Publications (124)325.69 Total impact
 Physical Review Letters 11/2015; 115(21). DOI:10.1103/PhysRevLett.115.212001 · 7.51 Impact Factor

Article: Hadronic Light by Light Contributions to the Muon Anomalous Magnetic Moment With Physical Pions
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ABSTRACT: The current measurement of muonic $g  2$ disagrees with the theoretical calculation by about 3 standard deviations. Hadronic vacuum polarization (HVP) and hadronic light by light (HLbL) are the two types of processes that contribute most to the theoretical uncertainty. The current value for HLbL is still given by models. I will describe results from a firstprinciples lattice calculation with a 139 MeV pion in a box of 5.5 fm extent. Our current numerical strategies, including noise reduction techniques, evaluating the HLbL amplitude at zero external momentum transfer, and important remaining challenges, in particular those associated with finite volume effects, will be discussed. 
Article: On calculating disconnectedtype hadronic lightbylight scattering diagrams from lattice QCD
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ABSTRACT: For reliable comparison of the standard model prediction to the muon g2 with its experimental value, the hadronic lightbylight scattering (HLbL) contribution must be calculated by lattice QCD simulation. HLbL contribution has many types of disconnectedtype diagrams. Here, we start with recalling the point that must be taken care of in every method to calculate them by lattice QCD, and present one concrete method called nonperturbative QED method. 
Article: Lattice Calculation of Hadronic LightbyLight Contribution to the Muon Anomalous Magnetic Moment
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ABSTRACT: The anomalous magnetic moment of muon, $g2$, is a very precisely measured quantity. However, the current measurement disagrees with standard model by about 3 standard deviations. Hadronic vacuum polarization and hadronic light by light are the two types of processes that contribute most to the theoretical uncertainty. I will describe how lattice methods are wellsuited to provide a firstprinciple's result for the hadronic light by light contribution, the various numerical strategies that are presently being used to evaluate it, our current results and the important remaining challenges which must be overcome. 
Conference Paper: Polyhedral User Mapping and Assistant Visualizer Tool for the RStream AutoParallelizing Compiler
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ABSTRACT: Existing highlevel, sourcetosource compilers can accept input programs in a highlevel language (e.g., C) and perform complex automatic parallelization and other mappings using various optimizations. These optimizations often require tradeoffs and can benefit from the user's involvement in the process. However, because of the inherent complexity, the barrier to entry for new users of these highlevel optimizing compilers can often be high. We propose visualization as an effective gateway for nonexpert users to gain insight into the effects of parameter choices and so aid them in the selection of levels best suited to their specific optimization goals. A popular optimization paradigm is polyhedral mapping which achieves optimization by loop transformations. We have augmented a commercial polyhedralmodel sourcetosource compiler (RStream) with an interactive visual tool we call the Polyhedral User Mapping and Assistant Visualizer (PUMAV). PUMAV is tightly integrated with the RStream sourcetosource compiler and allows users to explore the effects of difficult mappings and express their goals to optimize tradeoffs. It implements advanced multivariate visualization paradigms such as parallel coordinates and correlation graphs and applies them in the novel setting of compiler optimizations. We believe that our tool allows programmers to better understand complex program transformations and deviations of mapping properties on well understood programs. This in turn will achieve experience and performance portability across programs architectures as well as expose new communities in the computational sciences to the rich features of autoparallelizing highlevel sourcetosource compilers.3rd IEEE Working Conference on Software Visualization (VISSOFT 2015), Bremen, Germany; 09/2015  [Show abstract] [Hide abstract]
