3,775 research outputs found
Electromagnetic structure of charmed baryons in Lattice QCD
As a continuation of our recent work on the electromagnetic properties of the
doubly charmed baryon, we compute the charge radii and the magnetic
moments of the singly charmed , and the doubly charmed
baryons in 2+1 flavor Lattice QCD. In general, the charmed
baryons are found to be compact as compared to the proton. The charm quark acts
to decrease the size of the baryons to smaller values. We discuss the mechanism
behind the dependence of the charge radii on the light valence- and sea-quark
masses. The magnetic moments are found to be almost stable with respect to
changing quark mass. We investigate the individual quark sector contributions
to the charge radii and the magnetic moments. The magnetic moments of the
singly charmed baryons are found to be dominantly determined by the light quark
and the role of the charm quark is significantly enhanced for the doubly
charmed baryons.Comment: Updated results, improved analysis. Version to appear in JHE
Electromagnetic properties of doubly charmed baryons in Lattice QCD
We compute the electromagnetic properties of \Xi_cc baryons in 2+1 flavor
Lattice QCD. By measuring the electric charge and magnetic form factors of
\Xi_cc baryons, we extract the magnetic moments, charge and magnetic radii as
well as the \Xi_cc \Xi_cc \rho coupling constant, which provide important
information to understand the size, shape and couplings of the doubly charmed
baryons. We find that the two heavy charm quarks drive the charge radii and the
magnetic moment of \Xi_cc to smaller values as compared to those of, e.g., the
proton.Comment: 15 pages, 5 figures; added discussions and references, version
accepted by PL
Absorption Line Survey of H3+ toward the Galactic Center Sources III. Extent of the Warm and Diffuse Clouds
We present follow-up observations to those of Geballe & Oka (2010), who found
high column densities of H3+ ~100 pc off of the Galactic center (GC) on the
lines of sight to 2MASS J17432173-2951430 (J1743) and 2MASS J17470898-2829561
(J1747). The wavelength coverages on these sightlines have been extended in
order to observe two key transitions of H3+, R(3,3)l and R(2,2)l, that
constrain the temperatures and densities of the environments. The profiles of
the H3+ R(3,3)l line, which is due only to gas in the GC, closely matches the
differences between the H3+ R(1,1)l and CO line profiles, just as it does for
previously studied sightlines in the GC. Absorption in the R(2,2)l line of H3+
is present in J1747 at velocities between -60 and +100 km/s. This is the second
clear detection of this line in the interstellar medium after GCIRS 3 in the
Central Cluster. The temperature of the absorbing gas in this velocity range is
350 K, significantly warmer than in the diffuse clouds in other parts of the
Central Molecular Zone. This indicates that the absorbing gas is local to Sgr B
molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005)
apparently extends to ~100 pc, but there is a hint that its temperature is
somewhat lower in the line of sight to J1743 than elsewhere in the GC. The
observation of H3+ toward J1747 is compared with the recent Herschel
observation of H2O+ toward Sgr B2 and their chemical relationship and
remarkably similar velocity profiles are discussed.Comment: 6 pages, 3 figures, 2 tables, Accepted for publication in
Publications of the Astronomical Society of Japa
The Interstellar Medium of IRAS 08572+3915 NW: H3+ and Warm High Velocity CO
We confirm the first detection of the molecular ion H3+ in an extragalactic
object, the highly obscured ultraluminous galaxy IRAS 08572+3915 NW. We also
have detected absorption lines of the fundamental band of CO in this galaxy.
The CO absorption consists of a cold component close to the systemic velocity
and warm, highly blueshifted and redshifted components. The warm blueshifted
component is remarkably strong and broad and extends at least to -350 km/s.
Some analogies can be drawn between the H3+ and cold CO in IRAS08572+3915 NW
and the same species seen toward the Galactic center. The profiles of the warm
CO components are not those expected from a dusty torus of the type thought to
obscure active galactic nuclei. They are probably formed close to the dust
continuum surface near the buried and active nucleus and are probably
associated with an unusual and energetic event there.Comment: 21 pages, 4 postscript figures, accepted by Ap
Low-lying Baryons with spin 1/2 in Two-flavor Lattice QCD
Low-lying baryons with spin 1/2 are analyzed in full (unquenched)
lattice QCD. We construct cross correlators from flavor SU(3)
"octet" and "singlet" baryon operators, and diagonalize them so as to extract
information of two low-lying states for each parity. The two-flavor CP-PACS
gauge configurations are used, which are generated in the renormalization-group
improved gauge action and the -improved quark action. Three
different 's, , 1.95 and 2.10, are employed, whose
corresponding lattice spacings are , 0.1555 and 0.1076 fm. For each
cutoff, we use four hopping parameters, (),
which correspond to the pion masses ranging about from 500 MeV to 1.1 GeV.
Results indicate that there are two negative-parity states nearly
degenerate at around 1.6 GeV, while no state as low as is
observed. By decomposing the flavor components of each state, we find that the
lowest (1st-excited) negative-parity state is dominated by flavor-singlet
(flavor-octet) component. We also discuss meson-baryon components of each
state, which has drawn considerable attention in the context of multi-quark
pictures of .Comment: 11 pages, 11 figures, 3 tables; version to appear in Phys. Rev.
Levi problem and semistable quotients
A complex space is in class if it is a semistable
quotient of the complement to an analytic subset of a Stein manifold by a
holomorphic action of a reductive complex Lie group . It is shown that every
pseudoconvex unramified domain over is also in .Comment: Version 2 - minor edits; 8 page
Chiral Symmetry of Nucleon Resonances in QCD sum rules
The QCD sum rule approach is employed in order to study chiral properties of
positive- and negative-parity nucleon resonances. It is pointed out that
nucleons with an ``exotic'' chiral property, which can be represented by local
five-quark operators, can be paired with a standard nucleon forming a single
chiral multiplet. The sum rules of the five-quark operators, however, are shown
not to couple strongly to chirally-``exotic'' nucleon resonances at the mass
region of less than 2 GeV.Comment: 11 page
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