The nucleon axial form factors -- axial $G_A$, induced pseudoscalar $\widetilde{G}_P$ and pseudoscalar $G_P$ -- have displayed large systematics in lattice QCD calculations. The major symptoms were the violation of the partially conserved axial current (PCAC) relation between the three form factors, and the underestimation of the induced pseudoscalar coupling $g_P^\ast$ and the axial charge radius $r_A$ compared to phenomenological estimates. The small $g_P^\ast$ was a consequence of the failure of the pion-pole dominance (PPD) hypothesis, especially at low $M_π^2$. The small charge radius $r_A$ and the underestimate of $g_A$ were related. The dominant systematic responsible is the lack of inclusion of low-energy ($N π$) states that are not manifest in the multiexponential fit to the nucleon two-point correlator. We show that this low-energy state can be determined from the three-point correlator $\langle N A_4 N \rangle $ with the insertion of the temporal component of the axial current $A_4$ within the nucleon state, ie, the strategy labeled $S_{A4}$ [1]. Including this low-energy state in fits to control excited-state contamination (ESC) gives results for $g_A$, $r_A$, and $g_P^\ast$ that are consistent with experimental/phenomenological values. However, the systematic uncertainties, especially in data at small $Q^2$, are now much larger.
Precise estimates of the nucleon charges $g_A$, $g_S$ and $g_T$ are needed in many phenomenological analyses of SM and BSM physics. In this talk, we present results from two sets of calculations using clover fermions on 9 ensembles of 2+1+1-flavor HISQ and 4 ensembles of 2+1-flavor clover lattices. We show that high statistics can be obtained cost-effectively using the truncated solver method with bias correction and the coherent source sequential propagator technique. By performing simulations at 4--5 values of the source-sink separation $t_{\rm sep}$, we demonstrate control over excited-stat…
Updates on results for the electric, magnetic and axial vector form factors are presented. The data analyzed cover high statistics measurements on 11 ensembles generated with 2+1+1 flavors of HISQ fermions by the MILC collaboration. The data cover the range $0.057\;\mathrm{fm} < a < 0.15\;\mathrm{fm}$ in lattice spacing, $135\;\mathrm{MeV} < M_π< 320\;\mathrm{MeV}$ in the pion mass and $3.3 < M_πL < 5.5 $ in the lattice size. Fits to control excited-state contamination use up to 3-states in the spectral decomposition of the 3-point functions. The simultaneous chiral-continuum-finite-volume fit…
We present high statistics ($\mathcal{O}(2\times 10^5)$ measurements) preliminary results on (i) the isovector charges, $g^{u-d}_{A,S,T}$, and form factors, $G^{u-d}_E(Q^2)$, $G^{u-d}_M(Q^2)$, $G^{u-d}_A(Q^2)$, $\widetilde G^{u-d}_P(Q^2)$, $G^{u-d}_P(Q^2)$, on six 2+1-flavor Wilson-clover ensembles generated by the JLab/W&M/LANL/MIT collaboration with lattice parameters given in Table 1. Examples of the impact of using different estimates of the excited state spectra are given for the clover-on-clover data, and as discussed in [1], the biggest difference on including the lower energy (close to…
We compare correlators for pseudoscalar and vector mesons made from valence strange quarks using the clover quark and highly improved staggered quark (HISQ) formalisms in full lattice QCD. We use fully nonperturbative methods to normalise vector and axial vector current operators made from HISQ quarks, clover quarks and from combining HISQ and clover fields. This allows us to test expectations for the renormalisation factors based on perturbative QCD, with implications for the error budget of lattice QCD calculations of the matrix elements of clover-staggered $b$-light weak currents, as well a…
The Fermilab Lattice and MILC collaborations have shown in one-loop lattice QCD perturbation theory that the renormalization constants of vector and axial-vector mixed clover-asqtad currents are closely related to the product of those for clover-clover and asqtad-asqtad (local) vector currents. To be useful for future higher precision calculations this relationship must be valid beyond one-loop and very general. We test its validity nonperturbatively using clover and Highly Improved Staggered (HISQ) strange quarks, utilising the absolute normalization of the HISQ temporal axial current. We fin…
We match the continuum and lattice axial vector and vector currents at one loop in perturbation theory. For the heavy quarks we use the nonrelativistic QCD (NRQCD) action and for the light quarks the Highly Improved Staggered Quark (HISQ) action. We present results for both massless and massive HISQ quarks and as part of the matching procedure we include a discussion of the one loop HISQ renormalisation parameters.
