Search

Isospin-breaking corrections to the hadron vacuum polarization component of the anomalous magnetic moment of the muon are needed to ensure the theoretical precision of $g_\mu -2$ is below the experimental precision. We describe the status of our work calculating, using lattice QCD, the QED correction to the light and strange connected hadronic vacuum polarization in a Dashen scheme. We report results using physical $N_f=2+1+1$ HISQ ensembles at three lattice spacings and three heavier-than-light valence quark masses., Comment: 9 pages, 4 figures, to be published in Proceedings of Science, contribution to the 39th International Symposium on Lattice Field Theory, LATTICE2022, Bonn, Germany

This work continues our program of lattice-QCD baryon physics using staggered fermions for both the sea and valence quarks. We present a proof-of-concept study that demonstrates, for the first time, how to calculate baryon matrix elements using staggered quarks for the valence sector. We show how to relate the representations of the continuum staggered flavor-taste group $\text{SU}(8)_{FT}$ to those of the discrete lattice symmetry group. The resulting calculations yield the normalization factors relating staggered baryon matrix elements to their physical counterparts. We verify this methodology by calculating the isovector vector and axial-vector charges $g_V$ and $g_A$. We use a single ensemble from the MILC Collaboration with 2+1+1 flavors of sea quark, lattice spacing $a\approx 0.12$ fm, and a pion mass $M_\pi\approx305$ MeV. On this ensemble, we find results consistent with expectations from current conservation and neutron beta decay. Thus, this work demonstrates how highly-improved staggered quarks can be used for precision calculations of baryon properties, and, in particular, the isovector nucleon charges., Comment: 19 pages, 9 figures

We review lattice results related to pion, kaon,D-meson,B-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor$$f_+(0)$$f+(0)arising in the semileptonic$$K \rightarrow \pi $$K→πtransition at zero momentum transfer, as well as the decay constant ratio$$f_K/f_\pi $$fK/fπand its consequences for the CKM matrix elements$$V_{us}$$Vusand$$V_{ud}$$Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of$$SU(2)_L\times SU(2)_R$$SU(2)L×SU(2)Rand$$SU(3)_L\times SU(3)_R$$SU(3)L×SU(3)RChiral Perturbation Theory. We review the determination of the$$B_K$$BKparameter of neutral kaon mixing as well as the additional fourBparameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for$$m_c$$mcand$$m_b$$mbas well as those forD- andB-meson decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant$$\alpha _s$$αs. Finally, in this review we have added a new section reviewing results for nucleon matrix elements of the axial, scalar and tensor bilinears, both isovector and flavor diagonal.

We report updates to an ongoing lattice-QCD calculation of the form factors for the semileptonic decays $B \to \pi \ell \nu$, $B_s \to K \ell \nu$, $B \to \pi \ell^+ \ell^-$, and $B \to K \ell^+ \ell^-$. The tree-level decays $B_{(s)} \to \pi (K) \ell \nu$ enable precise determinations of the CKM matrix element $|V_{ub}|$, while the flavor-changing neutral-current interactions $B \to \pi (K) \ell^+ \ell^-$ 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 of the seven ensembles. The valence sector is comprised of a clover $b$ quark (in the Fermilab interpretation) and HISQ light and $s$ quarks. We present preliminary results for the form factors $f_0$, $f_+$, and $f_T$, including studies of systematic errors.

We present an update on the ongoing calculations by the Fermilab Lattice, HPQCD, and MILC Collaboration of the leading-order (in electromagnetism) hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon. Our project employs ensembles with four flavors of highly improved staggered fermions, physical light-quark masses, and four lattice spacings ranging from $a \approx 0.06$ to 0.15 fm for most of the results thus far.

We discuss preliminary results for the vector form factors $f_+^{\{\pi,K\}}$ at zero-momentum transfer for the decays $D\to\pi\ell\nu$ and $D\to K \ell\nu$ using MILC's $N_f = 2+1+1$ HISQ ensembles at four lattice spacings, $a \approx 0.042, 0.06, 0.09$, and 0.12 fm, and various HISQ quark masses down to the (degenerate) physical light quark mass. We use the kinematic constraint $f_+(q^2)= f_0(q^2)$ at $q^2 = 0$ to determine the vector form factor from our study of the scalar current, which yields $f_0(0)$. Results are extrapolated to the continuum physical point in the framework of hard pion/kaon SU(3) heavy-meson-staggered $\chi$PT and Symanzik effective theory. Our calculation improves upon the precision achieved in existing lattice-QCD calculations of the vector form factors at $q^2=0$. We show the values of the CKM matrix elements $|V_{cs}|$ and $|V_{cd}|$ that we would obtain using our preliminary results for the form factors together with recent experimental results, and discuss the implications of these values for the second row CKM unitarity.