ABSTRACT: We report the first lattice QCD calculation of the complex kaon decay amplitude $A_0$ with physical kinematics, using a $32^3\times 64$ lattice volume and a single lattice spacing $a$, with $1/a= 1.379(7)$ GeV. We find Re$(A_0) = 4.62(0.99)(1.20) \times 10^{7}$ GeV and Im$(A_0) = 1.90(1.22)(1.04) \times 10^{11}$ GeV, where the first error is statistical and the second systematic. The first value is in approximate agreement with the experimental result: Re$(A_0) = 3.3201(18) \times 10^{7}$ GeV while the second can be used to compute the direct CP violating ratio Re$(\varepsilon'/\varepsilon)=1.36(5.21)(4.49)\times 10^{4}$, which is $2.1\sigma$ below the experimental value $16.6(2.3)\times10^{4}$. The real part of $A_0$ is CP conserving and serves as a test of our method while the result for Re$(\varepsilon'/\varepsilon)$ provides a new test of the standardmodel theory of CP violation, one which can be made more accurate with increasing computer capability.  [Show abstract] [Hide abstract]
ABSTRACT: We present a method to couple finitevolume QCD to infinitevolume QED by an appropriate twistaveraging procedure. We demonstrate the prescription numerically for the leadingorder hadronic contribution to the anomalous magnetic moment of the muon and the electromagnetic pion mass splitting.  [Show abstract] [Hide abstract]
ABSTRACT: We calculate the form factors for B>pi l nu & Bs>K l nu decay in lattice QCD. We use the (2+1)flavor RBCUKQCD gauge fieldensembles generated with the domainwall fermion and Iwasaki gauge actions. For the b quarks we use the anisotropic clover action with the relativistic heavyquark interpretation. We analyze data at 2 lattice spacings a~0.11, 0.086 fm with pion masses as light as M_pi~290 MeV. We extrapolate our numerical results to the physical lightquark masses and to the continuum and interpolate in the pion/kaon energy using SU(2) "hardpion" chiral perturbation theory. We provide complete systematic error budgets for the vector & scalar form factors f+(q^2) & f0(q2) for B>pi l nu & Bs >K l nu at 3 momenta that span the q^2 range accessible in our numerical simulations. Next we extrapolate these results to q^2 = 0 using a modelindependent zparameterization based on analyticity & unitarity. We present our final results for f+(q^2) & f0(q^2) as the z coefficients and matrix of correlations between them; this parameterizes the form factors over the entire kinematic range. Our results agree with other 3flavor latticeQCD determinations using staggered light quarks, and have comparable precision, thereby providing important independent checks. Both B>pi l nu & Bs>K l nu decays enable determinations of the CKM element Vub. To illustrate this, we perform a combined zfit of our numerical B >pi l nu formfactor data with experimental measurements of the branching fraction; we obtain Vub = 3.61(32) x 10^{3}, where the error includes statistical and systematic uncertainties. The same approach can be applied to Bs>K l nu to provide an alternative determination of Vub once the process has been measured experimentally. Finally, we make predictions for B>pi l nu & Bs>K l nu differential branching fractions and forwardbackward asymmetries in the Standard Model.Physical Review D 01/2015; 91(7). DOI:10.1103/PhysRevD.91.074510 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report initial nucleon structure results computed on lattices with 2+1 dynamical M\"obius domain wall fermions at the physical point generated by the RBC and UKQCD collaborations. At this stage, we evaluate only connected quark contributions. In particular, we discuss the nucleon vector and axialvector form factors, nucleon axial charge and the isovector quark momentum fraction. From currently available statistics, we estimate the stochastic accuracy of the determination of $g_A$ and $ _{ud}$ to be around 10%, and we expect to reduce that to 5% within the next year. To reduce the computational cost of our calculations, we extensively use acceleration techniques such as loweigenmode deflation and allmodeaveraging (AMA). We present a method for choosing optimal AMA parameters.  [Show abstract] [Hide abstract]
ABSTRACT: We present results for several light hadronic quantities ($f_\pi$, $f_K$, $B_K$, $m_{ud}$, $m_s$, $t_0^{1/2}$, $w_0$) obtained from simulations of 2+1 flavor domain wall lattice QCD with large physical volumes and nearlyphysical pion masses at two lattice spacings. We perform a short, O(3)%, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum `global fit' with a number of other ensembles with heavier pion masses. We use the physical values of $m_\pi$, $m_K$ and $m_\Omega$ to determine the two quark masses and the scale  all other quantities are outputs from our simulations. We obtain results with subpercent statistical errors and negligible chiral and finitevolume systematics for these light hadronic quantities, including: $f_\pi$ = 130.2(9) MeV; $f_K$ = 155.5(8) MeV; the average up/down quark mass and strange quark mass in the $\overline {\rm MS}$ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, $B_K$, in the RGI scheme, 0.750(15) and the $\overline{\rm MS}$ scheme at 3 GeV, 0.530(11). 