We present preliminary simulation results for the I = 0 charmonium state $X(3872)(1^{++})$ and the I = 1 charmonium state $Z_c^+(3900)(1^{+-})$. The study is performed on gauge field configurations with 2+1+1 flavors of highly improved staggered sea quarks (HISQ) with clover (Fermilab interpretation) charm quarks and HISQ light valence quarks. Since the $X(3872)$ lies very close to the open charm $D \bar D^*$ threshold, we use a combination of $\bar c c$ and $D \bar D^* + \bar D D^*$ interpolating operators. For the $Z_c^+(3900)$ we use a combination of $J/ψπ$ and $D \bar D^* + \bar D D^*$ cha…
The Deep Underground Neutrino Experiment (DUNE) is an upcoming neutrino oscillation experiment that is poised to answer key questions about the nature of neutrinos. Lattice QCD has the ability to make significant impact upon DUNE, beginning with computations of nucleon-neutrino interactions with weak currents. Nucleon amplitudes involving the axial form factor are part of the primary signal measurement process for DUNE, and precise calculations from LQCD can significantly reduce the uncertainty for inputs into Monte Carlo generators. Recent calculations of the nucleon axial charge have demonst…
Flavor diagonal nucleon charges using clover fermions on MILC HISQ ensembles
Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Thomas Jefferson National Accelerator Facility（托马斯·杰斐逊国家加速器设施）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Ibsyn Scientific（Ibsyn科学公司）；Michigan State University（密歇根州立大学）；NVIDIA Corporation（英伟达公司）
We report the status of an ongoing lattice-QCD calculation of form factors for exclusive semileptonic decays of $B$ mesons with both charged currents ($B\toπ\ellν$, $B_s\to K\ellν$) and neutral currents ($B\toπ\ell^+\ell^-$, $B\to K\ell^+\ell^-$). The results are important for constraining or revealing physics beyond the Standard Model. This work uses MILC's (2+1+1)-flavor ensembles with the HISQ action for the sea and light valence quarks and the clover action in the Fermilab interpretation for the $b$ quark. Simulations are carried out at three lattice spacings down to $0.088$ fm, with both …
We present preliminary study of parton distribution inside the pion using mixed action approach with HYP smeared valence clover quarks on HISQ sea within the framework of Large Momentum Effective Theory. We use 2+1 flavor $48^3 \times 64$ HISQ lattices with lattices spacing of a=0.06 fm and valence quark masses corresponding to pion mass of 300 MeV.
