2,585 research outputs found
Annihilation Rate of Heavy 0^{++} P-wave Quarkonium in Relativistic Salpeter Method
Two-photon and two-gluon annihilation rates of P-wave scalar charmonium and
bottomonium up to third radial excited states are estimated in the relativistic
Salpeter method. We solved the full Salpeter equation with a well defined
relativistic wave function and calculated the transition amplitude using the
Mandelstam formalism. Our model dependent estimates for the decay widths:
keV,
keV, eV and eV. We also give estimates of total widths by the two-gluon
decay rates: MeV,
MeV, MeV and
MeV.Comment: 8 pages, 1 figure, 4 table
NLO QCD Corrections to -to-Charmonium Form Factors
The meson to S-wave Charmonia transition form factors are
calculated in next-to-leading order(NLO) accuracy of Quantum
Chromodynamics(QCD). Our results indicate that the higher order corrections to
these form factors are remarkable, and hence are important to the
phenomenological study of the corresponding processes. For the convenience of
comparison and use, the relevant expressions in asymptotic form at the limit of
for the radiative corrections are presented
Real-time visualization of a sparse parametric mixture model for BTF rendering
Bidirectional Texture Functions (BTF) allow high quality visualization of real world materials exhibiting complex appearance and details that can not be faithfully represented using simpler analytical or parametric representations. Accurate representations of such materials require huge amounts of data, hindering real time rendering. BTFs compress the raw original data, constituting a compromise between visual quality and rendering time. This paper presents an implementation of a state of the art BTF representation on the GPU, allowing interactive high fidelity visualization of complex geometric models textured with multiple BTFs. Scalability with respect to the geometric complexity, amount of lights and number of BTFs is also studied.Fundação para a Ciência e Tecnologi
A dynamical model for longitudinal wave functions in light-front holographic QCD
We construct a Schrodinger-like equation for the longitudinal wave function
of a meson in the valence qq-bar sector, based on the 't Hooft model for
large-N two-dimensional QCD, and combine this with the usual transverse
equation from light-front holographic QCD, to obtain a model for mesons with
massive quarks. The computed wave functions are compared with the wave function
ansatz of Brodsky and De Teramond and used to compute decay constants and
parton distribution functions. The basis functions used to solve the
longitudinal equation may be useful for more general calculations of meson
states in QCD.Comment: 12 pages, 2 figures, RevTeX 4.1; expanded discussion, with
calculation details moved to appendice
Epidemiology of a Daphnia-Multiparasite System and Its Implications for the Red Queen
The Red Queen hypothesis can explain the maintenance of host and parasite diversity. However, the Red Queen requires genetic specificity for infection risk (i.e., that infection depends on the exact combination of host and parasite genotypes) and strongly virulent effects of infection on host fitness. A European crustacean (Daphnia magna) - bacterium (Pasteuria ramosa) system typifies such specificity and high virulence. We studied the North American host Daphnia dentifera and its natural parasite Pasteuria ramosa, and also found strong genetic specificity for infection success and high virulence. These results suggest that Pasteuria could promote Red Queen dynamics with D. dentifera populations as well. However, the Red Queen might be undermined in this system by selection from a more common yeast parasite (Metschnikowia bicuspidata). Resistance to the yeast did not correlate with resistance to Pasteuria among host genotypes, suggesting that selection by Metschnikowia should proceed relatively independently of selection by Pasteuria
Lorentz violation and the proper-time method
In this paper, we apply the proper-time method to generate the
Lorentz-violating Chern-Simons terms in the four-dimensional Yang-Mills and
non-linearized gravity theories. It is shown that the coefficient of the
induced Chern-Simons term is finite but regularization dependent.Comment: 11 pages, Revtex
Generalizing the O(N)-field theory to N-colored manifolds of arbitrary internal dimension D
We introduce a geometric generalization of the O(N)-field theory that
describes N-colored membranes with arbitrary dimension D. As the O(N)-model
reduces in the limit N->0 to self-avoiding polymers, the N-colored manifold
model leads to self-avoiding tethered membranes. In the other limit, for inner
dimension D->1, the manifold model reduces to the O(N)-field theory. We analyze
the scaling properties of the model at criticality by a one-loop perturbative
renormalization group analysis around an upper critical line. The freedom to
optimize with respect to the expansion point on this line allows us to obtain
the exponent \nu of standard field theory to much better precision that the
usual 1-loop calculations. Some other field theoretical techniques, such as the
large N limit and Hartree approximation, can also be applied to this model. By
comparison of low and high temperature expansions, we arrive at a conjecture
for the nature of droplets dominating the 3d-Ising model at criticality, which
is satisfied by our numerical results. We can also construct an appropriate
generalization that describes cubic anisotropy, by adding an interaction
between manifolds of the same color. The two parameter space includes a variety
of new phases and fixed points, some with Ising criticality, enabling us to
extract a remarkably precise value of 0.6315 for the exponent \nu in d=3. A
particular limit of the model with cubic anisotropy corresponds to the random
bond Ising problem; unlike the field theory formulation, we find a fixed point
describing this system at 1-loop order.Comment: 57 pages latex, 26 figures included in the tex
The , , and mesons in a double pole QCD Sum Rule
We use the method of double pole QCD sum rule which is basically a fit with
two exponentials of the correlation function, where we can extract the masses
and decay constants of mesons as a function of the Borel mass. We apply this
method to study the mesons: , , and
. We also present predictions for the toponiuns masses
of m(1S)=357 GeV and m(2S)=374 GeV.Comment: 14 pages, 11 figures in Braz J Phys (2016
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