We present the first computation in a program of lattice-QCD baryon physics using staggered fermions for sea and valence quarks. For this initial study, we present a calculation of the nucleon mass, obtaining $964\pm16$ MeV with all sources of statistical and systematic errors controlled and accounted for. This result is the most precise determination to date of the nucleon mass from first principles. We use the highly-improved staggered quark action, which is computationally efficient. Three gluon ensembles are employed, which have approximate lattice spacings $a=0.09$ fm, $0.12$ fm, and $0.15$ fm, each with equal-mass $u$/$d$, $s$, and $c$ quarks in the sea. Further, all ensembles have the light valence and sea $u$/$d$ quarks tuned to reproduce the physical pion mass, avoiding complications from chiral extrapolations or nonunitarity. Our work opens a new avenue for precise calculations of baryon properties, which are both feasible and relevant to experiments in particle and nuclear physics., Comment: 33 pages, 19 figures; published in Physical Review D

We present high-precision results from lattice QCD for the mass splittings of the low-lying charmonium states. For the valence charm quark, the calculation uses Wilson-clover quarks in the Fermilab interpretation. The gauge-field ensembles are generated in the presence of up, down, and strange sea quarks, based on the improved staggered (asqtad) action, and gluon fields, based on the one-loop, tadpole-improved gauge action. We use five lattice spacings and two values of the light sea quark mass to extrapolate the results to the physical point. An enlarged set of interpolating operators is used for a variational analysis to improve the determination of the energies of the ground states in each channel. We present and implement a continuum extrapolation within the Fermilab interpretation, based on power-counting arguments, and thoroughly discuss all sources of systematic uncertainty. We compare our results for various mass splittings with their experimental values, namely, the 1S hyperfine splitting, the 1P-1S splitting and the P-wave spin-orbit and tensor splittings. Given the uncertainty related to the width of the resonances, we find excellent agreement., Comment: 24 pages, 8 figures

In the near-future noisy intermediate-scale quantum (NISQ) era of quantum computing technology, applications of quantum computing will be limited to calculations of very modest scales in terms of the number of qubits used. The need to represent numeric quantities using limited resources leads to digitization errors which must be taken into account. As a first step towards quantum simulations of realistic high-energy physics problems, we explore classically the effects of digitizing elements of the $\mathrm{SU}(2)$ gauge group to a finite set. We consider several methods for digitizing the group, finding the best performance from an action-preserving projection onto a mesh. Working in (3+1) dimensions, we find that using $\sim 7$ (qu)bits to represent each $\mathrm{SU}(2)$ gauge link induces a digitization error on the order of $10\%$ in short-distance observables and $2\%$ in long-distance observables. Promisingly, our results indicate that each $\mathrm{SU}(2)$ gauge link can be represented by $\mathcal{O}(10)$ (qu)bits, from which we estimate that a $16^3$ $\mathrm{SU}(2)$ lattice could be simulated with no more than $\mathcal{O}(10^5)$ (qu)bits. Our results on digitization are also of interest as a form of lossy compression that could be used in high-performance classical computing to alleviate communications bottlenecks., Comment: 16 pages; 11 figures; To be submitted to Physical Review A

We present results for neutral $D$-meson mixing in 2+1-flavor lattice QCD. We compute the matrix elements for all five operators that contribute to $D$ mixing at short distances, including those that only arise beyond the Standard Model. Our results have an uncertainty similar to those of the ETM collaboration (with 2 and with 2+1+1 flavors). This work shares many features with a recent publication on $B$ mixing and with ongoing work on heavy-light decay constants from the Fermilab Lattice and MILC Collaborations./Users/ask/TeX/confs/lat16/307/lat-16-307.pdf

We discuss the reduction of errors in the calculation of the form factor $$f_+^{K \pi}(0)$$ with HISQ fermions on the $$N_f=2+1+1$$ MILC configurations from increased statistics on some key ensembles, new data on ensembles with lattice spacings down to 0.042 fm and the study of finite-volume effects within staggered ChPT. We also study the implications for the unitarity of the CKM matrix in the first row and for current tensions with leptonic determinations of $$\vert V_{us}\vert$$.