We report updates to an ongoing lattice-QCD calculation of the form factors for the semileptonic decays $B \to π\ell ν$, $B_s \to K \ell ν$, $B \to π\ell^+ \ell^-$, and $B \to K \ell^+ \ell^-$. The tree-level decays $B_{(s)} \to π(K) \ell ν$ enable precise determinations of the CKM matrix element $|V_{ub}|$, while the flavor-changing neutral-current interactions $B \to π(K) \ell^+ \ell^-$ are sensitive to contributions from new physics. This work uses MILC's (2+1+1)-flavor HISQ ensembles at approximate lattice spacings between $0.057$ and $0.15$ fm, with physical sea-quark masses on four out o…
We present preliminary results for the contributions to the neutron EDM arising from the QCD $θ$-term, the Weinberg three-gluon and the quark chromo-EDM operators from our ongoing lattice calculations using clover valence quarks on the MILC HISQ lattices. We use the gradient-flow technique to smooth the lattices and renormalize the gluonic operators, and use the Schwinger source method to incorporate the quark chromo-EDM interactions in the quark propagator. For the QCD $θ$-term and the Weinberg three-gluon operator, we report results in the gradient-flow scheme from 8 ensembles at four lattic…
We report on a preliminary scale determination with gradient-flow techniques on the $N_f = 2 + 1 + 1$ HISQ ensembles generated by the MILC collaboration. The ensembles include four lattice spacings, ranging from 0.15 to 0.06 fm, and both physical and unphysical values of the quark masses. The scales $\sqrt{t_0}/a$ and $w_0/a$ are computed using Symanzik flow and the cloverleaf definition of $\langle E \rangle$ on each ensemble. Then both scales and the meson masses $aM_π$ and $aM_K$ are adjusted for mistunings in the charm mass. Using a combination of continuum chiral perturbation theory and a…
We present our recent high precision calculations (Phys. Rev. D102 (2020) no.5, 054512 and JHEP 04 (2021) 044, JHEP 21 (2020) 004) of the first moment of nucleon isovector polarized, unpolarized and transversity distributions, i.e., momentum fraction, helicity and transversity moment, respectively. We use the standard method for the calculation of these moments (via matrix elements of twist two operators), and carry out a detailed analysis of the sources of systematic uncertainty, in particular of excited state contributions. Our calculations have been performed using two different lattice set…
The calculation of force is most difficult part in lattice Quantum Chromodynamics (QCD). This lecture gives the details of the force calculation in one-loop Symanzik improved action, Wilson fermion with clover term, asqtad fermion, HISQ fermion, rooted staggered fermion, smeared fermion, staggered Wilson fermion, overlap fermion and domain wall fermion. The even-odd precondition are also considered in these calculations.
We present high-statistics estimates of the isovector charges of the nucleon from four 2+1-flavor ensembles generated using Wilson-clover fermions with stout smearing and tree-level tadpole improved Symanzik gauge action at lattice spacings $a=0.114$ and $0.080$ fm and with $M_π\approx 315$ and 200 MeV. The truncated solver method with bias correction and the coherent source sequential propagator construction are used to cost-effectively achieve $O(10^5)$ measurements on each ensemble. Using these data, the analysis of two-point correlation functions is extended to include four states in the f…
We present an update on the calculation of matrix elements of iso-vector scalar, axial and tensor charges between a neutron and a proton state. These matrix elements are needed to probe novel scalar and tensor interactions in neutron beta-decay that can arise in extensions of the Standard Model at the TeV scale. Our calculations are being done using valence clover fermions on dynamical N_f=2+1+1 HISQ configurations generated by the MILC Collaboration. We provide preliminary estimates of the dependence of these matrix elements on the light quark masses, lattice spacing, and the time separation …
For the Stout Link Non-perturbative Clover (SLiNC) action we determine in one-loop lattice perturbation theory the critical hopping parameter $κ_c$ and the clover parameter $c_{SW}$ which is needed for $\mathcal{O}(a)$ improvement. Performing this calculation off-shell we are also able to compute the non gauge invariant quark field improvement coefficient $c_{NGI}$. Additionally, we present first results for the renormalization factors of the scalar, pseudoscalar, vector and axial vector currents. We discuss mean field improvement for the SLiNC action.
Algorithmic progress in recent years made it possible to simulate QCD with Nf=2 flavours of O(a)-improved Wilson fermions at very light quark masses. We present the current results for baryon spectrum states, the nucleon axial coupling and the lowest moment of unpolarised nucleon structure functions. Special emphasis is given to a comparison of our calculations with results from chiral effective theories.
