13,707 research outputs found
Lambda(1405) as a Resonance in the Baryon-Meson Scattering Coupled to the q^3 State in a Quark Model
In order to describe Lambda(1405) as a resonance in the baryon-meson
scattering, we have investigated q^3-q qbar scattering system with the
flavor-singlet q^3 (0s)^2(0p) state (the Lambda^1 pole). The scattering is
treated by the quark cluster model (QCM). The Lambda^1 pole is treated as a
bound state embedded in the continuum. We found that the peak appears below the
N Kbar threshold in the spin one half, isospin 0 channel even if the mass of
the Lambda^1 pole is above the threshold. This peak disappears when the
coupling to the Lambda^1 pole is switched off. To use the observed hadron mass
in the kinetic part of QCM is also found to be important to reproduce a peak
just below the N Kbar threshold.Comment: 16 pages and 7 figure
Peculiar mean velocity profiles within a porous bed of an open channel
Peer reviewedPublisher PD
Wobbling Motion in Atomic Nuclei with Positive-Gamma Shapes
The three moments of inertia associated with the wobbling mode built on the
superdeformed states in 163Lu are investigated by means of the cranked shell
model plus random phase approximation to the configuration with an aligned
quasiparticle. The result indicates that it is crucial to take into account the
direct contribution to the moments of inertia from the aligned quasiparticle so
as to realize J_x > J_y in positive-gamma shapes. Quenching of the pairing gap
cooperates with the alignment effect. The peculiarity of the recently observed
163Lu data is discussed by calculating not only the electromagnetic properties
but also the excitation spectra.Comment: 11 pages, 6 figure
High-K Precession modes: Axially symmetric limit of wobbling motion
The rotational band built on the high-K multi-quasiparticle state can be
interpreted as a multi-phonon band of the precession mode, which represents the
precessional rotation about the axis perpendicular to the direction of the
intrinsic angular momentum. By using the axially symmetric limit of the
random-phase-approximation (RPA) formalism developed for the nuclear wobbling
motion, we study the properties of the precession modes in W; the
excitation energies, B(E2) and B(M1) values. We show that the excitations of
such a specific type of rotation can be well described by the RPA formalism,
which gives a new insight to understand the wobbling motion in the triaxial
superdeformed nuclei from a microscopic view point.Comment: 14 pages, 8 figures (Spelling of the authors name was wrong at the
first upload, so it is corrected
Reevaluation of Neutron Electric Dipole Moment with QCD Sum Rules
We study the neutron electric dipole moment in the presence of the
CP-violating operators up to the dimension five in terms of the QCD sum rules.
It is found that the OPE calculation is robust when exploiting a particular
interpolating field for neutron, while there exist some uncertainties on the
phenomenological side. By using input parameters obtained from the lattice
calculation, we derive a conservative limit for the contributions of the CP
violating operators. We also show the detail of the derivation of the sum
rules.Comment: 33 pages, 5 figure
1D Modeling for Temperature-Dependent Upflow in the Dimming Region Observed by Hinode/EIS
We have previously found a temperature-dependent upflow in the dimming region
following a coronal mass ejection (CME) observed by the {\it Hinode} EUV
Imaging Spectrometer (EIS). In this paper, we reanalyzed the observations along
with previous work on this event, and provided boundary conditions for
modeling. We found that the intensity in the dimming region dramatically drops
within 30 minutes from the flare onset, and the dimming region reaches the
equilibrium stage after 1 hour later. The temperature-dependent upflows
were observed during the equilibrium stage by EIS. The cross sectional area of
the fluxtube in the dimming region does not appear to expand significantly.
From the observational constraints, we reconstructed the temperature-dependent
upflow by using a new method which considers the mass and momentum conservation
law, and demonstrated the height variation of plasma conditions in the dimming
region. We found that a super radial expansion of the cross sectional area is
required to satisfy the mass conservation and momentum equations. There is a
steep temperature and velocity gradient of around 7 Mm from the solar surface.
This result may suggest that the strong heating occurred above 7 Mm from the
solar surface in the dimming region. We also showed that the ionization
equilibrium assumption in the dimming region is violated especially in the
higher temperature range.Comment: accepted for publication in The Astrophysical Journa
Local Swift-BAT active galactic nuclei prefer circumnuclear star formation
We use Herschel data to analyze the size of the far-infrared 70micron
emission for z<0.06 local samples of 277 hosts of Swift-BAT selected active
galactic nuclei (AGN), and 515 comparison galaxies that are not detected by
BAT. For modest far-infrared luminosities 8.5<log(LFIR)<10.5, we find large
scatter of half light radii Re70 for both populations, but a typical Re70 <~ 1
kpc for the BAT hosts that is only half that of comparison galaxies of same
far-infrared luminosity. The result mostly reflects a more compact distribution
of star formation (and hence gas) in the AGN hosts, but compact AGN heated dust
may contribute in some extremely AGN-dominated systems. Our findings are in
support of an AGN-host coevolution where accretion onto the central black hole
and star formation are fed from the same gas reservoir, with more efficient
black hole feeding if that reservoir is more concentrated. The significant
scatter in the far-infrared sizes emphasizes that we are mostly probing spatial
scales much larger than those of actual accretion, and that rapid accretion
variations can smear the distinction between the AGN and comparison categories.
Large samples are hence needed to detect structural differences that favour
feeding of the black hole. No size difference AGN host vs. comparison galaxies
is observed at higher far-infrared luminosities log(LFIR)>10.5 (star formation
rates >~ 6 Msun/yr), possibly because these are typically reached in more
compact regions in the first place.Comment: 7 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic
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