6,695 research outputs found
Understanding ,
I briefly review the experimental observations concerning the charmed mesons
, and survey on some of the interpretations
proposed in order to understand their nature. I present an analysis of their
decay modes in the hypothesis that they can be identified with the scalar and
axial vector states of spectrum
(, ). The method is based on heavy quark symmetries
and Vector Meson Dominance ansatz. Comparison with present data supports the
interpretation.Comment: LaTex, 10 pages. Invited talk at Continuous Advances in QCD 2004,
Minneapolis, Minnesota, May 13-16 200
Open charm meson spectroscopy: Where to place the latest piece of the puzzle
We discuss how to classify the meson recently
discovered by the BaBar Collaboration. We consider four possible assignments,
together with signatures useful to distinguish among them.Comment: RevTeX, 5 pages, 1 eps figur
Dynamics and Current Fluctuations in AC driven Charge Shuttle
The behavior of a charge shuttle under a pure AC field has been recently
considered theoretically and experimentally. If the system presents an
asymmetry in the tunneling amplitudes the device acts as a
nano-electromechanical rectifier, transforming a pure AC voltage field into a
direct curren. In this paper we first review the model and the appearance of
the rectifying effect for bias voltages below the threshold of
self-oscillation. We discuss in some details the dynamics of the central island
that, like the current, presents strong dependence on the forcing AC field
frequency. In presence of both a constant and a small oscillating bias voltage
we analyze the transition from the static to self-oscillating solution. We then
consider current fluctuations (full counting statistics) for periodic motion of
the grain. We explicitly evaluate the current noise numerically and we find
that it shows clear signatures of correlated transport at certain locking
frequencies. In the adiabatic limit we obtain a simple expression for the
full-counting statistics and calculate explicitly the first four moments.Comment: 16 pages, 7 Figures. Invited paper for the special issue on NEMS on
New Journal of Physic
Properties of Mesoscopic Hybrid Superconducting Systems
In this paper we review several aspects of mesoscopic hybrid superconducting
systems. In particular we consider charge and heat transport properties in
hybrid superconducting-metal structures and the effect of charging energy in
superconducting nanostructures.Comment: 27 pages, 8 figure
QCD Interactions of Heavy Mesons with Pions by Light-Cone Sum Rules
Light-cone QCD sum rules are employed to compute the strong coupling
constants: g_{B^* B^* pi}, g_{B_1 B_0 pi} and g_{B_1 B^* pi}, where (B,B^*) and
(B_0,B_1) are negative and positive parity (0^-,1^-) and (0^+,1^+) \bar qQ
doublets. The couplings are calculated both for finite values of the heavy
quark mass and in the infinite heavy quark mass limit, deriving sum rules for
m_Q \to \infty.Comment: Latex, 23 pages, 6 figures. Revised version to appear in Z. Phys.
B -> X_u l nu decay distributions to order alpha_s
An analytic result for the O(alpha_s corrections to the triple differential B
-> X_u l nu decay rate is presented, to leading order in the heavy-quark
expansion. This is relevant for computing partially integrated decay
distributions with arbitrary cuts on kinematic variables. Several double and
single differential distributions are derived, most of which generalize known
results. In particular, an analytic result for the O(alpha_s) corrections to
the hadronic invariant mass spectrum is presented. The effects of Fermi motion,
which are important for the description of decay spectra close to infrared
sensitive regions, are included. The behaviour of perturbation theory in the
region of time-like momenta is also investigatedComment: 24 pages, 11 figures, 1 typo in eq.(5.4) corrected; version published
in JHEP06(1999)01
Huge nonequilibrium magnetoresistance in hybrid superconducting spin valves
A hybrid ferromagnet-superconductor spin valve is proposed. Its operation
relies on the interplay between nonequilibrium transport and proximity-induced
exchange coupling in superconductors. Huge tunnel magnetoresistance values as
large as some 10^6% can be achieved in suitable ferromagnet-superconductor
combinations under proper voltage biasing. The controllable spin-filter nature
of the structure combined with its intrinsic simplicity make this setup
attractive for low-temperature spintronic applications where reduced power
dissipation is an additional requirement.Comment: 4 pages, 4 figure
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