In this work we present preliminary results on the nucleon axial and tensor charges, the quark momentum fraction and the first moment of the helicity distribution. The simulations have been performed using two $N_f{=}2$ and $N_f{=}2{+}1{+}1$ ensembles. Both ensembles have a twisted mass action with a clover term with the quark masses fixed at their physical values (physical point) and volumes of $64^3{\times}128$. The extracted quantities are compared with results from an existing $N_f{=}2$ ($48^3{\times}96$) ensemble. This comparison allows one to address volume and quenching effects.
Using the O(a) Symanzik improved action an estimate is given for the strange quark mass for unquenched (nf=2) QCD. The determination is via the axial Ward identity (AWI) and includes a non-perturbative evaluation of the renormalisation constant. Numerical results have been obtained at several lattice spacings, enabling the continuum limit to be taken. Results indicate a value for the strange quark mass (in the MSbar-scheme at a scale of 2GeV) in the range 100 - 130MeV.
We calculate axial vector and vector form factors for the semileptonic decay Ds to phi using HISQ valence quarks on MILC ensembles with 2+1 flavours of asqtad sea quarks. Using twisted boundary conditions to tune the quarks' momenta, we compute form factors at q^2 = 0 on coarse lattices. We find V(0)=0.903(67), A_1(0)= 0.603(20), A_2(0)=0.401(80) and A_0(0)=0.686(17), which we compare to experimental data and previous quenched lattice QCD calculations.
Flavor singlet and non-singlet axial Ward identities are investigated using the Wilson formulation of lattice QCD with Clover O(a)-improvement, which breaks explicitly chiral symmetry. The matching at one-loop order of all the relevant renormalization constants with the continuum \bar{MS} scheme is presented. Our calculations include: 1) the contributions arising from the Clover term of the action; 2) the complete mixing of the gluon operator G \tilde{G} with the divergence of the singlet axial current; 3) the use of both local and extended definitions of the fermionic bilinear operators. A de…
We present preliminary results for the axial and tensor charge of the nucleon obtained from simulations with N_f=2 clover fermions. A comparison with chiral perturbation theory is attempted.
We perform fully dynamical simulations at small quark masses by reweighting in the quark mass, calculating the weight factors stochastically. This approach avoids some of the technical difficulties associated with direct simulations. We find that the weight factors fluctuate only moderately on nHYP smeared dynamical Wilson-clover ensembles, and demonstrate that the overlap between the original and reweighted configurations is large both for short and long distance observables. We could successfully reweight 16^4, (1.85fm)^4 volume configurations from m_q 20 MeV to m_q~5 MeV, and 24^4, (2.77fm)…
We report on a scale determination with gradient-flow techniques on the $N_f=2+1+1$ highly improved staggered quark ensembles generated by the MILC Collaboration. The ensembles include four lattice spacings, ranging from approximately 0.15 to 0.06 fm, and both physical and unphysical values of the quark masses. The scales $\sqrt{t_0}/a$ and $w_0/a$ and their tree-level improvements, $\sqrt{t_{0,{\rm imp}}}$ and $w_{0,{\rm imp}}$, are computed on each ensemble using Symanzik flow and the cloverleaf definition of the energy density $E$. Using a combination of continuum chiral-perturbation theory…
This talk provides an update on the calculation of matrix elements of flavor diagonal axial, scalar and tensor quark bilinear operators between the nucleon ground state. The simulations are done using Wilson-clover fermions on a sea of eight 2+1+1-flavor HISQ ensembles generated by the MILC collaboration. We discuss the signal in the connected and disconnected contributions, calculation of the renormalization constants and mixing in the RI-sMOM scheme, and control over the simultaneous chiral-continuum-finite-volume fit used to extract the final charges.
