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Register a new userB-physics from HQET in two-flavour lattice QCD
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We present our analysis of B physics quantities using non-perturbatively matched Heavy Quark Effective Theory (HQET) in Nf= 2 lattice QCD on the CLS ensembles. Using all-to-all propagators, HYP-smeared static quarks, and the Generalized Eigenvalue Problem (GEVP) approach with a conservative plateau selection procedure, we are able to systematically control all sources of error. With significantly increased statistics compared to last year, our preliminary results are mb (mb) = 4.22(10)(4)z GeV for the MS b-quark mass, and fB = 193(9)stat (4)_chi MeV and fBs = 219(12)stat MeV for the B-meson decay constants.
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We present preliminary results on the axial form factor $G_A(Q^2)$ and the induced pseudoscalar form factor $G_P(Q^2)$ of the nucleon. A systematic analysis of the excited-state contributions to form factors is performed on the CLS ensemble `N6 with $m_pi = 340 text{MeV}$ and lattice spacing $a sim 0.05 text{fm}$. The relevant three-point functions were computed with source-sink separations ranging from $t_s sim 0.6 text{fm}$ to $t_s sim 1.4 text{fm}$. We observe that the form factors suffer from non-trivial excited-state contributions at the source-sink separations available to us. It is noted that naive plateau fits underestimate the excited-state contributions and that the method of summed operator insertions correctly accounts for these effects.
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We present a new determination of the $B_s$ leptonic decay constant from lattice QCD simulations that use gluon configurations from MILC and a highly improved discretization of the relativistic quark action for both valence quarks. Our result, $f_{B_s} = 0.225(4)$,GeV, is almost three times more accurate than previous determinations. We analyze the dependence of the decay constant on the heavy quarks mass and obtain the first empirical evidence for the leading $1/sqrt{m_h}$ dependence predicted by Heavy Quark Effective Theory (HQET). As a check, we use our analysis technique to calculate the $m_{B_s}-m_{eta_b}/2$ mass difference. Our result agrees with experiment to within errors of $11,mathrm{MeV}$ (better than 2%). We discuss how to extend our analysis to other quantities in $B_s$ and $B$ physics, making 2%-precision possible for the first time.
We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.
We study the deconfinement transition in two-flavour lattice QCD with dynamical overlap fermions. Our simulations have been carried out on a $16^3 times 6$ lattice at a pion mass around 500 MeV with a special HMC algorithm without any approximation such as fixed topology. We consider several temperatures from 220 MeV which is close to the deconfinement to 280 MeV which is above it. The dependence of the Polyakov loop, the chiral condensate, the Dirac spectra and the connected part of chiral susceptibility on the inverse gauge coupling has been studied. Our data indicates that the transition point lies between $beta = 7.6$ and $beta = 8.1$, but a more precise determination is not possible with our present statistics.
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