571 research outputs found
The eta' meson from lattice QCD
We study the flavour singlet pseudoscalar mesons from first principles using
lattice QCD. With N_f=2 flavours of light quark, this is the so-called eta_2
meson and we discuss the phenomenological status of this. Using maximally
twisted-mass lattice QCD, we extract the mass of the eta_2 meson at two values
of the lattice spacing for lighter quarks than previously discussed in the
literature. We are able to estimate the mass value in the limit of light quarks
with their physical masses.Comment: 16 pages: version accepted for publicatio
Nucleon scalar and tensor charges using lattice QCD simulations at the physical value of the pion mass
We present results on the light, strange and charm nucleon scalar and tensor
charges from lattice QCD, using simulations with flavors of twisted
mass Clover-improved fermions with a physical value of the pion mass. Both
connected and disconnected contributions are included, enabling us to extract
the isoscalar, strange and charm charges for the first time directly at the
physical point. Furthermore, the renormalization is computed non-perturbatively
for both isovector and isoscalar quantities. We investigate excited state
effects by analyzing several sink-source time separations and by employing a
set of methods to probe ground state dominance. Our final results for the
scalar charges are , ,
, and for the tensor charges
, ,
, in the scheme at 2~GeV. The first error is statistical, the second is the
systematic error due to the renormalization and the third the systematic
arising from possible contamination due to the excited states.Comment: 20 pages and 13 figure
An estimate of the flavour singlet contributions to the hyperfine splitting in charmonium
We explore the splitting between flavour singlet and non-singlet mesons in
charmonium. This has implications for the hyperfine splitting in charmonium
The scalar spectrum of many-flavour QCD
The LatKMI collaboration is studying systematically the dynamical properties
of N_f = 4,8,12,16 SU(3) gauge theories using lattice simulations with (HISQ)
staggered fermions. Exploring the spectrum of many-flavour QCD, and its scaling
near the chiral limit, is mandatory in order to establish if one of these
models realises the Walking Technicolor scenario. Although lattice technologies
to study the mesonic spectrum are well developed, scalar flavour-singlet states
still require extra effort to be determined. In addition, gluonic observables
usually require large-statistic simulations and powerful noise-reduction
techniques. In the following, we present useful spectroscopic methods to
investigate scalar glueballs and scalar flavour-singlet mesons, together with
the current status of the scalar spectrum in N_f = 12 QCD from the LatKMI
collaboration.Comment: 9 pages, 5 figures, 1 table. To appear in the Proceedings of SCGT 12,
KMI, Nagoya University, Dec. 4-7, 201
and masses and decay constants
We present preliminary results for the masses and decay constants of the
and mesons using CLS ensembles. One of the
major challenges in these calculations are the large statistical fluctuations
due to disconnected quark loops. We tackle these by employing a combination of
noise reduction techniques which are tuned to minimize the statistical error at
a fixed cost. On the analysis side we carefully assess excited states
contributions by using a direct fit approach.Comment: 8 pages, 7 figures, talk presented at the 35th International
Symposium on Lattice Field Theory, 18-24 June 2017, Granada, Spain. v2:
corrected axis labe
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