We present an update of our analysis of statistical and systematic errors in the calculation of iso-vector scalar, axial and tensor charges of the nucleon. The calculations are done using $N_f=2+1+1$ flavor HISQ ensembles generated by the MILC Collaboration at three values of the lattice spacing ($a=0.12,\ 0.09,$ and $0.06$ fm) and three values of the quark mass ($M_π\approx 310,\ 220$ and $130$ MeV); and clover fermions for calculating the correlation functions, i.e., we use a clover-on-HISQ lattice formulation. The all-mode-averaging method allows us to increase the statistics by a factor of…
This talk provides an update on the calculation of matrix elements of flavor diagonal axial, scalar and tensor quark bilinear operators between the nucleon ground state. The simulations are done using Wilson-clover fermions on a sea of eight 2+1+1-flavor HISQ ensembles generated by the MILC collaboration. We discuss the signal in the sum of the connected and disconnected contributions for the up, down and strange quarks, control over fits to remove excited state contamination, and the simultaneous chiral-continuum fit used to extract the charges.
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.
Starting in 2001, the MILC Collaboration began a large scale calculation of heavy-light meson decay constants using clover valence quarks on ensembles of three flavor configurations. For the coarse configurations, with a=0.12 fm, eight combinations of dynamical light and strange quarks have been analyzed. For the fine configurations, with a=0.09 fm, three combinations of quark masses are studied. Since we last reported on this calculation, statistics have been increased on the fine ensembles, and, more importantly, a preliminary value for the perturbative renormalization of the axial-vector cu…
We present results for the isovector axial, induced pseudoscalar, electric, and magnetic form factors of the nucleon. The calculations were done using $2+1+1$-flavor HISQ ensembles generated by the MILC collaboration with lattice spacings $a \approx$ 0.12, 0.09, 0.06$\mathrm{fm}$ and pion masses $M_π\approx$ 310, 220, 130$\mathrm{MeV}$. Excited-states contamination is controlled by using four-state fits to two-point correlators and by comparing two- versus three-states in three-point correlators. The $Q^2$ behavior is analyzed using the model independent z-expansion and the dipole ansatz. Fina…
We present results on the isovector and isoscalar nucleon axial form factors including disconnected contributions,using an ensemble of $N_f =2$ twisted mass clover- improved Wilson fermions simulated with approximately the physical value of the pion mass. The light disconnected quark loops are computed using exact deflation, while the strange and the charm quark loops are evaluated using the truncated solver method. Techniques such as the summation and the two-state fits have been employed to access ground-state dominance.
We present results on the nucleon axial and induced pseudo-scalar form factors using an ensemble of two degenerate twisted mass clover-improved fermions generated at the physical value of the pion mass. We evaluate the isovector and the isoscalar, as well as, the strange and the charm axial form factors. The disconnected contributions are evaluated using recently developed methods that include deflation of the lower eigenstates, allowing us to extract the isoscalar, strange and charm axial form factors. We find that the disconnected quark loop contributions are non-zero and particularly large …
For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order $O(a)$ effects. Including these operators the axial Ward…
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.
We study the influence of Gribov copies, in the Landau gauge, on the lattice renormalisation constant of the axial current, obtained from a Ward identity on quark state correlation functions, with the Clover action, in quenched SU(3) gauge theory. A comparison between the gauge invariant determination of the renorma= lization constant and the gauge dependent one is discussed. We find that the residual gauge freedom associated to Gribov copies induces observable effects, which, at the level of numerical accuracy of our simulation, are included in the statistical uncertainty inherent in a Monte …
We report on the determination of the improvement coefficient $c_{\rm A}$ for the non-singlet axial-vector current $A^{a}_μ(x)$ in the framework of stabilised Wilson-Clover fermions within three flavour lattice QCD. This is done by requiring the PCAC relation to hold for two different pseudo-scalar states. To generate these states, wavefunctions altering spatial structures on the boundaries of a Schrödinger functional lattice are employed and some variations of the (previously applied) wavefunction method are explored. The improvement coefficient is determined on a few ensembles for a range of…
We have studied transitions between vector and pseudoscalar mesons using the HISQ action for the valence quarks. We have calculated all of the axial and vector form factors that appear in the decay rate for $D_s \to ϕ\ell ν$ over the full $q^2$ range and compared them to the shape of the experimental decay distributions. We use nonperturbatively normalised currents for the vector and axial vector currents. The same set up for the three point correlations functions also allow us to study radiative decays and we have calculated the decay rate for $J/ψ\to η_c γ$.
