Internet Archive Search: creator:"U. M. Heller"

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Arxiv.org

35 35

How to Put a Heavier Higgs on the Lattice

Sep 18, 2013 09/13

by U. M. Heller; H. Neuberger; P. Vranas

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Lattice work, exploring the Higgs mass triviality bound, seems to indicate that a strongly interacting scalar sector in the minimal standard model cannot exist while low energy QCD phenomenology seems to indicate that it could. We attack this puzzle using the 1/N expansion and discover a simple criterion for selecting a lattice action that is more likely to produce a heavy Higgs particle. Our large $N$ calculation suggests that the Higgs mass bound might be around $850 GeV$, which is about 30%...
Source: http://arxiv.org/abs/hep-lat/9107001v1

Arxiv.org

49 49

Hadron Spectrum in QCD with Valence Wilson Fermions and Dynamical Staggered Fermions at $6/g^2=5.6

Sep 21, 2013 09/13

by K. M. Bitar; T. A. DeGrand; R. G. Edwards; S. Gottlieb; U. M. Heller; A. D. Kennedy; J. B. Kogut; A. Krasnitz; W. Liu; M. C. Ogilvie; R. L. Renken; P. Rossi; D. K. Sinclair; R. L. Sugar; D. Toussaint; K. C. Wang

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We present an analysis of hadronic spectroscopy for Wilson valence quarks with dynamical staggered fermions at lattice coupling $6/g^2 = \beta=5.6$ at sea quark mass $am_q=0.01$ and 0.025, and of Wilson valence quarks in quenched approximation at $\beta=5.85$ and 5.95, both on $16^3 \times 32$ lattices. We make comparisons with our previous results with dynamical staggered fermions at the same parameter values but on $16^4$ lattices doubled in the temporal direction.
Source: http://arxiv.org/abs/hep-lat/9204008v1

Arxiv.org

34 34

Leptonic decay constants f_Ds and f_D in three flavor lattice QCD

Sep 20, 2013 09/13

by J. N. Simone; C. Aubin; C. Bernard; C. DeTar; M. di Pierro; A. X. El-Khadra; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; P. B. Mackenzie; D. P. Menscher; M. Nobes; M. Okamoto; M. B. Oktay; J. Osborn; R. Sugar; D. Toussaint; H. D. Trottier; :; The Fermilab Lattice; MILC; HPQCD Collaborations

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We determine the leptonic decay constants in three flavor unquenched lattice QCD. We use O(a^2)-improved staggered light quarks and O(a)-improved charm quarks in the Fermilab heavy quark formalism. Our preliminary results, based upon an analysis at a single lattice spacing, are f_Ds = 263(+5-9)(+/-24) MeV and f_D = 225(+11-13)(+/-21) MeV. In each case, the first reported error is statistical while the is the combined systematic uncertainty.
Source: http://arxiv.org/abs/hep-lat/0410030v1

Arxiv.org

53 53

B- and D-meson decay constants from three-flavor lattice QCD

Sep 23, 2013 09/13

by A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; R. Jain; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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We calculate the leptonic decay constants of B_{(s)} and D_{(s)} mesons in lattice QCD using staggered light quarks and Fermilab bottom and charm quarks. We compute the heavy-light meson correlation functions on the MILC asqtad-improved staggered gauge configurations which include the effects of three light dynamical sea quarks. We simulate with several values of the light valence- and sea-quark masses (down to ~m_s/10) and at three lattice spacings (a ~ 0.15, 0.12, and 0.09 fm) and extrapolate...
Source: http://arxiv.org/abs/1112.3051v1

Arxiv.org

36 36

Predictions from Lattice QCD

Sep 18, 2013 09/13

by Andreas S. Kronfeld; I. F. Allison; C. Aubin; C. Bernard; C. T. H. Davies; C. DeTar; M. Di Pierro; E. D. Freeland; Steven Gottlieb; A. Gray; E. Gregory; U. M. Heller; J. E. Hetrick; A. X. El-Khadra; L. Levkova; P. B. Mackenzie; F. Maresca; D. Menscher; M. Nobes; M. Okamoto; M. B. Oktay; J. Osborn; D. Renner; J. N. Simone; R. Sugar; D. Toussaint; H. D. Trottier

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In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the $q^2$ dependence of the form factor in semileptonic $D\to Kl\nu$ decay, the decay constant of the $D$ meson, and the mass of the $B_c$ meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.
Source: http://arxiv.org/abs/hep-lat/0509169v2

