40,371 research outputs found
The kaon semileptonic form factor with near physical domain wall quarks
No full textWe present a new calculation of the K → π semileptonic form factor at zero momentum transfer in domain wall lattice QCD with N f = 2+1 dynamical quark flavours. By using partially twisted boundary conditions we simulate directly at the phenomenologically relevant point of zero momentum transfer. We perform a joint analysis for all available ensembles which include three different lattice spacings (a = 0.09 - 0.14 fm), large physical volumes (m π L > 3.9) and pion masses as low as 171 MeV. The comprehensive set of simulation points allows for a detailed study of systematic effects leading to the prediction f+Kπ(0)=0.9670(20) (-46+18), where the first error is statistical and the second error systematic. The result allows us to extract the CKM-matrix element | Vu|=0.2237(-8+13) and confirm first-row CKM-unitarity in the Standard Model at the sub per mille level. © 2013 SISSA, Trieste, Italy.RBC/UKQCD collaboration, P.A. Boyle, J.M. Flynn, N. Garron, A. Jüttner, C.T. Sachrajda, K. Sivalingam, and J.M. Zanott
Effects of finite volume on the KL-KS mass difference
No full textPhenomena that involve two or more on-shell particles are particularly sensitive to the effects of finite volume and require special treatment when computed using lattice QCD. In this paper we generalize the results of Lüscher and Lellouch and Lüscher, which determine the leading-order effects of finite volume on the two-particle spectrum and two-particle decay amplitudes to determine the finite-volume effects in the second-order mixing of the K0 and K0 ̄ states. We extend the methods of Kim, Sachrajda, and Sharpe to provide a direct, uniform treatment of these three, related, finite-volume corrections. In particular, the leading, finite-volume corrections to the KL-KS mass difference ΔMK and the CP-violating parameter εK are determined, including the potentially large effects which can arise from the near degeneracy of the kaon mass and the energy of a finite-volume, two-pion state
Renormalons and the heavy quark effective theory
No full textWe propose a non-perturbative method for defining the higher dimensional operators which appear in the Heavy Quark Effective Theory (HQET), such that their matrix elements are free of renormalon singularities, and diverge at most logarithmically with the ultra-violet cut-off. Matrix elements of these operators can be computed numerically in lattice simulations of the HQET. We illustrate our procedures by presenting physical definitions of the binding energy (\lb) and of the kinetic energy (-\lambda_1/2m_Q) of the heavy quark in a hadron. This allows us to define a ``subtracted pole mass", whose inverse can be used as the expansion parameter in applications of the HQET.We propose a non-perturbative method for defining the higher dimensional operators which appear in the Heavy Quark Effective Theory (HQET), such that their matrix elements are free of renormalon singularities, and diverge at most logarithmically with the ultra-violet cut-off. Matrix elements of these operators can be computed numerically in lattice simulations of the HQET. We illustrate our procedures by presenting physical definitions of the binding energy (\lb) and of the kinetic energy (-) of the heavy quark in a hadron. This allows us to define a ``subtracted pole mass", whose inverse can be used as the expansion parameter in applications of the HQET.We propose a non-perturbative method for defining the higher dimensional operators which appear in the Heavy Quark Effective Theory (HQET), such that their matrix elements are free of renormalon singularities, and diverge at most logarithmically with the ultra-violet cut-off. Matrix elements of these operators can be computed numerically in lattice simulations of the HQET. We illustrate our procedures by presenting physical definitions of the binding energy (\lb) and of the kinetic energy (-) of the heavy quark in a hadron. This allows us to define a ``subtracted pole mass", whose inverse can be used as the expansion parameter in applications of the HQET.We propose a non-perturbative method for defining the higher dimensional operators which appear in the Heavy Quark Effective Theory (HQET), such that their matrix elements are free of renormalon singularities, and diverge at most logarithmically with the ultra-violet cut-off. Matrix elements of these operators can be computed numerically in lattice simulations of the HQET. We illustrate our procedures by presenting physical definitions of the binding energy ( Λ and of the kinetic energy ( −λ 1 2m Q ) of the heavy quark in a hadron. This allows us to define a “subtracted pole mass”, whose inverse can be used as the expansion parameter in applications of the HQET. We also discuss the determination of the Wilson coefficients of the subtracted operators, necessary for predictions of physical quantities, such as the running quark mass m Q in the MS scheme
