1,721,029 research outputs found
Phenomenological applications of non-perturbative heavy quark effective theory
No full textWe briefly review the strategy to perform non-perturbative heavy quark effective theory computations and we specialize to the case of the b quark mass which has recently been computed including the 1/m term. © 2008 IOP Publishing Ltd
Non-perturbative renormalization and running of ΔF = 2 four-fermion operators in the SF scheme
Full text linkWe present preliminary results of a non-perturbative study of the scale-dependent renormalization constants of a complete basis of ∆F = 2 parity-odd four-fermion operators that enter the computation of hadronic B-parameters within the Standard Model (SM) and beyond. We consider non-perturbatively O(a) improved Wilson fermions and our gauge configurations contain two flavors of massless sea quarks. The mixing pattern of these operators is the same as for a regularization that preserves chiral symmetry, in particular there is a "physical" mixing between some of the operators. The renormalization group running matrix is computed in the continuum limit for a family of Schrödinger Functional (SF) schemes through finite volume recursive techniques. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale, together with the non-perturbative matching matrix between the lattice regularized theory and the various
SF schemes
Renormalization of HQET Delta B=2 operators: O(a) improvement and 1/m matching with QCD
No full textWe determine a basis of dimension-7 operators which arise at O(a) in the Symanzik expansion of the ∆B = 2 operators with static heavy quarks. We consider both Wilson-like and Ginsparg-Wilson light quarks. Exact chiral symmetry reduces the number of these O(a) counterterms by a factor of two. Only a subset of these operators has previously appeared in the literature. We then
extend the analysis to the O(1/m) operators contributing beyond the static approximation
Heavy quark effective theory computation of the mass of the bottom quark
No full textWe present a fully non-perturbative computation of the mass of the b-quark in the quenched approximation. Our strategy starts from the matching of HQET to QCD in a finite volume and finally relates the quark mass to the spin averaged mass of the Bs meson in HQET. All steps include the terms of order Λ2/mb. Expanding on [1], we discuss the computation and renormalization of correlation functions at order 1/mb. With the strange quark mass fixed from the Kaon mass and the QCD scale set through r0 ≤ 0.5fm, we obtain a renormalization group invariant mass Mb ≤ 6.758(86)GeV or b(b) ≤ 4.347(48)GeV in the scheme. The uncertainty in the computed Λ2/m b terms contributes little to the total error and Λ3/mb 2 terms are negligible. The strategy is promising for full QCD as well as for other B-physics observables. © SISSA 2007
Extracting excited states from lattice QCD: the Roper resonance
No full textAbstractWe present a new method for extracting excited states from a single two-point correlation function calculated on the lattice. Our method simply combines the correlation function evaluated at different time slices so as to “subtract” the leading exponential decay (ground state) and to give access to the first excited state. The method is applied to a quenched lattice study (volume=243×64, β=6.2, a−1=2.55 GeV) of the first excited state of the nucleon using the local interpolating operator O=ɛabc[uaTCγ5db]uc. The results are consistent with the identification of our extracted excited state with the Roper resonance N′(1440). The switching of the level ordering with respect to the negative-parity partner of the nucleon, N*(1535), is not seen at the simulated quark masses and, basing on crude extrapolations, is tentatively expected to occur close to the physical point
New extended interpolating operators for hadron correlation functions
Full text linkNew extended interpolating operators made of quenched three dimensional fermions are introduced in the context of lattice QCD. The mass of the 3D fermions can be tuned in a controlled way to find a better overlap of the extended operators with the states of interest. The extended operators have good renormalisation properties and are easy to control when taking the continuum limit. Moreover the short distance behaviour of the two point functions built from these operators is greatly improved. The operators have been numerically implemented and a comparison to point sources and Jacobi smeared sources has been performed on the new CLS configurations
Non-perturbative renormalization of static-light four-fermion operators in quenched lattice QCD
No full textWe perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by non-perturbatively improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered.We perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by non-perturbatively improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered
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