Arxiv.org

2 2.0

Review of lattice results concerning low-energy particle physics

Jun 29, 2018 06/18

by S. Aoki; Y. Aoki; D. Becirevic; C. Bernard; T. Blum; G. Colangelo; M. Della Morte; P. Dimopoulos; S. Dürr; H. Fukaya; M. Golterman; Steven Gottlieb; S. Hashimoto; U. M. Heller; R. Horsley; A. Jüttner; T. Kaneko; L. Lellouch; H. Leutwyler; C. -J. D. Lin; V. Lubicz; E. Lunghi; R. Mawhinney; T. Onogi; C. Pena; C. T. Sachrajda; S. R. Sharpe; S. Simula; R. Sommer; A. Vladikas; U. Wenger; H. Wittig

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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...
Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice
Source: http://arxiv.org/abs/1607.00299

Arxiv.org

49 49

Looking for Effects of Topology in the Dirac Spectrum of Staggered Fermions

Sep 23, 2013 09/13

by P. H. Damgaard; U. M. Heller; R. Niclasen; K. Rummukainen

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We classify SU(3) gauge field configurations in different topological sectors by the smearing technique. In each sector we compute the distribution of low lying eigenvalues of the staggered Dirac operator. In all sectors we find perfect agreement with the predictions for the sector of topological charge zero. The smallest Dirac operator eigenvalues of staggered fermions at presently realistic lattice couplings are thus insensitive to gauge field topology. On the smeared configurations, $4\nu$...
Source: http://arxiv.org/abs/hep-lat/9909017v1

Arxiv.org

36 36

Light hadron properties with improved staggered quarks

Sep 19, 2013 09/13

by C. Bernard; T. Burch; T. DeGrand; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Osborn; R. Sugar; D. Toussaint

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Preliminary results from simulations with 2+1 dynamical quark flavors at a lattice spacing of 0.09 fm are combined with earlier results at a=0.13 fm. We examine the approach to the continuum limit and investigate the dependence of the pseudoscalar masses and decay constants as the sea and valence quark masses are separately varied.
Source: http://arxiv.org/abs/hep-lat/0208041v1

Arxiv.org

37 37

A Quark-Antiquark Condensate in Three-Dimensional QCD

Sep 18, 2013 09/13

by P. H. Damgaard; U. M. Heller; A. Krasnitz; T. Madsen

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Three-dimensional lattice QCD is studied by Monte Carlo simulations within the quenched approximation. At zero temperature a quark-antiquark condensate is observed in the limit of vanishing quark masses. The condensate vanishes continuously at the finite-temperature deconfinement phase transition of the theory. A natural interpretation of this phenomenon in the full theory with dynamical quarks is in terms of the spontaneous flavor symmetry breaking $U(N_f) \to U(N_f/2)\times U(N_f/2)$. In...
Source: http://arxiv.org/abs/hep-lat/9803012v3

Arxiv.org

33 33

Screening Masses and Improvement in Pure SU(2) Lattice Gauge Theory at High Temperatures

Sep 19, 2013 09/13

by U. M. Heller; F. Karsch; J. Rank

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From the long-distance behaviour of gluon and Polyakov loop correlation functions we extract masses resp. energies in the electric and magnetic sectors. We discuss their dependence on the temperature and on the momentum as well as the relevance of an improvement of the lattice discretization of the action.
Source: http://arxiv.org/abs/hep-lat/9709065v1

Arxiv.org

34 34

The $N_t=6$ equation of state for two flavor QCD

Sep 18, 2013 09/13

by C. Bernard; T. Blum; C. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; L. Karkkainen; K. Rummukainen; R. Sugar; D. Toussaint; M. Wingate

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We improve the calculation of the equation of state for two flavor QCD by simulating on $N_t=6$ lattices at appropriate values of the couplings for the deconfinement/chiral symmetry restoration crossover. For $am_q=0.0125$ the energy density rises rapidly to approximately 1 ${\rm GeV/fm^3}$ just after the crossover($m_\pi/m_\rho\approx 0.4$ at this point). Comparing with our previous result for $N_t=4$~\cite{eos}, we find large finite $N_t$ corrections as expected from free field theory on...
Source: http://arxiv.org/abs/hep-lat/9509093v1

Arxiv.org

44 44

The B -> pi l nu semileptonic form factor from three-flavor lattice QCD: A model-independent determination of |V(ub)|