We non-perturbatively determine the renormalization factor of the axial vector current in lattice QCD with $N_f=3$ flavors of Wilson-clover fermions and the tree-level Symanzik-improved gauge action. The (by now standard) renormalization condition is derived from the massive axial Ward identity and it is imposed among Schrödinger functional states with large overlap on the lowest lying hadronic state in the pseudoscalar channel, in order to reduce kinematically enhanced cutoff effects. We explore a range of couplings relevant for simulations at lattice spacings of $\approx 0.09$ fm and below. …
By imposing axial and vector Ward identities for flavour-non-singlet currents, we estimate in the quenched approximation the non-perturbative values of combinations of improvement coefficients, which appear in the expansion around the massless case of the renormalization constants of axial, pseudoscalar, vector, scalar non-singlet currents and of the renormalized mass. These coefficients are relevant for the completion of the improvement programme to O(a) of such operators. The simulations are performed with a clover Wilson action non-perturbatively improved.
Heavy hadron spectrum from 2+1+1 flavor MILC lattices
School of Physical Sciences, National Institute of Science Education and Research, An OCC of Homi Bhabha National Institute（国家科学教育与研究中心物理科学学院，霍米·巴巴国立学院附属机构）；The Institute of Mathematical Sciences（数学科学研究所）；Homi Bhabha National Institute（霍米·巴巴国立学院）
We present preliminary results of the calculation of the positive-parity ground state charm baryon spectrum using of N_f=2+1+1$ dynamical quarks. The calculation uses a relativistic heavy-quark action for the valence charm quark, clover-Wilson fermions for the valence light quarks and HISQ sea quarks. The spectrum is calculated with a lightest pion mass around 220 MeV and two lattice spacings ($a\sim0.12$ fm and 0.09 fm) are used to extrapolate to continuum limit. Our preliminary results are consistent with the currently measured baryon spectrum, except for the isospin-averaged $J=1/2$ $Ξ_{cc}…
We show the first lattice QCD results on the axial charge $g_A^{N^*N^*}$ of $N^*(1535)$ and $N^*(1650)$. The measurements are performed with two flavors of dynamical quarks employing the renormalization-group improved gauge action at $β$=1.95 and the mean-field improved clover quark action with the hopping parameters, $κ$=0.1375, 0.1390 and 0.1400. In order to properly separate signals of $N^*(1535)$ and $N^*(1650)$, we construct 2$\times$2 correlation matrices and diagonalize them. Wraparound contributions in the correlator, which can be another source of signal contaminations, are eliminated…
We compute the two-loop renormalization functions, in the RI' scheme, of local bilinear quark operators $\barψΓψ$, where $Γ$ corresponds to the Vector, Axial-Vector and Tensor Dirac operators, in the lattice formulation of QCD. We consider both the flavor nonsinglet and singlet operators. We use the clover action for fermions and the Wilson action for gluons. Our results are given as a polynomial in $c_{SW}$, in terms of both the renormalized and bare coupling constant, in the renormalized Feynman gauge. Finally, we present our results in the MSbar scheme, for easier comparison with calculatio…
We investigate the Symanzik improvement of the Wilson quark action on anisotropic lattices. Taking first a general action with nearest-neighbor and clover interactions, we study the mass dependence of the ratio of the hopping parameters, the clover coefficients, and an improvement coefficient for heavy-light vector and axial vector currents. We show how tree-level improvement can be achieved. For a particular choice of the spatial Wilson coupling, the results simplify, and $O(m_0a_τ)$ improvement is possible. (Here $m_0$ is the bare quark mass and $a_τ$ the temporal lattice spacing.) With this…
