796 research outputs found
Exotic hadrons in s-wave chiral dynamics
We study s-wave scattering of a hadron and a Nambu-Goldstone boson induced by
the model-independent low energy interaction in the flavor SU(3) symmetric
limit. Establishing the general structure of the low energy interaction based
on group theoretical arguments, we find that the interaction in the exotic
channels are in most cases repulsive, and that for possible attractive channels
the interaction strengths are weak and uniquely given independent of channel.
Solving the scattering problem with this interaction, we show that the
attraction in the exotic channels is not strong enough to generate a bound
state from the physically known target hadrons. We also find that there are no
attractive interaction in the exotic channels in large Nc limit.Comment: RevTeX4, 4 pages, 1 figure, 2 tables, typos correcte
Study of exotic hadrons in S-wave scatterings induced by chiral interaction in the flavor symmetric limit
We study s-wave bound states of a hadron and a light pseudoscalar meson
induced by the Weinberg-Tomozawa (WT) interaction in the flavor SU(3) symmetric
limit. The WT interaction is a driving force to generate quasibound states
dynamically in the chiral unitary approaches. The strength and sign of the WT
interaction are determined only by the group theoretical structure of the
target hadrons, and we present a general expression of the strengths for the
flavor SU(3) case. We show that, for the channels which are more exotic than
the target, the interaction is repulsive in most cases, and the strength of the
attractive interaction is universal for any possible target states. We
demonstrate that the attractive coupling is not strong enough to generate an
exotic state from the physically known masses of target hadrons. In addition,
we also find a nontrivial Nc dependence of the coupling strengths. We show that
the channels which are attractive at Nc=3 changes into repulsive ones for large
Nc, and, therefore, no attractive interaction exists in exotic channels in the
large-Nc limit.Comment: RevTeX4, 16 pages, 5 figure, 6 tables, This manuscript is a full
paper of Phys. Rev. Lett. 97, 192002 (hep-ph/0609014), typos corrected, final
versio
The nature of Lambda(1405) hyperon resonance in chiral dynamics
The nature of the Lambda(1405) is discussed based on the unitarised
coupled-channels approach with chiral dynamics (chiral unitary model). This
approach describes the Kbar N scattering cross sections and the Lambda(1405)
spectra phenomenologically very well. With this successful description of
Lambda(1405), it is found that the Lambda(1405) is composed by two resonance
states having different coupling nature to the meson-baryon states. As a
consequence, the resonance position in the pi Sigma invariant mass spectrum
depends on the initial channel of the Lambda(1405) production. To observe the
Lambda(1405) initiated by the Kbar N channel, K^- d to Lambda(1405) n is one of
the most favorable reactions. Hadronic molecule states with kaons are also
discussed by emphasizing an important role of Lambda(1405) as a quasibound
state of Kbar N.Comment: 8 pages, three figures. Talk given at 10th International Conference
on Hypernuclear and Strange Particle Physics (HYP-X), Tokai, Ibaraki, Japan,
14-18 Sep 2009
X-Ray Observations of the Galactic Center with Suzaku
We report on the diffuse X-ray emissions from the Galactic center (GCDX)
observed with the X-ray Imaging Spectrometer (XIS) on board the Suzaku
satellite. The highly accurate energy calibrations and extremely low background
of the XIS provide many new facts on the GCDX. These are (1) the origin of the
6.7/7.0keV lines is collisional excitation in hot plasma, (2) new SNR and
super-bubble candidates are found, (3) most of the 6.4keV line is fluorescence
by X-rays, and (4) time variability of the 6.4keV line is found from the SgrB2
complex.Comment: 4 pages, 6 figure, proceedings of the XMM-Newton workshop, June 2007,
accepted for publication in A
Real-time Loss Estimation for Instrumented Buildings
Motivation. A growing number of buildings have been instrumented to measure and record
earthquake motions and to transmit these records to seismic-network data centers to be archived and
disseminated for research purposes. At the same time, sensors are growing smaller, less expensive to
install, and capable of sensing and transmitting other environmental parameters in addition to
acceleration. Finally, recently developed performance-based earthquake engineering methodologies
employ structural-response information to estimate probabilistic repair costs, repair durations, and
other metrics of seismic performance. The opportunity presents itself therefore to combine these
developments into the capability to estimate automatically in near-real-time the probabilistic seismic
performance of an instrumented building, shortly after the cessation of strong motion. We refer to
this opportunity as (near-) real-time loss estimation (RTLE).
