Flavour physics from lattice QCD

I review recent results and prospects for improvement in calculations of hadronic matrix elements relevant to quark flavour phenomenology. I will focus on key quantities for CKM unitarity triangle analyses and for the study of discrepancies between experiment and SM predictions for some flavour observables.Comment: Invited talk at the Xth Conference on Quark Confinement and the Hadron Spectrum (Munich, 8-12 October 2012). 10 pages. Reference adde

Up-, down-, strange-, charm-, and bottom-quark masses from four-flavor lattice QCD

We calculate the up-, down-, strange-, charm-, and bottom-quark masses using the MILC highly improved staggered-quark ensembles with four flavors of dynamical quarks. We use ensembles at six lattice spacings ranging from a≈0.15 to 0.03 fm and with both physical and unphysical values of the two light and the strange sea-quark masses. We use a new method based on heavy-quark effective theory (HQET) to extract quark masses from heavy-light pseudoscalar meson masses. Combining our analysis with our separate determination of ratios of light-quark masses we present masses of the up, down, strange, charm, and bottom quarks. Our results for the MS¯-renormalized masses are mu(2  GeV)=2.130(41)  MeV, md(2  GeV)=4.675(56)  MeV, ms(2  GeV)=92.47(69)  MeV, mc(3  GeV)=983.7(5.6)  MeV, and mc(mc)=1273(10)  MeV, with four active flavors; and mb(mb)=4195(14)  MeV with five active flavors. We also obtain ratios of quark masses mc/ms=11.783(25), mb/ms=53.94(12), and mb/mc=4.578(8). The result for mc matches the precision of the most precise calculation to date, and the other masses and all quoted ratios are the most precise to date. Moreover, these results are the first with a perturbative accuracy of αs4. As byproducts of our method, we obtain the matrix elements of HQET operators with dimension 4 and 5: Λ¯MRS=555(31)  MeV in the minimal renormalon-subtracted (MRS) scheme, μπ2=0.05(22)  GeV2, and μG2(mb)=0.38(2)  GeV2. The MRS scheme [Phys. Rev. D 97, 034503 (2018)PRVDAQ2470-001010.1103/PhysRevD.97.034503] is the key new aspect of our method.This work was supported in part by the U.S. Department of Energy under Grants No. DEFG02- 91ER40628 (C. B., N. B.), No. DE-FC02- 12ER41879 (C. D.), No. DE-SC0010120 (S. G.), No. DE-FG02-91ER40661 (S. G.), No. DE-FG02- 13ER42001 (A. X. K.), No. DE-SC0015655 (A. X. K.), No. DE-SC0010005 (E. T. N.), No. DE-FG02- 13ER41976 (D. T.); by the U.S. National Science Foundation under Grants No. PHY14-14614 and No. PHY17-19626 (C. D.), PHY14-17805 (J. L.), and PHY13-16748 and PHY16-20625 (R. S.); by the MINECO (Spain) under Grants No. FPA2013-47836-C- 1-P and No. FPA2016-78220-C3-3-P (E. G.); by the Junta de Andalucía (Spain) under Grant No. FQM-101 (E. G.); by the DFG cluster of excellence “Origin and Structure of the Universe” (N. B., A. V.); by the UK Science and Technology Facilities Council (J. K.); by the German Excellence Initiative and the European Union Seventh Framework Program under Grant Agreement No. 291763 as well as the European Union’s Marie Curie COFUND program (J. K., A. S. K.). Brookhaven National Laboratory is supported by the United States Department of Energy, Office of Science, Office of High Energy Physics, under Contract No. DE-SC0012704. This document was prepared by the Fermilab Lattice, MILC, and TUMQCD Collaborations using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DEAC02- 07CH11359

D-meson semileptonic decays to pseudoscalars from four-flavor lattice QCD

We present lattice-QCD calculations of the hadronic form factors for the semileptonic decays D→πℓν, D→Kℓν, and Ds→Kℓν. Our calculation uses the highly improved staggered quark (HISQ) action for all valence and sea quarks and includes Nf=2+1+1 MILC ensembles with lattice spacings ranging from a≈0.12 fm down to 0.042 fm. At most lattice spacings, an ensemble with physical-mass light quarks is included. The HISQ action allows all the quarks to be treated with the same relativistic light-quark action, allowing for nonperturbative renormalization using partial conservation of the vector current. We combine our results with experimental measurements of the differential decay rates to determine |Vcd|D→π=0.2238(11)Expt(15)QCD(04)EW(02)SIB[22]QED and |Vcs|D→K=0.9589(23)Expt(40)QCD(15)EW(05)SIB[95]QED. This result for |Vcd| is the most precise to date, with a lattice-QCD error that is, for the first time for the semileptonic extraction, at the same level as the experimental error. Using recent measurements from BES III, we also give the first-ever determination of |Vcd|Ds→K=0.258(15)Expt(01)QCD[03]QED from Ds→Klν. Our results also furnish new Standard Model calculations of the lepton flavor universality ratios Rμ/eD→π=0.98671(17)QCD[500]QED, Rμ/eD→K=0.97606(16)QCD[500]QED, and Rμ/eDs→K=0.98099(10)QCD[500]QED, which are consistent within 2σ with experimental measurements. Our extractions of |Vcd| and |Vcs|, when combined with a value for |Vcb|, provide the most precise test of second-row Cabibbo-Kobayashi-Maskawa unitarity, finding agreement with unitarity at the level of one standard deviation.Fermi Research Alliance, LLC DE-AC02-07CH11359National Science Foundation ACI-1548562, OAC-1818253, PHY17-19626, PHY20-13064 NSFOffice of Science DE-AC02-06CH11357, DE-AC05-00OR22725, DE-SC0010005, DE-SC0010120, DE-SC0011090, DE-SC0015655, DE-SC0021006 SCLawrence Berkeley National Laboratory DE-AC02-05CH11231 LBNLSociety for Research on Adolescence PID2019–106087GB-C21 SRAEuropean Regional Development Fund P18-FR-4314, RYC2020-030244-I / AEI / 10.13039/501100011033 ERDFJunta de Andalucía A-FQM-467-UGR18, FQM-10

