We present the first lattice QCD calculation of the decay constants f_B and f_{B_s} with physical light quark masses. We use configurations generated by the MILC collaboration including the effect of u, d, s and c HISQ sea quarks at three lattice spacings and with three u/d quark mass values going down to the physical value. We use improved NRQCD for the valence b quarks. Our results are f_B = 0.186(4) GeV, f_{B_s} = 0.224(5) GeV, f_{B_s}/f_B = 1.205(7) and M_{B_s}-M_B=85(2) MeV, superseding earlier results with NRQCD b quarks. We discuss the implications of our results for the Standard Model rates for B_s -> mu+ mu- and B -> tau nu.
Lattice NRQCD with leading finite lattice spacing errors removed is used to calculate decay constants of mesons made up of heavy quarks. Quenched simulations are done with a tadpole improved gauge action containing plaquette and six-link rectangular terms. The tadpole factor is estimated using the Landau link. For each of the three values of the coupling constant considered, quarkonia are calculated for five masses spanning the range from charmonium through bottomonium, and one set of quark masses is tuned to the B(c). "Perturbative" and nonperturbative meson masses are compared. One-loop pert…
We present a progress report on new calculations of B and B_s meson decay constants employing NRQCD heavy and HISQ light valence quarks and using MILC N_f = 2+1 AsqTad lattices. Bare quark masses have been retuned in accord with HPQCD's new r_1 scale. We find significant reductions in discretization effects compared to previous calculations with AsqTad light valence quarks. Matching of the NRQCD/HISQ heavy-light axial vector current is carried out at one-loop order including all relevant dimension 4 current corrections.
The masses of spin-singlet and spin-triplet S-wave mesons containing a single heavy quark are computed in the quenched approximation. The light quark action and gauge field action are both classically-improved and tadpole-improved, and the couplings to the heavy quark are organized by the 1/M expansion of tadpole-improved NRQCD. At each of two lattice spacings, near 0.22fm and 0.26fm, meson masses are obtained for heavy quarks spanning the region between charmed and bottom mesons. Results up to O(1/M), O(1/M^2) and O(1/M^3) are displayed separately, so that the convergence of the heavy quark e…
Results for the spectrum of S and P-wave charmed mesons are obtained in the quenched approximation from a tadpole-improved anisotropic gauge field action and a D234 quark action. This is compared to the spectrum obtained from an NRQCD charm quark and a D234 light antiquark. NRQCD results for bottom mesons are also discussed.
We discuss recent results on the excitation spectra of B and D-mesons obtained in the framework of non-relativistic lattice QCD in the quenched approximation. The results allow for the determination of the $\msbar$-mass of $m_{b,\msbar}(m_{b,\msbar})= 4.34(7)$ GeV in ${\cal O}(α_s^3)$ in the perturbative matching. The determination of the decay constants f_{B_s} and f_{D_s} is discussed in detail. Results for the matrix elements of semi-leptonic B to D decays are shown.
The mass spectrum of S and P-wave mesons containing a single heavy quark is computed in the quenched approximation, using NRQCD up to third order in the inverse heavy quark mass expansion. Previous results found third order contributions which are as large in magnitude as the total second order contribution for the charmed S-wave spin splitting. The present work considers variations such as anisotropic lattices, Landau link tadpole improvement, and a highly-improved light quark action, and finds that the second order correction to the charmed S-wave spin splitting is about 20% of the leading o…
Preliminary results on spectrum and decay constant of $B$ mesons from a quenched simulation at $β= 6.0$ on an $16^3\times48$ lattice are discussed. The heavy quark has been implemented using both an NRQCD and the static formulation, the light one with a clover improved Wilson formulation. Both the NRQCD Hamiltonian and the heavy-light current consistently include terms of $O(1/M_{Q})$, the inverse heavy quark mass.
