107 research outputs found
Study of hyperfine structure in simple atoms and precision tests of the bound state QED
We consider the most accurate tests of bound state QED, precision theory of
simple atoms, related to the hyperfine splitting in light hydrogen-like atoms.
We discuss the HFS interval of the 1s state in muonium and positronium and of
the 2s state in hydrogen, deuterium and helium-3 ion. We summarize their QED
theory and pay attention to involved effects of strong interactions. We also
consider recent optical measurements of the 2s HFS interval in hydrogen and
deuterium.Comment: presented at The International Workshop "e+e- collisions from phi to
psi
Recent results from e+ e- --> hadrons
New results on the low energy e+ e- annihilation into hadrons from
Novosibirsk and Beijing are described. Implications of the new measurements for
the evaluation of the hadronic contribution to the muon anomalous magnetic
moment are discussed.Comment: Invited talk at the Seventh International Workshop on Tau Lepton
Physics (TAU02), Santa Cruz, Ca, USA, Sept 2002, 7 pages, 4 figure
DECAY
The decay modes and are considered in the framework of the low energy effective chiral
Lagrangian. The obtained values of the decay widths and keV do not contradict the existing upper limits and seem to be big
enough for the corresponding processes to be observed in future high luminosity
experiments.Comment: 6 pages, LaTeX, without figure. Submitted to Phys. Lett.
Monte-Carlo Generator Photon Jets for the process e+e- -> gamma gamma
Monte-Carlo generator with photon jets radiation in collinear regions for the
process \eegg is described in detail. Radiative corrections in the first order
of are treated exactly. Large leading logarithmic corrections coming
from collinear regions are taken into account in all orders of by
applying the Structure Function approach. Theoretical precision of the cross
section with radiative corrections is estimated to be 0.2%. This process is
considered as an additional tool to measure luminosity in forthcoming
experiments with the CMD-3 detector at the collider VEPP-2000.Comment: 6 pages, 5 figure
Novosibirsk hadronic currents for tau -> 4pi channels of tau decay library TAUOLA
The new parameterization of form factors developed for 4pi channels of the
tau lepton decay and based on Novosibirsk data on e^+e^- -> 4pi has been coded
in a form suitable for the TAUOLA Monte Carlo package. Comparison with results
from TAUOLA using another parameterization, i.e. the CLEO version of 1998 is
also included.Comment: 19 pages, 21 figures, LaTe
High Precision Mass Measurements in and Families Revisited
High precision mass measurements in and families performed
in 1980-1984 at the VEPP-4 collider with OLYA and MD-1 detectors are revisited.
The corrections for the new value of the electron mass are presented. The
effect of the updated radiative corrections has been calculated for the
and mass measurements.Comment: 5 pages, 1 table, submitted to Phys. Lett.
Study of the process e+e- to pi+pi-pi+pi-pi0 with CMD-2 detector
The process e+e- to pi+ pi- pi+ pi- pi0 has been studied in the center of
mass energy range 1280 -- 1380 MeV using 3.0 1/pb of data collected with the
CMD-2 detector in Novosibirsk. Analysis shows that the cross section of the
five pion production is dominated by the contributions of the eta pi+pi- and
omega pi+pi- intermediate states.Comment: 8 pages, 3 figure. Submitted to Phys. Lett.
Measurement of (1020) meson leptonic width with CMD-2 detector at VEPP-2M Collider
The (1020) meson leptonic width has been determined from the combined
analysis of 4 major decay modes of the resonance () studied with the CMD-2 detector at
the VEPP-2M collider. The following value has been obtained:
keV.
The meson parameters in four main decay channels have been also
recalculated: , , , .Comment: 14 pages, 3 figure
Cross section of the reaction below 1 GeV at CMD-2
Using 3.07 of data collected in the energy range 0.60-0.97 GeV by
CMD-2, about 150 events of the process \epm \to \pch have been selected. The
energy dependence of the cross section agrees with the assumption of the
intermediate state which is dominant above 1 GeV. For the first
time \fourpi events are observed at the meson energy. Under the
assumption that all these events come from the meson decay, the value of
the cross section at the meson peak corresponds to the following decay
width:
\Gamma(\rho^0 \to \fourpi) = (2.8 \pm 1.4 \pm 0.5) {keV} or to the branching
ratio
B(\rho^0 \to \fourpi) = (1.8 \pm 0.9 \pm 0.3) \cdot 10 ^{-5}.Comment: 15 pages, 5 figure
Study of KS KL Coupled Decays and KL -Be Interactions with the CMD-2 Detector at VEPP-2M Collider
The integrated luminosity about 4000 inverse nanobarn of around phi meson
mass ( 5 millions of phi mesons) has been collected with the CMD-2 detector at
the VEPP-2M collider. A latest analysis of the KS KL coupled decays based on 30
% of available data is presented in this paper.
The KS KL pairs from phi meson decays were reconstructed in the drift chamber
when both kaons decayed into two charged particles. From a sample of 1423
coupled decays a selection of candidates to the CP violating KL into pi+ pi-
decay was performed. CP violating decays were not identified because of the
domination of events with a KL regenerating at the Be beam pipe into KS and a
background from KL semileptonic decays.
The regeneration cross section of 110 MeV/c KL mesons was found to be 53 +-
17 mb in agreement with theoretical expectations. The angular distribution of
KS mesons after regeneration and the total cross section of KL for Be have been
measured.Comment: 14 pages, 8 figure
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