Article: K_{L}k_{s}.
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ABSTRACT: We report on the first complete calculation of the K_{L}K_{S} mass difference, ΔM_{K}, using lattice QCD. The calculation is performed on a 2+1 flavor, domain wall fermion ensemble with a 330 MeV pion mass and a 575 MeV kaon mass. We use a quenched charm quark with a 949 MeV mass to implement GlashowIliopoulosMaiani cancellation. For these heavierthanphysical particle masses, we obtain ΔM_{K}=3.19(41)(96)×10^{12} MeV, quite similar to the experimental value. Here the first error is statistical, and the second is an estimate of the systematic discretization error. An interesting aspect of this calculation is the importance of the disconnected diagrams, a dramatic failure of the OkuboZweigIizuka rule.Physical Review Letters 09/2014; 113(11):112003. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The composition of nucleons has long been known to be subatomic particles called quarks and gluons, which interact through the strong force and theoretically can be described by Quantum Chromodynamics (QCD). Lattice QCD (LQCD), in which the continuous spacetime is translated into grid points on a fourdimensional lattice and ab initio Monte Carlo simulations are performed, is by far the only modelindependent method to study QCD with controllable errors. We report the successful application of a novel algorithm, AllModeAveraging, in the LQCD calculations of nucleon internal structure on the Gordon supercomputer our award of roughly 6 million service units through XSEDE. The application of AMA resulted in as much as a factor of 30 speedup in computational efficiency.  [Show abstract] [Hide abstract]
ABSTRACT: The form factor that yields the lightbylight scattering contribution to the muon anomalous magnetic moment is computed in lattice QCD+QED and QED. A nonperturbative treatment of QED is used and is checked against perturbation theory. The hadronic contribution is calculated for unphysical quark and muon masses, and only the diagram with a single quark loop is computed. Statistically significant signals are obtained. Initial results appear promising, and the prospect for a complete calculation with physical masses and controlled errors is discussed.Physical Review Letters 07/2014; 114(1). DOI:10.1103/PhysRevLett.114.012001 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Neutral $B$ meson mixing matrix elements and $B$ meson decay constants are calculated. Static approximation is used for $b$ quark and domainwall fermion formalism is employed for light quarks. The calculations are carried out on $2+1$ flavor dynamical ensembles generated by RBC/UKQCD Collaborations with lattice spacings $0.086$fm ($a^{1}\sim 2.3$GeV) and $0.11$fm ($1.7$GeV), and a fixed physical spatial volume of about $(2.7{\rm fm})^3$. In the static quark action, linksmearings are used to improve the signaltonoise ratio. We employ two kinds of linksmearings, HYP1 and HYP2, and their results are combined in taking the continuum limit. For the matching between the lattice and the continuum theory, oneloop perturbative $O(a)$ improvements are made to reduce discretization errors. As the most important quantity of this work, we obtain SU(3) breaking ratio $\xi=1.208(60)$, where the error includes statistical and systematic one. We also find other neutral $B$ meson mixing quantities $f_B\sqrt{\hat{B}_B}=240(22)$MeV, $f_{B_s}\sqrt{\hat{B}_{B_s}}=290(22)$MeV, $\hat{B}_B=1.17(22)$, $\hat{B}_{B_s}=1.22(13)$ and $B_{B_s}/B_B=1.028(74)$, $B$ meson decay constants $f_B=219(17)$MeV, $f_{B_s}=264(19)$MeV and $f_{B_s}/f_B=1.193(41)$, in the static limit of $b$ quark.Physical Review D 06/2014; 91(11). DOI:10.1103/PhysRevD.91.114505 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report on the first complete calculation of the $K_LK_S$ mass difference, $\Delta M_K$, using lattice QCD. The calculation is performed on a 2+1 flavor, domain wall fermion (DWF) ensemble with a 330~MeV pion mass and a 575~MeV kaon mass. We use a quenched charm quark with a 949~MeV mass to implement GlashowIliopoulosMaiani (GIM) cancellation. For these heavierthanphysical particle masses, we obtain $\Delta M_K =3.19(41)(96)\times 10^{12}$~MeV, quite similar to the experimental value. Here the first error is statistical and the second is an estimate of the systematic discretization error. An interesting aspect of this calculation is the importance of the disconnected diagrams, a dramatic failure of the OZI rule.Physical Review Letters 06/2014; 113(11). DOI:10.1103/PhysRevLett.113.112003 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We calculate the Bmeson decay constants f_B, f_Bs, and their ratio in unquenched