Sep 22, 2013 09/13

by Jon A. Bailey; C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. Okamoto; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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We calculate the form factor f_+(q^2) for B-meson semileptonic decay in unquenched lattice QCD with 2+1 flavors of light sea quarks. We use Asqtad-improved staggered light quarks and a Fermilab bottom quark on gauge configurations generated by the MILC Collaboration. We simulate with several light quark masses and at two lattice spacings, and extrapolate to the physical quark mass and continuum limit using heavy-light meson staggered chiral perturbation theory. We then fit the lattice result...
Source: http://arxiv.org/abs/0811.3640v3

Arxiv.org

44 44

Moments of nucleon spin-dependent generalized parton distributions

Sep 22, 2013 09/13

by W. Schroers; R. C. Brower; P. Dreher; R. Edwards; G. Fleming; Ph. Hagler; U. M. Heller; Th. Lippert; J. W. Negele; A. V. Pochinsky; D. B. Renner; D. Richards; K. Schilling

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We present a lattice measurement of the first two moments of the spin-dependent GPD H-tilde(x,xi,t). From these we obtain the axial coupling constant and the second moment of the spin-dependent forward parton distribution. The measurements are done in full QCD using Wilson fermions. In addition, we also present results from a first exploratory study of full QCD using Asqtad sea and domain-wall valence fermions.
Source: http://arxiv.org/abs/hep-lat/0309065v1

Arxiv.org

116 116

Preliminary heavy-light decay constants from the MILC collaboration

Jul 20, 2013 07/13

by C. Bernard; T. Blum; A. De; T. DeGrand; C. DeTar; Steven Gottlieb; U. M. Heller; N. Ishizuka; L. Kärkkäinen; J. Labrenz; A. Soni; R. Sugar; D. Toussaint

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Preliminary results from the MILC collaboration for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios are presented. We compute in the quenched approximation at $\beta=6.3$, 6.0 and 5.7 with Wilson light quarks and static and Wilson heavy quarks. We attempt to quantify systematic errors due to finite volume, finite lattice spacing, large $am$, and fitting and extrapolation uncertainties. The hopping parameter approach of Henty and Kenway is used to treat the heavy quarks; the sources are...
Source: http://arxiv.org/abs/hep-lat/9411080v1

Arxiv.org

30 30

From Spectroscopy to the Strong Coupling Constant with Heavy Wilson Quarks

Sep 19, 2013 09/13

by M. Wingate; T. DeGrand; S. Collins; U. M. Heller

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In this work we present lattice calculations of the masses of P-wave mesons using Monte Carlo simulations. Our valence fermions are defined by the Wilson action. Our gauge fields are generated with both dynamical staggered fermions at a lattice coupling $\beta\equiv 6/g^2=5.6$ for sea quark masses of $am_q=0.010$ and 0.025, and in the quenched approximation at $\beta=6.0$. We present results for charm and charmonium spectroscopy and use them to compute the strong coupling constant $\alpha_s$....
Source: http://arxiv.org/abs/hep-lat/9501034v1

Arxiv.org

69 69

Heavy-light meson decay constants from NRQCD: an analysis of the 1/M corrections

Sep 18, 2013 09/13

by S. Collins; U. M. Heller; J. Sloan; J. Shigemitsu; A. Ali-Khan; C. Davies

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We present {\it preliminary} results for the decay constants of heavy-light mesons using NRQCD heavy and tadpole improved Clover light quarks. A comparison is made with data obtained using Wilson light quarks. We present an analysis of the 1/M corrections to the decay constants in the static limit and compare with the predictions of HQET.
Source: http://arxiv.org/abs/hep-lat/9509065v1

Arxiv.org

39 39

QCD with dynamical Wilson fermions at $β=5.5$

Sep 23, 2013 09/13

by K. M. Bitar; R. G. Edwards; U. M. Heller; A. D. Kennedy

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We study QCD with two flavors of dynamical Wilson fermions at $\beta = 5.5$ and three values of $\kappa$. The corresponding pion masses are 0.375, 0.324 and 0.262 in lattice units, with pion to rho mass ratios of 0.76, 0.71 and 0.62, respectively. We use the configurations to compute the heavy quark potential, leading to lattice spacings of 0.110, 0.105 and 0.099 fm, and to compute spectroscopy for several different valence quark $\kappa$'s.
Source: http://arxiv.org/abs/hep-lat/9607043v1

Arxiv.org

4 4.0

Gradient flow and scale setting on MILC HISQ ensembles

Jun 27, 2018 06/18

by MILC Collaboration; A. Bazavov; C. Bernard; N. Brown; C. DeTar; J. Foley; Steven Gottlieb; U. M. Heller; J. Komijani; J. Laiho; L. Levkova; R. L. Sugar; D. Toussaint; R. S. Van de Water

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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...
Topic: High Energy Physics - Lattice
Source: http://arxiv.org/abs/1503.02769

