5,101 research outputs found
Effective theory of NN interactions in a separable representation
We consider the effective field theory of the NN system in a separable
representation. The pionic part of the effective potential is included
nonperturbatively and approximated by a separable potential. The use of a
separable representation allows for the explicit solution of the
Lippmann-Schwinger equation and a consistent renormalization procedure. The
phase shifts in the channel are calculated to subleading order.Comment: 7 page
Strong coupling constant from bottomonium fine structure
From a fit to the experimental data on the fine structure, the
two-loop coupling constant is extracted. For the 1P state the fitted value is
at the scale GeV, which corresponds to the QCD constant MeV (n_f = 4) and \alpha_s(\mu_2) = 0.40 \pm 0.02(exp)\pm 0.02(th)\mu_2 = 1.02 \pm 0.2\alpha_s(1.0) \approx 0.40\alpha_s\alpha_s$ are found to be about 15%.Comment: 18 pages LaTe
Disentangling Intertwined Embedded States and Spin Effects in Light-Front Quantization
Naive light-front quantization, carried out by a light-front energy
integration of covariant amplitudes, is not guaranteed to generate the
corresponding Feynman amplitudes. In an explicit example we show that the
nonvalence contribution to the minus-component of the EM current of a meson
with fermion constituents has a persistent end-point singularity. Only after
this term is subtracted, the result is covariant and satisfies current
conservation. If the spin-1/2 constituents are replaced by spin zero ones, the
singularity does not occur and the result is, without any adjustment, identical
to the Feynman amplitude. Numerical estimates of valence and nonvalence
contributions are presented for the cases of fermion and boson constituents.Comment: 17 pages and 9 figure
The leptonic widths of high -resonances in unitary coupled-channel model
The leptonic widths of high -resonances are calculated in a
coupled-channel model with unitary inelasticity, where analytical expressions
for mixing angles between (n+1)\,^3S_1 and n\,^3D_1 states and
probabilities of the component are derived. Since these factors
depend on energy (mass), different values of mixing angles
and ,
, and are obtained. It gives
the leptonic widths ~keV,
~keV in good agreement with
experiment. For the leptonic width
~keV is calculated, while for the missing
resonance we predict ~MeV and
~keV.Comment: 10 pages, 6 references corrected, some new material adde
Pauli-Potential and Green Function Monte-Carlo Method for Many-Fermion Systems
The time evolution of a many-fermion system can be described by a Green's
function corresponding to an effective potential, which takes
anti-symmetrization of the wave function into account, called the
Pauli-potential. We show that this idea can be combined with the Green's
Function Monte Carlo method to accurately simulate a system of many
non-relativistic fermions. The method is illustrated by the example of systems
of several (2-9) fermions in a square well.Comment: 12 pages, LaTeX, 4 figure
The heavy-quark pole masses in the Hamiltonian approach
From the fact that the nonperturbative self-energy contribution
to the heavy meson mass is small: ; MeV \cite{ref.01}, strong restrictions on the pole
masses and are obtained. The analysis of the and the
spectra with the use of relativistic (string) Hamiltonian gives
(2-loop) GeV and (2-loop) GeV which
correspond to the running mass GeV and GeV. The masses
and , which define the heavy quarkonia spin structure, are shown to
be by MeV larger than the pole ones.Comment: 18 pages, no figures, 8 table
Spin filter in deeply virtual Compton scattering amplitudes
Whether the kinematics includes the hard transverse photon momenta or not makes a dramatic difference in computing deeply virtual Compton scattering in terms of the widely used reduced operators that define generalized parton distributions. Our tree-level complete deeply virtual Compton scattering amplitude including the lepton current plays the role of spin filter to analyze such kinematic dependence on the contribution of longitudinally polarized virtual photon as well as the conservation of angular momentum. © 2011 American Physical Society
The interaction above threshold and the radiative decay
Radiative decays of are studied in single-channel approximation
(SCA) and in the coupled-channel (CC) approach, where the decay channels are described with the string breaking mechanism. In SCA the transition
rate ~keV and
large ~keV
are obtained, giving for their ratio the value
. In the
CC approach three factors are shown to be equally important. First, the
admixture of the component in the normalized wave function of
due to the CC effects. Its weight is calculated. Secondly, the use of the multipole function
instead of in the overlap integrals, determining the partial widths.
Thirdly, the choice of the gluon-exchange interaction for , as well as
for other states above threshold. If for the gluon-exchange potential
is taken the same as for low-lying charmonium states, then in the CC approach
~keV is very small,
giving the large ratio .
Arguments are presented why the gluon-exchange interaction may be suppressed
for and in this case ~keV, ~keV, and
are predicted for the minimal value , while for the maximal value we obtained
~keV, ~keV, and , which
agrees with the LHCb data.Comment: 12 pages, no figure
- …