1,573 research outputs found
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
Isoscalar meson spectroscopy from lattice QCD
We extract to high statistical precision an excited spectrum of
single-particle isoscalar mesons using lattice QCD, including states of high
spin and, for the first time, light exotic JPC isoscalars. The use of a novel
quark field construction has enabled us to overcome the long-standing challenge
of efficiently including quark-annihilation contributions. Hidden-flavor mixing
angles are extracted and while most states are found to be close to ideally
flavor mixed, there are examples of large mixing in the pseudoscalar and axial
sectors in line with experiment. The exotic JPC isoscalar states appear at a
mass scale comparable to the exotic isovector states.Comment: 4 pages, 4 figure
Recommended from our members
Resonances in coupled πk,ηK scattering from lattice QCD
Coupled-channel and scattering amplitudes are determined by
studying the finite-volume energy spectra obtained from dynamical lattice QCD
calculations. Using a large basis of interpolating operators, including both
those resembling a construction and those resembling a pair of
mesons with relative momentum, a reliable excited-state spectrum can be
obtained. Working at , we find a gradual increase in
the phase-shift which may be identified with a broad scalar
resonance that couples strongly to and weakly to . The
low-energy behavior of this amplitude suggests a virtual bound-state that may
be related to the resonance. A bound state with is found
very close to the threshold energy, whose coupling to the
channel is compatible with that of the experimental . Evidence is
found for a narrow resonance in . Isospin--3/2 scattering is
also studied and non-resonant phase-shifts spanning the whole elastic
scattering region are obtained.We thank our colleagues within the Hadron Spectrum
Collaboration. We also thank R. Briceno, M.R. Pennington,
C.J.Shultz and A.P. Szczepaniak for fruitful discussions.
Chroma [63] and QUDA [64, 65] were used to perform
this work on clusters at Jefferson Laboratory under the
USQCD Initiative and the LQCD ARRA project. Gauge
configurations were generated using resources awarded
from the U.S. Department of Energy INCITE program
at Oak Ridge National Lab, the NSF Teragrid at the
Texas Advanced Computer Center and the Pittsburgh
Supercomputer Center, as well as at Jefferson Lab. RGE
and JJD acknowledge support from U.S. Department of
Energy contract DE-AC05-06OR23177, under which Jefferson
Science Associates, LLC, manages and operates
Jefferson Laboratory. JJD acknowledges support from
the U.S. Department of Energy Early Career award contract
DE-SC0006765. CET acknowledges partial support
from the Science and Technology Facilities Council
(U.K.) [grant number ST/L000385/1].This is the accepted manuscript. The final version is available at http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.054008
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
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