1,886 research outputs found
Is the anomalous decay ratio of D_{sJ}(2632) due to isospin breaking?
Quark pair annihilation into gluons is suppressed at large momenta due to the
asymptotic freedom. As a consequence, mass eigenvalues of heavy states should
be almost diagonal with respect to up and down quark masses, thereby breaking
isospin. We suggest the particle observed by the SELEX Collaboration,
D_{sJ}(2632) to be to a good extent a [cd][dbar sbar] state, which would
explain why its D^0 K^+ mode is anomalously suppressed with respect to D_s eta.
Predictions for the rates of the yet unobserved modes D_s pi^0 and D^+ K^0 are
given.Comment: 3 pages, 1 figur
A new look at scalar mesons
Light scalar mesons are found to fit rather well a diquark-antidiquark
description. The resulting nonet obeys mass formulae which respect, to a good
extent, the OZI rule. OZI allowed strong decays are reasonably reproduced by a
single amplitude describing the switch of a qbar-q pair, which transforms the
state into two colourless pseudoscalar mesons. Predicted heavy states with one
or more quarks replaced by charm or beauty are briefly described; they should
give rise to narrow states with exotic quantum numbers.Comment: 4 pages, 1 figure, misprints corrected, references added, accepted
for publication in Phys. Rev. Let
Consistent analysis of the reaction and
The production of mesons in the reactions and
is described consistently within a relativistic meson exchange
model of hadronic interactions. The photoproduction can be described quite well
over the entire energy range of available data by considering an and a
resonance, in addition to the -channel mesonic current. The
observed angular distribution is due to the interference between the
-channel and the nucleon resonance - and -channel contributions. Our
analysis yields positions close to 1650 MeV and 1870 MeV for the and
resonances, respectively. We argue that, at present, identifying these
states with the known resonance and the missing
resonance predicted at 1880 MeV, respectively, would be premature. It is found
that the nucleonic current is relatively small and that the
coupling constant cannot be much larger than . As for the
reaction, different current contributions are
constrained by a combined analysis of this and the photoproduction reaction.
Difficulties to simultaneously account for the 47-MeV and 144-MeV angular
distributions measured by the COSY-11 and DISTO collaborations, respectively,
are addressed.Comment: minor revision, scheduled to a appear in Phys. Rev. C 69 (May 2004),
revtex, 17 pages, 10 figures, 3 table
Weak mixing angle at low energies
We determine the weak mixing angle in the MS-bar scheme at energy scales
relevant for present and future low energy electroweak measurements. We relate
the renormalization group evolution of the weak mixing angle to the
corresponding evolution of the QED coupling and include higher-order terms in
alpha_s and alpha that had not been treated in previous analyses. We also
up-date the analysis of non-perturbative hadronic contributions and argue that
the associated uncertainty is small compared to anticipated experimental
errors. The resulting value of the low-energy weak mixing angle is sin^2
theta_W (0) = 0.23867 +- 0.00016.Comment: 21 pages; 1 figure and some references added, some changes in text;
final version as publishe
Stereo Computation for a Single Mixture Image
This paper proposes an original problem of \emph{stereo computation from a
single mixture image}-- a challenging problem that had not been researched
before. The goal is to separate (\ie, unmix) a single mixture image into two
constitute image layers, such that the two layers form a left-right stereo
image pair, from which a valid disparity map can be recovered. This is a
severely illposed problem, from one input image one effectively aims to recover
three (\ie, left image, right image and a disparity map). In this work we give
a novel deep-learning based solution, by jointly solving the two subtasks of
image layer separation as well as stereo matching. Training our deep net is a
simple task, as it does not need to have disparity maps. Extensive experiments
demonstrate the efficacy of our method.Comment: Accepted by European Conference on Computer Vision (ECCV) 201
Diquark-Antidiquarks with Hidden or Open Charm and the Nature of X(3872)
Heavy-light diquarks can be the building blocks of a rich spectrum of states
which can accommodate some of the newly observed charmonium-like resonances not
fitting a pure c-cbar assignment. We examine this possibility for hidden and
open charm diquark-antidiquark states deducing spectra from constituent quark
masses and spin-spin interactions. Taking the X(3872) as input we predict the
existence of a 2++ state that can be associated to the X(3940) observed by
Belle and re-examine the state claimed by SELEX, X(2632). The possible
assignment of the previously discovered states D_s(2317) and D_s(2457) is
discussed. We predict X(3872) to be made of two components with a mass
difference related to (m_u-m_d) and discuss the production of X(3872) and of
its charged partner X^(+-) in the weak decays of B^(+,0).Comment: 11 pages, 2 figures, revtex, minor typos correcte
On-chip quantum interference between silicon photon-pair sources
Large-scale integrated quantum photonic technologies1, 2 will require on-chip integration of identical photon sources with reconfigurable waveguide circuits. Relatively complex quantum circuits have been demonstrated already1, 2, 3, 4, 5, 6, 7, but few studies acknowledge the pressing need to integrate photon sources and waveguide circuits together on-chip8, 9. A key step towards such large-scale quantum technologies is the integration of just two individual photon sources within a waveguide circuit, and the demonstration of high-visibility quantum interference between them. Here, we report a silicon-on-insulator device that combines two four-wave mixing sources in an interferometer with a reconfigurable phase shifter. We configured the device to create and manipulate two-colour (non-degenerate) or same-colour (degenerate) path-entangled or path-unentangled photon pairs. We observed up to 100.0 ± 0.4% visibility quantum interference on-chip, and up to 95 ± 4% off-chip. Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits and is a first step towards fully integrated quantum technologies
Probing black holes in non-perturbative gauge theory
We use a 0-brane to probe a ten-dimensional near-extremal black hole with N
units of 0-brane charge. We work directly in the dual strongly-coupled quantum
mechanics, using mean-field methods to describe the black hole background
non-perturbatively. We obtain the distribution of W boson masses, and find a
clear separation between light and heavy degrees of freedom. To localize the
probe we introduce a resolving time and integrate out the heavy modes. After a
non-trivial change of coordinates, the effective potential for the probe agrees
with supergravity expectations. We compute the entropy of the probe, and find
that the stretched horizon of the black hole arises dynamically in the quantum
mechanics, as thermal restoration of unbroken U(N+1) gauge symmetry. Our
analysis of the quantum mechanics predicts a correct relation between the
horizon radius and entropy of a black hole.Comment: 30 pages, LaTeX, 8 eps figures. v2: references added. v3: more
reference
- …