331 research outputs found
Microscopic derivation of the pion coupling to heavy-light mesons
The Goldberger--Treiman relation for heavy--light systems is derived in the
context of a quark model. As a paradigmatic example, the case of is studied in detail. The fundamental role played by the pion
two-component wave function, in the context of the Salpeter equation, is
emphasized.Comment: 6 pages, 2 figures, version to appear in Phys. Rev.
Parity doublers in chiral potential quark models
The effect of spontaneous breaking of chiral symmetry over the spectrum of
highly excited hadrons is addressed in the framework of a microscopic chiral
potential quark model (Generalised Nambu-Jona-Lasinio model) with a vectorial
instantaneous quark kernel of a generic form. A heavy-light quark-antiquark
bound system is considered, as an example, and the Lorentz nature of the
effective light-quark potential is identified to be a pure Lorentz-scalar, for
low-lying states in the spectrum, and to become a pure spatial Lorentz vector,
for highly excited states. Consequently, the splitting between the partners in
chiral doublets is demonstrated to decrease fast in the upper part of the
spectrum so that neighboring states of an opposite parity become almost
degenerate. A detailed microscopic picture of such a "chiral symmetry
restoration" in the spectrum of highly excited hadrons is drawn and the
corresponding scale of restoration is estimated.Comment: LaTeX2e, 4 pages, uses aipproc class, Talk given by A.Nefediev at the
conference "Quark Confinement and the Hadron Spectrum VII", 2-7 September
2006, Acores, Portugal, to appear in Proceeding
Confinement and parity doubling in heavy-light mesons
In this paper, we study the chiral symmetry restoration in the hadronic
spectrum in the framework of generalised Nambu-Jona-Lasinio quark models with
instantaneous confining quark kernels. We investigate a heavy-light quarkonium
and derive its bound-state equation in the form of a Schroedingerlike equation
and, after the exact inverse Foldy-Wouthuysen transformation, in the form of a
Diraclike quation. We discuss the Lorentz nature of confinement for such a
system and demonstrate explicitly the effective chiral symmetry restoration for
highly excited states in the mesonic spectrum. We give an estimate for the
scale of this restoration.Comment: RevTeX4, 21 pages, 6 Postscript figures, uses epsfig.sty, to appear
in Phys.Rev.
Insights on scalar mesons from their radiative decays
We estimate the rates for radiative transitions of the lightest scalar mesons
f_0(980) and a_0(980) to the vector mesons rho and omega. We argue that
measurements of the radiative decays of those scalar mesons can provide
important new information on their structure.Comment: 20 pages, 5 figures; appendix added, to be published in Phys. Rev.
Chiral symmetry restoration in excited hadrons, quantum fluctuations, and quasiclassics
In this paper, we discuss the transition to the semiclassical regime in
excited hadrons, and consequently, the restoration of chiral symmetry for these
states. We use a generalised Nambu-Jona-Lasinio model with the interaction
between quarks in the form of the instantaneous Lorentz-vector confining
potential. This model is known to provide spontaneous breaking of chiral
symmetry in the vacuum via the standard selfenergy loops for valence quarks. It
has been shown recently that the effective single-quark potential is of the
Lorentz-scalar nature, for the low-lying hadrons, while, for the high-lying
states, it becomes a pure Lorentz vector and hence the model exhibits the
restoration of chiral symmetry. We demonstrate explicitly the quantum nature of
chiral symmetry breaking, the absence of chiral symmetry breaking in the
classical limit as well as the transition to the semiclassical regime for
excited states, where the effect of chiral symmetry breaking becomes only a
small correction to the classical contributions.Comment: RevTeX4, 20 pages, 4 Postscript figures, uses epsfig.sty, typos
correcte
Reconciling the X(3872) with the near-threshold enhancement in the D^0\bar{D}^{*0} final state
We investigate the enhancement in the D^0\bar{D}^0\pi^0 final state with the
mass M=3875.2\pm 0.7^{+0.3}_{-1.6}\pm 0.8 MeV found recently by the Belle
Collaboration in the B\to K D^0\bar{D}^0\pi^0 decay and test the possibility
that this is yet another manifestation of the well-established resonance
X(3872). We perform a combined Flatte analysis of the data for the
D^0\bar{D}^0\pi^0 mode, and for the \pi^+\pi^- J/\psi mode of the X(3872). Only
if the X(3872) is a virtual state in the D^0\bar{D}^{*0} channel, the data on
the new enhancement comply with those on the X(3872). In our fits, the mass
distribution in the D^0\bar{D}^{*0} mode exhibits a peak at 2-3 MeV above the
D^0\bar{D}^{*0} threshold, with a distinctive non-Breit-Wigner shape.Comment: RevTeX4, 17 pages, some references updated and corrected, version
published in Phys. Rev.
Subjective well-being as a result of the realization of projects of the elderly's involvement into the social life
The paper analyses the subjective well-being and Successful Aging concepts. Unbiased analysis of such conditions is rather problematic by virtue of such facts as time-specific emotional state, climate of residence, culture, current developments and etc. The study concludes that there is no correlation between subjective well-being and economic health or objective socioeconomic factors. The subjective well-being is influenced in most cases by subjective factors: one’s health status satisfaction, financial situation, the level of self-reliance or independence, family interaction and other human relations. But the main factor is the recognition of their mission by the elderly which places the faith and hope in their future modeling. Two categories of the elderly are sorted out for the study: the involved and noninvolved in social activity. The research concludes that any formal or informal activity of the elderly is one of the main factors of the successful aging. Pursuit of activities is uncharacteristic for noninvolved in social activity elderly people. The paper analyses the projects organized and implemented by not only the elderly people themselves but also state and social structures.. Conducted analysis indicates that the level of subjective well-being of the two categories of the elderly is increasing as the result of these projects realization
Three-body dynamics for the X(3872)
We investigate the role played by the three-body dynamics on
the near-threshold resonance X(3872) charmonium state, which is assumed to be
formed by nonperturbative dynamics. It is demonstrated that, as
compared to the naive static-pions approximation, the imaginary parts that
originate from the inclusion of dynamical pions reduce substantially the width
from the intermediate state. In particular, for a resonance
peaked at 0.5 MeV below the threshold, this contribution to
the width is reduced by about a factor of 2, and the effect of the pion
dynamics on the width grows as long as the resonance is shifted towards the
threshold. Although the physical width of the is
dominated by inelastic channels, our finding should still be of importance for
the line shapes in the channel below threshold.
For example, in the scattering length approximation, the imaginary part of the
scattering length includes effects of all the pion dynamics and does not only
stem from the width. Meanwhile, we find that another important quantity
for the phenomenology, the residue at the pole, is weakly sensitive to
dynamical pions. In particular, we find that the binding energy dependence of
this quantity from the full calculation is close to that found from a model
with pointlike interactions only, consistent with earlier claims.
Coupled-channel effects (inclusion of the charged channel) turn
out to have a moderate impact on the results.Comment: 34 pages, 6 figures, version to appear in Phys.Rev.
- …