3,233 research outputs found
KKbar molecules with momentum-dependent interactions
It is shown that the momentum-dependent kaon-antikaon interactions generated
via vector meson exchange from the standard SU_V(3) x SU_A(3) interaction
Lagrangian lead to a non-local potential in coordinate space that can be
incorporated without approximation into a non-relativistic version of the
Bethe-Salpeter wave equation containing a radial-dependent effective kaon mass
appearing in a fully symmetrized kinetic energy operator, in addition to a
local potential. Estimates of the mass and decay widths of f_0(980) and
a_0(980), considered as KKbar molecules of isospin 0 and 1, as well as for
K^+K^- atomic bound states (kaonium) are presented, and compared with previous
studies of a similar nature. It is argued that without a better knowledge of
hadronic form factors it is not possible to distinguish between the molecular
versus elementary particle models for the structure of the light scalar mesons.Comment: 14 pages, 2 tables, 5 figures. Added subsection on s-channel
exchange, additional remarks on the possible effect of gluon exchange, and 1
additional figur
Entanglement induced by a single-mode heat environment
A thermal field, which frequently appears in problems of decoherence,
provides us with minimal information about the field. We study the interaction
of the thermal field and a quantum system composed of two qubits and find that
such a chaotic field with minimal information can nevertheless entangle the
qubits which are prepared initially in a separable state. This simple model of
a quantum register interacting with a noisy environment allows us to understand
how memory of the environment affects the state of a quantum register.Comment: 13pages, 3 figure
The Zel'dovich effect and evolution of atomic Rydberg spectra along the Periodic Table
In 1959 Ya. B. Zel'dovich predicted that the bound-state spectrum of the
non-relativistic Coulomb problem distorted at small distances by a short-range
potential undergoes a peculiar reconstruction whenever this potential alone
supports a low-energy scattering resonance. However documented experimental
evidence of this effect has been lacking. Previous theoretical studies of this
phenomenon were confined to the regime where the range of the short-ranged
potential is much smaller than Bohr's radius of the Coulomb field. We go beyond
this limitation by restricting ourselves to highly-excited s states. This
allows us to demonstrate that along the Periodic Table of elements the
Zel'dovich effect manifests itself as systematic periodic variation of the
Rydberg spectra with a period proportional to the cubic root of the atomic
number. This dependence, which is supported by analysis of experimental and
numerical data, has its origin in the binding properties of the ionic core of
the atom.Comment: 17 pages, 12 figure
Angular asymmetries in the reactions pp \to d\pi^+\eta and pn \to d\pi^0\eta and a_0-f_0 mixing
The reactions pp\to d\pi^+\eta and pn\to d\pi^0\eta are of special interest
for investigating the a_0(980) (J^P=0^+) resonance in the process NN \to da_0
\to d\pi\eta. We study some aspects of those reactions within a general
formalism and also in a concrete phenomenological model. In particular, it is
shown that the presence of nonresonant (i.e. without excitation of the a_0
resonance) contributions to these reactions yields nonvanishing values for
specific polarization observables, i.e. to effects like those generated by
a_0-f_0 mixing. An experimental determination of these observables for the
reaction pp\to d\pi^+\eta would provide concrete information on the magnitude
of those nonresonant contributions to \pi\eta production. We discuss also the
possibility of extracting information about a_0-f_0 mixing from the reaction pn
\to d\pi^0\eta with polarized proton beam.Comment: 14 pages, 3 figure
Proposed Search for Mixing in Polarization Phenomena
The and meson mass difference induces the mixing of the
and resonances, the amplitude of which, between the
and thresholds, is large in magnitude, of the order of , and possesses the
phase sharply varying by about 90. We suggest performing the polarized
target experiments on the reaction at high energy in
which the fact of the existence of mixing can be
unambiguously and very easily established through the presence of a strong jump
in the azimuthal asymmetry of the wave production cross section
near the thresholds. The presented estimates of the polarization
effect to be expected in experiment are to a great extent model independent.Comment: RevTeX, 9 pages, 1 figure. A number of typographical and grammatical
errors correcte
Kink interactions in
There are classes of kink solutions in . We show how
interactions between various kinks depend on the classes of individual kinks as
well as on their orientations with respect to each other in the internal space.