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 present a calculation of the $$D\to K \ell \nu$$ and $$D\to\pi \ell \nu$$ semileptonic form factors at $q^2=0$, which enable determinations of the CKM matrix elements $$\lvert{V_{cs}}\rvert$$ and $$\lvert{V_{cd}}\rvert$$, respectively. We use gauge-field configurations generated by the MILC collaboration with four flavors of highly-improved staggered (HISQ) quarks, analyzing several ensembles including those with physical pion masses and approximate lattice spacings ranging from 0.12~fm to 0.042~fm. We also use the HISQ action for the valence quarks. We employ twisted boundary conditions to calculate the form factors at zero momentum transfer directly. We use heavy-light-meson chiral perturbation theory modified for energetic pions and kaons, and supplemented by terms to describe the lattice-spacing dependence, to obtain preliminary results at the physical point and in the continuum limit.

Recent calculations of the decay constants in lattice QCD are reviewed and compared to experiment.

We present the status of on-going calculations of the $$K\to\pi l\nu$$ and $$D\to K(\pi) l\nu$$ semileptonic form factors at $q^2=0$. These form factors are important for the determination of the CKM matrix elements $$\lvert{V_{us}}\rvert$$ and $$\lvert{V_{cs(d)}}\rvert$$ respectively. This work uses the HISQ action for both valence quarks and sea quarks on MILC $N_f=2+1+1$ configurations. We employ twisted boundary conditions to calculate the form factors at zero momentum transfer directly. The $$K\to\pi$$ results are an update to previously published results with new data at the physical point. The $$D\to K(\pi)$$ results are preliminary.

We present results for the mass splittings of low-lying charmonium states from a calculation with Wilson clover valence quarks with the Fermilab interpretation on an asqtad sea. We use five lattice spacings and two values of the light sea quark mass to extrapolate our results to the physical point. Sources of systematic uncertainty in our calculation are discussed and we compare our results for the 1S hyperfine splitting, the 1P-1S splitting and the P-wave spin orbit and tensor splittings to experiment.

In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the q2 dependence of the form factor in semileptonic D → Klν decay, the decay constant of the D meson, and the mass of the Bc meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.

We present a calculation of the charmonium spectrum with three flavors of dynamical staggered quarks from gauge configurations that were generated by the MILC collaboration. We use the Fermilab action for the valence charm quarks. Our calculation of the spin-averaged 1P--1S and 2S--1S splittings yields a determination of the strong coupling, with $\ams(M_Z) = 0.119 (4)$., 6 pages, uses espcrc2.sty, Lattice2002(heavyquark)

We pursue a new method, based on lattice QCD, for determining the quantities Λ , λ1, and λ2 of heavy-quark effective theory. We combine Monte Carlo data for the meson mass spectrum with perturbative calculations of the short-distance behavior, to extract Λ and λ1 from a formula from HQET. Taking into account uncertainties from fitting the mass dependence and from taking the continuum limit, we find Λ =0.68 +0.02 −0.12 GeV and λ 1 =−(0.45±0.12) GeV 2 in the quenched approximation.

Quarkonia is studied in lattice QCD using Wilson heavy quarks improved to O(a) in the lattice spacing a. The quarkonia spectrum is compared to experiment and provides a check on lattice spacing errors. Careful attention to systematic errors in quarkonia permits determinations of the QCD coupling αs and the heavy quark masses.

We investigate the masses of the light quarks with lattice QCD. We show that most of the large dependence on the lattice spacing, a, observed in previous determinations using Wilson fermions is removed with the use of an O(a) corrected action. In the quenched approximation, we obtain for the strange quark MS bar mass m_s(2 GeV) = 95 (16) MeV, and for the average of the up and down quark masses m_l(2 GeV) = 3.6 (6) MeV. Short distance arguments and existing staggered fermion calculations make it likely that the answers including the effects of quark loops lie 20 % to 40 % below this: m_s(2 GeV) in the range 54-92 MeV, and m_l(2 GeV) in the range 2.1-3.5 MeV. We argue that almost all lattice determinations of the light quark masses are consistent with these values. These low values are outside the range usually given by conventional phenomenology., Comment: 4 pages, two embedded figures

We use the dynamical gluon configurations provided by the MILC collaboration in a study of the charmonium spectrum and psi leptonic width. We examine sea quark effects on mass splitting and on the leptonic decay matrix element for light masses as low as m_s/5, while keeping the strange quark mass fixed and the lattice spacing nearly constant., Comment: Lattice2003(heavy)

We present our preliminary results for semileptonic form factors of $D$ mesons in unquenched lattice QCD. Simulations are carried out with $n_f=2+1$ dynamical quarks using gauge configurations generated by the MILC collaboration. For the valence quarks, we adopt an improved staggered light quark action and the clover heavy quark action. Our results for $D \to K$ and $D \to \pi$ form factors at $q^2=0$ are in agreement with the experimental values., Comment: Lattice2003(heavy), 3 pages

We describe the construction of large scale clusters for lattice QCD computing being developed under the umbrella of the U.S. DoE SciDAC initiative. We discuss the study of floating point and network performance that drove the design of the cluster, and present our plans for future multi-Terascale facilities.

