Publications (167)287.84 Total impact

Article: $D$meson semileptonic form factors at zero momentum transfer in (2+1+1)flavor lattice QCD
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ABSTRACT: We present a calculation of the $D\to K \ell \nu$ and $D\to\pi \ell \nu$ semileptonic form factors at $q^2=0$, which enable determinations of the CKM matrix elements $\lvert{V_{cs}}\rvert$ and $\lvert{V_{cd}}\rvert$, respectively. We use gaugefield configurations generated by the MILC collaboration with four flavors of highlyimproved staggered (HISQ) quarks, analyzing several ensembles including those with physical pion masses and approximate lattice spacings ranging from 0.12~fm to 0.042~fm. We also use the HISQ action for the valence quarks. We employ twisted boundary conditions to calculate the form factors at zero momentum transfer directly. We use heavylightmeson chiral perturbation theory modified for energetic pions and kaons, and supplemented by terms to describe the latticespacing dependence, to obtain preliminary results at the physical point and in the continuum limit.  [Show abstract] [Hide abstract]
ABSTRACT: We give a progress report on a project aimed at a highprecision calculation of the decay constants $f_B$ and $f_{B_s}$ from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valencequark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light seaquark mass ratios $m_{ud}/m_s$, including approximately physical seaquark masses. This range of parameters provides excellent control of the continuum limit and of heavyquark discretization errors. We present a preliminary error budget with projected uncertainties of 2.2~MeV and 1.5~MeV for $f_B$ and $f_{B_s}$, respectively.  [Show abstract] [Hide abstract]
ABSTRACT: We study the exclusive semileptonic $B$meson decays $B\to K(\pi)\ell^+\ell^$, $B \to K(\pi)\nu\bar\nu$, and $B\to\pi\tau\nu$, computing observables in the Standard model using the recent latticeQCD results for the underlying form factors from the Fermilab Lattice and MILC Collaborations. These processes provide theoretically clean windows into physics beyond the Standard Model because the hadronic uncertainties are now under good control. The resulting partiallyintegrated branching fractions for $B \to \pi \mu^+\mu^$ and $B \to K\mu^+\mu^$ outside the charmonium resonance region are 12$\sigma$ higher than the LHCb Collaboration's recent measurements, where the theoretical and experimental errors are commensurate. The combined tension is 1.7$\sigma$. Combining the StandardModel rates with LHCb's measurements yields values for the CabibboKobayashiMaskawa (CKM) matrix elements $V_{td}=7.45{(69)}\times10^{3}$, $V_{ts}=35.7(1.5)\times10^{3}$, and $V_{td}/V_{ts}=0.201{(20)}$, which are compatible with the values obtained from neutral $B_{(s)}$meson oscillations and have competitive uncertainties. Alternatively, taking the CKM matrix elements from unitarity, we constrain newphysics contributions at the electroweak scale. The constraints on the Wilson coefficients ${\rm Re}(C_9)$ and ${\rm Re}(C_{10})$ from $B \to \pi\mu^+\mu^$ and $B \to K\mu^+\mu^$ are competitive with those from $B\to K^* \mu^+\mu^$, and display a 2.0$\sigma$ tension with the Standard Model. Our predictions for $B \to K(\pi)\nu\bar\nu$ and $B\to\pi\tau\nu$ are close to the current experimental limits.  [Show abstract] [Hide abstract]
ABSTRACT: The rare decay B→πℓ+ℓ arises from b→d flavorchanging neutral currents and could be sensitive to physics beyond the standard model. Here, we present the first ab initio QCD calculation of the B→π tensor form factor fT. Together with the vector and scalar form factors f+ and f0 from our companion work [J.A. Bailey et al., Phys. Rev. D 92, 014024 (2015)], these parametrize the hadronic contribution to B→π semileptonic decays in any extension of the standard model. We obtain the total branching ratio BR(B+→π+μ+μ)=20.4(2.1)×109 in the standard model, which is the most precise theoretical determination to date, and agrees with the recent measurement from the LHCb experiment [R. Aaij et al., J. High Energy Phys. 12 (2012) 125].Physical Review Letters 10/2015; 115(15). DOI:10.1103/PhysRevLett.115.152002 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: For some time, the MILC Collaboration has been studying electromagnetic effects on light mesons. These calculations use fully dynamical QCD, but only quenched photons, which suffices to NLO in XPT. That is, the sea quarks are electrically neutral, while the valence quarks carry charge. For the photons we use the noncompact formalism. We have new results with lattice spacing as small as 0.045 fm and a large range of volumes. We consider how well chiral perturbation theory describes these results and the implications for light quark massesJournal of Physics Conference Series 09/2015; 640(1):012052. DOI:10.1088/17426596/640/1/012052  [Show abstract] [Hide abstract]