Heavy-light mesons can be studied using the 1/M expansion of NRQCD, provided the heavy quark mass is sufficiently large. Calculations of the S-wave charmed meson masses from a classically and tadpole-improved action are presented. A comparison of O(1/M), O(1/M^2) and O(1/M^3) results allows convergence of the expansion to be discussed. It is shown that the form of discretized heavy quark propagation must be chosen carefully.
We present {\it preliminary} results for the decay constants of heavy-light mesons using NRQCD heavy and tadpole improved Clover light quarks. A comparison is made with data obtained using Wilson light quarks. We present an analysis of the 1/M corrections to the decay constants in the static limit and compare with the predictions of HQET.
Lattice simulations of $B\toπlν$ decays are problematic in the low $q^{2}$ region when the pion has to have large momentum in the lattice frame for a $B$ meson at rest or moving slowly. The moving-NRQCD formalism provides a way around this by giving an accurate discretization of a $b$ quark moving at arbitrary velocity $v$, and therefore a $B$ meson moving at high momentum in the lattice frame. Here we show results from simulations of the moving-NRQCD action complete through $O(1/M)$ coupled to the asqtad action on a MILC fine ensemble. We show $B$, $B^{*}$ masses as a function of $v$ and demo…
Recent results for B meson decay constants with NRQCD b-quarks and clover light quarks are discussed. Perturbative matching factors through O($α/M$) are now available and incorporated into the analyses. An O($αa$) improvement term to the heavy-light axial current is identified and included. The slope of $f_{PS}\sqrt{M_{PS}}$ versus $1/M_{PS}$ is significantly reduced by these corrections.
We present a quenched lattice calculation of heavy-light meson decay constants, using non-relativistic (NRQCD) heavy quarks in the mass region of the $b$ quark and heavier, and clover-improved light quarks. The NRQCD Hamiltonian and the heavy-light current include the corrections at first order in the expansion in the inverse heavy quark mass. We study the dependence of the decay constants on the heavy meson mass $M$, for light quarks with the tree level ($c_{SW}$ = 1), as well as the tadpole improved clover coefficient. We compare decay constants from NRQCD with results from clover ($c_{SW}=1…
The masses of S- and P-wave heavy-light mesons are computed in quenched QCD using a classically and tadpole-improved action on anisotropic lattices. Of particular interest are the splittings among P-wave states, which have not yet been resolved experimentally; even the ordering of these states continues to be discussed in the literature. The present work leads to upper bounds for these splittings, and is suggestive, but not conclusive, about the ordering.
We determine the normalisation of scalar and pseudoscalar current operators made from non-relativistic $b$ quarks and Highly Improved Staggered light quarks in lattice Quantum Chromodynamics (QCD) through $\mathcal{O}(α_s)$ and $Λ_{\text{QCD}}/m_b$. We use matrix elements of these operators to extract $B$ meson decay constants and form factors, then compare to those obtained using the standard vector and axial-vector operators. This provides a test of systematic errors in the lattice QCD determination of the $B$ meson decay constants and form factors. We provide a new value for the $B$ and $B_…
We present results on the spectrum of B mesons and heavy baryons, using a non-relativistic formulation for the heavy and a clover action for the light quark. We also discuss B meson decay constants and their dependency upon the heavy meson mass.
We present quenched results for B meson decay constants using NRQCD b quarks and O(a) tadpole improved clover light quarks. For the first time, one-loop matching factors between lattice and continuum currents are incorporated through O(α/M) taking operator mixing fully into account. This includes an important O(αa) discretization correction to the heavy-light axial vector current. We find f_B = 0.147(11)(^{+8}_{-12})(9)(6) MeV and f_{B_s}/f_B = 1.20(4)(^{+4}_{-0}). PACS numbers: 12.38.Gc, 12.39.Hg, 13.20.He, 14.40.Nd
We present preliminary results from our study of the heavy-light spectrum and decay constants. For the heavy quark, we use NRQCD at various masses around and above the $b$ quark mass. For the first time, the heavy quark action and the heavy-light current consistently include corrections at second order in the non-relativistic expansion, as well as the leading finite $a$ corrections. The light quarks are simulated using a tadpole-improved Clover action at various masses in the strange and $c$ quark region.
