2,069 research outputs found
Exotic Tetraquark states with two -quarks and and states in a nonperturbatively-tuned Lattice NRQCD setup
We use Wilson-clover gauge-field ensembles from the CLS consortium
in a Lattice NRQCD setup to predict the binding energy of a
tetraquark and a
tetraquark. We determine the binding energies with respect to the relevant
and thresholds respectively to be MeV for the
, and MeV for the . We
also determine the ground-state and mesons
to lie and MeV below the and thresholds
respectively. Our errors are entirely dominated by systematics due to
discretisation effects. To achieve these measurements, we performed a neural
network based nonperturbative tuning of the Lattice NRQCD Hamiltonian's
parameters against the basic bottomonium spectrum. For all lattice spacings
considered we can reproduce the continuum splittings of low-lying bottomonia.
It is worth remarking that our nonperturbative tuning parameters deviate from 1
by significant amounts, particularly the term .Comment: 48 pages, 16 figure
Charmonia in moving frames
Lattice simulation of charmonium resonances with non-zero momentum provides
additional information on the two-meson scattering matrices. However, the
reduced rotational symmetry in a moving frame renders a number of states with
different in the same lattice irreducible representation. The
identification of for these states is particularly important, since
quarkonium spectra contain a number of states with different in a
relatively narrow energy region. Preliminary results concerning
spin-identification are presented in relation to our study of charmonium
resonances in flight on the Nf=2+1 CLS ensembles.Comment: 6 pages, presented at the 35th International Symposium on Lattice
Field Theory, 18-24 June 2017, Granada, Spai
Charmonium mass splittings at the physical point
We present results from an ongoing study of mass splittings of the lowest
lying states in the charmonium system. We use clover valence charm quarks in
the Fermilab interpretation, an improved staggered (asqtad) action for sea
quarks, and the one-loop, tadpole-improved gauge action for gluons. This study
includes five lattice spacings, 0.15, 0.12, 0.09, 0.06, and 0.045 fm, with two
sets of degenerate up- and down-quark masses for most spacings. We use an
enlarged set of interpolation operators and a variational analysis that permits
study of various low-lying excited states. The masses of the sea quarks and
charm valence quark are adjusted to their physical values. This large set of
gauge configurations allows us to extrapolate results to the continuum physical
point and test the methodology.Comment: 7 pp, 6 figs, Lattice 201
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