ABSTRACT: We compute the form factors for the $B \to Kl^+l^$ semileptonic decay process in lattice QCD using gaugefield ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0.045 fm and have multiple seaquark masses to help control the chiral extrapolation. The asqtad improved staggered action is used for the light valence and sea quarks, and the clover action with the Fermilab interpretation is used for the heavy $b$ quark. We present results for the form factors $f_+(q^2)$, $f_0(q^2)$, and $f_T(q^2)$, where $q^2$ is the momentum transfer, together with a comprehensive examination of systematic errors. Lattice QCD determines the form factors for a limited range of $q^2$, and we use the modelindependent $z$ expansion to cover the whole kinematically allowed range. We present our final formfactor results as coefficients of the $z$ expansion and the correlations between them, where the errors on the coefficients include statistical and all systematic uncertainties. We use this complete description of the form factors to test QCD predictions of the form factors at high and low $q^2$. We also compare a StandardModel calculation of the branching ratio for $B \to Kl^+l^$ with experimental data.  [Show abstract] [Hide abstract]
ABSTRACT: On April 2015, the JPARC E56 (JSNS2: JPARC Sterile Neutrino Search using neutrinos from JPARC Spallation Neutron Source) experiment officially obtained stage1 approval from JPARC. We have since started to perform liquid scintillator R&D for improving energy resolution and fast neutron rejection. Also, we are studying Avalanche PhotoDiodes (SiPM) inside the liquid scintillator. In addition to the R&D work, a background measurement for the proton beam bunch timing using a small liquid scintillator volume was planned, and the safety discussions for the measurement have been done. This report describes the status of the R&D work and the background measurements, in addition to the milestones required before stage2 approval.  [Show abstract] [Hide abstract]
ABSTRACT: The rare decay $B\to\pi\ell^+\ell^$ is sensitive to $b\to d$ flavorchanging neutral currents, which could arise from 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.$, arXiv:1503.07839], these parameterize the hadronic contribution to $B\to\pi$ semileptonic decays in any extension of the Standard Model. We obtain the total branching ratio $\text{BR}(B^+\to\pi^+\mu^+\mu^)=19.5(2.2)\times10^{9}$ in the Standard Model, which is the most precise theoretical determination to date, and agrees with the recent measurement from LHCb [R. Aaij, $et~al.$, JHEP $\mathbf{1212}$, 125 (2012)].  [Show abstract] [Hide abstract]
ABSTRACT: We report on a calculation of the B*Bpi coupling in lattice QCD. The strong matrix element for a B* to Bpi transition is directly related to the leading order lowenergy constant in heavy meson chiral perturbation theory (HMChPT) for B mesons. We carry out our calculation directly at the bquark mass using a nonperturbatively tuned clover action that controls discretization effects of order pa and (ma)^n for all n. Our analysis is performed on RBC/UKQCD gauge configurations using domainwall fermions and the Iwasaki gauge action at two lattice spacings of ainverse = 1.729(25) GeV, ainverse = 2.281(28) GeV, and unitary pion masses down to 290 MeV. We achieve good statistical precision and control all systematic uncertainties, giving a final result for the HMChPT coupling g_b = 0.56(3)stat(7)sys in the continuum and at the physical lightquark masses. This is the first calculation performed directly at the physical bquark mass and lies in the region one would expect from carrying out an interpolation between previous results at the charm mass and at the static point.  [Show abstract] [Hide abstract]