Methodology. This report presents a methodology for RTLE for instrumented buildings. Seismic
performance is to be measured in terms of probabilistic repair cost, precise location of likely physical
damage, operability, and life-safety. The methodology uses the instrument recordings and a Bayesian
state-estimation algorithm called a particle filter to estimate the probabilistic structural response of
the system, in terms of member forces and deformations. The structural response estimate is then
used as input to component fragility functions to estimate the probabilistic damage state of structural
and nonstructural components. The probabilistic damage state can be used to direct structural
engineers to likely locations of physical damage, even if they are concealed behind architectural
finishes. The damage state is used with construction cost-estimation principles to estimate
probabilistic repair cost. It is also used as input to a quantified, fuzzy-set version of the FEMA-356
performance-level descriptions to estimate probabilistic safety and operability levels.
CUREE demonstration building. The procedure for estimating damage locations, repair costs, and
post-earthquake safety and operability is illustrated in parallel demonstrations by CUREE and
Kajima research teams. The CUREE demonstration is performed using a real 1960s-era, 7-story, nonductile
reinforced-concrete moment-frame building located in Van Nuys, California. The building is
instrumented with 16 channels at five levels: ground level, floors 2, 3, 6, and the roof. We used the
records obtained after the 1994 Northridge earthquake to hindcast performance in that earthquake.
The building is analyzed in its condition prior to the 1994 Northridge Earthquake. It is found that,
while hindcasting of the overall system performance level was excellent, prediction of detailed damage
locations was poor, implying that either actual conditions differed substantially from those shown on
the structural drawings, or inappropriate fragility functions were employed, or both. We also found
that Bayesian updating of the structural model using observed structural response above the base of
the building adds little information to the performance prediction. The reason is probably that
Real-Time Loss Estimation for Instrumented Buildings
ii
structural uncertainties have only secondary effect on performance uncertainty, compared with the
uncertainty in assembly damageability as quantified by their fragility functions. The implication is
that real-time loss estimation is not sensitive to structural uncertainties (saving costly multiple
simulations of structural response), and that real-time loss estimation does not benefit significantly
from installing measuring instruments other than those at the base of the building.
Kajima demonstration building. The Kajima demonstration is performed using a real 1960s-era
office building in Kobe, Japan. The building, a 7-story reinforced-concrete shearwall building, was not
instrumented in the 1995 Kobe earthquake, so instrument recordings are simulated. The building is
analyzed in its condition prior to the earthquake. It is found that, while hindcasting of the overall
repair cost was excellent, prediction of detailed damage locations was poor, again implying either that
as-built conditions differ substantially from those shown on structural drawings, or that
inappropriate fragility functions were used, or both. We find that the parameters of the detailed
particle filter needed significant tuning, which would be impractical in actual application. Work is
needed to prescribe values of these parameters in general.
Opportunities for implementation and further research. Because much of the cost of applying
this RTLE algorithm results from the cost of instrumentation and the effort of setting up a structural
model, the readiest application would be to instrumented buildings whose structural models are
already available, and to apply the methodology to important facilities. It would be useful to study
under what conditions RTLE would be economically justified. Two other interesting possibilities for
further study are (1) to update performance using readily observable damage; and (2) to quantify the
value of information for expensive inspections, e.g., if one inspects a connection with a modeled 50%
failure probability and finds that the connect is undamaged, is it necessary to examine one with 10%
failure probability
- …