S. Gottlieb - Indiana U

S. Gottlieb
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Name
S. Gottlieb
Affiliation
Indiana U
Country
United States

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High Energy Physics - Lattice (41)
 
High Energy Physics - Phenomenology (27)
 
High Energy Physics - Experiment (10)
 
Mathematics - Numerical Analysis (8)
 
Physics - Computational Physics (4)
 
High Energy Physics - Theory (2)
 
Nuclear Theory (2)
 
Cosmology and Nongalactic Astrophysics (2)
 
Computer Science - Computational Engineering; Finance; and Science (1)
 
Physics - Instrumentation and Detectors (1)
 
Physics - Accelerator Physics (1)
 
Computer Science - Distributed; Parallel; and Cluster Computing (1)

Publications Authored By S. Gottlieb

When evolving in time the solution of a hyperbolic partial differential equation, it is often desirable to use high order strong stability preserving (SSP) time discretizations. These time discretizations preserve the monotonicity properties satisfied by the spatial discretization when coupled with the first order forward Euler, under a certain time-step restriction. While the allowable time-step depends on both the spatial and temporal discretizations, the contribution of the temporal discretization can be isolated by taking the ratio of the allowable time-step of the high order method to the forward Euler time-step. Read More

The commonly used one step methods and linear multi-step methods all have a global error that is of the same order as the local truncation error (as defined in \cite{gustafsson1995time,quarteroni2010numerical,AllenIsaacson,IsaacsonKeller,Sewell}). In fact, this is true of the entire class of general linear methods. In practice, this means that the order of the method is typically defined solely by the order conditions which are derived by studying the local truncation error. Read More

We present a progress report on our calculation of the decay constants $f_B$ and $f_{B_s}$ from lattice-QCD simulations with highly-improved staggered quarks. Simulations are carried out with several heavy valence-quark masses on $(2+1+1)$-flavor ensembles that include charm sea quarks. We include data at six lattice spacings and several light sea-quark masses, including an approximately physical-mass ensemble at all but the smallest lattice spacing, 0. Read More

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 $\vert V_{us}\vert$. Read More

We review our work done to optimize the staggered conjugate gradient (CG) algorithm in the MILC code for use with the Intel Knights Landing (KNL) architecture. KNL is the second gener- ation Intel Xeon Phi processor. It is capable of massive thread parallelism, data parallelism, and high on-board memory bandwidth and is being adopted in supercomputing centers for scientific research. Read More

We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0), arising in the semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK/fpi and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)LxSU(2)R and SU(3)LxSU(3)R Chiral Perturbation Theory. Read More

Lattice gauge theory was formulated by Kenneth Wilson in 1974. In the ensuing decades, improvements in actions, algorithms, and computers have enabled tremendous progress in QCD, to the point where lattice calculations can yield sub-percent level precision for some quantities. Beyond QCD, lattice methods are being used to explore possible beyond the standard model (BSM) theories of dynamical symmetry breaking and supersymmetry. Read More

2016Jun
Affiliations: 1NISER, 2University of Iowa, 3Washington University, 4University of Utah, 5School of the Art Institute of Chicago, 6University of Utah, 7Indiana University, 8American Physical Society, 9Washington University, 10Syracuse University, 11Washington University, 12Argonne National Laboratory, 13University of California, Santa Barbara, 14Indiana University, 15University of Arizona, 16Fermilab, 17Fermilab

The MILC Collaboration has completed production running of electromagnetic effects on light mesons using asqtad improved staggered quarks. In these calculations, we use quenched photons in the noncompact formalism. We study four lattice spacings from $\approx\!0. Read More

This draft report summarizes and details the findings, results, and recommendations derived from the ASCR/HEP Exascale Requirements Review meeting held in June, 2015. The main conclusions are as follows. 1) Larger, more capable computing and data facilities are needed to support HEP science goals in all three frontiers: Energy, Intensity, and Cosmic. Read More