ABSTRACT: The second workshop to discuss the development of liquid argon time projection chambers (LArTPCs) in the United States was held at Fermilab on July 89, 2014. The workshop was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that was initiated by the American Physical Society Division of Particles and Fields. All presentations at the workshop were made in six topical plenary sessions: $i)$ Argon Purity and Cryogenics, $ii)$ TPC and High Voltage, $iii)$ Electronics, Data Acquisition and Triggering, $iv)$ Scintillation Light Detection, $v)$ Calibration and Test Beams, and $vi)$ Software. This document summarizes the current efforts in each of these areas. It primarily focuses on the work in the US, but also highlights work done elsewhere in the world.Journal of Instrumentation 04/2015; 9(05). DOI:10.1088/17480221/9/05/T05005 · 1.40 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a latticeQCD 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+1flavor lattice configurations at four lattice spacings and lightquark masses down to 1/20 of the physical strangequark mass. We extrapolate the lattice form factors to the continuum using staggered chiral perturbation theory in the hardpion and SU(2) limits. We employ a modelindependent $z$ parameterization to extrapolate our lattice form factors from largerecoil momentum to the full kinematic range. We introduce a new functional method to propagate information from the chiralcontinuum extrapolation to the $z$ expansion. We present our results together with a complete systematic error budget, including a covariance matrix to enable the combination of our form factors with other latticeQCD and experimental results. To obtain $V_{ub}$, we simultaneously fit the experimental data for the $B\to\pi\ell\nu$ differential decay rate obtained by the BaBar and Belle collaborations together with our lattice formfactor results. We find $V_{ub}=(3.72\pm 0.16)\times 10^{3}$ where the error is from the combined fit to lattice plus experiments and includes all sources of uncertainty. Our formfactor results bring the QCD error on $V_{ub}$ to the same level as the experimental error. We also provide results for the $B\to\pi\ell\nu$ vector and scalar form factors obtained from the combined lattice and experiment fit, which are more preciselydetermined than from our latticeQCD calculation alone. These results can be used in other phenomenological applications and to test other approaches to QCD. 
Article: The $B \to D \ell \nu$ form factors at nonzero recoil and $V_{cb}$ from $2+1$flavor lattice QCD
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ABSTRACT: We present the first unquenched latticeQCD 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 gaugefield configurations generated with 2+1 flavors of asqtadimproved 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 seaquark masses ranging from 0.05 to 0.4. For the $b$ and $c$ valence quarks we use improved Wilson fermions with the Fermilab interpretation, while for the light valence quarks we use asqtadimproved staggered fermions. We extrapolate our results to the physical point using rooted staggered heavylight meson chiral perturbation theory. We then parameterize the form factors and extend them to the full kinematic range using modelindependent functions based on analyticity and unitarity. We present our final results for $f_+(q^2)$ and $f_0(q^2)$, including statistical and systematic errors, as coefficients of a series in the variable $z$ and the covariance matrix between these coefficients. We then fit the lattice formfactor data jointly with the experimentally measured differential decay rate from BaBar to determine the CKM matrix element, $V_{cb}=(39.6 \pm 1.7_{\rm QCD+exp} \pm 0.2_{\rm QED})\times 10^{3}$. As a byproduct of the joint fit we obtain the form factors with improved precision at large recoil. Finally, we use them to update our calculation of the ratio $R(D)$ in the Standard Model, which yields $R(D) = 0.299(11)$.  [Show abstract] [Hide abstract]
