Heavy meson masses and decay constants from relativistic heavy quarks in full lattice QCD

TL;DR

This paper calculates heavy meson masses and decay constants using relativistic lattice QCD, covering charm to bottom quarks, and compares results with models and other meson systems.

Contribution

It introduces a fully relativistic formalism for heavy quarks in lattice QCD to determine meson properties across a range of heavy quark masses.

Findings

Calculated f_{B_c} = 0.427(6) GeV and m_{B_c} = 6.285(10) GeV.

Found f_{} = 0.667(6) GeV, close to f_{} and confirming small spin effects.

Observed B_c meson behavior resembles heavy-light systems more than heavy-heavy.

Abstract

We determine masses and decay constants of heavy-heavy and heavy-charm pseudoscalar mesons as a function of heavy quark mass using a fully relativistic formalism known as Highly Improved Staggered Quarks for the heavy quark. We are able to cover the region from the charm quark mass to the bottom quark mass using MILC ensembles with lattice spacing values from 0.15 fm down to 0.044 fm. We obtain f_{B_c} = 0.427(6) GeV; m_{B_c} = 6.285(10) GeV and f_{\eta_b} = 0.667(6) GeV. Our value for f_{\eta_b} is within a few percent of f_{\Upsilon} confirming that spin effects are surprisingly small for heavyonium decay constants. Our value for f_{B_c} is significantly lower than potential model values being used to estimate production rates at the LHC. We discuss the changing physical heavy-quark mass dependence of decay constants from heavy-heavy through heavy-charm to heavy-strange mesons. A comparison between the three different systems confirms that the B_c system behaves in some ways more like a heavy-light system than a heavy-heavy one. Finally we summarise current results on decay constants of gold-plated mesons.