Lattice NRQCD has proven successful in describing the physics of the upsilon system and B-mesons, though some concerns arise when it is used in simulations of charm quarks. It is certainly possible that the NRQCD expansion is not converging fast enough at this scale. We present some preliminary results on the low-mass breakdown of NRQCD, in particular the behaviour of heavy quarkonium and heavy-light meson spectra as the bare heavy quark mass is decreased well below 1, with the aim of understanding more about the manifestation of this breakdown.
We present a lattice investigation of the heavy-light meson decay constants using Wilson light quarks and NRQCD heavy quarks, partially including the effects of dynamical sea quarks. We calculate the pseudoscalar and vector decay constants over a wide range in heavy quark mass and are able to perform a detailed analysis of heavy quark symmetry. We find consistency between the extrapolation of the NRQCD results and the static case, as expected. We find the slope of the decay constants with $1/M$ is significantly larger than naive expectations and the results of previous lattice calculations. Fo…
Using NRQCD b quarks and HISQ light, strange and charm quarks we have calculated B meson masses and B^*-B splittings. We quote results for a range of lattice spacings and sea quark masses, enabling controlled extrapolation to the physical point. Since the $b$ quark masses and lattice spacing are fixed from the Υand other meson masses, this allows accurate, parameter-free tests of B, B_s, and B_c masses against experiment. We can also predict the mass of the B^*_c meson.
We present a lattice NRQCD study of the B meson decay constant in the quenched approximation with emphasis given to the scaling behavior. The NRQCD action and the heavy-light axial current we use include all terms of order 1/M and the perturbative $O(α_s a)$ and $O(α_s/M)$ corrections. Using simulations at three value of couplings $β$=5.7, 5.9 and 6.1 on lattices of size $12^3\times 32, 16^3\times 48$ and $24^3\times 64$, we find no significant $a$ dependence in $f_B$ if the $O(α_s a)$ correction is included in the axial current. We obtain $f_B = 167(7)(15)$ MeV, $f_{B_s}= 191(4)(17)(^{+4}_{-0…
We present results from the fastsum collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature. Three different methods of extracting spectral information are discussed: a Maximum Likelihood approach using a Gaussian spectral function for the ground state, the Backus Gilbert method, and the Kernel Ridge Regression machine learning procedure. We employ the fastsum anisotropic lattices with 2+1 dynamical quark flavours, with temperatures ranging from 47 to 375 MeV.
One leading source of uncertainty in the lattice computation of semi-leptonic form factors in B decay, and to a lesser extent B meson decay constants, comes from the extrapolation of the light quark mass to the physical up/down mass. This talk presents first explorations of simulating the light quark with staggered fermion actions, which are free of the spurious zero modes that effect Wilson-like Dirac operators and are less costly. Methods for fitting to Euclidean-time NRQCD-staggered meson propagators are discussed, and some preliminary spectrum results are presented.
