arXiv subjects

P. McCallum

Publications and source records attributed to P. McCallum.

4 recordsLinked to original sources

arXiv1998

Scaling of the Upsilon Spectrum in Lattice NRQCD

We present results for the spectrum of b-bbar bound states in the quenched approximation for three different values of the lattice spacing, in the range 0.05fm to 0.15fm. We find our results for spin-independent splittings in physical units to be independent of the lattice spacing, indicating the absence of systematic errors from discretisation effects. Spin-dependent splittings are more sensitive to the lattice spacing and higher order corrections to the action; we discuss the size of these effects and what can be done to arrive at a physical result.

hep-lat↗

arXiv1998

New results on heavy hadron spectroscopy with NRQCD

We present results for the spectrum of b-bbar bound states in the quenched approximation for three different values of the lattice spacing. Results for spin-independent splittings are shown to have good scaling behaviour; spin-dependent splittings are more sensitive to discretisation effects. We discuss what needs to be done to match the experimental spectrum.

hep-lat↗

arXiv1997

Further Precise Determinations of $α_s$ from Lattice QCD

We present a new determination of the strong coupling constant from lattice QCD simulations. We use four different short-distance quantities to obtain the coupling, three different (infrared) meson splittings to tune the simulation parameters, and a wide range of lattice spacings, quark masses, and lattice volumes to test for systematic errors. Our final result consists of ten different determinations of $α^{(3)}_{P}(8.2 GeV)$, which agree well with each other and with our previous results. The most accurate of these, when evolved perturbatively to the $Z^0$ mass, gives $α^{(5)}_{\msbar}(M_Z) = .1174(24)$. We compare our results with those obtained from other recent lattice simulations.

hep-lat↗

arXiv1995

Update on Quarkonium Spectroscopy and $α_{strong}$ from NRQCD

NRQCD results for Upsilon and Charmonium using both dynamical and quenched configurations are presented. We investigate dependence on the light dynamical quark mass. Preliminary dynamical ($n_f = 2$) Charmonium data are combined with quenched results to extract the strong coupling constant $α_P^{(n_f)}$ for the physical number of light dynamical quarks, $n_f = 3$. Good agreement is found with calculations based on the Upsilon system. We show that a discrepancy in $α_P^{(n_f=0)}$, found between the Upsilon and Charmonium systems in the quenched theory, disappears upon extrapolating to the physical number of flavors. Results for the strong coupling constant $α_{\overline{MS}}$ are presented and sources of systematic error investigated.

hep-lat↗