22,197 research outputs found
The Y(3940), Z(3930) and the X(4160) as dynamically generated resonances from the vector-vector interaction
We study the vector-vector interaction within the framework of the hidden
gauge formalism for the sector with quantum numbers charm C=0 and strangeness
S=0 in the region around 4000 MeV. We get five poles, three of which could be
identified with the Y(3940), Z(3930) and X(4160). These poles appear with
quantum numbers I=0 and and , respectively, and
can be considered as hadronic molecules made of ,
.Comment: to appear in Proceedings of XIII International Conference on Hadron
Spectroscopy, November 29 - December 4, 2009, Florida State Universit
Screening in three-dimensional QED with arbitrary fermion mass
We compute the quark--antiquark potential in three dimensional massive
Quantum Electrodynamics for arbitrary fermion mass. The result indicates that
screening prevails for any quark masses, contrary to the classical
expectations, generalizing our previous result obtained for large masses. We
also test the validity of several approximation schemes using a detailed
numerical analysis. The classical result is still reproduced for small
separation of the quarks.Comment: latex, 10 pages, 4 figures (6 ps-files
Detailed atmospheric abundance analysis of the optical counterpart of the IR source IRAS 16559-2957
We have undertaken a detailed abundance analysis of the optical counterpart
of the IR source IRAS16559-2957 with the aim of confirming its possible
post-AGB nature. The star shows solar metallicity and our investigation of a
large number of elements including CNO and 12C/13C suggests that this object
has experienced the first dredge-up and it is likely still at RGB stage.Comment: 10 pages, 4 figures, 4 tables. To be published by Revista Mexicana de
Astronomia y Astrofisica, April 201
Decays of doubly charmed meson molecules
Several observed states close to the and
thresholds, as the X(3872) and some XYZ particles
can be described in terms of a two-meson molecule. Furthermore, doubly charmed
states are also predicted. These new states are near the and
thresholds, % Therefore, if the previous XYZ are molecules, then,
there should be doubly charmed mesons with around the
threshold.
%For this reason, it is important to evaluate observables related to them.
Because of the spin, they do not decay into . In this article we
compute decays to and radiative decays of doubly charmed meson molecules
into . and have spin-parity . Their natural decay
modes are , and and
. We evaluate the widths of these states, named here as
and , and obtain 44 MeV for the non-strangeness,
and 24 MeV for the doubly charm-strange state. Essentially, the decay modes are
and , being the and emitted by
one of the meson which forms the molecule.Comment: 31 pages, 9 figures, 20 table
Light- and strange-quark mass dependence of the meson revisited
Recent lattice data on -scattering phase shifts in the
vector-isovector channel, pseudoscalar meson masses and decay constants for
strange-quark masses smaller or equal to the physical value allow us to study
the strangeness dependence of these observables for the first time. We perform
a global analysis on two kind of lattice trajectories depending on whether the
sum of quark masses or the strange-quark mass is kept fixed to the physical
point. The quark mass dependence of these observables is extracted from
unitarized coupled-channel one-loop Chiral Perturbation Theory. This analysis
guides new predictions on the meson properties over trajectories
where the strange-quark mass is lighter than the physical mass, as well as on
the SU(3) symmetric line. As a result, the light- and strange-quark mass
dependence of the meson parameters are discussed and precise values
of the Low Energy Constants present in unitarized one-loop Chiral Perturbation
Theory are given. Finally, the current discrepancy between two- and
three-flavor lattice results for the meson is studied.Comment: 44 pages, 41 figures, 11 table
Spectral statistics of molecular resonances in erbium isotopes: How chaotic are they?
We perform a comprehensive analysis of the spectral statistics of the
molecular resonances in Er and Er observed in recent ultracold
collision experiments [Frisch et al., Nature {\bf 507}, 475 (2014)] with the
aim of determining the chaoticity of this system. We calculate different
independent statistical properties to check their degree of agreement with
random matrix theory (RMT), and analyze if they are consistent with the
possibility of having missing resonances. The analysis of the short-range
fluctuations as a function of the magnetic field points to a steady increase of
chaoticity until G. The repulsion parameter decreases for higher
magnetic fields, an effect that can be interpreted as due to missing
resonances. The analysis of long-range fluctuations allows us to be more
quantitative and estimate a fraction of missing levels. Finally, a
study of the distribution of resonance widths provides additional evidence
supporting missing resonances of small width compared with the experimental
magnetic field resolution. We conclude that further measurements with increased
resolution will be necessary to give a final answer to the problem of missing
resonances and the agreement with RMT.Comment: 9 pages, 6 figure
Length-dependent oscillations of the conductance through atomic chains: The importance of electronic correlations
We calculate the conductance of atomic chains as a function of their length.
Using the Density Matrix Renormalization Group algorithm for a many-body model
which takes into account electron-electron interactions and the shape of the
contacts between the chain and the leads, we show that length-dependent
oscillations of the conductance whose period depends on the electron density in
the chain can result from electron-electron scattering alone. The amplitude of
these oscillations can increase with the length of the chain, in contrast to
the result from approaches which neglect the interactions.Comment: 7 pages, 4 figure
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