15857007
Unitarity and the heavy quark expansion in the determination of semileptonic form factors
We discuss prospects for improving the q 2 extrapolation of the B → πlν form factors with model-independent constraints based on unitarity and heavy quark power-counting. As an illustration, we apply the method to preliminary results of calculations of the form factors, which we generated using the MILC gauge configurations and the Fermilab action for the heavy b-quark. Unitarity, the heavy quark expansion, and semileptonic form factors Ruth S. Van de Water
59427655
B-meson decay constants from 2+1-flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks
We calculate the B-meson decay constants fB, fBs, and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b-quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall 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 Mπ ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b-quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector 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 heavy-light current through O(αsa). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain fB0 = 196.2(15.7) MeV, fB+ = 195.4(15.8) MeV, fBs =more » 235.4(12.2) MeV, fBs/fB0 = 1.193(59), and fBs/fB+ = 1.220(82), where the errors are statistical and total systematic added in quadrature. In addition, these results are in good agreement with other published results and provide an important independent cross check of other three-flavor determinations of B-meson decay constants using staggered light quarks.« less
53317918
The CKM matrix and flavor physics from lattice QCD
I discuss the role of lattice QCD in testing the Standard Model and searching for physics beyond the Standard Model in the quark flavor sector. I first review the Standard Model CKM framework. I then present the current status of the CKM matrix, focusing on determinations of CKM matrix elements and constraints on the CKM unitarity triangle that rely on lattice QCD calculations of weak matrix elements. I also show the potential impact of improved lattice QCD calculations on the global CKM unitarity triangle fit. I then describe several hints of new physics in the quark flavor sector that rely on lattice QCD calculations of weak matrix elements, such as evidence of a ~2-3 sigma tension in the CKM unitarity triangle and the "f_{D_s} puzzle". I finish with a discussion of lattice QCD calculations of rare B- and K-decays needed to probe physics beyond the Standard Model at future experiments.
119241694
Matrix Elements for D- and B-Mixing from 2+1 Flavor Lattice QCD
C.C. Chang∗ a f , C. Bernard b, C.M. Bouchard c, A.X. El-Khadra a f , E.D. Freeland d, E. Gamiz e, A.S. Kronfeld f , J. Laiho g, R.S. van de Water f aPhysics Department, University of Illinois, Urbana, IL 61801, USA bDepartment of Physics, Washington University, St. Louis, MO 63130, USA cDepartment of Physics, The Ohio State University, Columbus, OH 43210, USA dLiberal Arts Department, The School of the Art Institute of Chicago, Chicago, IL 60603, USA eCAFPE and Departamento de Fisica Teorica y del Cosmos, Universidad de Granada, E-18002 Granada, Spain fTheoretical Physics Department, Fermi National Accelerator Laboratory†, Batavia, IL 60510, USA gSUPA, Department of Physics and Astronomy, University of Glasgow, Glasgow, G12-8QQ, United Kingdom
123473314
Heavy-Quark Masses from the Fermilab Method in Three-Flavor Lattice QCD
We report on heavy quark mass calculations using Fermilab heavy quarks. Lattice calculations of heavy-strange meson masses are combined with one-loop (automated) lattice perturbation theory to arrive at the quark mass. Mesons are constructed from Fermilab heavy quarks and staggered light quarks. We use the MILC ensembles at three lattice spacings and sea quark mass ratios of m{sub u,d}/m{sub s} = 0.1 to 0.4. Preliminary results for the bottom quark are given in the potential subtracted scheme.
35146463
Neutral kaon mixing parameter BK from unquenched mixed-action lattice QCD
We calculate the neutral kaon mixing parameter B_K in unquenched lattice QCD using asqtad-improved staggered sea quarks and domain-wall valence quarks. We use the "2+1" flavor gauge configurations generated by the MILC Collaboration, and simulate with multiple valence and sea quark masses at two lattice spacings of a ~ 0.12 fm and a ~ 0.09 fm. We match the lattice determination of B_K to the continuum value using the nonperturbative method of Rome-Southampton, and extrapolate B_K to the continuum and physical quark masses using mixed action chiral perturbation theory. The "mixed-action" method enables us to control all sources of systematic uncertainty and therefore to precisely determine B_K; we find a value of B_K^{MSbar, NDR}(2 GeV) = 0.527(6)(20), where the first error is statistical and the second is systematic.
124314895
Investigation of the decays anti-B0 ---> D*+ lepton- anti-neutrino and anti-B ---> D** lepton- anti-neutrino
120707119
A measurement of the inclusive semileptonic decay fraction of charmed hadrons
Abstract Using the ARGUS detector at the DORIS-II storage ring at DESY, we have measured the inclusive semileptonic branching ratio of charmed hadrons produced in e + e − annihilition at =10 GeV to be BR(c→ev e X)=(9.8±0.9± 0.5 0.6 )% and BR(c→ μv μ X)=(8.6±1.7± 0.7 0.8 )%.
123971124
Latest Oscillation Results from SNO
The Sudbury Neutrino Observatory has been successfully taking quality neutrino data for over two years now. This paper reports on analysis of the solar charge current and elastic scattering neutrino fluxes from the first year of pure D2O running. Combined with the SuperK elastic scattering flux, there is strong evidence that solar neutrinos are oscillating, and that predictions of the standard solar model are in good agreement with data.
122042804
A Model independent determination of the inclusive semileptonic decay fraction of B mesons
Abstract With the ARGUS detector at the e + e - storage ring DORIS II, we have determined decay fraction and electron momentum spectrum of the inclusive decay mode B → eν X. Usinng lepton tags from the second B meson. in 209 000 γ(4 S ) → B B decays, we could determine the spectrum for all electron momenta p e > 0.6 GeV/ c . Including the small extrapolation to p e > 0, we find the model-independent decay fraction B (B → eν X) = (9.6 ± 0.5 ± 0.4)%. Adding D meson tags, our result is (9.7 ± 0.5 ± 0.4)%.
120865332
Observation of a new charmed baryon
Abstract Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, we have observed a new charmed baryon state in the channel Λ c + π + π − . (All references to a specific charged state also imply the charge conjugate state.) The mass of this state was measured to be (2626.6 ± 0.5 ± 1.5) MeV/ c 2 . The product of the production cross section and branching ratio for this channel was determined to be (11.5 ± 2.5 ± 3.0) pb, and the natural width estimated to be smaller than 3.2 MeV/ c 2 at 90% CL.