Arxiv.org

8 8.0

$The $B \to D \ell \nu$ form factors at nonzero recoil and $|V_{cb}|$ from $2+1$-flavor lattice QCD$

The $B \to D \ell \nu$ form factors at nonzero recoil and $|V_{cb}|$ from $2+1$-flavor lattice QCD

Jun 27, 2018 06/18

by Fermilab Lattice; MILC Collaborations; :; Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; Si-Wei Qiu; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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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 0.045 to 0.12 fm) and ratios of light (up and down) to strange sea-quark masses ranging from...
Topic: High Energy Physics - Lattice
Source: http://arxiv.org/abs/1503.07237

Arxiv.org

43 43

Excited States in Staggered Meson Propagators

Sep 22, 2013 09/13

by MILC Collaboration; C. Bernard; T. Burch; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Osborn; R. Sugar; D. Toussaint

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We report on preliminary results from multi-particle fits to meson propagators with three flavors of light dynamical quarks. We are able to measure excited states in propagators with pion quantum numbers, which we interpret as the pion 2S state, and is evidence of locality of the action. In the a_0 (0^{++}) propagators we find evidence for excited states which are probably the expected decay channels, pi+eta and K+Kbar.
Source: http://arxiv.org/abs/hep-lat/0309117v1

Arxiv.org

40 40

Group-theoretical construction of extended baryon operators in lattice QCD

Sep 20, 2013 09/13

by S. Basak; R. G. Edwards; G. T. Fleming; U. M. Heller; C. Morningstar; D. Richards; I. Sato; S. Wallace

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The design and implementation of large sets of spatially-extended, gauge-invariant operators for use in determining the spectrum of baryons in lattice QCD computations are described. Group-theoretical projections onto the irreducible representations of the symmetry group of a cubic spatial lattice are used in all isospin channels. The operators are constructed to maximize overlaps with the low-lying states of interest, while minimizing the number of sources needed in computing the required...
Source: http://arxiv.org/abs/hep-lat/0506029v2

Arxiv.org

31 31

Universal Scaling of the Chiral Condensate in Finite-Volume Gauge Theories

Sep 21, 2013 09/13

by P. H. Damgaard; R. G. Edwards; U. M. Heller; R. Narayanan

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We confront exact analytical predictions for the finite-volume scaling of the chiral condensate with data from quenched lattice gauge theory simulations. Using staggered fermions in both the fundamental and adjoint representations, and gauge groups SU(2) and SU(3), we are able to test simultaneously all of the three chiral universality classes. With overlap fermions we also test the predictions for gauge field sectors of non-zero topological charge. Excellent agreement is found in most cases,...
Source: http://arxiv.org/abs/hep-lat/9907016v2

Arxiv.org

53 53

Eigenvalue Distributions of the QCD Dirac Operator

Sep 17, 2013 09/13

by P. H. Damgaard; U. M. Heller; R. Niclasen; K. Rummukainen

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We compute by Monte Carlo methods the individual distributions of the $k$th smallest Dirac operator eigenvalues in QCD, and compare them with recent analytical predictions. We do this for both massless and massive quarks in an SU(3) gauge theory with staggered fermions. Very precise agreement is found in all cases. As a simple by-product we also extract the microscopic spectral density of the Dirac operator in SU(3) gauge theory with dynamical massive fermions for $N_f=1$ and 2, and obtain...
Source: http://arxiv.org/abs/hep-lat/0007041v2

Arxiv.org

36 36

The Phase Diagram of High Temperature QCD with Three Flavors of Improved Staggered Quarks

Sep 22, 2013 09/13

by The MILC Collaboration; C. Bernard; T. Burch; C. E. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. E. Hetrick; R. L. Sugar; D. Toussaint

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We report on progress in our study of high temperature QCD with three flavors of improved staggered quarks. Simulations are being carried out with three degenerate quarks with masses less than or equal to the strange quark mass, $m_s$, and with degenerate up and down quarks with masses in the range $0.1 m_s \leq m_{u,d}\leq 0.6 m_s$, and the strange quark mass fixed near its physical value. For the quark masses studied to date we find rapid crossovers, which sharpen as the quark mass is...
Source: http://arxiv.org/abs/hep-lat/0309118v1

