Light hadrons in 2+1 flavor lattice QCD

This talk will focus on recent results by the MILC collaboration from simulations of light hadrons in 2+1 flavor lattice QCD. We have achieved high precision results in the pseudoscalar sector, including masses and decay constants, plus quark masses and Gasser-Leutwyler parameters from well controlled chiral perturbation theory fits to our data. We also show spectroscopy results for vector mesons and baryons.Comment: To appear in the proceedings of the First Meeting of the APS Topical Group on Hadronic Physics, Fermilab, Batavia, Illinois, Oct. 24-26, 200

Hadronic matrix elements for B-mixing in the Standard Model and beyond

We use lattice QCD to calculate the B-mixing hadronic matrix elements for a basis of effective four-quark operators that spans the space of all possible contributions in, and beyond, the Standard Model. We present results for the SU(3)-breaking ratio and discuss our ongoing calculation of the mixing matrix elements, including the first calculation of the beyond the Standard Model matrix elements from unquenched lattice QCD.Comment: 3 pages, 1 figure. Proceedings for CIPANP 2012 - Eleventh Conference on the Intersections of Particle and Nuclear Physics, St. Petersburg FL, May 29 - June 3 201

New results on cut-off effects in spectroscopy with the fixed point action

Our study on the cut-off effects in quenched light hadron spectroscopy and pion scattering length with the fixed point action is extended by results obtained at a lattice spacing a=0.102 fm in a box of size L=1.8 fm. The cut-off effects are small, but clearly seen as the resolution is increased from a=0.153 fm to a=0.102 fm. In the quark mass region where the errors are small and under control, our results on the APE plot lie close to the extrapolated numbers of the CP-PACS Collaboration.Comment: 15 pages, 11 figures, reference correcte

Semileptonic form factors for B -> D*lv at nonzero recoil from 2+1-flavor lattice QCD

We present the first unquenched lattice-QCD calculation of the form factors for the decay B -> D*t nu at nonzero recoil. Our analysis includes 15 MILC ensembles with N-f = 2 + 1 flavors of asqtad sea quarks, with a strange quark mass close to its physical mass. The lattice spacings range from a asymptotic to 0.15 fm down to 0.045 fm, while the ratio between the light-and the strange-quark masses ranges from 0.05 to 0.4. The valence b and c quarks are treated using the Wilson-clover action with the Fermilab interpretation, whereas the light sector employs asqtad staggered fermions. We extrapolate our results to the physical point in the continuum limit using rooted staggered heavy-light meson chiral perturbation theory. Then we apply a model independent parametrization to extend the form factors to the full kinematic range. With this parametrization we perform a joint lattice-QCD/experiment fit using several experimental datasets to determine the CKM matrix element |V-cb|. We obtain |V-cb| = (38.40 +/- 0.68(th) +/- 0.34(exp) +/- 0.18(EM)) x 10(-3). The first error is theoretical, the second comes from experiment and the last one includes electromagnetic and electroweak uncertainties, with an overall chi(2)/dof = 126/84, which illustrates the tensions between the experimental data sets, and between theory and experiment. This result is in agreement with previous exclusive determinations, but the tension with the inclusive determination remains. Finally, we integrate the differential decay rate obtained solely from lattice data to predict R(D*) = 0.265 +/- 0.013, which confirms the current tension between theory and experiment.United States Department of Energy (DOE)National Science Foundation's Teragrid/XSEDE ProgramUnited States Department of Energy (DOE) DE-FG02-13ER41976 DE-SC0009998 DE-SC0010120 DE-SC0015655National Science Foundation (NSF) PHY17-19626 PHY14-17805 SRA (Spain) P18-FR-4314Consejeria de Economia, Innovacion, Ciencia y Empleo, Junta de Andalucia (Spain) P18-FR-4314 A-FQM-467-UGR18Fermilab Distinguished Scholars Progra

B Mixing in the Standard Model and Beyond: Lattice QCD

We give a brief overview and progress report on our lattice QCD calculation of neutral B mixing hadronic matrix elements needed for Standard Model and Beyond the Standard Model physics. Reference [1] contains more details and results.Comment: 3 pages, 0 figures, Proceedings of the 19th Particles and Nuclei International Conference (PANIC11), Cambridge, MA, U.S.A., July 201

Sea quark effects in B_K from N_f=2 clover-improved Wilson fermions

We report calculations of the parameter B_K appearing in the Delta S=2 neutral kaon mixing matrix element, whose uncertainty limits the power of unitarity triangle constraints for testing the standard model or looking for new physics. We use two flavours of dynamical clover-improved Wilson lattice fermions and look for dependence on the dynamical quark mass at fixed lattice spacing. We see some evidence for dynamical quark effects and in particular B_K decreases as the sea quark masses are reduced towards the up/down quark mass.Comment: 17 pages, 4 figures, uses JHEP3.cls, added comments and reference

Searching for chiral logs in the static-light decay constant

Using the clover fermion action in unquenched QCD with pion masses as low as 420 MeV, we look for evidence for chiral logs in the static-light decay constant. There is some evidence for a chiral log term, if the original static theory of Eichten and Hill is used. However, the more precise data from the static action of the ALPHA collaboration do not show any evidence for non-linear dependence of the static-light decay constant on the light quark mass. We make some comments on the connection between chiral perturbation theory for decay constants of the pion and static-light meson

The equation of state in lattice QCD: with physical quark masses towards the continuum limit

The equation of state of QCD at vanishing chemical potential as a function of temperature is determined for two sets of lattice spacings. Coarser lattices with temporal extension of N_t=4 and finer lattices of N_t=6 are used. Symanzik improved gauge and stout-link improved staggered fermionic actions are applied. The results are given for physical quark masses both for the light quarks and for the strange quark. Pressure, energy density, entropy density, quark number susceptibilities and the speed of sound are presented.Comment: 14 pages, 9 figures. Version published in JHEP: discussions added in Sects. 1, 2. Fig. 1 changed and a new figure for the interaction measure added. Information on statistics added in Table 1. Raw values of the pressure added in Table 3. A few references adde

Update on the physics of light pseudoscalar mesons

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 statistics for $a \approx 0.09$ fm with the light quark mass equal to one-tenth the strange quark mass, and initial results for our smallest lattice spacing, $a \approx 0.06$ fm with light quark mass two-fifths of the strange quark mass.Comment: 7 pages, 4 figures. To be published in Proceedings of Science (Lattice 2006) 163 (2006

Heavy-Light Decay Constants: Conclusions from the Wilson Action

We report on the results of a MILC collaboration calculation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios. We discuss the most important errors in more detail than we have elsewhere.Comment: LATTICE98(heavyqk) 3 latex pages and 3 postscript figures. The perturbative correction calculated by Kuramashi has been adjusted to take into account the fact that we match to the continuum at the kinetic mass of the heavy meson, not the pole mass. This produces a 2 to 4 MeV change in final results for decay constants, and has negligible effect on decay constant ratio