1,721,151 research outputs found
Sea quark effects in B(K) from N(f)=2 clover-improved Wilson fermions
No full textWe report calculations of BK using two flavours of dynamical clover-improved Wilson lattice fermions and look for dependence on the dynamical quark mass at fixed lattice spacing. We see some evidence for dynamical quark effects. In particular BK decreases as the sea quark masses are reduced towards the up/down quark mass. Our meson masses are quite heavy and a firm prediction of BK is a task for future simulations
First results from the UKQCD collaboration
No full textWe present the first physics results for quenched QCD and for pure SU(2) gauge theory from the UKQCD collaboration. We report preliminary results for static quark potentials, the string tension and the quenched hadron spectrum on a 243 × 48 lattice at β = 6.2 using the standard Wilson fermion action and an O(a) improved nearest-neighbour Wilson fermion action. Our codes run at in excess of 1.5 Gflops in the 64-node Meiko i860-based Computing Surface at Edinburgh. We have also simulated pure gauge SU(2) theory on a 483 × 56 lattice at β = 2.85 to explore the approach to the continuum limit. © 1992
Recent lattice QCD results from the UKQCD collaboration
No full textThe lattice technique of studying the strong interaction of matter is used to obtain predictions of the hadronic spectrum. These simulations were performed by the UKQCD collaboration using full (unquenched) QCD. Details of the results, a comparison with quenched data, and novel methods of extracting spectral properties are described
Geometrical volume effects in the computation of the slope of the isgur-wise function
No full textWe use a method recently suggested for evaluating the slope of the Isgur-Wise function, at the zero-recoil point, on the lattice. The computations are performed in the quenched approximation to lattice QCD, on a 24(3) x 48 lattice at beta = 6.2, using an O(a)-improved action for the fermions. We have found unexpectedly large finite-volume effects in such a calculation. These volume corrections turned out to be purely geometrical and independent of the dynamics of the system. After the study of these effects on a smaller volume and for different quark masses, we give approximate expressions that account for them. Using these approximations we find xi'(1) = -1.7 (+2)(-2) and xi'(1) = -1.4 (+2)(-1) for the slope of the Isgur-Wise function, for two mesons composed of a heavy quark slightly heavier and lighter, respectively, than the charm quark, and in both cases, a light antiquark whose mass is about that of the strange quark
Scaling and asymptotic scaling in the SU(2) gauge theory
Full text linkFingberg J, Heller UM, Karsch F. Scaling and asymptotic scaling in the SU(2) gauge theory. Nuclear Physics, B. 1993;392(2):493-517.We determine the critical couplings for the deconfinement phase transition in SU(2) gauge theory on N(tau) x N(sigma)3 lattices with N(tau) = 8 and 16 and N(sigma) varying between 16 and 48. A comparison with string tension data shows scaling of the ratio T(c)/square-root sigma in the entire coupling regime beta = 2.30-2.75, while the individual quantities still exhibit large scaling violations. We find T(c)/square-root sigma = 0.69(2). We also discuss in detail the extrapolation of T(c)/LAMBDA(MSBAR) and square-root sigma/LAMBDA(MSBAR) to the continuum limit. Our result, which is consistent with the above ratio, is T(c)/LAMBDA(MSBAR) = 1.23(11) and square-root sigma/LAMBDA(MSBAR) = 1.79(12). We also comment upon corresponding results for SU(3) gauge theory and four-flavour QCD
An exploratory study of B(K) from N(f) = 2 clover-improved Wilson fermions
No full textWe report calculations of Bk using two flavours of dynamical clover-improved Wilson lattice fermions and look for dependence on the dynamical quark mass at fixed lattice spacing. We see some evidence for dynamical quark effects. In particular Bk decreases as the sea quark masses are reduced towards the up/down quark mass. Our meson masses are quite heavy and a firm prediction of the Bk value is a task for future simulations
The kaon semileptonic form factor with near physical domain wall quarks
No full textWe present a new calculation of the K → π semileptonic form factor at zero momentum transfer in domain wall lattice QCD with N f = 2+1 dynamical quark flavours. By using partially twisted boundary conditions we simulate directly at the phenomenologically relevant point of zero momentum transfer. We perform a joint analysis for all available ensembles which include three different lattice spacings (a = 0.09 - 0.14 fm), large physical volumes (m π L > 3.9) and pion masses as low as 171 MeV. The comprehensive set of simulation points allows for a detailed study of systematic effects leading to the prediction f+Kπ(0)=0.9670(20) (-46+18), where the first error is statistical and the second error systematic. The result allows us to extract the CKM-matrix element | Vu|=0.2237(-8+13) and confirm first-row CKM-unitarity in the Standard Model at the sub per mille level. © 2013 SISSA, Trieste, Italy.RBC/UKQCD collaboration, P.A. Boyle, J.M. Flynn, N. Garron, A. Jüttner, C.T. Sachrajda, K. Sivalingam, and J.M. Zanott
The axial charge of the nucleon on the lattice and in chiral perturbation theory
No full textWe present recent Monte Carlo data for the axial charge of the nucleon obtained by the QCDSF-UKQCD collaboration for Nf=2 dynamical quarks. We compare them with formulae from chiral perturbation theory in finite and infinite volume and find a remarkably consistent picture
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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