In particular, we find that the attractive or repulsive nature of the
interaction depends on the trace of the product of charges of the two kinks. We
calculate the interaction potential for all combinations of kinks and antikinks
in and study their collisions. The outcome of kink-antikink
collisions, as expected from previous studies, is sensitive to their initial
relative velocity. We find that heavier kinks tend to break up into lighter
ones, while interactions between the lightest kinks and antikinks in this model
can be repulsive as well as attractive.Comment: 11 pages, 9 figures. Two insignificant sign errors corrected in the
revised versio
Prevalence of symptoms, ever having received a diagnosis and treatment of depression and anxiety, and associations with health service use amongst the general population in two Russian cities
BACKGROUND: Little is known about the burden of common mental disorders in Russia despite high levels of suicide and alcohol-related mortality. Here we investigated levels of symptoms, self-reports of ever having received a diagnosis and treatment of anxiety and depression in two Russian cities. METHODS: The study population was men and women aged 35-69 years old participating in cross-sectional population-based studies in the cities of Arkhangelsk and Novosibirsk (2015-18). Participants completed an interview which included the PHQ-9 and GAD-7 scales, questions on whether participants had ever received a diagnosis of depression or anxiety, and health service use in the past year. Participants also reported current medication use and medications were coded in line with the WHO anatomical therapeutic classification (ATC). Depression was defined as PHQ-9 ≥ 10 and Anxiety as GAD-7 ≥ 10. RESULTS: Age-standardised prevalence of PHQ-9 ≥ 10 was 10.7% in women and 5.4% in men (GAD-7 ≥ 10 6.2% in women; 3.0% in men). Among those with PHQ-9 ≥ 10 17% reported ever having been diagnosed with depression (equivalent finding for anxiety 29%). Only 1.5% of those with PHQ-9 ≥ 10 reported using anti-depressants and 0.6% of those with GAD-7 ≥ 10 reported using anxiolytics. No men with PHQ-9 ≥ 10 and/or GAD-7 ≥ 10 reported use of anti-depressants or anxiolytics. Use of health services increased with increasing severity of both depression and anxiety. CONCLUSION: There was a large gap between symptoms and reporting of past diagnosis and treatment of common mental disorders in two Russian cities. Interventions aimed at improving mental health literacy and reducing stigma could be of benefit in closing this substantial treatment gap
THE INTERPLAY OF THE K+K- ATOM AND THE f_0(975) RESONANCE
We predict that production of the K+K- atom in pd-3^HeX and similar reactions
exhibits a drastic missing mass spectrum due to the interplay with f_0(975)
resonance. We point out that high precision studies of the K+K- atom may shed a
new light on the nature of f_0(975).Comment: 13 page
Electron affinity of Li: A state-selective measurement
We have investigated the threshold of photodetachment of Li^- leading to the
formation of the residual Li atom in the state. The excited residual
atom was selectively photoionized via an intermediate Rydberg state and the
resulting Li^+ ion was detected. A collinear laser-ion beam geometry enabled
both high resolution and sensitivity to be attained. We have demonstrated the
potential of this state selective photodetachment spectroscopic method by
improving the accuracy of Li electron affinity measurements an order of
magnitude. From a fit to the Wigner law in the threshold region, we obtained a
Li electron affinity of 0.618 049(20) eV.Comment: 5 pages,6 figures,22 reference
Spectral and localization properties of the Dirichlet wave guide with two concentric Neumann discs
Bound states of the Hamiltonian describing a quantum particle living on three
dimensional straight strip of width are investigated. We impose the Neumann
boundary condition on the two concentric windows of the radii and
located on the opposite walls and the Dirichlet boundary condition on the
remaining part of the boundary of the strip. We prove that such a system
exhibits discrete eigenvalues below the essential spectrum for any .
When and tend to the infinity, the asymptotic of the eigenvalue is
derived. A comparative analysis with the one-window case reveals that due to
the additional possibility of the regulating energy spectrum the anticrossing
structure builds up as a function of the inner radius with its sharpness
increasing for the larger outer radius. Mathematical and physical
interpretation of the obtained results is presented; namely, it is derived that
the anticrossings are accompanied by the drastic changes of the wave function
localization. Parallels are drawn to the other structures exhibiting similar
phenomena; in particular, it is proved that, contrary to the two-dimensional
geometry, at the critical Neumann radii true bound states exist.Comment: 25 pages, 7 figure
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