We present preliminary results for light, strange and charmed pseudoscalar meson physics from simulations using four flavors of dynamical quarks with the highly improved staggered quark (HISQ) action. These simulations include lattice spacings ranging from 0.15 to 0.06 fm, and sea-quark masses both above and at their physical value. The major results are charm meson decay constants f_D, f_{D_s} and f_{D_s}/f_D and ratios of quark masses. This talk will focus on our procedures for finding the decay constants on each ensemble, the continuum extrapolation, and estimates of systematic error., Proceedings of Lattice 2012 Int. Symposium

R is a language system for statistical computation. It is widely used in statistics, bioinformatics, machine learning, data mining, quantitative finance, and the analysis of clinical drug trials. Among the advantages of R are: it has become the standard language for developing statistical techniques, it is being actively developed by a large and growing global user community, it is open source software, it is highly portable (Linux, OS-X and Windows), it has a built-in documentation system, it produces high quality graphics and it is easily extensible with over four thousand extension library packages available covering statistics and applications. This report gives a very brief introduction to R with some examples using lattice QCD simulation results. It then discusses the development of R packages designed for chi-square minimization fits for lattice n-pt correlation functions.

The experimentally measured rates of the semileptonic decays K {yields} {pi}/{nu} and D {yields} K({pi})/{nu} can be combined with lattice calculations of the associated form factors to precisely extract the CKM matrix elements |V{sub us}| and |V{sub cs(d)}|. We report on the status of form factor calculations with Fermilab charm quarks and staggered light quarks on the 2+1 flavor asqtad staggered MILC ensembles. Analysis of data for the D {yields} {pi}/{nu} form factor provides a nontrivial test of our methods via comparison with CLEO data. We discuss the use of HISQ valence quarks to calculate the K {yields} {pi}/{nu} form factor f{sub +}{sup K{pi}}(0) and describe tests of our method.

PUBLISHED, We present an update of our calculation of the form factors and partial widths of semileptonic heavy-to-light meson decays, in the quenched approximation. Our complete data set has now been analysed and our results include chiral extrapolations and a study of the lattice spacing dependence., Fermilab is operated by Universities Research Association, Inc. for the U.S. Department of Energy.

Euclidean four-point Green functions D → K π are studied on the lattice using Wilson fermions in the quenched approximation. The mass dependence of amplitudes “at rest” are compared with the vacuum saturation model. We estimate an effective 1 N value for D decays. Factorization and vacuum saturation are tested for amplitudes that are leading order and next to leading order in 1 N . We note the possibility of a scalar resonance affecting the isospin 1 2 amplitude in D → K π.

This paper discusses the application of existing workflow management systems to a real world science application (LQCD). Typical workflows and execution environment used in production are described. Requirements for the LQCD production system are discussed. The workflow management systems Askalon and Swift were tested by implementing the LQCD workflows and evaluated against the requirements. We report our findings and future work.

Exclusive two body nonleptonic weak decay matrix elements are studied for D mesons using lattice techniques with Wilson fermions in the quenched approximation.

In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the q{sup 2} dependence of the form factor in semileptonic D {yields} K/{nu} decay, the decay constant of the D meson, and the mass of the B{sub c} meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.

We have greatly extended an earlier calculation of the charmonium spectrum on three flavor dynamical quark ensembles by using more recent ensembles generated by the MILC collaboration. The heavy quarks are treated using the Fermilab formulation. The charmonium state masses are in reasonable agreement with the observed spectrum; however, some of the spin splittings may still be too small., 6 pages, 6 figures, presented at Lattice2005(Heavy quark physics), Dublin, July 25-30, 2005, to appear in Proceedings of Science

We present the first lattice QCD calculation with realistic sea quark content of the D^+ meson decay constant f_{D^+}. We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain f_{D^+} = 201 +/- 3 +/- 17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain f_{D_s} = 249 +/- 3 +/- 16 MeV for the D_s meson., note added on recent CLEO measurement; PRL version

