445 research outputs found
Quantum control of the motional states of trapped ions through fast switching of trapping potentials
We propose a new scheme for supplying voltages to the electrodes of
microfabricated ion traps, enabling access to a regime in which changes to the
trapping potential are made on timescales much shorter than the period of the
secular oscillation frequencies of the trapped ions. This opens up
possibilities for speeding up the transport of ions in segmented ion traps and
also provides access to control of multiple ions in a string faster than the
Coulomb interaction between them. We perform a theoretical study of ion
transport using these methods in a surface-electrode trap, characterizing the
precision required for a number of important control parameters. We also
consider the possibilities and limitations for generating motional state
squeezing using these techniques, which could be used as a basis for
investigations of Gaussian-state entanglement.Comment: Accepted by New Journal of Physic
Dispersive analysis of the pion transition form factor
We analyze the pion transition form factor using dispersion theory. We
calculate the singly-virtual form factor in the time-like region based on data
for the cross section, generalizing previous studies on
decays and scattering, and verify our
result by comparing to data. We perform the analytic
continuation to the space-like region, predicting the poorly-constrained
space-like transition form factor below 1 GeV, and extract the slope of the
form factor at vanishing momentum transfer .
We derive the dispersive formalism necessary for the extension of these results
to the doubly-virtual case, as required for the pion-pole contribution to
hadronic light-by-light scattering in the anomalous magnetic moment of the
muon.Comment: 13 pages, 5 figures, journal versio
MesonNet Workshop on Meson Transition Form Factors
The mini-proceedings of the Workshop on Meson Transition Form Factors held in
Cracow from May 29th to 30th, 2012 introduce the meson transition form factor
project with special emphasis on the interrelations between the various form
factors (on-shell, single off-shell, double off-shell). Short summaries of the
talks presented at the workshop follow.Comment: 69 pages, 14 figures; all talks can be found at
https://sites.google.com/site/mesonnetwork/home/activities/form-factor-workshop-2012;
v2: workshop link updated (as the page had to be moved to a commercial
server), table 6 correcte
In-Medium Properties of Hadrons - Observables II
In this review we discuss the observable consequences of in-medium changes of
hadronic properties in reactions with elementary probes, and in particular
photons, on nuclei. After an outline of the theoretical method used we focus on
a discussion of actual observables in photonuclear reactions; we discuss in
detail - and vector-meson production. We show that the
photoproduction data can be well described by final state interactions of the
pions produced whereas the semi-charged channel exhibits a major
discrepancy with theory. For production on nuclei in the TAPS/CB@ELSA
experiment we analyse the decay channel, and illustrate the
strength of the method by simulating experimental acceptance problems.
Completely free of final state interactions is dilepton production in the few
GeV range. We show that the sensitivity of this decay channel to changes of
hadronic properties in medium in photonuclear reactions on nuclei is as large
as in ultrarelativistic heavy ion collisions and make predictions for the
on-going G7 experiment at JLAB. Finally we discuss that hadron production in
nuclei at 10 -- 20 GeV photon energies can give important information on the
hadronization process, and in particular on the time-scales involved. We show
here detailed calculations for the low-energy (12 GeV) run at HERMES and
predictions for planned experiments at JLAB.Comment: Invited Talk by U. Mosel, Proceedings of the Int. School on Nuclear
Physics, 26th Course, "Lepton scattering and the structure of hadrons and
nuclei", Erice (Sicily), September 16th-24th, 2004, short piece of text adde
The spectral function of the omega meson in nuclear matter from a coupled-channel resonance model
We calculate the spectral function of the omega meson in nuclear matter at
zero temperature by means of the low-density theorem. The omega N forward
scattering amplitude is calculated within a unitary coupled-channel effective
Lagrangian model that has been applied successfully to the combined analysis of
pion- and photon-induced reactions. While the peak of the omega spectral
distribution is shifted only slightly, we find a considerable broadening of the
omega meson due to resonance-hole excitations. For omega mesons at rest with
respect to the surrounding nuclear medium, we find an additional width of about
60 MeV at saturation density.Comment: 26 pages, 10 figures, added short discussio
Strong coupling constants of bottom and charmed mesons with scalar, pseudoscalar and axial vector kaons
The strong coupling constants, , ,
, , and
, where , and are scalar, pseudoscalar
and axial vector kaon mesons, respectively are calculated in the framework of
three-point QCD sum rules. In particular, the correlation functions of the
considered vertices when both and mesons are off-shell
are evaluated. In the case of , which is either or
, the mixing between these two states are also taken into account. A
comparison of the obtained result with the existing prediction on
as the only coupling constant among the considered
vertices, previously calculated in the literature, is also made.Comment: 20 Pages, 3 Figures and 8 Table
Valence and magnetic instabilities in Sm compounds at high pressures
We report on the study of the response to high pressures of the electronic
and magnetic properties of several Sm-based compounds, which span at ambient
pressure the whole range of stable charge states between the divalent and the
trivalent. Our nuclear forward scattering of synchrotron radiation and specific
heat investigations show that in both golden SmS and SmB6 the pressure-induced
insulator to metal transitions (at 2 and about 4-7 GPa, respectively) are
associated with the onset of long-range magnetic order, stable up to at least
19 and 26 GPa, respectively. This long-range magnetic order, which is
characteristic of Sm(3+), appears already for a Sm valence near 2.7. Contrary
to these compounds, metallic Sm, which is trivalent at ambient pressure,
undergoes a series of pressure-induced structural phase transitions which are
associated with a progressive decrease of the ordered 4f moment.Comment: 15 pages (including 7 figures) submitted to J. Phys.: Condens. Matte
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