We calculate---for the first time in three-flavor lattice QCD---the hadronic matrix elements of all five local operators that contribute to neutral $B^0$- and $B_s$-meson mixing in and beyond the Standard Model. We present a complete error budget for each matrix element and also provide the full set of correlations among the matrix elements. We also present the corresponding bag parameters and their correlations, as well as specific combinations of the mixing matrix elements that enter the expression for the neutral $B$-meson width difference. Read More

2015Nov
Affiliations: 1U Iowa, 2U Iowa, 3U Iowa, 4U Iowa, 5Wash U, 6William and Mary U, 7Wash U, 8U Utah, 9Syracuse U, 10U Illinois Urbana, 11School of the Art Institute of Chicago, 12U Granada, 13Indiana U, 14APS, 15Wash U, 16Fermilab, 17Syracuse U, 18U Utah, 19Fermilab, 20U Utah, 21U Arizona, 22U Utah, 23U Colorado, 24Fermilab, 25UC Santa Barbara, 26U Arizona, 27Fermilab, 28Fermilab

We give a progress report on a project aimed at a high-precision calculation of the decay constants $f_B$ and $f_{B_s}$ from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios $m_{ud}/m_s$, including approximately physical sea-quark masses. This range of parameters provides excellent control of the continuum limit and of heavy-quark discretization errors. Read More

Computing plays an essential role in all aspects of high energy physics. As computational technology evolves rapidly in new directions, and data throughput and volume continue to follow a steep trend-line, it is important for the HEP community to develop an effective response to a series of expected challenges. In order to help shape the desired response, the HEP Forum for Computational Excellence (HEP-FCE) initiated a roadmap planning activity with two key overlapping drivers -- 1) software effectiveness, and 2) infrastructure and expertise advancement. Read More

2015Oct
Affiliations: 1NISER, Bhubaneswar, 2University of Iowa, 3Washington University, 4University of Utah, 5School of the Art Institute of Chicago, 6University of Utah, 7Indiana University, 8American Physical Society, 9Washington University, 10Syracuse University, 11University of Utah, 12Indiana University, 13Argonne National Laboratory, 14University of California, Santa Barbara, 15Indiana University, 16University of Arizona, 17Fermilab, 18Fermilab

For some time, the MILC Collaboration has been studying electromagnetic effects on light mesons. These calculations use fully dynamical QCD, but only quenched photons, which suffices to NLO in XPT. That is, the sea quarks are electrically neutral, while the valence quarks carry charge. Read More

We study the exclusive semileptonic $B$-meson decays $B\to K(\pi)\ell^+\ell^-$, $B\to K(\pi)\nu\bar\nu$, and $B\to\pi\tau\nu$, computing observables in the Standard model using the recent lattice-QCD results for the underlying form factors from the Fermilab Lattice and MILC Collaborations. These processes provide theoretically clean windows into physics beyond the Standard Model because the hadronic uncertainties are now under good control for suitably binned observables. For example, the resulting partially integrated branching fractions for $B\to\pi\mu^+\mu^-$ and $B\to K\mu^+\mu^-$ outside the charmonium resonance region are 1-2$\sigma$ higher than the LHCb Collaboration's recent measurements, where the theoretical and experimental errors are commensurate. Read More

We compute the form factors for the $B \to Kl^+l^-$ semileptonic decay process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0. Read More

The rare decay $B\to\pi\ell^+\ell^-$ arises from $b\to d$ flavor-changing neutral currents and could be sensitive to physics beyond the Standard Model. Here, we present the first $ab$-$initio$ QCD calculation of the $B\to\pi$ tensor form factor $f_T$. Together with the vector and scalar form factors $f_+$ and $f_0$ from our companion work [J. Read More

High order strong stability preserving (SSP) time discretizations are advantageous for use with spatial discretizations with nonlinear stability properties for the solution of hyperbolic PDEs. The search for high order strong stability time-stepping methods with large allowable strong stability time-step has been an active area of research over the last two decades. Recently, multiderivative time-stepping methods have been implemented with hyperbolic PDEs. Read More

