1,215 research outputs found
Towards a Relativistic Description of Exotic Meson Decays
This work analyses hadronic decays of exotic mesons, with a focus on the
lightest one, the , in a fully relativistic formalism,
and makes comparisons with non-relativistic results. We also discuss Coulomb
gauge decays of normal mesons that proceed through their hybrid components. The
relativistic spin wave functions of mesons and hybrids are constructed based on
unitary representations of the Lorentz group. The radial wave functions are
obtained from phenomenological considerations of the mass operator. Fully
relativistic results (with Wigner rotations) differ significantly from
non-relativistic ones. We also find that the decay channels are favored, in agreement with results obtained using
other models.Comment: 14 pages, 7 figure
Asymptotic stability of the Cauchy and Jensen functional equations
The aim of this note is to investigate the asymptotic stability behaviour of
the Cauchy and Jensen functional equations. Our main results show that if these
equations hold for large arguments with small error, then they are also valid
everywhere with a new error term which is a constant multiple of the original
error term. As consequences, we also obtain results of hyperstability character
for these two functional equations
Acceleration of the universe in the Einstein frame of a metric-affine f(R) gravity
We show that inflation and current cosmic acceleration can be generated by a
metric-affine f(R) gravity formulated in the Einstein conformal frame, if the
gravitational Lagrangian L(R) contains both positive and negative powers of the
curvature scalar R. In this frame, we give the equations for the expansion of
the homogeneous and isotropic matter-dominated universe in the case
L(R)=R+{R^3}/{\beta^2}-{\alpha^2}/{3R}, where \alpha and \beta are constants.
We also show that gravitational effects of matter in such a universe at very
late stages of its expansion are weakened by a factor that tends to 3/4, and
the energy density of matter \epsilon scales the same way as in the \Lambda-CDM
model only when \kappa*\epsilon<<\alpha.Comment: 12 pages; published versio
The cosmic snap parameter in f(R) gravity
We derive the expression for the snap parameter in f(R) gravity. We use the
Palatini variational principle to obtain the field equations and regard the
Einstein conformal frame as physical. We predict the present-day value of the
snap parameter for the particular case f(R)=R-const/R, which is the simplest
f(R) model explaining the current acceleration of the universe.Comment: 9 pages; published versio
Four-fermion interaction from torsion as dark energy
The observed small, positive cosmological constant may originate from a
four-fermion interaction generated by the spin-torsion coupling in the
Einstein-Cartan-Sciama-Kibble gravity if the fermions are condensing. In
particular, such a condensation occurs for quark fields during the
quark-gluon/hadron phase transition in the early Universe. We study how the
torsion-induced four-fermion interaction is affected by adding two terms to the
Dirac Lagrangian density: the parity-violating pseudoscalar density dual to the
curvature tensor and a spinor-bilinear scalar density which measures the
nonminimal coupling of fermions to torsion.Comment: 6 pages; published versio
Gravitational Field Equations and Theory of Dark Matter and Dark Energy
The main objective of this article is to derive a new set of gravitational
field equations and to establish a new unified theory for dark energy and dark
matter. The new gravitational field equations with scalar potential
are derived using the Einstein-Hilbert functional, and the scalar potential
is a natural outcome of the divergence-free constraint of the
variational elements. Gravitation is now described by the Riemannian metric
, the scalar potential and their interactions, unified by the
new gravitational field equations. Associated with the scalar potential
is the scalar potential energy density , which represents a new type of
energy caused by the non-uniform distribution of matter in the universe. The
negative part of this potential energy density produces attraction, and the
positive part produces repelling force. This potential energy density is
conserved with mean zero: . The sum of this new potential
energy density and the coupling energy between the
energy-momentum tensor and the scalar potential field gives
rise to a new unified theory for dark matter and dark energy: The negative part
of this sum represents the dark matter, which produces attraction, and the
positive part represents the dark energy, which drives the acceleration of
expanding galaxies. In addition, the scalar curvature of space-time obeys
. Furthermore, the new field equations resolve a
few difficulties encountered by the classical Einstein field equations.Comment: Some statements are made more precise and a conclusion section is
adde
On the nonsymmetric purely affine gravity
We review the vacuum purely affine gravity with the nonsymmetric connection
and metric. We also examine dynamical effects of the second Ricci tensor and
covariant second-rank tensors constructed from the torsion tensor in the
gravitational Lagrangian.Comment: 15 pages; published versio
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at √s=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
Measurement of the mass and lifetime of the baryon
A proton-proton collision data sample, corresponding to an integrated
luminosity of 3 fb collected by LHCb at and 8 TeV, is used
to reconstruct , decays. Using the , decay mode for calibration, the lifetime ratio and absolute
lifetime of the baryon are measured to be \begin{align*}
\frac{\tau_{\Omega_b^-}}{\tau_{\Xi_b^-}} &= 1.11\pm0.16\pm0.03, \\
\tau_{\Omega_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the
uncertainties are statistical, systematic and from the calibration mode (for
only). A measurement is also made of the mass difference,
, and the corresponding mass, which
yields \begin{align*} m_{\Omega_b^-}-m_{\Xi_b^-} &= 247.4\pm3.2\pm0.5~{\rm
MeV}/c^2, \\ m_{\Omega_b^-} &= 6045.1\pm3.2\pm 0.5\pm0.6~{\rm MeV}/c^2.
\end{align*} These results are consistent with previous measurements.Comment: 11 pages, 5 figures, All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-008.htm
Constraints on the unitarity triangle angle from Dalitz plot analysis of decays
The first study is presented of CP violation with an amplitude analysis of
the Dalitz plot of decays, with , and . The analysis is based on a data sample corresponding to
of collisions collected with the LHCb detector. No
significant CP violation effect is seen, and constraints are placed on the
angle of the unitarity triangle formed from elements of the
Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated
with the decay are determined for the first time. These
measurements can be used to improve the sensitivity to of existing and
future studies of the decay.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-059.html;
updated to correct figure 9 (numerical results unchanged
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