427 research outputs found
Three-body decays: structure, decay mechanism and fragment properties
We discuss the three-body decay mechanisms of many-body resonances. R-matrix
sequential description is compared with full Faddeev computation. The role of
the angular momentum and boson symmetries is also studied. As an illustration
we show the computed -particle energy distribution after the decay of
12C(1^+) resonance at 12.7 MeV.Comment: 4 pages, 3 figures. Proceedings of the workshop "Critical Stability
of Few-Body Quantum Systems" 200
Neutron scattering and molecular correlations in a supercooled liquid
We show that the intermediate scattering function for neutron
scattering (ns) can be expanded naturely with respect to a set of molecular
correlation functions that give a complete description of the translational and
orientational two-point correlations in the liquid. The general properties of
this expansion are discussed with special focus on the -dependence and hints
for a (partial) determination of the molecular correlation functions from
neutron scattering results are given. The resulting representation of the
static structure factor is studied in detail for a model system using
data from a molecular dynamics simulation of a supercooled liquid of rigid
diatomic molecules. The comparison between the exact result for and
different approximations that result from a truncation of the series
representation demonstrates its good convergence for the given model system. On
the other hand it shows explicitly that the coupling between translational
(TDOF) and orientational degrees of freedom (ODOF) of each molecule and
rotational motion of different molecules can not be neglected in the
supercooled regime.Further we report the existence of a prepeak in the
ns-static structure factor of the examined fragile glassformer, demonstrating
that prepeaks can occur even in the most simple molecular liquids. Besides
examining the dependence of the prepeak on the scattering length and the
temperature we use the expansion of into molecular correlation
functions to point out intermediate range orientational order as its principle
origin.Comment: 13 pages, 7 figure
Comparison of Isoscalar Vector Meson Production Cross Sections in Proton-Proton Collisions
The reaction was investigated with the TOF
spectrometer, which is an external experiment at the accelerator COSY
(Forschungszentrum J\"ulich, Germany). Total as well as differential cross
sections were determined at an excess energy of (). Using the total cross section of for the
reaction determined here and existing data for the reaction
, the ratio
turns out to be
significantly larger than expected by the Okubo-Zweig-Iizuka (OZI) rule. The
uncertainty of this ratio is considerably smaller than in previous
determinations. The differential distributions show that the
production is still dominated by S-wave production at this excess energy,
however higher partial waves clearly contribute. A comparison of the measured
angular distributions for production to published distributions for
production at shows that the data are consistent with an
identical production mechanism for both vector mesons
Strong rescattering in K-> 3pi decays and low-energy meson dynamics
We present a consistent analysis of final state interactions in
decays in the framework of Chiral Perturbation Theory.
The result is that the kinematical dependence of the rescattering phases cannot
be neglected. The possibility of extracting the phase shifts from future
interference experiments is also analyzed.Comment: 14 pages in RevTex, 3 figures in postscrip
Nuclear structure corrections in the energy spectra of electronic and muonic deuterium
The one-loop nuclear structure corrections of order (Z alpha)^5 to the Lamb
shift and hyperfine splitting of the deuterium are calculated. The contribution
of the deuteron structure effects to the isotope shift (ep)-(ed), (mu p)-(mu d)
in the interval (1S - 2S) is obtained on the basis of modern experimental data
on the deuteron electromagnetic form factors. The comparison with the similar
contributions to the Lamb shift for electronic and muonic hydrogen shows, that
the relative contribution due to the nucleus structure increases when passing
from the hydrogen to the deuterium.Comment: Talk presented at the Conference "Physics of Fundamental
Interactions" of the Nuclear Physics Section of the Physics Department of
RAS, ITEP, Moscow, 2-6 December, 2002; 8 pages, REVTE
Energy-Charge Correlation in the Decay of and of Tagged Neutral Kaons
We relate the asymmetries in the charged pions energy in the decay into
of and of the tagged neutral kaons. The former
asymmetry is a given combination of , , and
. Moreover, the non-violating CP asymmetry allows a test for the
PT predictions within the Zel'dovich approach for the final state
interaction.Comment: 15 A4-pages LaTeX + 2 figures (available in hard copies from the
authors upon request to [email protected]), preprint DSF-93/52, SUHEP-58
Muonic hydrogen ground state hyperfine splitting
Corrections of orders alpha^5, alpha^6 are calculated in the hyperfine
splitting of the muonic hydrogen ground state. The nuclear structure effects
are taken into account in the one- and two-loop Feynman amplitudes by means of
the proton electromagnetic form factors. The modification of the hyperfine
splitting part of the Breit potential due to the electron vacuum polarization
is considered. Total numerical value of the 1S state hyperfine splitting
182.638 meV in the (mu p) can play the role of proper estimation for the
corresponding experiment with the accuracy 30 ppm.Comment: 18 pages, Talk presented at the 11th Lomonosov Conference on
Elementary Particle Physics, Moscow State University, August 200
Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen
While measurements of the hyperfine structure of hydrogen-like atoms are
traditionally regarded as test of bound-state QED, we assume that theoretical
QED predictions are accurate and discuss the information about the
electromagnetic structure of protons that could be extracted from the
experimental values of the ground state hyperfine splitting in hydrogen and
muonic hydrogen. Using recent theoretical results on the proton polarizability
effects and the experimental hydrogen hyperfine splitting we obtain for the
Zemach radius of the proton the value 1.040(16) fm. We compare it to the
various theoretical estimates the uncertainty of which is shown to be larger
that 0.016 fm. This point of view gives quite convincing arguments in support
of projects to measure the hyperfine splitting of muonic hydrogen.Comment: Submitted to Phys. Rev.
Higher-Order Nuclear-Polarizability Corrections in Atomic Hydrogen
Nuclear-polarizability corrections that go beyond unretarded-dipole
approximation are calculated analytically for hydrogenic (atomic) S-states.
These retardation corrections are evaluated numerically for deuterium and
contribute -0.68 kHz, for a total polarization correction of 18.58(7) kHz. Our
results are in agreement with one previous numerical calculation, and the
retardation corrections completely account for the difference between two
previous calculations. The uncertainty in the deuterium polarizability
correction is substantially reduced. At the level of 0.01 kHz for deuterium,
only three primary nuclear observables contribute: the electric polarizability,
, the paramagnetic susceptibility, , and the third Zemach
moment, . Cartesian multipole decomposition of the virtual
Compton amplitude and its concomitant gauge sum rules are used in the analysis.Comment: 26 pages, latex, 1 figure -- Submitted to Phys. Rev. C -- epsfig.sty
require
Theory of muonic hydrogen - muonic deuterium isotope shift
We calculate the corrections of orders alpha^3, alpha^4 and alpha^5 to the
Lamb shift of the 1S and 2S energy levels of muonic hydrogen (mu p) and muonic
deuterium (mu d). The nuclear structure effects are taken into account in terms
of the proton r_p and deuteron r_d charge radii for the one-photon interaction
and by means of the proton and deuteron electromagnetic form factors in the
case of one-loop amplitudes. The obtained numerical value of the isotope shift
(mu d) - (mu p) for the splitting (1S-2S) 101003.3495 meV can be considered as
a reliable estimation for corresponding experiment with the accuracy 10^{-6}.
The fine structure interval E(1S)-8E(2S) in muonic hydrogen and muonic
deuterium are calculated.Comment: 22 pages, 7 figure
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