Rare decays of B mesons, such as B \to K^*γand B\to K^{(*)}\ell^+\ell^- are loop suppressed in the Standard Model and sensitive to new physics. The final state meson in heavy-light decays at large recoil has sizeable momentum in the rest frame of the decaying meson. To reduce the resulting discretization errors we formulate the nonrelativistic heavy quark action in a moving frame. We discuss the perturbative renormalization of the leading order heavy-light operators in the resulting theory which is known as m(oving)NRQCD. We also present radiative corrections to the NRQCD action computed using…
The mass spectrum of charmed and bottom baryons has been computed on anisotropic lattices using quenched lattice nonrelativistic QCD. Masses are extracted by using mass splittings which are more accurate than masses obtained directly by using the nonrelativistic mass-energy relation. Of particular interest are the mass splittings between spin-1/2 and spin-3/2 heavy baryons, and we find that these color hyperfine effects are not suppressed in the baryon sector although they are known to be suppressed in the meson sector. Results are compared with those obtained in a previous NRQCD calculation a…
Using lowest-order lattice NRQCD to create heavy meson propagators and applying the spin-dependent interaction, $c_B^{} \frac{-g}{2m_q}\vecσ\cdot\vec{B}$, at varying intermediate time slices, we compute the off-diagonal matrix element of the Hamiltonian for the quarkonium-hybrid two-state system. Thus far, we have results for one set of quenched lattices with an interpolation in quark mass to match the bottomonium spectrum. After diagonalization of the two-state Hamiltonian, we find the ground state of the $Υ$ to show a $0.0035(1)c_B^2$ (with $c_B^2 \sim 1.5-3.1$) probability admixture of hybr…
The HPQCD collaboration has used radiatively-improved NonRelativistic QCD (NRQCD) for $b$ quarks in bottomonium to determine the decay rate of $Υ$ and $Υ^\prime$ mesons to leptons in lattice QCD. Using time-moments of vector bottomonium current-current correlators, we are also able to determine the $b$ quark mass in the $\overline{\mathrm{MS}}$ scheme. We use the same NRQCD $b$ quarks and Highly Improved Staggered Quark (HISQ) light quarks -- with masses down to their physical values -- to give a complete picture of heavy-light meson decay constants including those for vector mesons. We also s…
On a cubic lattice the zero-momentum meson states have one of 20 possible Lambda^{PC} combinations where Lambda labels the irreducible representation of the octahedral group. Each continuum bottomonium state with specific J^{PC} quantum numbers is contained within one or more of the lattice Lambda^{PC} states. In this work, bottomonium quark-antiquark operators are constructed for all 20 lattice Lambda^{PC} combinations which allows many continuum high angular momentum states to be accessible as ground states of their associated lattice channels. From a dynamical simulation, realistic results …
Non-relativistic QCD is applied for a lattice computation of the heavy-light meson decay constant in quenched approximation at $β=6.0$. Clear signals are obtained for the ground state at large times in the correlators, allowing a reliable extraction of the decay constant. Estimating the current renormalization factor by the tadpole improvement procedure, we find $f_{B}=$ 164(17) MeV for the $B$ meson with $a^{-1}=$ 2.3 GeV, while an extrapolation to the static limit yields $f_{B}^{\mbox{static}}=$ 247(26) MeV.
We report on exploratory studies of heavy-light meson semileptonic decays using Asqtad light quarks, NRQCD heavy quarks and Symanzik improved glue on coarse quenched lattices. Oscillatory contributions to three-point correlators coming from the staggered light quarks are found to be handled well by Bayesian fitting methods. B meson decays to both the Goldstone pion and to one of the point-split non-Goldstone pions are investigated. One-loop perturbative matching of NRQCD/Asqtad heavy-light currents is incorporated.
We present a lattice investigation, partially including the effects of dynamical quarks, of the heavy-light mesons using NRQCD for the heavy quark and the Wilson action for the light quark. We performed an extensive calculation of the spectrum employing a multi-state, multi-exponential fitting analysis which enabled us to extract the $2S{-}1S$ splitting as well as the $^1P_1{-}\bar{S}$ and hyperfine splittings. The Wilson action introduces a large systematic error into the calculation, and within this uncertainty we obtain agreement with experiment. We performed a comprehensive calculation of …
We formulate Non-Relativistic Quantum Chromodynamics (NRQCD) on a lattice which is boosted relative to the usual discretization frame. Moving NRQCD (mNRQCD) allows us to treat the momentum for the heavy quark arising from the frame choice exactly. We derive mNRQCD through O(1/m^2,v^4), as accurate as the NRQCD action in present use, both in the continuum and on the lattice with O(a^4) improvements. We have carried out extensive tests of the formalism through calculations of two-point correlators for both heavy-heavy (bottomonium) and heavy-light (B_s) mesons in 2+1 flavor lattice QCD and obtai…
We present {\it preliminary} results for the spectrum and decay constants of B mesons using NRQCD heavy and Wilson light quarks on configurations at $β=5.6$ with two dynamical flavours of staggered fermions. All terms to order $1/M_Q$ are included in the NRQCD action; matrix elements are corrected to this order by calculating the small components of the heavy quark propagator.
