2,077 research outputs found
Hybrid meson production by electromagnetic and weak interactions in a flux-tube simulation of lattice QCD
We calculate rates for hybrid meson production by electromagnetic and weak
interactions in the flux-tube model. Applications include photo and
electroproduction at Jefferson Laboratory and HERA, and the production of light
strange and charmed hybrids in the weak decays of heavy flavours.
Photoproduction of some light hybrids is predicted to be prominent in charge
exchange reactions, and accessible in . Production of light or charmed hybrids in and decays may be
feasible with high statistics. Photoproduction of the axial hybrid meson is
predicted to be large courtesy of exchange, and its strange counterpart
is predicted in with . Production
rates for exotic hybrid candidates are given special
attention. Selection rules that can help to distinguish between hybrid and
conventional states with the same are noted.Comment: uses psfrag; One reference correcte
Electroweak production of hybrid mesons in a Flux-Tube simulation of Lattice QCD
We make the first calculation of the electroweak couplings of hybrid mesons
to conventional mesons appropriate to photoproduction and to the decays of
or mesons. amplitudes are found to be large and may contribute in
charge exchange allowing production of (amongst others)
the charged exotic hybrid off exchange. Axial hybrid meson
photoproduction is predicted to be large courtesy of exchange, and its
strange hybrid counterpart is predicted in with . Higher multipoles, and some implications for hybrid charmonium
are briefly discussed.Comment: 4 page
Pentaquark Symmetries, Selection Rules and another potentially Narrow State
We identify essential differences between the pentaquark and chiral soliton
models of \10bar and {\bf 8} pentaquarks and conventional {\bf 8}
states, which are experimentally measurable. We show how the decays of
states in particular can test models of the pentaquarks, recommend study of the
relative branching ratios of e.g. , and
predict that the decay amplitude is zero at leading order
in pentaquark models for any mixture of \10bar and the associated {\bf 8}.
We also include a pedagogic discussion of wavefunctions in the pentaquark
picture and show that pentaquark models have this {\bf 8} with ,
in leading order forbidding . The role of Fermi-Dirac
symmetry in the wavefunction and its implications for the width of
pentaquarks are briefly discussed. The relative couplings for . A further potentially
narrow state in {\bf 8} with is predicted around
1650 MeV.Comment: Revised version, corrects PDF margin problems, minor changes to tex
Systems approach provides management control of complex programs
Integrated program management process provides management visual assistance through three interrelated charts - system model that identifies each function to be performed, matrix that identifies personnel responsibilities for these functions, process chart that breaks down the functions into discrete tasks
Charmonium in lattice QCD and the non-relativistic quark-model
We compare the results of a numerical lattice QCD calculation of the
charmonium spectrum with the structure of a general non-relativistic potential
model. To achieve this we form the non-relativistic reduction of
derivative-based fermion bilinear interpolating fields used in lattice QCD
calculations and compute their overlap with c-cbar meson states at rest
constructed in the non-relativistic quark model, providing a bound-state model
interpretation for the lattice data. Essential gluonic components in the
bound-states, usually called hybrids, are identified by considering
interpolating fields that involve the gluonic field-strength tensor and which
have zero overlap onto simple c-cbar model states
Options for the SELEX state D_{s\J}^+(2632)
We consider possible assignments for the D_{s\J}^+(2632), which was
recently reported in D and DK final states by the SELEX
Collaboration at Fermilab. The most plausible quark model assignment for this
state is the first radial excitation () of the
D, although the predicted mass and strong decay branching fractions
for this assignment are not in agreement with the SELEX data. The reported
dominance of D over DK appears especially problematic. An intriguing
similarity to the K is noted. --^3\D_1 configuration
mixing is also considered, and we find that this effect is unlikely to resolve
the branching fraction discrepancy. Other interpretations as a -hybrid
or a two-meson molecule are also considered, but appear unlikely. Thus, if this
state is confirmed, it will require reconsideration of the systematics of
charmed meson spectroscopy and strong decays.Comment: 6 revtex4 pages, 2 eps figure
S and D-wave phase shifts in isospin-2 pi pi scattering from lattice QCD
The isospin-2 pi pi system provides a useful testing ground for determining
elastic hadron scattering parameters from finite-volume spectra obtained using
lattice QCD computations. A reliable determination of the excited state
spectrum of two pions in a cubic box follows from variational analysis of
correlator matrices constructed using a large basis of operators. A general
operator construction is presented which respects the symmetries of a
multi-hadron system in flight. This is applied to the case of pi pi and allows
for the determination of the scattering phase-shifts at a large number of
kinematic points, in both S-wave and D-wave, within the elastic region. The
technique is demonstrated with a calculation at a pion mass of 396 MeV, where
the elastic scattering is found to be well described by a scattering length
parameterisation.Comment: Tables of little-group CGCs in ancillary file; v2: minor changes to
reflect published versio
Pentaquark implications for exotic mesons
If the exotic baryon is a correlated with , then there should exist an exotic meson, GeV with width MeV. The
may be broad members of {\bf 10} \10bar in such a
picture. Vector mesons in the 1.4 - 1.7GeV mass range are also compared with
this picture
Exotic and excited-state radiative transitions in charmonium from lattice QCD
We compute, for the first time using lattice QCD methods, radiative
transition rates involving excited charmonium states, states of high spin and
exotics. Utilizing a large basis of interpolating fields we are able to project
out various excited state contributions to three-point correlators computed on
quenched anisotropic lattices. In the first lattice QCD calculation of the
exotic 1-+ eta_c1 radiative decay, we find a large partial width Gamma(eta_c1
-> J/psi gamma) ~ 100 keV. We find clear signals for electric dipole and
magnetic quadrupole transition form factors in chi_c2 -> J/psi gamma,
calculated for the first time in this framework, and study transitions
involving excited psi and chi_c1,2 states. We calculate hindered magnetic
dipole transition widths without the sensitivity to assumptions made in model
studies and find statistically significant signals, including a non-exotic
vector hybrid candidate Y_hyb? -> eta_c gamma. As well as comparison to
experimental data, we discuss in some detail the phenomenology suggested by our
results and the extent to which it mirrors that of quark potential models and
make suggestions for the interpretation of our results involving exotic quantum
numbered states
A Novel Hybrid CNN-AIS Visual Pattern Recognition Engine
Machine learning methods are used today for most recognition problems.
Convolutional Neural Networks (CNN) have time and again proved successful for
many image processing tasks primarily for their architecture. In this paper we
propose to apply CNN to small data sets like for example, personal albums or
other similar environs where the size of training dataset is a limitation,
within the framework of a proposed hybrid CNN-AIS model. We use Artificial
Immune System Principles to enhance small size of training data set. A layer of
Clonal Selection is added to the local filtering and max pooling of CNN
Architecture. The proposed Architecture is evaluated using the standard MNIST
dataset by limiting the data size and also with a small personal data sample
belonging to two different classes. Experimental results show that the proposed
hybrid CNN-AIS based recognition engine works well when the size of training
data is limited in siz
- …