8,146 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
Implications of chiral symmetry on -wave pionic resonances and the scalar charmed mesons
The chiral symmetry of QCD requires energy-dependent pionic strong
interactions at low energies. This constraint, however, is not fulfilled by the
usual Breit--Wigner parameterization of pionic resonances, leading to masses
larger than the real ones. We derive relations between nonleptonic three-body
decays of the -meson into a -meson and a pair of light pseudoscalar
mesons based on SU(3) chiral symmetry. Employing effective field theory
methods, we demonstrate that taking into account the final-state interactions,
the experimental data of the decays , , , and
can all be described by the nonperturbative
- scattering amplitudes previously obtained from a
combination of chiral effective field theory and lattice QCD calculations. The
results provide a strong support of the scenario that the broad scalar charmed
meson should be replaced by two states, the lower one of which
has a mass of around 2.1 GeV, much smaller than that extracted from
experimental data using a Breit--Wigner parameterization.Comment: 26 pages, 9 figuere
One-loop renormalization of the chiral Lagrangian for spinless matter fields in the SU(N) fundamental representation
We perform the leading one-loop renormalization of the chiral Lagrangian for
spinless matter fields living in the fundamental representation of SU(N). The
Lagrangian can also be applied to any theory with a spontaneous symmetry
breaking of to and spinless matter fields in
the fundamental representation. For QCD, the matter fields can be kaons or
pseudoscalar heavy mesons. Using the background field method and heat kernel
expansion techniques, the divergences of the one-loop effective generating
functional for correlation functions of single matter fields are calculated up
to . They are absorbed by counterterms not only from the
third order but also from the second order chiral Lagrangian.Comment: 13 page
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.
One-loop analysis of the interactions between charmed mesons and Goldstone bosons
We derive the scattering amplitude for Goldstone bosons of chiral symmetry
off the pseudoscalar charmed mesons up to leading one-loop order in a covariant
chiral effective field theory, using the so-called extended-on-mass-shell
renormalization scheme. Then we use unitarized chiral perturbation theory to
fit to the available lattice data of the S-wave scattering lengths. The lattice
data are well described. However, most of the low-energy constants determined
from the fit bear large uncertainties. Lattice simulations in more channels are
necessary to pin down these values which can then be used to make predictions
in other processes related by chiral and heavy quark symmetries.Comment: 34 pages, 7 figures, 7 tables, the final version to be published in
JHE
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
Study of open-charm states in unitarized chiral effective theory with one-loop potentials
Chiral potentials are derived for the interactions between Goldstone bosons
and pseudoscalar charmed mesons up to next-to-next-to-leading order in a
covariant chiral effective field theory with explicit vector charmed-meson
degrees of freedom. Using the extended-on-mass-shell scheme, we demonstrate
that the ultraviolet divergences and the so-called power counting breaking
terms can be properly absorbed by the low-energy constants of the chiral
Lagrangians. We calculate the scattering lengths by unitarizing the one-loop
potentials and fit them to the data extracted from lattice QCD. The obtained
results are compared to the ones without an explicit contribution of vector
charmed mesons given previously. It is found that the difference is negligible
for -wave scattering in the threshold region. This validates the use of
-less one-loop potentials in the study of the pertinent scattering
lengths. We search for dynamically generated open-charm states with
as poles of the -matrix on various Riemann sheets. The trajectories of those
poles for varying pion masses are presented as well.Comment: 25 pages, 6 figures and 5 table
The third peak structure in the double spectrum
Recently, the CMS and ATLAS collaborations have reported their and invariant mass distributions, respectively, for
searching for fully charmed tetraquarks. Both of them reported the existence of
a peak structure around 7.2~\gev. In this article, we exhibit the role of the
channel, which is close to this peak position, by
studying the and invariant mass
distributions for the potential quantum numbers or by
considering both the coherence and incoherence with the background
contribution. All these frameworks can describe the experimental data very
well, however with different pole structures. For instance, in the case of
description of these structures, there always exists a pole slightly
below the threshold. For the case, a similar pole can
also be found below the threshold however with a much lower
mass. More importantly, the number of the poles is found to be case-dependent.
For the () case, the peak structure around 7.2~\gev can
(cannot) be produced due to the presence (absence) of the
channel. Although the pole positions are case-dependent,
the relation between the peak structure in the invariant mass
distribution and the dip structure in the invariant mass
distribution around 7.2~\gev is unambiguous. We suggest experimentalists to
detailed scan both the and the invariant
mass distributions, especially around 7.2~\gev to probe the nature of the
third fully charmed state.Comment: 15 pages, 5 figure
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