First results are obtained for B mesons using a heavy propagator calculated using NRQCD, and a light Wilson propagator. Results from 13 quenched configurations of size 16^3 x 48 at β= 6.0 give a value for f_{B} of less than 200 Mev and a B^{*}-B splitting of 32(8) MeV. Superior signal/noise behaviour is observed over static propagators on the same configurations. No extrapolation to the b mass for the heavy quark is required.
Preliminary results from an extensive lattice calculation of the B, B_c, and Υspectrum at quenched β= 6.0 are presented. The study includes radially and orbitally excited mesons, and baryons containing b quarks. The b quarks are formulated using NRQCD; for light and c quarks, a tadpole-improved clover action is used.
We give results for B, Bs, Bc and bottomonium spectroscopy using NRQCD heavy quarks and HISQ valence and sea quarks. Five MILC ensembles of gluon configurations with three values of the lattice spacing and m(light)/m(strange) values down to 0.1 are used that include 2+1+1 flavours of sea quark. Systematic errors in the NRQCD action are improved through the radiative correction of the coefficients of terms at v^4. Improved results for S-wave and P-wave bottomonium states are discussed as well as a prediction for the full D-wave spectrum. Preliminary results for the ground state B meson masses a…
One-loop matching of heavy-light currents is carried out for a highly improved lattice action, including the effects of mixings with dimension 4 O(1/M) and O(a) operators. We use the NRQCD action for heavy quarks, the Asqtad improved naive action for light quarks, and the Symanzik improved glue action. These results are being used in recent heavy meson decay constant and semileptonic form factor calculations on the MILC dynamical configurations.
We present initial results from Monte Carlo simulations of NRQCD-light, static-light, and NRQCD-NRQCD mesons, using a variational technique (MOST), as part of our ongoing calculation of the $f_{B}$ decay constant. The basis states for the variational calculation are quark-antiquark operators separated by all possible relative distances not equivalent under the cubic group (for example, for a $20^{3}$ lattice there are 286 operators). The efficacy of the method is demonstrated by the good plateaus obtained for the ground state and the clean extraction of the wave functions of the ground and fir…
We present one-loop matching coefficients between continuum and lattice QCD for the heavy-light four-fermion operators relevant for neutral B meson mixing both within and beyond the Standard Model. For the lattice theory we use nonrelativistic QCD (NRQCD) to describe b quarks and improved staggered fermions (AsqTad) for light quarks. The gauge action is the tree-level Symanzik improved gauge action. Matching to full QCD is carried out through order alpha_s, Lambda_{QCD}/M_b, and alpha_s/(aM_b).
Using the lattice NRQCD action for heavy quark, we calculate the heavy quark expansion parameters $μ_π^2$ and $μ_G^2$ for heavy-light mesons and heavy-light-light baryons. The results are compared with the mass differences among heavy hadrons to test the validity of HQET relations on the lattice.
