1,389 research outputs found
The B_{s0} meson and the B_{s0}B K coupling from QCD sum rules
We evaluate the mass of the scalar meson and the coupling constant
in the vertex in the framework of QCD sum rules. We consider the
as a tetraquark state to evaluate its mass. We get m_{B_s0}=(6.04\pm
0.08) \GeV, which is bigger than predictions supposing it as a
state or a bound state with . To evaluate the coupling we use the three point correlation functions of the vertex,
considering as a normal state. The obtained coupling
constant is: g_{B_{s0} B K} =(16.3 \pm 3.2) \GeV. This number is in agreement
with light-cone QCD sum rules calculation. We have also compared the decay
width of the \BS\to BK process considering the \BS to be a state
and a molecular state. The width obtained for the molecular state is
twice as big as the width obtained for the state. Therefore, we
conclude that with the knowledge of the mass and the decay width of the \BS
meson, one can discriminate between the different theoretical proposals for its
structure.Comment: revised version to appear in Phys. Rev.
Deconfinement Through Chiral Transition In 2 Flavour QCD
We propose that in QCD with dynamical quarks, colour deconfinement occurs
when an external field induced by the chiral condensate strongly aligns the
Polyakov loop. This effect sets in at the chiral symmetry restoration
temperature and thus makes deconfinement and chiral symmetry
restoration coincide. The predicted singular behavior of Polyakov loop
susceptibilities at is shown to be supported by finite temperature
lattice calculations.Comment: Talk given at Lattice 2000 (Finite Temperature), 4 pages, 6
EPS-figure
Frustration and glassiness in spin models with cavity-mediated interactions
We show that the effective spin-spin interaction between three-level atoms
confined in a multimode optical cavity is long-ranged and sign-changing, like
the RKKY interaction; therefore, ensembles of such atoms subject to frozen-in
positional randomness can realize spin systems having disordered and frustrated
interactions. We argue that, whenever the atoms couple to sufficiently many
cavity modes, the cavity-mediated interactions give rise to a spin glass. In
addition, we show that the quantum dynamics of cavity-confined spin systems is
that of a Bose-Hubbard model with strongly disordered hopping but no on-site
disorder; this model exhibits a random-singlet glass phase, absent in
conventional optical-lattice realizations. We briefly discuss experimental
signatures of the realizable phases.Comment: 5 pages, 2 figure
Topologically decoherence-protected qubits with trapped ions
We show that trapped ions can be used to simulate a highly symmetrical
Hamiltonian with eingenstates naturally protected against local sources of
decoherence. This Hamiltonian involves long range coupling between particles
and provides a more efficient protection than nearest neighbor models discussed
in previous works. Our results open the perspective of experimentally realizing
in controlled atomic systems, complex entangled states with decoherence times
up to nine orders of magnitude longer than isolated quantum systems.Comment: 4 page
QCD sum rule approach for the light scalar mesons as four-quark states
We study the two point-function for the scalar mesons and as diquak-antidiquark states. We also study the decays
of these mesons into , and . We found that the
couplings are consistent with existing experimental data, pointing in favor of
the four-quark structure for the light scalar mesons.Comment: 6 pages, 4 figure
On the Spin Gap Phase of Strongly-Correlated Electrons
We discuss the possible existence of a spin-gap phase in the low-doping
regime of strongly-correlated two-dimensional electrons within the gauge field
description of the t-J model. The spin-gap phase was recently shown by Ubbens
and Lee to be destroyed by gauge field quantum fluctuations for a single-layer
2D system in the absence of disorder and for a full gap. We show that the same
conclusion applies both in the dirty limit and for the case of a gapless spinon
condensate.Comment: 7 pages, uuencoded Postscript, including 1 figur
Drift of a polymer chain in disordered media
We consider the drift of a polymer chain in a disordered medium, which is
caused by a constant force applied to the one end of the polymer, under
neglecting the thermal fluctuations. In the lowest order of the perturbation
theory we have computed the transversal fluctuations of the centre of mass of
the polymer, the transversal and the longitudinal size of the polymer, and the
average velocity of the polymer. The corrections to the quantities under
consideration, which are due to the interplay between the motion and the
quenched forces, are controlled by the driving force and the degree of
polymerization. The transversal fluctuations of the Brownian particle and of
the centre of mass of the polymer are obtained to be diffusive. The transversal
fluctuations studied in the present Letter may also be of relevance for the
related problem of the drift of a directed polymer in disordered media and its
applications.Comment: 11 pages, RevTex, Accepted for publication in Europhysics Letter
Resonant CP Violation in Higgs Radiation at e^+e^- Linear Collider
We study resonant CP violation in the Higgsstrahlung process e^+e^- ->
H_{1,2,3} (Z -> e^+e^-, \mu^+\mu^-) and subsequent decays H_{1,2,3} -> b
\bar{b}, \tau^-\tau^+, in the MSSM with Higgs-sector CP violation induced by
radiative corrections. At a high-energy e^+e^- linear collider, the recoil-mass
method enables one to determine the invariant mass of a fermion pair produced
by Higgs decays with a precision as good as 1 GeV. Assuming an integrated
luminosity of 100/fb, we show that the production lineshape of a coupled system
of neutral Higgs bosons decaying into b\bar{b} quarks is sensitive to the
CP-violating parameters. When the Higgs bosons decay into \tau^-\tau^+, two CP
asymmetries can be defined using the longitudinal and transverse polarizations
of the tau leptons. Taking into account the constraints from electric dipole
moments, we find that these CP asymmetries can be as large as 80 %, in a
tri-mixing scenario where all three neutral Higgs states of the MSSM are nearly
degenerate and mix significantly.Comment: 22 pages, 8 figures, to appear in Phys. Rev.
Axial anomaly: the modern status
The modern status of the problem of axial anomaly in QED and QCD is reviewed.
Two methods of the derivation of the axial anomaly are presented: 1) by
splitting of coordinates in the expression for the axial current and 2) by
calculation of triangle diagrams, where the anomaly arises from the surface
terms in momentum space. It is demonstrated, that the equivalent formulation of
the anomaly can be given, as a sum rule for the structure function in
dispersion representation of three point function of AVV interaction. It is
argued, that such integral representation of the anomaly has some advantages in
the case of description of the anomaly by contribution of hadronic states in
QCD. The validity of the t'Hooft consistency condition is discussed. Few
examples of the physical application of the axial anomaly are given.Comment: 17 pages, 3 figures, to be published in International Journal of
Modern Physics A, few minor correction were done, two references were adde
Analysis of and with QCD sum rules
In this article, we calculate the masses and the pole residues of the
heavy baryons and with the QCD
sum rules. The numerical values (or
) and (or ) are in good agreement
with the experimental data.Comment: 18 pages, 18 figures, slight revisio
- …