2015Mar
Affiliations: 1Seoul Nat. U, 2Seoul Nat. U, 3Seoul Nat. U, 4Seoul Nat. U, 5BNL, 6Washington U, 7College of William and Mary, 8U. Utah, 9U. Illinois, 10U. Illinois, 11U. Utah, 12School of the Art Institute of Chicago, 13U. Granada, 14Indiana U, 15American Physical Society, 16Washington U, 17FNAL, 18Syracuse U, 19U. Utah, 20U. Colorado, 21FNAL, 22U. Iowa, 23U. Colorado, 24U. Utah, 25FNAL, 26U. California Santa Barbara, 27U. Arizona, 28FNAL, 29Indiana U

We present a lattice-QCD calculation of the $B\to\pi\ell\nu$ semileptonic form factors and a new determination of the CKM matrix element $|V_{ub}|$. We use the MILC asqtad 2+1-flavor lattice configurations at four lattice spacings and light-quark masses down to 1/20 of the physical strange-quark mass. We extrapolate the lattice form factors to the continuum using staggered chiral perturbation theory in the hard-pion and SU(2) limits. Read More

2015Mar
Affiliations: 1Seoul Nat. U, 2Seoul Nat. U, 3Seoul Nat. U, 4Seoul Nat. U, 5BNL, 6Washington U, 7College of William and Mary, 8U. Utah, 9U. Illinois, 10U. Illinois, 11U. Utah, 12School of the Art Institute of Chicago, 13U. Granada, 14Indiana U, 15American Physical Society, 16Washington U, 17FNAL, 18Syracuse U, 19U. Utah, 20FNAL, 21U. Colorado, 22U. Utah, 23FNAL, 24U. California Santa Barbara, 25U. Arizona, 26FNAL, 27Indiana U

We present the first unquenched lattice-QCD calculation of the hadronic form factors for the exclusive decay $\overline{B} \rightarrow D \ell \overline{\nu}$ at nonzero recoil. We carry out numerical simulations on fourteen ensembles of gauge-field configurations generated with 2+1 flavors of asqtad-improved staggered sea quarks. The ensembles encompass a wide range of lattice spacings (approximately 0. Read More

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. Read More

We compute the $B\to\pi\ell\nu$ semileptonic form factors and update the determination of the CKM matrix element $|V_{ub}|$. We use the MILC asqtad ensembles with $N_f=2+1$ sea quarks at four different lattice spacings in the range $a \approx 0.045$~fm to $0. Read More

Electromagnetic effects play an important role in many phenomena such as isospin-symmetry breaking in the hadron spectrum and the hadronic contributions to g-2. We have generalized the MILC QCD code to include the electromagnetic field. In this work, we focus on simulations including charged sea quarks using the RHMC algorithm. Read More

We compute the leptonic decay constants $f_{D^+}$, $f_{D_s}$, and $f_{K^+}$, and the quark-mass ratios $m_c/m_s$ and $m_s/m_l$ in unquenched lattice QCD. We use the MILC highly improved staggered quark (HISQ) ensembles with four dynamical quark flavors. Our primary results are $f_{D^+} = 212. Read More

The conjugate gradient (CG) algorithm is among the most essential and time consuming parts of lattice calculations with staggered quarks. We test the performance of CG and dslash, the key step in the CG algorithm, on the Intel Xeon Phi, also known as the Many Integrated Core (MIC) architecture. We try different parallelization strategies using MPI, OpenMP, and the vector processing units (VPUs). Read More

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. Read More

We propose and test the first Reduced Radial Basis Function Method (R$^2$BFM) for solving parametric partial differential equations on irregular domains. The two major ingredients are a stable Radial Basis Function (RBF) solver that has an optimized set of centers chosen through a reduced-basis-type greedy algorithm, and a collocation-based model reduction approach that systematically generates a reduced-order approximation whose dimension is orders of magnitude smaller than the total number of RBF centers. The resulting algorithm is efficient and accurate as demonstrated through two- and three-dimensional test problems. Read More