We use the non-relativistic expansion of QCD (NRQCD) on the lattice to study the lowest hybrid configuration contribution to the ground state of heavy S-wave mesons. Using lowest-order lattice NRQCD to create the heavy-quark propagators, we form a basis of ``unperturbed'' S-wave and hybrid states. We then apply the lowest-order coupling of the quark spin and chromomagnetic field at an intermediate time slice to create ``mixed'' correlators between the S-wave and hybrid states. From the resulting amplitudes, we extract the off-diagonal element of our two-state Hamiltonian. Diagonalizing this Ha…
We present a new determination of the B and B_s meson decay constants using NRQCD b-quarks, HISQ light and strange valence quarks and the MILC collaboration N_f=2+1 lattices. The new calculations improve on HPQCD's earlier work with NRQCD b-quarks by replacing AsqTad with HISQ valence quarks, by including a more chiral MILC fine ensemble in the analysis, and by employing better tuned quark masses and overall scale. We find f_B = 0.191(9)GeV, f_{B_s} = 0.228(10)GeV and f_{B_s}/f_B = 1.188(18). Combining the new value for f_{B_s}/f_B with a recent very precise determination of the B_s meson deca…
We present updated results for the radiative improvement of the σ.B term and the spin-dependent four-fermion terms in the lattice NRQCD action, and first results for the radiative corrections to the NRQCD Darwin term and spin-independent four-fermion terms. The spin-dependent terms have significant impact on getting the correct hyperfine splitting for both bottomonium and heavy-light mesons, while the spin-independent terms suffer from a conspiracy between lattice artifacts and severe IR divergences that complicates their evaluation.
We calculate the heavy-light meson decay constant using lattice NRQCD action for the heavy quark and Wilson quark action for the light quark over a wide range in the heavy quark mass. Simulations are carried out on a 16^3 x 32 lattice with 120 quenched gauge configurations generated with the plaquette action at beta=5.8. For the heavy quark part of the calculation, two sets of lattice NRQCD action and current operator are employed. The first set includes terms up to O(1/m_Q) both in the action and the current operator, and the second set up to O(1/m_Q^2), where m_Q is the bare mass of the heav…
We present highlights of the spectrum of mesons and baryons calculated using NRQCD for heavy quarks and tadpole improved clover action for the light quarks.
We combine a light AsqTad antiquark with a nonrelativistic heavy quark to compute the decay constants of heavy-light pseudoscalar mesons using the ensemble of 3-flavor gauge field configurations generated by the MILC collaboration. Preliminary results for $f_{B_s}$ and $f_{D_s}$ are given and status of the chiral extrapolation to $f_B$ is reported. We also touch upon results of the perturbative calculation which matches matrix elements in the effective theory to the full theory at 1-loop order.
The temporal component of the heavy-light axial vector current is constructed to one-loop order in perturbation theory and to order 1/M, where M is the heavy quark mass, in terms of operators suitable for use in lattice simulations of B and D mesons. The O(a)-improved clover action is used for the massless light quark, where a is the lattice spacing, and propagation of the heavy quark is described by a nonrelativistic lattice action.
We report on a study of B mesons on N_f = 2 full QCD configurations using an RG-improved gauge action, NRQCD heavy quark action and tadpole-improved clover light quark action. Results on the heavy-light spectrum and the decay constants from 16^3x32 lattices at a^{-1} ~ 1.5 GeV are presented, and compared with quenched results obtained with the same action combination at matching lattice spacings.
