ImprovedΥspectrum with dynamical Wilson fermions

Abstract

We present results for the bb spectrum obtained using an O(M b v 6 )-correct non-relativistic lattice QCD action, where M b denotes the bare b-quark mass and v 2 is the mean squared quark velocity. Propagators are evaluated on SESAM's three sets of dynamical gauge configurations generated with two flavours of Wilson fermions at β = 5.6. These results, the first of their kind obtained with dynamical Wilson fermions, are compared to a quenched analysis at equivalent lattice spacing, β = 6.0. Using our three sea-quark values we perform the "chiral" extrapolation to m eff = m s /3, where m s denotes the strange quark mass. The light quark mass dependence is found to be small in relation to the statistical errors. Comparing the full QCD result to our quenched simulation we find better agreement of our dynamical data with experimental results in the spin-independent sector but observe no unquenching effects in hyperfine-splittings. To pin down the systematic errors we have also compared quenched results in different "tadpole" schemes as well as using a lower order action. We find * email: spitz@hlrz.kfa-juelich.de † email: hoeber@theorie.physik.uni-wuppertal.de 1 that spin-splittings with an O(M b v 4 ) action are O(10 %) higher compared to O(M b v 6 ) results. Relative to the results obtained with the plaquette method the Landau gauge mean link tadpole scheme raises the spin splittings by about the same margin so that our two improvements are opposite in effect.2

αSfromΥspectroscopy with dynamical Wilson fermions

“…We did not tune the bare b-quark mass but kept am b = 1.7 throughout the simulation. This value reproduces the correct Υ mass in the quenched approximation [13] and it turns out to be adequate in the full theory, too, leading to kinetic masses m kin (Υ) = 9.97(28), 9.63(24), 9.68(27) GeV for κ = 0.1560, 0.1570, 0.1575, respectively.…”

Mass of theηbandαsfrom the Nonrelativistic Renormalization Group

“…Our prediction for the bottomonium HFS can be compared with those obtained either on the lattice [26] or with potential models (for a recent discussion see Ref. [27], and references therein).…”

Production of singletP-wavecc¯andbb¯Godfrey1, Rosner2 2002Phys. Rev. D8818860View full textAdd to dashboardCite

“…For QCD-motivated potential models the triplet-singlet splittings test the Lorentz nature of the confining potential with different combinations of Lorentz scalar, vector, etc., giving rise to different orderings of the triplet-singlet splittings in the heavy quarkonium P-wave mesons. Furthermore, the observation of cc and bb states and the measurement of their masses is an important validation of lattice QCD calculations [29,30,31,32,33,34], which will lead to greater confidence in their application in extracting electroweak quantities from hadronic processes. Under the assumption of a Fermi-Breit Hamiltonian and only vector-like and scalar-like components in the central potential, Stubbe and Martin [35] predicted that the n 1 P 1 mass lies no lower than the spin-averaged 3 P J masses (weighted with the factors 2J + 1), denoted by n 3 P cog .…”