Arxiv.org

44 44

Computation of the Spatial String Tension in High Temperature SU(2) Gauge Theory

Sep 20, 2013 09/13

by G. S. Bali; J. Fingberg; U. M. Heller; F. Karsch; K. Schilling

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A detailed investigation of the temperature dependence of the spatial string tension $\sigma_s$ in $SU(2)$ gauge theory is presented. A sustained performance of 3~GFLOPS on a 64K Connection Machine CM-2 equivalent has been achieved. Scaling of $\sigma_s$ between $\beta=2.5115$ and $\beta=2.74$, on large lattices, is demonstrated. Below the critical temperature, $T_c$, $\sigma_s$ remains constant. For temperatures larger than $2T_c$ the temperature dependence can be parametrized by $\sigma_s(T)...
Source: http://arxiv.org/abs/hep-lat/9308003v2

Arxiv.org

50 50

Thermodynamics with 2+1 and 3 Flavors of Improved Staggered Quarks

Sep 18, 2013 09/13

by C. Bernard; T. Burch; S. Datta; T. A. DeGrand; C. E. DeTar; Steven Gottlieb; U. M. Heller; K. Orginos; R. L. Sugar; D. Toussaint

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We present preliminary results from exploring the phase diagram of finite temperature QCD with three degenerate flavors and with two light flavors and the mass of the third held approximately at the strange quark mass. We use an order $\alpha_s^2 a^2, a^4$ Symanzik improved gauge action and an order $\alpha_s a^2, a^4$ improved staggered quark action. The improved staggered action leads to a dispersion relation with diminished lattice artifacts, and hence better thermodynamic properties. It...
Source: http://arxiv.org/abs/hep-lat/0110030v1

Arxiv.org

75 75

Update on the physics of light pseudoscalar mesons

Jul 20, 2013 07/13

by The MILC Collaboration; C. Bernard; C. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; L. Levkova; J. Osborn; D. Renner; R. Sugar; D. Toussaint

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We present an update of the MILC investigation of the properties of light pseudoscalar mesons using three flavors of improved staggered quarks. Results are presented for the $\pi$ and $K$ leptonic decay constants, the CKM matrix element $V_{us}$, the up, down and strange quark masses, and the coefficients of the $O(p^4)$ chiral lagrangian. We have new data for lattice spacing $a \approx 0.15$ fm with several values of the light quark mass down to one-tenth the strange quark mass, higher...
Source: http://arxiv.org/abs/hep-lat/0609053v1

Arxiv.org

10 10.0

$$B\to\pi\ell\ell$ form factors for new-physics searches from lattice QCD$

$B\to\pi\ell\ell$ form factors for new-physics searches from lattice QCD

Jun 28, 2018 06/18

by Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; A. S. Kronfeld; J. Laiho; L. Levkova; Yuzhi Liu; E. Lunghi; P. B. Mackenzie; Y. Meurice; E. Neil; Si-Wei Qiu; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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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. A. Bailey $et~al.$, Phys. Rev. D 92, 014024 (2015)], these parameterize the hadronic contribution to $B\to\pi$ semileptonic decays in any extension of the...
Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice
Source: http://arxiv.org/abs/1507.01618

Arxiv.org

35 35

Baryonic Operators for Lattice Simulations

Sep 22, 2013 09/13

by LHP Collaboration; R. Edwards; R. Fiebig; G. Fleming; U. M. Heller; C. Morningstar; D. Richards; I. Sato; S. Wallace

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The construction of baryonic operators for determining the N* excitation spectrum is discussed. The operators are designed with one eye towards maximizing overlaps with the low-lying states of interest, and the other eye towards minimizing the number of sources needed in computing the required quark propagators. Issues related to spin identification are outlined. Although we focus on tri-quark baryon operators, the construction method is applicable to both mesons and penta-quark operators.
Source: http://arxiv.org/abs/hep-lat/0309079v1

Arxiv.org

42 42

Charmed meson decay constants in three-flavor lattice QCD

Sep 20, 2013 09/13

by C. Aubin; C. Bernard; C. DeTar; M. Di Pierro; E. D. Freeland; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. X. El-Khadra; A. S. Kronfeld; L. Levkova; P. B. Mackenzie; D. Menscher; F. Maresca; M. Nobes; M. Okamoto; D. Renner; J. Simone; R. Sugar; D. Toussaint; H. D. Trottier

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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.
Source: http://arxiv.org/abs/hep-lat/0506030v2

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43 43

Extracting $F_π$ from small lattices: unquenched results

Sep 21, 2013 09/13

by P. H. Damgaard; U. M. Heller; K. Splittorff; B. Svetitsky; D. Toublan

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We calculate the response of the microscopic Dirac spectrum to an imaginary isospin chemical potential for QCD with two dynamical flavors in the chiral limit. This extends our previous calculation from the quenched to the unquenched theory. The resulting spectral correlation function in the $\epsilon$-regime provides here, too, a new and efficient way to measure $F_\pi$ on the lattice. We test the method in a hybrid Monte Carlo simulation of the theory with two staggered quarks.
Source: http://arxiv.org/abs/hep-lat/0602030v1

