0000000000061941
AUTHOR
Ciaran Hughes
Improving the kinetic couplings in lattice nonrelativistic QCD
We improve the non-relativistic QCD (NRQCD) action by comparing the dispersion relation to that of the continuum through $\mathcal{O}(p^6)$ in perturbation theory. The one-loop matching coefficients of the $\mathcal{O}(p^4)$ kinetic operators are determined, as well as the scale at which to evaluate $\alpha_s$ in the $V$-scheme for each quantity. We utilise automated lattice perturbation theory using twisted boundary conditions as an infrared regulator. The one-loop radiative corrections to the mass renormalisation, zero-point energy and overall energy-shift of an NRQCD $b$-quark are also found. We also explore how a Fat$3$-smeared NRQCD action and changes of the stability parameter $n$ aff…
Hindered M1 radiative decay ofϒ(2S)from lattice NRQCD
We present a calculation of the hindered M1 $\mathrm{\ensuremath{\Upsilon}}(2S)\ensuremath{\rightarrow}{\ensuremath{\eta}}_{b}(1S)\ensuremath{\gamma}$ decay rate using lattice nonrelativistic quantum chromodynamics. The calculation includes spin-dependent relativistic corrections to the NRQCD action through $\mathcal{O}({v}^{6})$ in the quark's relative velocity, relativistic corrections to the leading order current which mediates the transition through the quark's magnetic moment, radiative corrections to the leading spin-magnetic coupling and for the first time a full error budget. We also use gluon field ensembles at multiple lattice spacing values, all of which include $u$, $d$, $s$ and…