Numerical simulations of the quarkonium spin splittings are done in the framework of lattice nonrelativistic quantum chromodynamics (NRQCD). At leading order in the velocity expansion the spin splittings are of $O(M_Q v^4)$, where $M_Q$ is the renormalized quark mass and $v^2$ is the mean squared quark velocity. A systematic analysis is done of all next-to-leading order corrections. This includes the addition of $O(M_Q v^6)$ relativistic interactions, and the removal of $O(a^2 M_Q v^4)$ discretization errors in the leading-order interactions. Simulations are done for both S- and P-wave mesons,…
We present a determination of the b-quark mass accurate through O(α_s^2) in perturbation theory and including partial contributions at O(α_s^3). Nonperturbative input comes from the calculation of the Upsilon and B_s energies in lattice QCD including the effect of u, d and s sea quarks. We use an improved NRQCD action for the b-quark. This is combined with the heavy quark energy shift in NRQCD determined using a mixed approach of high-beta simulation and automated lattice perturbation theory. Comparison with experiment enables the quark mass to be extracted: in the MS bar scheme we find m_b(m_…
We present results for the B_s meson decay constant f_{B_s} from simulations at three lattice spacings in the range a^{-1}=1.1 to 2.6 GeV using NRQCD heavy quarks and clover light quarks in the quenched approximation. We study scaling of this quantity and check the consistency between mesons decaying from rest and from a state with nonzero spatial momentum. The cancellation of power law contributions that arise in the NRQCD formulation of heavy-light currents is discussed. On the coarsest lattice the D_s meson decay constant f_{D_s} is calculated. Our best values for the decay constants are gi…
We investigate higher order effects in the nonrelativistic expansion of lattice QCD on the heavy-light meson decay constants and some other quantities in order to understand the truncation error of NRQCD. While our numerical results have large $O(a)$ and $O(α_s)$ errors due to the use of Wilson light quark action and the tree-level matching, we find that the truncation error of higher order relativistic corrections are adequately small around the mass of the $b$ quark. We also present a perturbatively matched results through 1-loop level without operator mixing effects.
Dynamical 2+1 flavor lattice QCD is used to calculate the masses of bottom hadrons, including B mesons, singly and doubly bottom baryons, and for the first time also the triply-bottom baryon Omega_bbb. The domain wall action is used for the up-, down-, and strange quarks (both valence and sea), while the bottom quark is implemented with non-relativistic QCD. A calculation of the bottomonium spectrum is also presented.
We present progress results from the FASTSUM collaboration's programme to determine the spectrum of the bottomonium system as a function of temperature using a variety of approaches. In this contribution, the Backus Gilbert method is used to reconstruct spectral functions from NRQCD meson correlator data from FASTSUM's anisotropic ensembles at nonzero temperature. We focus in particular on the resolving power of the method, providing a demonstration of how the underlying resolution functions can be probed by exploiting the Laplacian nature of the NRQCD kernel. We conclude with estimates of the…
We present a lattice QCD calculation of the heavy quark expansion parameters $μ_π^2$ and $μ_G^2$ for heavy-light mesons and heavy-light-light baryons. The calculation is carried out on a 20$^3\times$48 lattice at $β$ = 6.0 in the quenched approximation, using the lattice NRQCD action for heavy quarks. We obtain the parameters $μ_π^2$ and $μ_G^2$ in two different methods: a direct calculation of the matrix elements and an indirect calculation through the mass spectrum, and confirm that the both methods give consistent results. We also discuss an application to the lifetime ratios.
The moving NRQCD (mNRQCD) formalism facilitates the simulation of heavy meson decays at large recoil. We present preliminary results for a number of quantities including the energy splittings and the $B$ meson decay constant that demonstrate that the formalism is accurate over a range of momenta.
Recently we studied the B, Bs, D and Ds meson decay constants using various treatments for the heavy quark. For B mesons, we determined fB, fBs, and fBs/fB with NRQCD bottom quarks. We then combined the ratio fBs/fB and another very precise determination from HPQCD for fBs using heavy HISQ quarks, and extracted fB with 2% total errors. We also calculated fD, fDs, and fDs/fD using HISQ charm quarks. Here we review our results and briefly discuss their implications for the determination of the CKM matrix elements |Vcd| and |Vcs|.
Using a ``wall'' of quark point sources, we invert the chirally improved Dirac operator to create an ``incoherent'' collection of quark propagators which originate from all spatial points of the source time slice. The lowest-order NRQCD approximation is used to create heavy-quark propagators from the same wall source. However, since the numerical cost involved in computing such heavy-quark propagators is low, we are able to use a number of source gauge paths to establish coherence between the heavy and light quarks at several spatial separations. The resulting collection of heavy-light meson c…