We report on the MILC Collaboration calculation of electromagnetic effects on light pseudoscalar mesons. The simulations employ asqtad staggered dynamical quarks in QCD plus quenched photons, with lattice spacings varying from 0.12 to 0. Read More

We present results for the equation of state in (2+1)-flavor QCD using the highly improved staggered quark action and lattices with temporal extent $N_{\tau}=6,~8,~10$, and $12$. We show that these data can be reliably extrapolated to the continuum limit and obtain a number of thermodynamic quantities and the speed of sound in the temperature range $(130-400)$ MeV. We compare our results with previous calculations, and provide an analytic parameterization of the pressure, from which other thermodynamic quantities can be calculated, for use in phenomenology. Read More

2014Jul
Affiliations: 1Fermilab Lattice and MILC Collaborations, 2Fermilab Lattice and MILC Collaborations, 3Fermilab Lattice and MILC Collaborations, 4Fermilab Lattice and MILC Collaborations, 5Fermilab Lattice and MILC Collaborations, 6Fermilab Lattice and MILC Collaborations, 7Fermilab Lattice and MILC Collaborations, 8Fermilab Lattice and MILC Collaborations, 9Fermilab Lattice and MILC Collaborations, 10Fermilab Lattice and MILC Collaborations, 11Fermilab Lattice and MILC Collaborations, 12Fermilab Lattice and MILC Collaborations, 13Fermilab Lattice and MILC Collaborations, 14Fermilab Lattice and MILC Collaborations, 15Fermilab Lattice and MILC Collaborations, 16Fermilab Lattice and MILC Collaborations, 17Fermilab Lattice and MILC Collaborations, 18Fermilab Lattice and MILC Collaborations, 19Fermilab Lattice and MILC Collaborations, 20Fermilab Lattice and MILC Collaborations, 21Fermilab Lattice and MILC Collaborations, 22Fermilab Lattice and MILC Collaborations, 23Fermilab Lattice and MILC Collaborations

We compute the leptonic decay constants $f_{D^+}$, $f_{D_s}$, and $f_{K^+}$, and the quark-mass ratios $m_c/m_s$ and $m_s/m_l$ in unquenched lattice QCD using the experimentally determined value of $f_{\pi^+}$ for normalization. We use the MILC highly improved staggered quark (HISQ) ensembles with four dynamical quark flavors---up, down, strange, and charm---and with both physical and unphysical values of the light sea-quark masses. The use of physical pions removes the need for a chiral extrapolation, thereby eliminating a significant source of uncertainty in previous calculations. Read More

In this paper, we extend the recently developed reduced collocation method \cite{ChenGottlieb} to the nonlinear case, and propose two analytical preconditioning strategies. One is parameter independent and easy to implement, the other one has the traditional affinity with respect to the parameters which allows for efficient implementation through an offline-online decomposition. Overall, the preconditioning improves the quality of the error estimation uniformly on the parameter domain, and speeds up the convergence of the reduced solution to the truth approximation. Read More

We present a study of the $D$ and $B$ leptonic decay constants on the MILC $N_f=2+1$ asqtad gauge ensembles using asqtad-improved staggered light quarks and clover heavy quarks in the Fermilab interpretation. Our previous analysis \cite{Bazavov:2011aa} computed the decay constants at lattice spacings $a \approx 0.14, 0. Read More

High order spatial discretizations with monotonicity properties are often desirable for the solution of hyperbolic PDEs. These methods can advantageously be coupled with high order strong stability preserving time discretizations. The search for high order strong stability time-stepping methods with large allowable strong stability coefficient has been an active area of research over the last two decades. Read More

