7,346 research outputs found
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
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
Towards a new paradigm for heavy-light meson spectroscopy
Since 2003 many new hadrons, including the lowest-lying positive-parity
charm-strange mesons and , were observed
that do not conform with quark model expectations. It was recently demonstrated
that various puzzles in the charm meson spectrum find a natural resolution, if
the SU(3) multiplets for the lightest scalar and axial-vector states, amongst
them the and the , owe their existence to
the nonperturbative dynamics of Goldstone-Boson scattering off and
mesons. Most importantly the ordering of the lightest strange and
nonstrange scalars becomes natural. In this work we demonstrate for the first
time that this mechanism is strongly supported by the recent high quality data
on the provided by the LHCb experiment. This implies
that the lowest quark-model positive-parity charm mesons, together with their
bottom counterparts, if realized in nature, do not form the ground-state
multiplet. This is similar to the pattern that has been established for the
scalar mesons made from light up, down and strange quarks, where the lowest
multiplet is considered to be made of states not described by the quark model.
In a broader view, the hadron spectrum must be viewed as more than a collection
of quark model states.Comment: 8 pages, 5 figures. Discussion significantly extended, suggestion for
lattice and more comparison with LHCb data added; version accepted for
publication in PR
Recommended from our members
Cortical Neural Stem Cell Lineage Progression Is Regulated by Extrinsic Signaling Molecule Sonic Hedgehog.
Neural stem cells (NSCs) in the prenatal neocortex progressively generate different subtypes of glutamatergic projection neurons. Following that, NSCs have a major switch in their progenitor properties and produce γ-aminobutyric acid (GABAergic) interneurons for the olfactory bulb (OB), cortical oligodendrocytes, and astrocytes. Herein, we provide evidence for the molecular mechanism that underlies this switch in the state of neocortical NSCs. We show that, at around E16.5, mouse neocortical NSCs start to generate GSX2-expressing (GSX2+) intermediate progenitor cells (IPCs). In vivo lineage-tracing study revealed that GSX2+ IPC population gives rise not only to OB interneurons but also to cortical oligodendrocytes and astrocytes, suggesting that they are a tri-potential population. We demonstrated that Sonic hedgehog signaling is both necessary and sufficient for the generation of GSX2+ IPCs by reducing GLI3R protein levels. Using single-cell RNA sequencing, we identify the transcriptional profile of GSX2+ IPCs and the process of the lineage switch of cortical NSCs
The critical behaviour of the 2D Ising model in Transverse Field; a Density Matrix Renormalization calculation
We have adjusted the Density Matrix Renormalization method to handle two
dimensional systems of limited width. The key ingredient for this extension is
the incorporation of symmetries in the method. The advantage of our approach is
that we can force certain symmetry properties to the resulting ground state
wave function. Combining the results obtained for system sizes up-to and finite size scaling, we derive the phase transition point and the
critical exponent for the gap in the Ising model in a Transverse Field on a two
dimensional square lattice.Comment: 9 pages, 8 figure
Strong tuning of Rashba spin orbit interaction in single InAs nanowires
A key concept in the emerging field of spintronics is the gate voltage or
electric field control of spin precession via the effective magnetic field
generated by the Rashba spin orbit interaction. Here, we demonstrate the
generation and tuning of electric field induced Rashba spin orbit interaction
in InAs nanowires where a strong electric field is created either by a double
gate or a solid electrolyte surrounding gate. In particular, the electrolyte
gating enables six-fold tuning of Rashba coefficient and nearly three orders of
magnitude tuning of spin relaxation time within only 1 V of gate bias. Such a
dramatic tuning of spin orbit interaction in nanowires may have implications in
nanowire based spintronic devices.Comment: Nano Letters, in pres
Aspects of the low-energy constants in the chiral Lagrangian for charmed mesons
We investigate the numerical values of the low-energy constants in the chiral effective Lagrangian for the interactions between the charmed mesons and the lightest pseudoscalar mesons, the Goldstone bosons of the spontaneous breaking of chiral symmetry for QCD. This problem is tackled from two sides: estimates using the resonance-exchange model and positivity constraints from the general properties of the S-matrix including analyticity, crossing symmetry, and unitarity. These estimates and constraints are compared with the values determined from fits to lattice data of the scattering lengths. Tensions are found, and possible reasons are discussed. We conclude that more data from lattice calculations and experiments are necessary to fix these constants better. As a byproduct, we also estimate the coupling constant gDDa2, with a2 the light tensor meson, via the QCD sum rule approach
Ballistic Composite Fermions in Semiconductor Nanostructures
We report the results of two fundamental transport measurements at a Landau
level filling factor of 1/2. The well known ballistic electron transport
phenomena of quenching of the Hall effect in a mesoscopic cross-junction and
negative magnetoresistance of a constriction are observed close to B~=~0 and
. The experimental results demonstrate semi-classical charge
transport by composite fermions, which consist of electrons bound to an even
number of flux quanta.Comment: 9 pages TeX 3.1415 C version 6.1, 3 PostScript figure
Hierarchically Porous Gd3+-Doped CeO2 Nanostructures for the Remarkable Enhancement of Optical and Magnetic Properties
Rare earth ion-doped CeO2 has attracted more and more attention because of its special electrical, optical, magnetic, or catalytic properties. In this paper, a facile electrochemical deposition route was reported for the direct growth of the porous Gd-doped CeO2. The formation process of Gd-doped CeO2 composites was investigated. The obtained deposits were characterized by SEM, EDS, XRD, and XPS. The porous Gd3+- doped CeO2 (10 at% Gd) displays a typical type I adsorption isotherm and yields a large specific surface area of 135 m2/g. As Gd3+ ions were doped into CeO2 lattice, the absorption spectrum of Gd3+-doped CeO2 nanocrystals exhibited a red shift compared with porous CeO2 nanocrystals and bulk CeO2, and the luminescence of Gd3+-doped CeO2 deposits was remarkably enhanced due to the presence of more oxygen vacancies. In addition, the strong magnetic properties of Gd-doped CeO2 (10 at% Gd) were observed, which may be caused by Gd3+ ions or more oxygen defects in deposits. In addition, the catalytic activity of porous Gd-doped CeO2 toward CO oxidation was studied
- …