We use lattice QCD to predict the mass of the $B_c$ meson. We use the MILC Collaboration's ensembles of lattice gauge fields, which have a quark sea with two flavors much lighter than a third. Our final result is $m_{B_c}=6304\pm12^{+18}_{- 0} MeV$. The first error bar is a sum in quadrature of statistical and systematic uncertainties, and the second is an estimate of heavy-quark discretization effects., 4 pages, 3 figures; shorten to fit in PRL; published version

We present the first three-flavor lattice QCD calculations for $D\to \pi l\nu$ and $D\to K l\nu$ semileptonic decays. Simulations are carried out using ensembles of unquenched gauge fields generated by the MILC collaboration. With an improved staggered action for light quarks, we are able to simulate at light quark masses down to 1/8 of the strange mass. Consequently, the systematic error from the chiral extrapolation is much smaller than in previous calculations with Wilson-type light quarks. Our results for the form factors at $q^2=0$ are $f_+^{D\to\pi}(0)=0.64(3)(6)$ and $f_+^{D\to K}(0) = 0.73(3)(7)$, where the first error is statistical and the second is systematic, added in quadrature. Combining our results with experimental branching ratios, we obtain the CKM matrix elements $|V_{cd}|=0.239(10)(24)(20)$ and $|V_{cs}|=0.969(39)(94)(24)$, where the last errors are from experimental uncertainties., Comment: Fermilab Lattice, MILC, and HPQCD Collaborations; 4 pp

We perform a precise calculation of the mass of the B_c meson using unquenched configurations from the MILC collaboration including 2+1 flavours of improved staggered quarks. Lattice NRQCD and the Fermilab formalism are used to describe the b and c quarks respectively. We find the mass of the B_c meson to be 6.304(16) GeV, Talk presented at Lattice2004(heavy), Fermilab, June 21-26. 3 pages, 2 figures

We argue that high-precision lattice QCD is now possible, for the first time, because of a new improved staggered quark discretization. We compare a wide variety of nonperturbative calculations in QCD with experiment, and find agreement to within statistical and systematic errors of 3% or less. We also present a new determination of alpha_msbar(Mz); we obtain 0.121(3). We discuss the implications of this breakthrough for phenomenology and, in particular, for heavy-quark physics., Comment: 2 figures, revtex

We present preliminary results for the D_s meson spectrum and decay constants in unquenched lattice QCD. Simulations are carried out with 2+1 dynamical quarks using gauge configurations generated by the MILC collaboration. We use the ``asqtad'' a^2 improved staggered action for the light quarks, and the clover heavy quark action with the Fermilab interpretation. We compare our spectrum results with the newly discovered 0+ and 1+ states in the D_s system., Comment: 3pp. Presented at 21st International Symposium on Lattice Field Theory (LATTICE 2003), Tsukuba, Ibaraki, Japan, 15-19 Jul 2003

We develop a new method in lattice QCD to calculate the form factor F(1) at zero recoil. This is the main theoretical ingredient needed to determine |V(cb)| from the exclusive decay anti-B --> D* lepton anti-neutrino. We introduce three ratios, in which most of statistical and systematic error cancels, making a precise calculation possible. We fit the heavy-quark mass dependence directly, and extract the 1/m_Q^2 and three of the four 1/m_Q^3 corrections in the heavy-quark expansion. In this paper we show how the method works in the quenched approximation, obtaining F(1) = 0.913 (+0.024-0.017)(+/-0.016)(+0.003-0.014)(+0.000-0.016)(+0.006-0.014) where the uncertainties come, respectively, from statistics and fitting, matching lattice gauge theory to QCD, lattice spacing dependence, light quark mass effects, and the quenched approximation. We also discuss how to reduce these uncertainties and, thus, to obtain a model-independent determination of |V(cb)|.

We present a lattice QCD calculation of the form factors and differential decay rates for semileptonic decays of the heavy-light mesons B and D to the final state $\ensuremath{\pi}l\ensuremath{\nu}.$ The results are obtained with three methodological improvements over previous lattice calculations: a matching procedure that reduces heavy-quark lattice artifacts, the first study of lattice-spacing dependence, and the introduction of kinematic cuts to reduce model dependence. We show that the main systematics are controllable (within the quenched approximation) and outline how the calculations could be improved to aid current experiments in the determination of $|{V}_{\mathrm{ub}}|$ and $|{V}_{\mathrm{cd}}|.$