lattice QCD using domainwall light quarks and relativistic bquarks. We use gaugefield ensembles generated by the RBC and UKQCD collaborations using the domainwall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ~ 0.11, 0.086 fm with unitary pion masses as light as M_pi ~ 290 MeV; this enables us to control the extrapolation to the physical lightquark masses and continuum. For the bquarks we use the anisotropic clover action with the relativistic heavyquark interpretation, such that discretization errors from the heavyquark action are of the same size as from the lightquark sector. We renormalize the lattice heavylight axialvector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavylight current through O(alpha_s a). We extrapolate our results to the physical lightquark masses and continuum using SU(2) heavymeson chiral perturbation theory, and provide a complete systematic error budget. We obtain f_B0 = 196.2(15.7) MeV, f_B+ = 195.4(15.8) MeV, f_Bs = 235.4(12.2) MeV, f_Bs/f_B0 = 1.193(59), and f_Bs/f_B+ = 1.220(82), where the errors are statistical and total systematic added in quadrature. These results are in good agreement with other published results and provide an important independent cross check of other threeflavor determinations of Bmeson decay constants using staggered light quarks.Physical Review D 04/2014; 91(5). DOI:10.1103/PhysRevD.91.054502 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The real and imaginary parts of the $K_LK_S$ mixing matrix receive contributions from all three charge2/3 quarks: up, charm and top. These give both short and longdistance contributions which are accessible through a combination of perturbative and lattice methods. We will discuss a strategy to compute both the mass difference, $\Delta M_K$ and $\epsilon_K$ to subpercent accuracy, looking in detail at the contributions from each of the three CKM matrix element products $V_{id}^*V_{is}$ for $i=u, c$ and $t$ as described in Ref. [1] 
Article: Covariant approximation averaging
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ABSTRACT: We present a new class of statistical error reduction techniques for MonteCarlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as allmode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domainwall fermions. This comparison indicates that AMA significantly reduces statistical errors in MonteCarlo calculations over conventional methods for the same cost.Physical Review D 02/2014; 91(11). DOI:10.1103/PhysRevD.91.114511 · 4.64 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Neutral B meson mixing matrix elements and B meson decay constants are calculated. Static approximation is used for b quark and domainwall fermion formalism is employed for light quarks. The calculations are done on 2+1 flavor dynamical ensembles, whose lattice spacings are 0.086 fm and 0.11 fm with a fixed physical spatial volume of about (2.7 fm)^3. In the static quark action, linksmearings are used to improve the signaltonoise ratio. We employ two kinds of linksmearings and their results are combined in taking a continuum limit. For the matching between the lattice and the continuum theory, oneloop perturbative calculations are used including O(a) improvements to reduce discretization errors. We obtain SU(3) braking ratio \xi=1.222(60) in the static limit of b quark.  [Show abstract] [Hide abstract]
ABSTRACT: We report on a calculation of the effects of isospin breaking in Lattice QCD+QED. This involves using Chiral Perturbation Theory with Electromagnetic corrections to find the renormalized, nondegenerate, light quark masses. The calculations are carried out on QCD ensembles generated by the RBC and UKQCD collaborations using Domain Wall Fermions and the Iwasaki and Iwasaki+DSDR Gauge Actions with unitary pion masses down to 170 MeV. Noncompact QED is treated in the quenched approximation. The simulations use a $32^3$ lattice size with $a^{1}=2.28(3)$ GeV (Iwasaki) and 1.37(1) (Iwasaki+DSDR). This builds on previous work from the RBC/UKQCD collaboration with lattice spacing $a^{1}=1.78(4)$ GeV.
Publication Stats
3k  Citations  
325.69  Total Impact Points  
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Institutions

20022015

Brookhaven National Laboratory
 Physics Department
New York, New York, United States


2012

University of Connecticut
 Department of Physics
Storrs, CT, United States


20002009

Kanazawa University
 • Institute for Theoretical Physics
 • Department of Physics
Kanazawa, Ishikawa, Japan


20052006

RIKEN
 Theoretical Nuclear Physics Laboratory
Вако, Saitama, Japan


19972000

University of Tsukuba
 Centre for Computational Sciences
Tsukuba, Ibaraki, Japan


19951996

The University of Tokyo
 Department of Physics
白山, Tōkyō, Japan