Arxiv.org

38 38

Spectroscopy using the Anisotropic Clover Action

Sep 18, 2013 09/13

by LHP Collaboration; R. G. Edwards; U. M. Heller; D. G. Richards

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The calculation of the light-hadron spectrum in the quenched approximation to QCD using an anisotropic clover fermion action is presented. The tuning of the parameters of the action is discussed, using the pion and rho dispersion relation. The adoption of an anisotropic lattice provides clear advantages in the determination of the baryonic resonances, and in particular that of the so-called Roper resonance, the lightest radial excitation of the nucleon.
Source: http://arxiv.org/abs/hep-lat/0303004v1

Arxiv.org

47 47

QCD equation of state at non-zero chemical potential

Sep 19, 2013 09/13

by The MILC Collaboration; S. Basak; A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; J. Osborn; R. Sugar; D. Toussaint

eye 47

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We present our new results for the QCD equation of state at nonzero chemical potential at N_t=6 and compare them with N_t=4. We use the Taylor expansion method with terms up to sixth order in simulations with 2+1 flavors of improved asqtad quarks along a line of constant physics with m_l=0.1 m_s and approximately physical strange quark mass m_s.
Source: http://arxiv.org/abs/0910.0276v1

Arxiv.org

59 59

HISQ action in dynamical simulations

Sep 23, 2013 09/13

by A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; J. Osborn; R. Sugar; D. Toussaint

eye 59

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We report on recent progress in employing the Highly Improved Staggered Quark (HISQ) action introduced by the HPQCD/UKQCD collaboration in simulations with dynamical fermions. The HISQ action is an order $a^2$ Symanzik-improved action with further suppressed taste symmetry violations. The improvement in taste symmetry is achieved by introducing Fat7 smearing of the original gauge links and reunitarization (projection to an element of U(3) or SU(3)) followed by Asq-type smearing. Major...
Source: http://arxiv.org/abs/0903.0874v1

Arxiv.org

36 36

Lattice QCD ensembles with four flavors of highly improved staggered quarks

Sep 23, 2013 09/13

by The MILC Collaboration; A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Komijani; J. Laiho; L. Levkova; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

eye 36

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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 0.06 fm to 0.15 fm, and three values of the light quark mass, including the value for which the Goldstone pion mass is equal to the physical pion mass. We...
Source: http://arxiv.org/abs/1212.4768v3

Arxiv.org

31 31

Visualization of semileptonic form factors from lattice QCD

Sep 22, 2013 09/13

by C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. Okamoto; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

eye 31

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Comparisons of lattice-QCD calculations of semileptonic form factors with experimental measurements often display two sets of points, one each for lattice QCD and experiment. Here we propose to display the output of a lattice-QCD analysis as a curve and error band. This is justified, because lattice-QCD results rely in part on fitting, both for the chiral extrapolation and to extend lattice-QCD data over the full physically allowed kinematic domain. To display an error band, correlations in the...
Source: http://arxiv.org/abs/0906.2498v2

Arxiv.org

62 62

$Lattice calculation of $1^{-+}$ hybrid mesons with improved Kogut-Susskind fermions$

Lattice calculation of $1^{-+}$ hybrid mesons with improved Kogut-Susskind fermions

Sep 20, 2013 09/13

by C. Bernard; T. Burch; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Osborn; R. Sugar; D. Toussaint

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We report on a lattice determination of the mass of the exotic $1^{-+}$ hybrid meson using an improved Kogut-Susskind action. Results from both quenched and dynamical quark simulations are presented. We also compare with earlier results using Wilson quarks at heavier quark masses. The results on lattices with three flavors of dynamical quarks show effects of sea quarks on the hybrid propagators which probably result from coupling to two meson states. We extrapolate the quenched results to the...
Source: http://arxiv.org/abs/hep-lat/0301024v2

Arxiv.org

34 34

The Spatial String Tension in the Deconfined Phase of the (3+1)-Dimensional SU(2) Gauge Theory

Sep 22, 2013 09/13

by G. S. Bali; J. Fingberg; U. M. Heller; F. Karsch; K. Schilling

eye 34

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We present results of a detailed investigation of the temperature dependence of the spatial string tension in SU(2) gauge theory. We show, for the first time, that the spatial string tension is scaling on the lattice and thus is non-vanishing in the continuum limit. It is temperature independent below Tc and rises rapidly above. For temperatures larger than 2Tc we find a scaling behaviour consistent with sigma_s(T) = 0.136(11) g^4(T) T^2, where g(T) is the 2-loop running coupling constant with...
Source: http://arxiv.org/abs/hep-lat/9306024v1

