81 research outputs found
Form Factors of Composite Systems by Generalized Wigner-Eckart Theorem for Poincar\'e group
The relativistic approach to electroweak properties of two-particle composite
systems developed previously is generalized here to the case of nonzero spin.
This approach is based on the instant form of relativistic Hamiltonian
dynamics. A special mathematical technique is used for the parametrization of
matrix elements of electroweak current operators in terms of form factors. The
parametrization is a realization of the generalized Wigner--Eckart theorem on
the Poincar\'e group, form factors are corresponding reduced matrix elements
and they have the sense of distributions (generalized functions). The
electroweak current matrix element satisfies the relativistic covariance
conditions and in the case of electromagnetic current it also automatically
satisfies the conservation law.Comment: Submitted to Theor. Math. Phy
Asymptotic estimation of some multiple integrals and the electromagnetic deuteron form factors at high momentum transfer
A theorem about asymptotic estimation of multiple integral of a special type
is proved for the case when the integrand peaks at the integration domain
bound, but not at a point of extremum. Using this theorem the asymptotic
expansion of the electromagnetic deuteron form factors at high momentum
transfers is obtained in the framework of two-nucleon model in both
nonrelativistic and relativistic impulse approximations. It is found that
relativistic effects slow down the decrease of deuteron form factors and result
in agreement between the relativistic asymptotics and experimental data at high
momentum transfers.Comment: 16 pages, 1 figur
Pointlike constituent quarks and scattering equivalences
In this paper scattering equivalences are used to simplify current operators
in constituent quark models. The simplicity of the method is illustrated by
applying it to a relativistic constituent quark model that fits the meson mass
spectrum. This model requires a non-trivial constituent quark current operator
to fit the pion form factor data. A model with a different confining
interaction, that has the identical spectrum and can reproduce the measured
pion form factor using only point-like constituent quark impulse currents is
constructed. Both the original and transformed models are relativistic
direct-interaction models with a light-front kinematic subgroup.Comment: 12 pages, 6 figures, corrected caption on fig
Lamb shift in muonic deuterium atom
We present new investigation of the Lamb shift (2P_{1/2}-2S_{1/2}) in muonic
deuterium (mu d) atom using the three-dimensional quasipotential method in
quantum electrodynamics. The vacuum polarization, nuclear structure and recoil
effects are calculated with the account of contributions of orders alpha^3,
alpha^4, alpha^5 and alpha^6. The results are compared with earlier performed
calculations. The obtained numerical value of the Lamb shift 202.4139 meV can
be considered as a reliable estimate for the comparison with forthcoming
experimental data.Comment: 24 pages, 11 figures. arXiv admin note: text overlap with
arXiv:hep-ph/061229
On the reliability of the theoretical internal conversion coefficients
Possible sources of uncertainties in the calculations of the internal
conversion coefficients are studied. The uncertainties induced by them are
estimated.Comment: 16 pages (including 3 figures inserted by 'epsfig' macro
Nonlinear collective nuclear motion
For each real number a Lie algebra of nonlinear vector fields on
three dimensional Euclidean space is reported. Although each algebra is
mathematically isomorphic to , only the vector
fields correspond to the usual generators of the general linear group. The
vector fields integrate to a nonstandard action of the general
linear group; the case integrates to a local Lie semigroup. For
each , a family of surfaces is identified that is invariant with
respect to the group or semigroup action. For positive the surfaces
describe fissioning nuclei with a neck, while negative surfaces
correspond to exotic bubble nuclei. Collective models for neck and bubble
nuclei are given by irreducible unitary representations of a fifteen
dimensional semidirect sum spectrum generating algebra spanned by its
nonlinear subalgebra plus an abelian nonlinear inertia tensor
subalgebra.Comment: 13 pages plus two figures(available by fax from authors by request
Ground State Hyperfine Structure of Muonic Helium Atom
On the basis of the perturbation theory in the fine structure constant
and the ratio of the electron to muon masses we calculate one-loop
vacuum polarization and electron vertex corrections and the nuclear structure
corrections to the hyperfine splitting of the ground state of muonic helium
atom . We obtain total result for the ground state hyperfine
splitting MHz which improves the previous
calculation of Lakdawala and Mohr due to the account of new corrections. The
remaining difference between the theoretical result and experimental value of
the hyperfine splitting equal to 0.522 MHz lies in the range of theoretical
error and requires the subsequent investigation of higher order corrections.Comment: Talk presented at the scientific session-conference of Nuclear
Physics Department RAS "Physics of fundamental interactions", 25-30 November
2007, ITEP, Moscow, 18 pages, 5 figure
Hyperfine structure of the ground state muonic He-3 atom
On the basis of the perturbation theory in the fine structure constant
and the ratio of the electron to muon masses we calculate one-loop
vacuum polarization and electron vertex corrections and the nuclear structure
corrections to the hyperfine splitting of the ground state of muonic helium
atom . We obtain total result for the ground state hyperfine
splitting MHz which improves the previous
calculation of Lakdawala and Mohr due to the account of new corrections of
orders and . The remaining difference between our
theoretical result and experimental value of the hyperfine splitting lies in
the range of theoretical and experimental errors and requires the subsequent
investigation of higher order corrections.Comment: Talk on poster section of XXIV spectroscopy congress, 28 February-5
March 2010, Moscow-Troitsk, Russia, 21 pages, LaTeX, 8 figure
Elastic Charge Form Factors of and K Mesons
The elastic charge form factors of the charged and mesons are
calculated in modified impulse approximation using instant form of relativistic
Hamiltonian dynamics. Our approach gives pion and kaon electromagnetic form
factors in the large range of momentum transfer. The results are in good
agreement with the available data. Relativistic effects are large at all values
of momentum transfers. The pion and kaon form factors at large depend
strongly on the choice of model. The experiments on pion form factor at large
momentum transfer planned at CEBAF will choose between such models. In the case
of kaon such a choosing may be performed only if supplemented by accurate
measurements of kaon MSR.Comment: 9 pages, LaTeX, 2 uuencoded PostScript figure
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