17,499 research outputs found
Exotic , and states
After constructing the possible and
tetraquark interpolating currents in a systematic way, we
investigate the two-point correlation functions and extract the corresponding
masses with the QCD sum rule approach. We study the ,
and systems with various isospins . Our numerical analysis indicates that the masses of doubly-bottomed
tetraquark states are below the threshold of the two bottom mesons, two bottom
baryons and one doubly bottomed baryon plus one anti-nucleon. Very probably
these doubly-bottomed tetraquark states are stable.Comment: 37 pages, 2 figure
The BCS Pairing Instability in the Thermodynamic Limit
The superconducting pairing instability---as determined by a divergence of
the two-particle susceptibility---is obtained in the mean field (BCS)
approximation in the thermodynamic limit. The usual practice is to examine this
property for a finite lattice. We illustrate that, while the conclusions remain
unchanged, the technical features are very different in the thermodynamic limit
and conform more closely with the usual treatment of phase transitions
encountered in, for example, the mean-field paramagnetic-ferromagnetic
transition. Furthermore, by going to the extreme dilute limit, one can
distinguish three dimensions from one and two dimensions, in which a pairing
instability occurs even for two particles.Comment: 4 pages + references, 4 figure
molecule interpretation of
We have used QCD sum rules to study the newly observed charged state
as a hidden-charm molecular state with the quantum
numbers . Using a molecular interpolating
current, we have calculated the two-point correlation function and the spectral
density up to dimension eight at leading order in . The extracted
mass is GeV. This result is compatible with the observed
mass of within the errors, which implies a possible molecule
interpretation of this new resonance. We also predict the mass of the
corresponding hidden-bottom molecular state:
GeV.Comment: 6 pages, 5 figures. Version appears in Eur. Phys. J.
Possible Exotic State
We study the possible exotic states with using the
tetraquark interpolating currents with the QCD sum rule approach. The extracted
masses are around 4.85 GeV for the charmonium-like states and 11.25 GeV for the
bottomomium-like states. There is no working region for the light tetraquark
currents, which implies the light state may not exist below 2 GeV.Comment: 13 pages, 11 figures, 2 table
- β¦