14,639 research outputs found
The Zeta Function Method and the Harmonic Oscillator Propagator
We show how the pre-exponential factor of the Feynman propagator for the
harmonic oscillator can be computed by the generalized -function method.
Besides, we establish a direct equivalence between this method and Schwinger's
propertime method.Comment: 12 latex pages, no figure
The One Dimensional Damped Forced Harmonic Oscillator Revisited
In this paper we give a general solution to the problem of the damped
harmonic oscillator under the influence of an arbitrary time-dependent external
force. We employ simple methods accessible for beginners and useful for
undergraduate students and professors in an introductory course of mechanics.Comment: 4 Latex page
Study of sequential semileptonic decays of b hadrons produced at the Tevatron
We present a study of rates and kinematical properties of lepton pairs
contained in central jets with transverse energy E_T > 15 GeV that are produced
at the Fermilab Tevatron collider. We compare the data to a QCD prediction
based on the HERWIG and QQ Monte Carlo generator programs.We find that the data
are poorly described by the simulation, in which sequential semileptonic decays
of single b quarks (b --> l c X with c --> l s X) are the major source of such
lepton pairs.Comment: 25 pages, 8 figures. Some typos were fixed in the text and
bibliography. Submitted to Phys. Rev.
Current-Phase Relation of a Bose-Einstein Condensate Flowing Through a Weak Link
We study the current-phase relation of a Bose-Einstein condensate flowing
through a repulsive square barrier by solving analytically the one dimensional
Gross-Pitaevskii equation. The barrier height and width fix the current-phase
relation , which tends to for weak
barriers and to the Josephson sinusoidal relation for
strong barriers. Between these two limits, the current-phase relation depends
on the barrier width. In particular, for wide enough barriers, we observe two
families of multivalued current-phase relations. Diagrams belonging to the
first family, already known in the literature, can have two different positive
values of the current at the same phase difference. The second family, new to
our knowledge, can instead allow for three different positive currents still
corresponding to the same phase difference. Finally, we show that the
multivalued behavior arises from the competition between hydrodynamic and
nonlinear-dispersive components of the flow, the latter due to the presence of
a soliton inside the barrier region.Comment: 6 pages, 5 figure
Phenomenological study of the atypical heavy flavor production observed at the Fermilab Tevatron
We address known discrepancies between the heavy flavor properties of jets
produced at the Tevatron collider and the prediction of conventional-QCD
simulations. In this study, we entertain the possibility that these effects are
real and due to new physics. We show that all anomalies can be simultaneously
fitted by postulating the additional pair production of light bottom squarks
with a 100% semileptonic branching fraction.Comment: 30 pages, 13 figures, 3 tables. Submitted to Phys. Rev.
Vacuum energies due to delta-like currents: simulating classical objects along branes with arbitrary codimensions
In this paper we investigate the vacuum energies of several models of quantum
fields interacting with static external currents (linear couplings)
concentrated along parallel branes with an arbitrary number of codimensions. We
show that we can simulate the presence of static charges distributions as well
as the presence of classical static dipoles in any dimension for massive and
massless fields. We also show that we can produce confining potentials with
massless self interacting scalar fields as well as long range anisotropic
potentials.Comment: 18 latex page
Diffractive photoproduction of opposite-charge pseudoscalar meson pairs at high energies
We calculate the cross section for diffractive photoproduction of
opposite-charge pseudoscalar meson pairs , ,
and in a broad range of center-of-mass energies relevant
for GlueX/Hall D, FOCUS, COMPASS and HERA experiments. In the case of
production we find that the interference of the resonance
and the two-pion continuum leads to a considerable deformation of the shape of
in agreement with the data from the ZEUS collaboration. We also
discuss the spectral shape of the as a function of the momentum
transfer and the contribution of higher partial waves to the mass
spectrum. We predict a sizeable energy-dependent forward-backward asymmetry in
the Gottfried-Jackson frame. For the heavy meson production we find that the
cross section for diffractive production increases much slower than the one for
open charm or bottom production. We discuss lower and upper limits for the
cross sections for diffractive production of and pairs,
which we find can be as large as 10% of the open flavor production.Comment: 14 pages, 19 figure
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