeev equations. We construct the
unitarized amplitude using the chiral unitary approach. As a result, we find a
peak in the three-body amplitude around 1739 MeV and a width of about 227 MeV.
The effect of the width of and is also discussed. We
associate this peak to the which has a mass of MeV
and a width of MeV
Baryon states with open charm in the extended local hidden gauge approach
In this paper we examine the interaction of and states,
together with their coupled channels, by using an extension of the local hidden
gauge formalism from the light meson sector, which is based on heavy quark spin
symmetry. The scheme is based on the use of the impulse approximation at the
quark level, with the heavy quarks acting as spectators, which occurs for the
dominant terms where there is the exchange of a light meson. The pion exchange
and the Weinberg-Tomozawa interactions are generalized and with this dynamics
we look for states generated from the interaction, with a unitary coupled
channels approach that mixes the pseudoscalar-baryon and vector-baryon states.
We find two states with nearly zero width which are associated to the
and . The lower state, with ,
couples to and , and the second one, with , to . In addition to these two states, we find four more states with
, one of them nearly degenerate in two states of .
Furthermore we find three states in , two of them degenerate in .Comment: v3: version to appear in Eur.Phys.J.
Growth of single-crystal columns of CoSi2 embedded in epitaxial Si on Si(111) by molecular beam epitaxy
The codeposition of Si and Co on a heated Si(111) substrate is found to result in epitaxial columns of CoSi2 if the Si:Co ratio is greater than approximately 3:1. These columns are surrounded by a Si matrix which shows bulk-like crystalline quality based on transmission electron microscopy and ion channeling. This phenomenon has been studied as functions of substrate temperature and Si:Co ratio. Samples with columns ranging in average diameter from approximately 25 to 130 nm have been produced
, and molecules
We investigate theoretically baryon systems made of three hadrons which
contain one nucleon and one D meson, and in addition another meson, or . The systems are studied using the Fixed Center Approximation
to the Faddeev equations. The study is made assuming scattering of a or a
on a cluster, which is known to generate the ,
or the scattering of a nucleon on the cluster, which has been shown
to generate a hidden charm resonance named X(3700). We also investigate the
configuration of scattering of on the cluster, which is known to
generate the . In all cases we find bound states, with the
system, of exotic nature, more bound than the .Comment: 9 figure
Multidimensional optical fractionation with holographic verification
The trajectories of colloidal particles driven through a periodic potential
energy landscape can become kinetically locked in to directions dictated by the
landscape's symmetries. When the landscape is realized with forces exerted by a
structured light field, the path a given particle follows has been predicted to
depend exquisitely sensitively on such properties as the particle's size and
refractive index These predictions, however, have not been tested
experimentally. Here, we describe measurements of colloidal silica spheres'
transport through arrays of holographic optical traps that use holographic
video microscopy to track individual spheres' motions in three dimensions and
simultaneously to measure each sphere's radius and refractive index with
part-per-thousand resolution. These measurements confirm previously untested
predictions for the threshold of kinetically locked-in transport, and
demonstrate the ability of optical fractionation to sort colloidal spheres with
part-per-thousand resolution on multiple characteristics simultaneously.Comment: 4 pages, 2 figures. Accepted for publication in Physical Review
Letter
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