369 research outputs found
Evidence that the a0(980) and f0(980) are not elementary particles
We study the interesting problem of whether it is possible to distinguish
composite from elementary particles. In particular we generalize a
model-independent approach of S. Weinberg to the case of unstable particles.
This allows us to apply our formalism to the case of the a0(980) and f0(980)
resonances and to address the question whether these particles are
predominantly genuine, confined quark states (of or
structure) or governed by mesonic components.Comment: 15 pages, 4 Figure
Resonant tunnelling features in the transport spectroscopy of quantum dots
We present a review of features due to resonant tunnelling in transport
spectroscopy experiments on quantum dots and single donors. The review covers
features attributable to intrinsic properties of the dot as well as extrinsic
effects, with a focus on the most common operating conditions. We describe
several phenomena that can lead to apparently identical signatures in a bias
spectroscopy measurement, with the aim of providing experimental methods to
distinguish between their different physical origins. The correct
classification of the resonant tunnelling features is an essential requirement
to understand the details of the confining potential or predict the performance
of the dot for quantum information processing.Comment: 18 pages, 7 figures. Short review article submitted to
Nanotechnology, special issue on 'Quantum Science and Technology at the
Nanoscale
Study of and from and Decays
We use the decay modes and to
study the scalar mesons and within perturbative QCD
framework. For , we perform our calculation in two
scenarios of the scalar meson spectrum. The results indicate that scenario II
is more favored by experimental data than scenario I. The important
contribution from annihilation diagrams can enhance the branching ratios about
50% in scenario I, and about 30% in scenario II. The predicted branching ratio
of in scenario I is also less favored by the experiments.
The direct CP asymmetries in are small, which are
consistent with the present experiments.Comment: More references are added. Published Versio
Embedded software developments in KM3NeT phase I
TheKM3NeT collaboration has already produced more than one thousand acquisition
boards, used for building two deep-sea neutrino detectors at the bottom of the Mediterranean Sea,
with the aim of instrumenting a volume of several cubic kilometers with light sensors to detect
the Cherenkov radiation produced in neutrino interactions. The so-called digital optical modules,
house the PMTs and the acquisition and control electronics of the module, the central logic board,
which includes a Xilinx FPGA and embedded soft processor. The present work presents the architecture and functionalities of the software embedded in the soft processor of the central logic
board
Estimating sigma-meson couplings from D \to 3\pi decays
Using recent experimental evidence from E791 on the sigma meson in D \to 3\pi
decays, we study the relevant couplings in D \to \sigma \pi and \sigma \to \pi\
pi within the accepted theoretical framework for non leptonic D decays. We also
review the linear sigma model, finding that it gives a description which is
consistent with the experimental data.Comment: 6 pages, no figures. Final version accepted for publication as a
Brief Report in Physical Review
Phase transformation-induced superconducting aluminium-silicon alloy rings
The development of a materials platform that exhibits both superconducting
and semiconducting properties is an important endeavour for a range of emerging
quantum technologies. We investigate the formation of superconductivity in
nanowires fabricated with silicon-on-insulator (SOI). Aluminium from deposited
contact electrodes is found to interdiffuses with the Si nanowire structures to
form an Al-Si alloy along the entire length of the predefined nanowire device
over micron length scales at temperatures well below that of the Al-Si
eutectic. The resultant transformed nanowire structures are layered in geometry
with a continuous Al-Si alloy wire sitting on the buried oxide of the SOI and a
residual Si cap sitting on top of the wire. The phase transformed material is
conformal with any predefined device patterns and the resultant structures are
exceptionally smooth-walled compared to similar nanowire devices formed by
silicidation processes. The superconducting properties of a mesoscopic AlSi
ring formed on a SOI platform are investigated. Low temperature
magnetoresistance oscillations, quantized in units of the fluxoid, h/2e, are
observed.Comment: 11 pages, 9 figure
Observation of the Higgs Boson of strong interaction via Compton scattering by the nucleon
It is shown that the Quark-Level Linear Model (QLLM) leads
to a prediction for the diamagnetic term of the polarizabilities of the nucleon
which is in excellent agreement with the experimental data. The bare mass of
the meson is predicted to be MeV and the two-photon
width keV. It is argued that the
mass predicted by the QLLM corresponds to the reaction, i.e. to a -channel pole of the reaction.
Large -angle Compton scattering experiments revealing effects of the
meson in the differential cross section are discussed. Arguments are presented
that these findings may be understood as an observation of the Higgs boson of
strong interaction while being part of the constituent quark.Comment: 17 pages, 6 figure
Mechanism for a next-to-lowest lying scalar meson nonet
Recent work suggests the existence of a non-conventional lowest-lying scalar
nonet containing the a0(980). Then the a0(1450) and also the K0*(1430) are
likely candidates to belong to a conventional p-wave nonet. However
a comparison of their properties with those expected on this basis reveals a
number of puzzling features. It is pointed out that these puzzles can be
resolved in a natural and robust way by assuming a ``bare'' conventional p-wave
scalar nonet to mix with a lighter four quark
scalar nonet to form new ``physical'' states. The essential mechanism is driven
by the fact that the isospinor is lighter than the isovector in the unmixed multiplet.Comment: 22 pages, 6 figure
Scalar Particles in Lattice QCD
We report a project to study scalar particles by lattice QCD simulations.
After a brief introduction of the current situation of lattice study of the
sigma meson, we describe our numerical simulations of scalar mesons,
and . We observe a low sigma mass, , for
which the disconnected diagram plays an important role. For the kappa meson, we
obtain higher mass than the experimental value, i.e., .Comment: 4 figures, to be published in Proceedings of `International Symposium
on Hadron Spectroscopy, Chiral Symmetry and Relativistic Description of Bound
Systems' (in a series of KEK proceedings
Radiative open charm decay of the Y(3940), Z(3930), X(4160) resonances
We determine the radiative decay amplitudes for decay into and , or and of some of the charmonium like
states classified as X,Y,Z resonances, plus some other hidden charm states
which are dynamically generated from the interaction of vector mesons with
charm. The mass distributions as a function of the or
invariant mass show a peculiar behavior as a consequence of
the nature of these states. The experimental search of these
magnitudes can shed light on the nature of these states.Comment: 18 pages, 9 figure
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