The invisible renormalon
No full textWe study the structure of renormalons in the Heavy Quark Effective Theory, by expanding the heavy quark propagator in powers of 1/m_Q. We demonstrate that the way in which renormalons appear depends on the regularisation scheme used to define the effective theory. In order to investigate the relation between ultraviolet renormalons and power divergences of matrix elements of higher-dimensional operators in the heavy quark expansion, we perform calculations in dimensional regularisation and in three different cut-off regularisation schemes. In the case of the kinetic energy operator, we find that the leading ultraviolet renormalon which corresponds to a quadratic divergence, is absent in all but one (the lattice) regularisation scheme. The nature of this ``invisible renormalon'' remains unclear.We study the structure of renormalons in the Heavy Quark Effective Theory, by expanding the heavy quark propagator in powers of . We demonstrate that the way in which renormalons appear depends on the regularisation scheme used to define the effective theory. In order to investigate the relation between ultraviolet renormalons and power divergences of matrix elements of higher-dimensional operators in the heavy quark expansion, we perform calculations in dimensional regularisation and in three different cut-off regularisation schemes. In the case of the kinetic energy operator, we find that the leading ultraviolet renormalon which corresponds to a quadratic divergence, is absent in all but one (the lattice) regularisation scheme. The nature of this ``invisible renormalon'' remains unclear.We study the structure of renormalons in the Heavy Quark Effective Theory, by expanding the heavy quark propagator in powers of . We demonstrate that the way in which renormalons appear depends on the regularisation scheme used to define the effective theory. In order to investigate the relation between ultraviolet renormalons and power divergences of matrix elements of higher-dimensional operators in the heavy quark expansion, we perform calculations in dimensional regularisation and in three different cut-off regularisation schemes. In the case of the kinetic energy operator, we find that the leading ultraviolet renormalon which corresponds to a quadratic divergence, is absent in all but one (the lattice) regularisation scheme. The nature of this ``invisible renormalon'' remains unclear.We study the structure of renormalons in the Heavy Quark Effective Theory, by expanding the heavy quark propagator in powers of . We demonstrate that the way in which renormalons appear depends on the regularisation scheme used to define the effective theory. In order to investigate the relation between ultraviolet renormalons and power divergences of matrix elements of higher-dimensional operators in the heavy quark expansion, we perform calculations in dimensional regularisation and in three different cut-off regularisation schemes. In the case of the kinetic energy operator, we find that the leading ultraviolet renormalon which corresponds to a quadratic divergence, is absent in all but one (the lattice) regularisation scheme. The nature of this ``invisible renormalon'' remains unclear.We study the structure of renormalons in the Heavy Quark Effective Theory, by expanding the heavy quark propagator in powers of 1/ m Q . We demonstrate that the way in which renormalons appear depends on the regularization scheme used to define the effective theory. In order to investigate the relation between ultraviolet renormalons and power divergences of matrix elements of higher-dimensional operators in the heavy quark expansion, we perform calculations in dimensional regularization and in three different cut-off regularization schemes. In the case of the kinetic energy operator, we find that the leading ultraviolet renormalon, which corresponds to a quadratic divergence, is absent in all but one (the lattice) regularization scheme. The nature of this “invisible renormalon” remains unclear
A High-Statistics Lattice Calculation of and in the meson