We compute the zero-recoil form factor for the semileptonic decay $\bar{B}^0\to D^{*+}\ell^-\bar{\nu}$ (and modes related by isospin and charge conjugation) using lattice QCD with three flavors of sea quarks. We use an improved staggered action for the light valence and sea quarks (the MILC \asqtad\ configurations), and the Fermilab action for the heavy quarks. Our calculations incorporate higher statistics, finer lattice spacings, and lighter quark masses than our 2008 work. Read More

In this paper, we discuss the nonlinear stability and convergence of a fully discrete Fourier pseudospectral method coupled with a specially designed second order time-stepping for the numerical solution of the "good" Boussinesq equation. Our analysis improves the existing results presented in earlier literature in two ways. First, an $l_\infty(0, T^*; H2)$ convergence for the solution and $l_\infty(0, T^*; l_2)$ convergence for the time-derivative of the solution are obtained in this paper, instead of the $l_\infty(0, T^*; l_2)$ convergence for the solution and the $l_\infty(0, T^*; H^{-2})$ convergence for the time-derivative, given in [17]. Read More

These reports present the results of the 2013 Community Summer Study of the APS Division of Particles and Fields ("Snowmass 2013") on the future program of particle physics in the U.S. Chapter 9, on Computing, discusses the computing challenges for future experiments in the Energy, Intensity, and Cosmic Frontiers, for accelerator science, and for particle theory, as well as structural issues in supporting the intense uses of computing required in all areas of particle physics. Read More

2013Dec
Affiliations: 1MILC collaboration, 2MILC collaboration, 3MILC collaboration, 4MILC collaboration, 5MILC collaboration, 6MILC collaboration, 7MILC collaboration, 8MILC collaboration, 9MILC collaboration, 10MILC collaboration, 11MILC collaboration, 12MILC collaboration, 13MILC collaboration, 14MILC collaboration

We present recent results on the QCD equation of state with 2+1+1 flavors of highly improved staggered quarks (HISQ). We focus on three sets of ensembles with temporal extent 6, 8 and 10, that reach up to temperatures of 967, 725 and 580 MeV, respectively. The strange and charm quark masses are tuned to the physical values and the light quarks mass is set to one fifth of the strange. Read More

We calculate the form factors for the semileptonic decays $B_s\to K\ell\nu$ and $B\to K\ell\ell$ with lattice QCD. We work at several lattice spacings and a range of light quark masses, using the MILC 2+1-flavor asqtad ensembles. We use the Fermilab method for the $b$ quark. Read More

We calculate the kaon semileptonic form factor $f_+(0)$ from lattice QCD, working, for the first time, at the physical light-quark masses. We use gauge configurations generated by the MILC collaboration with $N_f=2+1+1$ flavors of sea quarks, which incorporate the effects of dynamical charm quarks as well as those of up, down, and strange. We employ data at three lattice spacings to extrapolate to the continuum limit. Read More

2013Nov
Affiliations: 1Fermilab Lattice and MILC Collaborations, 2Fermilab Lattice and MILC Collaborations, 3Fermilab Lattice and MILC Collaborations, 4Fermilab Lattice and MILC Collaborations, 5Fermilab Lattice and MILC Collaborations, 6Fermilab Lattice and MILC Collaborations, 7Fermilab Lattice and MILC Collaborations, 8Fermilab Lattice and MILC Collaborations, 9Fermilab Lattice and MILC Collaborations, 10Fermilab Lattice and MILC Collaborations, 11Fermilab Lattice and MILC Collaborations, 12Fermilab Lattice and MILC Collaborations, 13Fermilab Lattice and MILC Collaborations, 14Fermilab Lattice and MILC Collaborations, 15Fermilab Lattice and MILC Collaborations, 16Fermilab Lattice and MILC Collaborations, 17Fermilab Lattice and MILC Collaborations, 18Fermilab Lattice and MILC Collaborations, 19Fermilab Lattice and MILC Collaborations, 20Fermilab Lattice and MILC Collaborations, 21Fermilab Lattice and MILC Collaborations, 22Fermilab Lattice and MILC Collaborations, 23Fermilab Lattice and MILC Collaborations

