4,614 research outputs found
Two-Loop Heavy-Flavor Contribution to Bhabha Scattering
We evaluate the two-loop QED corrections to the Bhabha scattering cross
section which involve the vacuum polarization by heavy fermions of arbitrary
mass m_f >> m_e. The results are valid for generic values of the Mandelstam
invariants s,t,u >> m_e^2.Comment: 13 pages, 6 figures. Equations in the appendix generalized to the
heavy-quark cas
Jarlskog Invariant of the Neutrino Mapping Matrix
The Jarlskog Invariant of the neutrino mapping matrix is
calculated based on a phenomenological model which relates the smallness of
light lepton masses and (of ) with the smallness of
violation. For small violating phase in the lepton sector,
is proportional to , but and are proportional
to . This leads to . Assuming
, we find
, consistent with the present experimental
data.Comment: 19 page
Final State Interactions in Decays of the Exotic Meson
We analyze the role of final state interactions in decay of the lighest
exotic meson, with \pi b_{1}\pi\rho\pi_{1}\pi_1(1600)\omega\pi_{1}\pi\rho$ mode cannot be generated through level
mixing.Comment: 7 pages, 11 figure
Forward dispersion relations and Roy equations in pi-pi scattering
We review results of an analysis of pipi interactions in S, P and D waves for
two-pion effective mass from threshold to about 1.4 GeV. In particular we show
a recent improvement of this analysis above the K anti-K threshold using more
data for phase shifts and including the S0 wave inelasticity from pipi -> K
anti-K. In addition, we have improved the fit to the f2(1270) resonance and
used a more flexible P wave parametrization above the K anti-K threshold and
included an estimation of the D2 wave inelasticity. The better accuracy thus
achieved also required a refinement of the Regge analysis above 1.42 GeV. We
have checked that the pipi scattering amplitudes obtained in this approach
satisfy remarkably well forward dispersion relations and Roy's equations.Comment: 6 pages, invited talk to the IV International Conference on Quarks
and Nuclear Physics QNP06, Madrid 5th-10th June 200
Simple quantum cosmology: Vacuum energy and initial state
A static non-singular 10-dimensional closed Friedmann universe of Planck
size, filled with a perfect fluid with an equation of state with w = -2/3, can
arise spontaneously by a quantum fluctuation from nothing in 11-dimensional
spacetime. A quantum transition from this state can initiate the inflationary
quantum cosmology outlined in Ref. 2 [General Relativity and Gravitation 33,
1415, 2001 - gr-qc/0103021]. With no fine-tuning, that cosmology predicts about
60 e-folds of inflation and a vacuum energy density depending only on the
number of extra space dimensions (seven), G, h, c and the ratio between the
strength of gravity and the strength of the strong force. The fraction of the
total energy in the universe represented by this vacuum energy depends on the
Hubble constant. Hubble constant estimates from WMAP, SDSS, the Hubble Key
Project and Sunyaev-Zeldovich and X-ray flux measurements range from 60 to 72
km/(Mpc sec). With a mid-range Hubble constant of 65 km/(Mpc sec), the model in
Ref. 2 predicts Omega-sub-Lambda = 0.7Comment: To be published in General Relativity and Gravitation, Vol. 37, May
2005. 5 pages, no figure
Relativistic description of the charmonium mass spectrum
The charmonium mass spectrum is considered in the framework of the
constituent quark model with the relativistic treatment of the c quark. The
obtained masses are in good agreement with the existing experimental data
including the mass of eta_c(2S).Comment: 5 page
decays
Effective chiral theory of mesons is applied to study the four decay modes of
. Theoretical values of the branching ratios are in
agreement with the data. The theory predicts that the resonance plays a
dominant role in these decays. There is no new parameter in this study.Comment: 12 pages and one figur
Static observables of relativistic three-fermion systems with instantaneous interactions
We show that static properties like the charge radius and the magnetic moment
of relativistic three-fermion bound states with instantaneous interactions can
be formulated as expectation values with respect to intrinsically defined
wavefunctions. The resulting operators can be given a natural physical
interpretation in accordance with relativistic covariance. We also indicate how
the formalism may be generalized to arbitrary moments. The method is applied to
the computation of static baryon properties with numerical results for the
nucleon charge radii and the baryon octet magnetic moments. In addition we make
predictions for the magnetic moments of some selected nucleon resonances and
discuss the decomposition of the nucleon magnetic moments in contributions of
spin and angular momentum, as well as the evolution of these contributions with
decreasing quark mass.Comment: 13 pages, including 2 figures and 3 tables, submitted to Eur.Phys.J.
Gravitational Corrections to the Energy-Levels of a Hydrogen Atom
The first order perturbations of the energy levels of a hydrogen atom in
central internal gravitational field are investigated. The internal
gravitational field is produced by the mass of the atomic nucleus. The energy
shifts are calculated for the relativistic 1S, 2S, 2P, 3S, 3P, 3D, 4S and 4P
levels with Schwarzschild metric. The calculated results show that the
gravitational corrections are sensitive to the total angular momentum quantum
number.Comment: 7 page
Electromagnetic form factors of hyperons in a relativistic quark model
The relativistically covariant constituent quark model developed by the Bonn
group is used to compute the EM form factors of strange baryons. We present
form-factor results for the ground-state and some excited hyperons. The
computed magnetic moments agree well with the experimental values and the
magnetic form factors follow a dipole dependence.Comment: 4 pages, 1 figure, Proceedings for NSTAR '04 conference in Grenoble,
France, March 24-27, 2004 (World Scientific
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