No full textWe present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found ~GeV, which is interesting for phenomenological applications. We also find GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found GeV, which is interesting for phenomenological applications. We also find GeV, corresponding to GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found GeV, which is interesting for phenomenological applications. We also find GeV, corresponding to GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found GeV, which is interesting for phenomenological applications. We also find GeV, corresponding to GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy − λ 1 /2 m b of the heavy quark inside the B -meson and of the chromo-magnetic term A2, related to the B ∗ −B mass splitting, performed in the HQET Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at β = 6.0, on a lattice volume 24 3 × 40 and using, for the meson correlators, the results obtained with the SW-Clover O ( a ) improved lattice action for the light quarks. For the kinetic energy we found −λ 1 = 〈B| h ̄ (iD) 2 h|B〉/(2M B ) = −(0.09 ± 0.14) GeV 2 , which is interesting for phenomenological applications. We also found λ 2 = 0.07 ± 0.01 GeV 2 , corresponding to M B∗ 2 − M B 2 = 4λ 2 = 0.280 ± 0.060 GeV 2 , which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified
Kappa to pi semileptonic form factor with 2+1 flavor domain wall fermions on the lattice
No full textD. J. Antonio, P. A. Boyle, C. Dawson, T. Izubuchi, A. Jüttner, C. Sachrajda, S. Sasaki, A. Soni, R. J. Tweedie, J. M. Zanotti, UKQCD and RBC Collaborationshttp://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=4
A general method for non-perturbative renormalization of lattice operators
No full textWe propose a non-perturbative method for computing the renormalization constants of generic composite operators. This method is intended to reduce some systematic errors, which are present when one tries to obtain physical predictions from the matrix elements of lattice operators. We also present the results of a calculation of the renormalization constants of several two-fermion operators, obtained, with our method, by numerical simulation of QCD, on a 16^3 \times 32 lattice, at \beta=6.0. The results of this simulation are encouraging, and further applications to four-fermion operators and to the heavy quark effective theory are proposed.We propose a non-perturbative method for computing the renormalization constants of generic composite operators. This method is intended to reduce some systematic errors, which are present when one tries to obtain physical predictions from the matrix elements of lattice operators. We also present the results of a calculation of the renormalization constants of several two-fermion operators, obtained, with our method, by numerical simulation of , on a lattice, at . The results of this simulation are encouraging, and further applications to four-fermion operators and to the heavy quark effective theory are proposed.We propose a non-perturbative method for computing the renormalization constants of generic composite operators. This method is intended to reduce some systematic errors, which are present when one tries to obtain physical predictions from the matrix elements of lattice operators. We also present the results of a calculation of the renormalization constants of several two-fermion operators, obtained, with our method, by numerical simulation of QCD, on a 16 3 x 32 lattice, at β = 6.0. The results of this simulation are encouraging, and further applications to four-fermion operators and to the heavy quark effective theory are proposed
A high statistics lattice calculation of the b-meson binding energy
No full textWe present a high statistics lattice calculation of the B--meson binding energy \overline{\Lambda} of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at \beta=6.0, 6.2 and 6.4 and using, for the meson correlators, the results obtained by the APE group at the same values of \beta. Our best estimate, obtained by combining results at different values of \beta, is \overline{\Lambda}=180^{+30}_{-20} MeV. For the \overline{MS} running mass, we obtain \overline{m}_{b}(\overline{m}_{b})=4.15 \pm 0.05 \pm 0.20 GeV, in reasonable agreement with previous determinations. The systematic error is the truncation of the perturbative series in the matching condition of the relevant operator of the Heavy Quark Effective Theory.We present a high statistics lattice calculation of the B -meson binding energy Λ of the heavy-quark inside the pseudoscalar B -meson. Our numerical results have been obtained from several independent numerical simulations at β = 6.0, 6.2 and 6.4, and using, for the meson correlators, the results obtained by the APE group at the same values of β. Our best estimate, obtained by combining results at different values of β, is Λ = 180 −20 +30 