26,690 research outputs found
Can only flavor-nonsinglet H dibaryons be stable against strong decays?
Using the QCD sum rule approach, we show that the flavor-nonsinglet
dibaryon states with J, J, I=1 (27plet) are nearly
degenerate with the J, I=0 singlet dibaryon, which has been
predicted to be stable against strong decay, but has not been observed. Our
calculation, which does not require an instanton correction, suggests that the
is slightly heavier than these flavor-nonsinglet s over a wide range
of the parameter space. If the singlet mass lies above the threshold (2231~MeV), then the strong interaction breakup to would produce a very broad resonance in the
invariant mass spectrum which would be very difficult to observe. On the other
hand, if these flavor-nonsinglet J=0 and 1 dibaryons are also above the
threshold, but below the breakup threshold (2254
MeV), then because the direct, strong interaction decay to the channel is forbidden, these flavor-nonsinglet states might be more
amenable to experimental observation. The present results allow a possible
reconciliation between the reported observation of
hypernuclei, which argue against a stable , and the possible existence of
dibaryons in general.Comment: 10 pages, 2 figure
Multi-excitonic complexes in single InGaN quantum dots
Cathodoluminescence spectra employing a shadow mask technique of InGaN layers
grown by metal organic chemical vapor deposition on Si(111) substrates are
reported. Sharp lines originating from InGaN quantum dots are observed.
Temperature dependent measurements reveal thermally induced carrier
redistribution between the quantum dots. Spectral diffusion is observed and was
used as a tool to correlate up to three lines that originate from the same
quantum dot. Variation of excitation density leads to identification of exciton
and biexciton. Binding and anti-binding complexes are discovered.Comment: 3 pages, 4 figure
General graviton exchange graph for four point functions in the AdS/CFT correspondence
In this note we explicitly compute the graviton exchange graph for scalar
fields with arbitrary conformal dimension \Delta in arbitrary spacetime
dimension d. This results in an analytical function in \Delta as well as in d.Comment: 14 pages, 2 figure
Running coupling and mass anomalous dimension of SU(3) gauge theory with two flavors of symmetric-representation fermions
We have measured the running coupling constant of SU(3) gauge theory coupled
to Nf=2 flavors of symmetric representation fermions, using the Schrodinger
functional scheme. Our lattice action is defined with hypercubic smeared links
which, along with the larger lattice sizes, bring us closer to the continuum
limit than in our previous study. We observe that the coupling runs more slowly
than predicted by asymptotic freedom, but we are unable to observe fixed point
behavior before encountering a first order transition to a strong coupling
phase. This indicates that the infrared fixed point found with the thin-link
action is a lattice artifact. The slow running of the gauge coupling permits an
accurate determination of the mass anomalous dimension for this theory, which
we observe to be small, gamma_m < 0.6, over the range of couplings we can
reach. We also study the bulk and finite-temperature phase transitions in the
strong coupling region.Comment: 17 pages, 16 figures. Substantial modifications to explain why the
fat-link result for the beta function supersedes our thin-link result; also
updated the phase diagram to reflect additional numerical work. Added
references. Final versio
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