We show the first lattice QCD results on the axial charges $g_A^{N^*N^*}$ of $N^*(1535)$ and $N^*(1650)$. The measurements are performed with two flavors of dynamical quarks employing the renormalization-group improved gauge action at $β$=1.95 and the mean-field improved clover quark action with the hopping parameters, $κ$=0.1375, 0.1390 and 0.1400. We construct 2$\times$2 correlation matrices and diagonalize them so that the signals of $N^*(1535)$ and $N^*(1650)$ are properly separated. Wraparound contributions in the correlator, which can be another source of signal contaminations, are elimi…
Impact of Dynamical Charm Quark and Mixed Action Effect on Light Hadron Masses and Decay Constants
School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院基础物理与数学学院，UCAS）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Computation-based Science and Technology Research Center, The Cyprus Institute（塞浦路斯理工学院计算科学与技术研究中心）；Department of Physics, Indiana University（印第安纳大学物理系）
We describe a procedure for extracting momentum derivatives of nucleon matrix elements on the lattice directly at $Q^2=0$. This is based on the Rome method for computing momentum derivatives of quark propagators. We apply this procedure to extract the nucleon isovector magnetic moment and charge radius as well as the isovector induced pseudoscalar form factor at $Q^2=0$ and the axial radius. For comparison, we also determine these quantities with the traditional approach of computing the corresponding form factors, i.e. $G^v_E(Q^2)$ and $G_M^v(Q^2)$ for the case of the vector current and $G_P^…
We present details of a lattice QCD calculation of the $B_s\to D_s^*$ axial form factor at zero recoil using the Highly Improved Staggered Quark (HISQ) formalism on the second generation MILC gluon ensembles that include up, down, strange and charm quarks in the sea. Using the HISQ action for all valence quarks means that the lattice axial vector current that couples to the $W$ can be renormalized fully non-perturbatively, giving a result free of the perturbative matching errors that previous lattice QCD calculations have had. We calculate correlation functions at three values of the lattice s…
The volume dependence of the octet baryon masses and relations among them are explored with Lattice QCD. Calculations are performed with n_f=2+1 clover fermion discretization in four lattice volumes, with spatial extent L ~ 2.0, 2.5, 3.0 and 3.9 fm, with an anisotropic lattice spacing of b_s ~ 0.123 fm in the spatial direction, and b_t = b_s/3.5 in the time direction, and at a pion mass of m_pi ~ 390 MeV. The typical precision of the ground-state baryon mass determination is ~0.2%, enabling a precise exploration of the volume dependence of the masses, the Gell-Mann--Okubo mass relation, and of…
We present the $x$-dependent nucleon and pion gluon distribution from lattice QCD using the pseudo-PDF approach, on lattice ensembles with $2+1+1$ flavors of highly improved staggered quarks (HISQ), generated by MILC Collaboration. We use clover fermions for the valence action and momentum smearing to achieve pion boost momentum up to 2.56~GeV on three lattice spacings $a\approx 0.9, 0.12$ and 0.15~fm and three pion masses $M_π\approx 220$, 310 and 690~MeV. We compare our pion and preliminary nucleon gluon results with the determination by global fits.
We present results for the axial charge and root-mean-square (RMS) radii of the nucleon obtained from 2+1 flavor lattice QCD at the physical point with a large spatial extent of about 10 fm. Our calculations are performed with the PACS10 gauge configurations generated by the PACS Collaboration with the six stout-smeared $O(a)$ improved Wilson-clover quark action and Iwasaki gauge action at $β$ = 1.82 and 2.00 corresponding to lattice spacings of 0.085 fm and 0.063 fm respectively. We first evaluate the value of $g_A/g_V$ , which is not renormalized in the continuum limit and thus ends up with …