We update our determinations of $f_{D^+}$, $f_{D_s}$, $f_K$, and quark mass ratios from simulations with four flavors of HISQ dynamical quarks. The availability of ensembles with light quarks near their physical mass means that we can extract physical results with only small corrections for valence- and sea-quark mass mistunings instead of a chiral extrapolation. The adjusted valence-quark masses and lattice spacings may be determined from an ensemble-by-ensemble analysis, and the results for the quark mass ratios then extrapolated to the continuum limit. Read More

We present results for the form factor $f_+^{K \pi}(0)$, needed to extract the CKM matrix element $|V_{us}|$ from experimental data on semileptonic $K$ decays, on the HISQ $N_f=2+1+1$ MILC configurations. The HISQ action is also used for the valence sector. The data set used for our final result includes three different values of the lattice spacing and data at the physical light quark masses. Read More

We update the lattice calculation of the $B\to\pi$ semileptonic form factors, which have important applications to the CKM matrix element $|V_{ub}|$ and the $B\to\pi\ell^+\ell^-$ rare decay. We use MILC asqtad ensembles with $N_f=2+1$ sea quarks and over a range of lattice spacings $a \approx 0.045$--$0. Read More

We report on a scale determination with gradient-flow techniques on the $N_f = 2 + 1 + 1$ HISQ ensembles generated by the MILC collaboration. The lattice scale $w_0/a$, originally proposed by the BMW collaboration, is computed using Symanzik flow at four lattice spacings ranging from 0.15 to 0. Read More

This report summarizes the findings of the DPF Theory Panel which was formed with a goal of understanding the scientific problems and opportunities of the next decade, as well as the challenges involved in sustaining a first-class program in theoretical particle physics research in the United States. Read More

High-order spatial discretizations with strong stability properties (such as monotonicity) are desirable for the solution of hyperbolic PDEs. Methods may be compared in terms of the strong stability preserving (SSP) time-step. We prove an upper bound on the SSP coefficient of explicit multistep Runge--Kutta methods of order two and above. Read More

We report on the calculation by the MILC Collaboration of the electromagnetic effects on kaon and pion masses. These masses are computed in QCD with dynamical (asqtad staggered) quarks plus quenched photons at three lattice spacings varying from 0.12 to 0. Read More

A calculation of the ratio of leptonic decay constants f_{K^+}/f_{\pi^+} makes possible a precise determination of the ratio of CKM matrix elements |V_{us}|/|V_{ud}| in the Standard Model, and places a stringent constraint on the scale of new physics that would lead to deviations from unitarity in the first row of the CKM matrix. We compute f_{K^+}/f_{\pi^+} numerically in unquenched lattice QCD using gauge-field ensembles recently generated that include four flavors of dynamical quarks: up, down, strange, and charm. We analyze data at four lattice spacings a ~ 0. Read More

Using staggered fermions and twisted boundary conditions, we calculate the K meson semileptonic decay vector form factor at zero momentum transfer. The HISQ formulation is used for the valence quarks, while the sea quarks are simulated with the asqtad action (MILC N_f=2+1 configurations). For the chiral and continuum extrapolation we use two-loop continuum CHPT, supplemented by partially quenched staggered CHPT at one loop. Read More

We present results from our simulations of quantum chromodynamics (QCD) with four flavors of quarks: u, d, s, and c. These simulations are performed with a one-loop Symanzik improved gauge action, and the highly improved staggered quark (HISQ) action. We are generating gauge configurations with four values of the lattice spacing ranging from 0. Read More

We present our methods to fit the two point correlators for light, strange, and charmed pseudoscalar meson physics with the highly improved staggered quark (HISQ) action. We make use of the least-squares fit including the full covariance matrix of the correlators and including Gaussian constraints on some parameters. We fit the correlators on a variety of the HISQ ensembles. Read More