Theoretical progress on the V_us determination from tau decays

9 páginas.-- Comunicación presentada a la Kaon International Conference (KAON'07) celebrada del 21 al 25 de MAyo de 2007 en Frascati (Italia).A very precise determination of V_us can be obtained from the semi-inclusive hadronic decay width of the tau lepton into final states with strangeness. The ratio of the Cabibbo-suppressed and Cabibbo-allowed tau decay widths directly measures (V_us/V_ud)^2, up to very small SU(3)-breaking corrections which can be theoretically estimated with the needed accuracy. Together with previous LEP and CLEO data, the recent measurements by Babar and Belle of some Cabibbo-suppressed tau decays imply V_us= 0.2165 +- 0.0026_exp +- 0.0005_th, which is already competitive with the standard extraction from K_l3 decays. The uncertainty is largely dominated by experimental errors and should be easily reduced with the high statistics of the B factories, providing the most accurate determination of this parameter. A 1% experimental precision on the Cabibbo-suppressed tau decay width would translate into a 0.6% uncertainty on V_us.This work has been supported by the European Commission MRTN FLAVIAnet [MRTN-CT- 2006-035482], theMEC (Spain) and FEDER (EC) [FPA2005-02211 (M.J.), FPA2004-00996 (A.P.) and FPA2006-05294 (J.P.)], the Deutsche Forschungsgemeinschaft (F.S.), the Junta de Andalucía [P05-FQM-101 (J.P.), P05-FQM-437 (E.G. and J.P.) and Sabbatical Grant PR2006-0369 (J.P.)] and the Generalitat Valenciana [GVACOMP2007-156 (A.P.)].Peer reviewe

Light-quark connected intermediate-window contributions to the muon g − 2 hadronic vacuum polarization from lattice QCD

We present a lattice-QCD calculation of the light-quark connected contribution to window observables associated with the leading-order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, aHVP;LO μ . We employ the MILC Collaboration’s isospin-symmetric QCD gauge-field ensembles, which contain four flavors of dynamical highly improved staggered quarks with four lattice spacings between a ≈ 0.06–0.15 fm and close-to-physical quark masses. We consider several effectivefield- theory-based schemes for finite volume and other lattice corrections and combine the results via Bayesian model averaging to obtain robust estimates of the associated systematic uncertainties. After unblinding, our final results for the intermediate and “W2” windows are all;W μ ðconnÞ ¼ 206.6ð1.0Þ × 10−10 and all;W2 μ ðconnÞ ¼ 100.7ð3.2Þ × 10−10, respectivelyUnited States Department of Energy (DOE)National Science Foundation (NSF) ACI-1548562 CNS-0521433 ACI-1532235 ACI-1532236 OCI-0725070 ACI-1238993 PHY17-19626 PHY20-13064 DGE 2040434Lilly Endowment, Inc.University of Colorado BoulderColorado State UniversityState of IllinoisBEISUK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) ST/P002307/1 ST/R002452/1 ST/R00689X/1United States Department of Energy (DOE) DE-SC0010005 DE-SC0010120 DE-SC0011090 DE-SC0021006 DE-SC0015655Funding Opportunity Announcement Scientific Discovery through Advanced Computing: High Energy Physics LAB 22-2580Simons Foundation under their Simons Fellows in Theoretical Physics programUniversities Research Association Visiting Scholarship Awards 20-S-12 21-S-05SRA (Spain) PID2019-106087 GB-C21Junta de Andalucia FQM-101 A-FQM-467-UGR18 P18-FR-4314Spanish Government RYC2020-030244-IUK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) ST/T000945/1Fermi Research Alliance, LLC (FRA) DE-AC02-07CH1135

Matching lattice and continuum four-fermion operators with nonrelativistic QCD and highly improved staggered quarks

We match continuum and lattice heavy-light four-fermion operators at one loop in perturbation theory. For the heavy quarks we use nonrelativistic QCD and for the massless light quarks the highly improved staggered quark action. We include the full set of Delta B = 2 operators relevant to neutral B mixing both within and beyond the standard model and match through order alpha(s), Lambda(QCD)/M-b, and alpha(s)/(aM(b))

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