MeV. For the MS running mass, we obtain m b ( m b ) = 4.15 ± 0.05 ± 0.20 GeV , in reasonable agreement with previous determinations. The systematic error is the truncation of the perturbative series in the matching condition of the relevant operator of the Heavy Quark Effective Theory.We present a high statistics lattice calculation of the B--meson binding energy of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at , and , and using, for the meson correlators, the results obtained by the APE group at the same values of . Our best estimate, obtained by combining results at different values of , is MeV. For the running mass, we obtain GeV, in reasonable agreement with previous determinations. The systematic error is the truncation of the perturbative series in the matching condition of the relevant operator of the Heavy Quark Effective Theory
First lattice calculation of the B-meson binding and kinetic energies
No full textWe present the first lattice calculation of the B-meson binding energy \labar and of the kinetic energy -\lambda_1/2 m_Q of the heavy-quark inside the pseudoscalar B-meson. This calculation has required the non-perturbative subtraction of the power divergences present in matrix elements of the Lagrangian operator \bar h D_4 h and of the kinetic energy operator \bar h \vec D^2 h. The non-perturbative renormalisation of the relevant operators has been implemented by imposing suitable renormalisation conditions on quark matrix elements, in the Landau gauge. Our numerical results have been obtained from several independent numerical simulations at \beta=6.0 and 6.2, and using, for the meson correlators, the results obtained by the APE group at the same values of \beta. Our best estimate, obtained by combining results at different values of \beta, is \labar =190 \err{50}{30} MeV. For the \overline{MS} running mass, we obtain \overline {m}_b(\overline {m}_b) =4.17 \pm 0.06 GeV, in reasonable agreement with previous determinations. From a subset of 36 configurations, we were only able to establish a loose upper bound on the b-quark kinetic energy in a B-meson, \lambda_1=\langle B \vert \bar h \vec{D}^{2} h \vert B \rangle /(2 M_B )<~1\, GeV^2. This shows that a much larger statistical sample is needed to determine this important parameter.We present the first lattice calculation of the B-meson binding energy \labar and of the kinetic energy of the heavy-quark inside the pseudoscalar B-meson. This calculation has required the non-perturbative subtraction of the power divergences present in matrix elements of the Lagrangian operator and of the kinetic energy operator . The non-perturbative renormalisation of the relevant operators has been implemented by imposing suitable renormalisation conditions on quark matrix elements, in the Landau gauge. Our numerical results have been obtained from several independent numerical simulations at and , and using, for the meson correlators, the results obtained by the APE group at the same values of . Our best estimate, obtained by combining results at different values of , is \labar =190 \err{50}{30} MeV. For the running mass, we obtain GeV, in reasonable agreement with previous determinations. From a subset of 36 configurations, we were only able to establish a loose upper bound on the -quark kinetic energy in a -meson, 1\, GeV. This shows that a much larger statistical sample is needed to determine this important parameter.We present the first lattice calculation of the B-meson binding energy Λ and of the kinetic energy − λ 1 /2 m Q of the heavy-quark inside the pseudoscalar B-meson. This calculation has required the non-perturbative subtraction of the power divergences present in matrix elements of the Lagrangian operator h − D 4 h and of the kinetic energy operator h − D 2 h . The non-perturbative renormalisation of the relevant operators has been implemented by imposing suitable renormalisation conditions on quark matrix elements, in the Landau gauge. Our numerical results have been obtained from several independent numerical simulations at β = 6.0 and 6.2, and using, for the meson correlators, the results obtained by the APE group at the same values of β. Our best estimate, obtained by combining results at different values of β, is Λ − = 190 −30 +50 MeV . For the MS running mass, we obtain m b ( m b ) = 4.17 ± 0.06 GeV , in reasonable agreement with previous determinations. From a subset of 36 configurations, we were only able to establish a loose upper bound on the b-quark kinetic energy in a B -meson, Λ = 〈B∥ h − D 2 h∥B〉/(2M B ) < 1 GeV 2 . This shows that a much larger statistical sample is needed to determine this important parameter
- …