Arxiv.org

49 49

Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD

Sep 22, 2013 09/13

by LHPC Collaboration; SESAM Collaboration; D. Dolgov; R. Brower; S. Capitani; P. Dreher; J. W. Negele; A. Pochinsky; D. B. Renner; N. Eicker; Th. Lippert; K. Schilling; R. G. Edwards; U. M. Heller

eye 49

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Moments of the quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD. Calculations of proton matrix elements of operators corresponding to these moments through the operator product expansion have been performed on $16^3 \times 32$ lattices for Wilson fermions at $\beta = 5.6$ using configurations from the SESAM collaboration and at $\beta = 5.5$ using configurations from SCRI. One-loop perturbative renormalization corrections are included. At quark...
Source: http://arxiv.org/abs/hep-lat/0201021v3

Arxiv.org

25 25

High temperature QCD with three flavors of improved staggered quarks

Sep 19, 2013 09/13

by The MILC Collaboration; C. Bernard; T. Burch; C. E. DeTar; Steven Gottlieb; Eric Gregory; U. M. Heller; J. Osborn; R. L. Sugar; D. Toussaint

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We present an update of our study of high temperature QCD with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad staggered quark action. Simulations are being carried out on lattices with Nt=4, 6 and 8 for the case of three degenerate quarks with masses less than or equal to the strange quark mass, $m_s$, and on lattices with Nt=6 and 8 for degenerate up and down quarks with masses in the range 0.2 m_s \leq m_{u,d} \leq 0.6 m_s, and the strange quark fixed near its...
Source: http://arxiv.org/abs/hep-lat/0209079v1

Arxiv.org

41 41

Mass spectrum of N* and source optimization

Sep 22, 2013 09/13

by LHP Collaboration; S. Basak; R. Edwards; R. Fiebig; G. Fleming; U. M. Heller; C. Morningstar; D. Richards; I. Sato; S. Wallace

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We have computed correlation functions for nucleons and extracted the masses for positive- and negative-parities. Use of group theory plays an important role in obtaining sources that have good overlap to higher spin states and minimum contamination from unwanted states. In the simulation three distinct sources and corresponding sinks that transform according to the $G_1$ irreducible representations are tested and used to form matrices of correlation functions. Diagonalizations give us clear...
Source: http://arxiv.org/abs/hep-lat/0309091v1

Arxiv.org

5 5.0

$$|V_{ub}|$ from $B\to\pi\ell\nu$ decays and (2+1)-flavor lattice QCD$

$|V_{ub}|$ from $B\to\pi\ell\nu$ decays and (2+1)-flavor lattice QCD

Jun 27, 2018 06/18

by Fermilab Lattice; MILC Collaborations; :; Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; Yuzhi Liu; P. B. Mackenzie; Y. Meurice; E. T. Neil; Si-Wei Qiu; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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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. We employ a model-independent $z$ parameterization to...
Topics: High Energy Physics - Experiment, High Energy Physics - Phenomenology, High Energy Physics - Lattice
Source: http://arxiv.org/abs/1503.07839

Arxiv.org

66 66

B and D Meson Decay Constants

Sep 23, 2013 09/13

by C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

eye 66

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We present an update of our calculations of the decay constants of the D, D_s, B, and B_s mesons in unquenched 2+1 flavor QCD. We use the MILC library of improved staggered gauge ensembles at lattice spacings 0.09, 0.12, and 0.15 fm, clover heavy quarks with the Fermilab normalizations, and improved staggered light valence quarks.
Source: http://arxiv.org/abs/0904.1895v1

Arxiv.org

38 38

Gluon Propagator on Coarse Lattices in Laplacian Gauges

Sep 19, 2013 09/13

by P. O. Bowman; U. M. Heller; D. B. Leinweber; A. G. Williams

eye 38

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The Laplacian gauge is a nonperturbative gauge fixing that reduces to Landau gauge in the asymptotic limit. Like Landau gauge, it respects Lorentz invariance, but it is free of Gribov copies; the gauge fixing is unambiguous. In this paper we study the infrared behavior of the lattice gluon propagator in Laplacian gauge by using a variety of lattices with spacings from $a = 0.125$ to 0.35 fm, to explore finite volume and discretization effects. Three different implementations of the Laplacian...
Source: http://arxiv.org/abs/hep-lat/0206010v2

