1,286 research outputs found
Semileptonic decays of baryons in a relativistic quark model
We calculate semileptonic decays of light and heavy baryons in a
relativistically covariant constituent quark model. The model is based on the
Bethe-Salpeter-equation in instantaneous approximation. It generates
satisfactory mass spectra for mesons and baryons up to the highest observable
energies. Without introducing additional free parameters we compute on this
basis helicity amplitudes of electronic and muonic semileptonic decays of
baryons. We thus obtain form factor ratios and decay rates in good agreement
with experiment.Comment: 8 pages, 10 figures, 2 tables, typos remove
Interference of multi-mode photon echoes generated in spatially separated solid-state atomic ensembles
High-visibility interference of photon echoes generated in spatially
separated solid-state atomic ensembles is demonstrated. The solid state
ensembles were LiNbO waveguides doped with Erbium ions absorbing at 1.53
m. Bright coherent states of light in several temporal modes (up to 3) are
stored and retrieved from the optical memories using two-pulse photon echoes.
The stored and retrieved optical pulses, when combined at a beam splitter, show
almost perfect interference, which demonstrates both phase preserving storage
and indistinguishability of photon echoes from separate optical memories. By
measuring interference fringes for different storage times, we also show
explicitly that the visibility is not limited by atomic decoherence. These
results are relevant for novel quantum repeaters architectures with photon echo
based multimode quantum memories
Interference of Spontaneous Emission of Light from two Solid-State Atomic Ensembles
We report an interference experiment of spontaneous emission of light from
two distant solid-state ensembles of atoms that are coherently excited by a
short laser pulse. The ensembles are Erbium ions doped into two LiNbO3 crystals
with channel waveguides, which are placed in the two arms of a Mach-Zehnder
interferometer. The light that is spontaneously emitted after the excitation
pulse shows first-order interference. By a strong collective enhancement of the
emission, the atoms behave as ideal two-level quantum systems and no which-path
information is left in the atomic ensembles after emission of a photon. This
results in a high fringe visibility of 95%, which implies that the observed
spontaneous emission is highly coherent
Universal description of S-wave meson spectra in a renormalized light-cone QCD-inspired model
A light-cone QCD-inspired model, with the mass squared operator consisting of
a harmonic oscillator potential as confinement and a Dirac-delta interaction,
is used to study the S-wave meson spectra. The two parameters of the harmonic
potential and quark masses are fixed by masses of rho(770), rho(1450), J/psi,
psi(2S), K*(892) and B*. We apply a renormalization method to define the model,
in which the pseudo-scalar ground state mass fixes the renormalized strength of
the Dirac-delta interaction. The model presents an universal and satisfactory
description of both singlet and triplet states of S-wave mesons and the
corresponding radial excitations.Comment: RevTeX, 17 pages, 7 eps figures, to be published in Phys. Rev.
Quark-antiquark composite systems: the Bethe-Salpeter equation in the spectral-integration technique
The Bethe-Salpeter equations for the light-quark composite systems, q q-bar,
are written in terms of spectral integrals. For the q q-bar -mesons
characterized by the mass M, spin J and radial quantum number n, the equations
are presented for the following (n,M^2)-trajectories: pi_J, eta_J, a_J, f_J,
rho_J, omega_J, h_J and b_J.Comment: 42 pages, 5 figures, typos correcte
The ionized and hot gas in M17 SW: SOFIA/GREAT THz observations of [C II] and 12CO J=13-12
With new THz maps that cover an area of ~3.3x2.1 pc^2 we probe the spatial
distribution and association of the ionized, neutral and molecular gas
components in the M17 SW nebula. We used the dual band receiver GREAT on board
the SOFIA airborne telescope to obtain a 5'.7x3'.7 map of the 12CO J=13-12
transition and the [C II] 158 um fine-structure line in M17 SW and compare the
spectroscopically resolved maps with corresponding ground-based data for low-
and mid-J CO and [C I] emission. For the first time SOFIA/GREAT allow us to
compare velocity-resolved [C II] emission maps with molecular tracers. We see a
large part of the [C II] emission, both spatially and in velocity, that is
completely non-associated with the other tracers of photon-dominated regions
(PDR). Only particular narrow channel maps of the velocity-resolved [C II]
spectra show a correlation between the different gas components, which is not
seen at all in the integrated intensity maps. These show different morphology
in all lines but give hardly any information on the origin of the emission. The
[C II] 158 um emission extends for more than 2 pc into the M17 SW molecular
cloud and its line profile covers a broader velocity range than the 12CO
J=13-12 and [C I] emissions, which we interpret as several clumps and layers of
ionized carbon gas within the telescope beam. The high-J CO emission emerges
from a dense region between the ionized and neutral carbon emissions,
indicating the presence of high-density clumps that allow the fast formation of
hot CO in the irradiated complex structure of M17 SW. The [C II] observations
in the southern PDR cannot be explained with stratified nor clumpy PDR models.Comment: 4 pages, 4 figures, letter accepted for the SOFIA/GREAT A&A 2012
special issu
Splitting of the pi - rho spectrum in a renormalized light-cone QCD-inspired model
We show that the splitting between the light pseudo-scalar and vector meson
states is due to the strong short-range attraction in the ^1S_0 sector which
makes the pion and the kaon light particles. We use a light-cone QCD-inspired
model of the mass squared operator with harmonic confinement and a Dirac-delta
interaction. We apply a renormalization method to define the model, in which
the pseudo-scalar ground state mass fixes the renormalized strength of the
Dirac-delta interaction.Comment: 9 pages, 2 figures, revtex, accepted by Phys. Rev. D; Corrected typo
FMNH2-dependent monooxygenases initiate catabolism of sulfonamides in Microbacterium sp. strain BR1 subsisting on sulfonamide antibiotics
Measurement of ultrashort bi-photon correlation times with an integrated two-colour broadband SU(1,1)-interferometer
The bi-photon correlation time, a measure for the conditional uncertainty in
the temporal arrival of two photons from a photon pair source, is a key
performance identifier for many quantum spectroscopy applications, with shorter
correlation times typically yielding better performance. Furthermore, it
provides fundamental insight into the effects of dispersion on the bi-photon
state. Here, we retrieve ultrashort bi-photon correlation times of around
by measuring simultaneously spectral and temporal
interferograms at the output of an SU(1,1) interferometer based on an
integrated broadband parametric down-conversion source in a
waveguideComment: 8 pages, 5 figure
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