Decay constants of B-mesons from non-perturbative HQET with two light dynamical quarks

We present a computation of B-meson decay constants from lattice QCD simulations within the framework of Heavy Quark Effective Theory for the b-quark. The next-to-leading order corrections in the HQET expansion are included non-perturbatively. Based on <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>N</mi></mrow><mrow><mi mathvariant="normal">f</mi></mrow></msub><mo>=</mo><mn>2</mn></math> gauge field ensembles, covering three lattice spacings <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>a</mi><mo>≈</mo><mo stretchy="false">(</mo><mn>0.08</mn><mtext>–</mtext><mn>0.05</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext>fm</mtext></math> and pion masses down to <math altimg="si3.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mn>190</mn><mtext> </mtext><mtext>MeV</mtext></math> , a variational method for extracting hadronic matrix elements is used to keep systematic errors under control. In addition we perform a careful autocorrelation analysis in the extrapolation to the continuum and to the physical pion mass limits. Our final results read <math altimg="si4.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>f</mi></mrow><mrow><mi mathvariant="normal">B</mi></mrow></msub><mo>=</mo><mn>186</mn><mo stretchy="false">(</mo><mn>13</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext>MeV</mtext></math> , <math altimg="si5.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>f</mi></mrow><mrow><msub><mrow><mi mathvariant="normal">B</mi></mrow><mrow><mi mathvariant="normal">s</mi></mrow></msub></mrow></msub><mo>=</mo><mn>224</mn><mo stretchy="false">(</mo><mn>14</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext>MeV</mtext></math> and <math altimg="si6.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>f</mi></mrow><mrow><msub><mrow><mi mathvariant="normal">B</mi></mrow><mrow><mi mathvariant="normal">s</mi></mrow></msub></mrow></msub><mo stretchy="false">/</mo><msub><mrow><mi>f</mi></mrow><mrow><mi mathvariant="normal">B</mi></mrow></msub><mo>=</mo><mn>1.203</mn><mo stretchy="false">(</mo><mn>65</mn><mo stretchy="false">)</mo></math> . A comparison with other results in the literature does not reveal a dependence on the number of dynamical quarks, and effects from truncating HQET appear to be negligible

Simulation of QCD with N f = 2 + 1 flavors of non-perturbatively improved Wilson fermions

We describe a new set of gauge configurations generated within the CLS effort. These ensembles have N f = 2 + 1 flavors of non-perturbatively improved Wilson fermions in the sea with the Lüscher-Weisz action used for the gluons. Open boundary conditions in time are used to address the problem of topological freezing at small lattice spacings and twisted-mass reweighting for improved stability of the simulations. We give the bare parameters at which the ensembles have been generated and how these parameters have been chosen. Details of the algorithmic setup and its performance are presented as well as measurements of the pion and kaon masses alongside the scale parameter t 0