Arxiv.org

42 42

The QCD equation of state with asqtad staggered fermions

Sep 19, 2013 09/13

by C. Bernard; T. Burch; C. DeTar; Steven Gottlieb; L. Levkova; U. M. Heller; J. E. Hetrick; D. B. Renner; D. Toussaint; R. Sugar

eye 42

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We report on our result for the equation of state (EOS) with a Symanzik improved gauge action and the asqtad improved staggered fermion action at $N_t=4$ and 6. In our dynamical simulations with 2+1 flavors we use the inexact R algorithm and here we estimate the finite step-size systematic error on the EOS. Finally we discuss the non-zero chemical potential extension of the EOS and give some preliminary results.
Source: http://arxiv.org/abs/hep-lat/0610017v1

Arxiv.org

34 34

The Effectiveness of Non-Perturbative O(a) Improvement in Lattice QCD

Sep 21, 2013 09/13

by R. G. Edwards; U. M. Heller; T. R. Klassen

eye 34

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The ALPHA collaboration has determined the O(a) improved Wilson quark action for lattice spacings $a\leq 0.1$ fm, in the quenched approximation. We extend this result to coarser lattices, $a\leq 0.17$ fm, and calculate the hadron spectrum on them. The large range of lattice spacings obtained by combining our results with earlier ones on finer lattices, allow us to present a convincing demonstration of the efficiency of non-perturbative O(a) improvement. We find that scaling violations of the...
Source: http://arxiv.org/abs/hep-lat/9711052v2

Arxiv.org

40 40

Exotic meson spectroscopy from the clover action at beta = 5.85 and 6.15

Sep 18, 2013 09/13

by C. Bernard; T. DeGrand; C. DeTar; Steven Gottlieb; U. M. Heller; J. Hetrick; C. McNeile; R. Sugar; D. Toussaint

eye 40

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We repeat our original simulations of the hybrid meson spectrum using the clover action, as a check on lattice artifacts. Our results for the 1-+ masses do not substantially change. We present preliminary results for the wave function of the 1-+ state in Coulomb gauge.
Source: http://arxiv.org/abs/hep-lat/9809087v1

Arxiv.org

40 40

Lattice Quark Propagator in Landau and Laplacian Gauges

Sep 18, 2013 09/13

by P. O. Bowman; U. M. Heller; A. G. Williams

eye 40

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We present results for the lattice quark propagator in both Landau and Laplacian gauges using standard and improved staggered quark actions. The standard Kogut-Susskind action has errors of \oa{2} while the improved ``Asqtad'' action has \oa{4}, \oag{2}{2} errors. This improvement is seen in the quark propagator. We demonstrate the application of tree-level corrections to these actions and see that Landau and Laplacian gauges produce very similar results.
Source: http://arxiv.org/abs/hep-lat/0110081v1

Arxiv.org

75 75

The Equation of State for QCD with 2+1 Flavors of Quarks

Sep 18, 2013 09/13

by C. Bernard; T. Burch; C. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; L. Levkova; F. Maresca; D. B. Renner; R. Sugar; D. Toussaint

eye 75

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We report results for the interaction measure, pressure and energy density for nonzero temperature QCD with 2+1 flavors of improved staggered quarks. In our simulations we use a Symanzik improved gauge action and the Asqtad $O(a^2)$ improved staggered quark action for lattices with temporal extent $N_t=4$ and 6. The heavy quark mass $m_s$ is fixed at approximately the physical strange quark mass and the two degenerate light quarks have masses $m_{ud} =0.1m_s$ or $0.2m_s$. The calculation of the...
Source: http://arxiv.org/abs/hep-lat/0509053v1

Arxiv.org

37 37

The equation of state for two flavor QCD at N_t=6

Sep 22, 2013 09/13

by The MILC Collaboration; C. W. Bernard; T. Blum; C. Detar; S. Gottlieb; U. M. Heller; J. E. Hetrick; L. Karkkainen; R. Rummukainen; R. L. Sugar; D. Toussaint; M. Wingate

eye 37

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We calculate the two flavor equation of state for QCD on lattices with lattice spacing a=(6T)^{-1} and find that cutoff effects are substantially reduced compared to an earlier study using a=(4T)^{-1}. However, it is likely that significant cutoff effects remain. We fit the lattice data to expected forms of the free energy density for a second order phase transition at zero-quark-mass, which allows us to extrapolate the equation of state to m_q=0 and to extract the speed of sound. We find that...
Source: http://arxiv.org/abs/hep-lat/9612025v1

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