831 research outputs found
Determination of transition frequencies in a single Ba ion
Transition frequencies between low-lying energy levels in a single trapped
Ba ion have been measured with laser spectroscopy referenced to
an optical frequency comb. By extracting the frequencies of one-photon and
two-photon components of the line shape using an eight-level optical Bloch
model, we achieved 0.1 MHz accuracy for the 5d D - 6p
P and 6s S - 5d D transition
frequencies, and 0.2 MHz for the 6s S - 6p P
transition frequency.Comment: 5 pages, 7 figures, submitted to Phys. Rev.
Non-Standard Neutrino Interactions from a Triplet Seesaw Model
We investigate non-standard neutrino interactions (NSIs) in the triplet
seesaw model featuring non-trivial correlations between NSI parameters and
neutrino masses and mixing parameters. We show that sizable NSIs can be
generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus,
these NSIs could lead to quite significant signals of lepton flavor violating
decays such as \mu^- \to e^- \nu_e anti\nu_\mu and \mu^+ \to e^+ anti\nu_e
\nu_\mu at a future neutrino factory, effects adding to the uncertainty in
determination of the Earth matter density profile, as well as characteristic
patterns of the doubly charged Higgs decays observable at the Large Hadron
Collider.Comment: 4 pages, 3 figures and 1 table; v2: minor corrections, Sect. IV
revise
Realistic constraints on the doubly charged bilepton couplings from Bhabha scattering with LEP data
Upper limits on doubly charged bilepton couplings and masses are extracted
from LEP data for Bhabha scattering at energy range GeV
using standard model program ZFITTER which calculates radiative corrections. We
find that at 95% C.L. for scalar and
vector bileptons.Comment: 5 pages, 1 EPS figur
Spontaneous Symmetry Breaking in Two-Channel Asymmetric Exclusion Processes with Narrow Entrances
Multi-particle non-equilibrium dynamics in two-channel asymmetric exclusion
processes with narrow entrances is investigated theoretically. Particles move
on two parallel lattices in opposite directions without changing them, while
the channels are coupled only at the boundaries. A particle cannot enter the
corresponding lane if the exit site of the other lane is occupied. Stationary
phase diagrams, particle currents and densities are calculated in a mean-field
approximation. It is shown that there are four stationary phases in the system,
with two of them exhibiting spontaneous symmetry breaking phenomena. Extensive
Monte Carlo computer simulations confirm qualitatively our predictions,
although the phase boundaries and stationary properties deviate from the
mean-field results. Computer simulations indicate that several dynamic and
phase properties of the system have a strong size dependency, and one of the
stationary phases predicted by the mean-field theory disappears in the
thermodynamic limit.Comment: 13 page
Spontaneous symmetry breaking in a two-lane model for bidirectional overtaking traffic
First we consider a unidirectional flux \omega_bar of vehicles each of which
is characterized by its `natural' velocity v drawn from a distribution P(v).
The traffic flow is modeled as a collection of straight `world lines' in the
time-space plane, with overtaking events represented by a fixed queuing time
tau imposed on the overtaking vehicle. This geometrical model exhibits platoon
formation and allows, among many other things, for the calculation of the
effective average velocity w=\phi(v) of a vehicle of natural velocity v.
Secondly, we extend the model to two opposite lanes, A and B. We argue that the
queuing time \tau in one lane is determined by the traffic density in the
opposite lane. On the basis of reasonable additional assumptions we establish a
set of equations that couple the two lanes and can be solved numerically. It
appears that above a critical value \omega_bar_c of the control parameter
\omega_bar the symmetry between the lanes is spontaneously broken: there is a
slow lane where long platoons form behind the slowest vehicles, and a fast lane
where overtaking is easy due to the wide spacing between the platoons in the
opposite direction. A variant of the model is studied in which the spatial
vehicle density \rho_bar rather than the flux \omega_bar is the control
parameter. Unequal fluxes \omega_bar_A and \omega_bar_B in the two lanes are
also considered. The symmetry breaking phenomenon exhibited by this model, even
though no doubt hard to observe in pure form in real-life traffic, nevertheless
indicates a tendency of such traffic.Comment: 50 pages, 16 figures; extra references adde
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