ABSTRACT: We report on a scale determination with gradientflow techniques on the $N_f=2+1+1$ HISQ 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 treelevel improvements, $\sqrt{t_{0,{\rm imp}}}$ and $w_{0,{\rm imp}}$, are computed on each ensemble using Symanzik flow and the cloverleaf definition of the energy density $E$. Using a combination of continuum chiral perturbation theory and a Taylorseries ansatz for the latticespacing and strongcoupling dependence, the results are simultaneously extrapolated to the continuum and interpolated to physical quark masses. We determine the scales $\sqrt{t_0} = 0.1416({}_{5}^{+8})$ fm and $w_0 = 0.1717({}_{11}^{+12})$ fm, where the errors are sums, in quadrature, of statistical and all systematic errors. The precision of $w_0$ and $\sqrt{t_0}$ is comparable to or more precise than the best previous estimates, respectively. We also find the continuum massdependence of $w_0$ that will be useful for estimating the scales of other ensembles. We also estimate the integrated autocorrelation length of $\langle E(t) \rangle$. For long flow times, the autocorrelation length of $\langle E \rangle$ appears to be comparable to or smaller than that of the topological charge.  [Show abstract] [Hide abstract]
ABSTRACT: A ShortBaseline Neutrino (SBN) physics program of three LArTPC detectors located along the Booster Neutrino Beam (BNB) at Fermilab is presented. This new SBN Program will deliver a rich and compelling physics opportunity, including the ability to resolve a class of experimental anomalies in neutrino physics and to perform the most sensitive search to date for sterile neutrinos at the eV massscale through both appearance and disappearance oscillation channels. Using data sets of 6.6e20 protons on target (P.O.T.) in the LAr1ND and ICARUS T600 detectors plus 13.2e20 P.O.T. in the MicroBooNE detector, we estimate that a search for muon neutrino to electron neutrino appearance can be performed with ~5 sigma sensitivity for the LSND allowed (99% C.L.) parameter region. In this proposal for the SBN Program, we describe the physics analysis, the conceptual design of the LAr1ND detector, the design and refurbishment of the T600 detector, the necessary infrastructure required to execute the program, and a possible reconfiguration of the BNB target and horn system to improve its performance for oscillation searches.  [Show abstract] [Hide abstract]
ABSTRACT: At the 17th JPARC PAC, which was held on September 2013, we proposed the sterile neutrino search at JPARC MLF. After reviewing the proposal, PAC recommended to have a background measurement at the detector's candidate site location in their report to investigate whether the background rates can be manageable for the real experiment or not. Therefore, we have performed the background measurements (MLF; 2013BU1301 test experiment) during the summer of 2014, also following the 18th JPARC PAC recommendations, and the measurements results are described here.  [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 present the status of our updated D and Bmeson decayconstant analysis, based on the MILC $N_f = 2+1$ asqtad gauge ensembles. Heavy quarks are incorporated using the Wilson clover action with the Fermilab interpretation. This analysis includes ensembles at five lattice spacings from a $\approx$ 0.045 to 0.15 fm, and light seaquark masses down to 1/20th of the strangequark mass. Projected error budgets for ratios of decay constants, in particular between bottom and charmmeson decay constants, are presented.  [Show abstract] [Hide abstract]
ABSTRACT: We report on the status of our calculation of the hadronic matrix elements for neutral $B$meson mixing with asqtad sea and valence light quarks and using the Wilson clover action with the Fermilab interpretation for the $b$ quark. We calculate the matrix elements of all five local operators that contribute to neutral $B$meson mixing both in and beyond the Standard Model. We use MILC ensembles with $N_f=2+1$ dynamical flavors at four different lattice spacings in the range $a \approx 0.045$$0.12$~fm, and with light seaquark masses as low as 0.05 times the physical strange quark mass. We perform a combined chiralcontinuum extrapolation including the socalled wrongspin contributions in simultaneous fits to the matrix elements of the five operators. We present a complete systematic error budget and conclude with an outlook for obtaining final results from this analysis.  [Show abstract] [Hide abstract]
ABSTRACT: We present an update on our calculation of the shortdistance $D^0$meson mixing hadronic matrix elements. The analysis is performed on the MILC collaboration's $N_f=2+1$ asqtad configurations. We use asqtad light valence quarks and the SheikoleslamiWohlert action with the Fermilab interpretation for the valence charm quark. SU(3), partially quenched, rooted, staggered heavymeson chiral perturbation theory is used to extrapolate to the chiralcontinuum limit. Systematic errors arising from the chiralcontinuum extrapolation, heavyquark discretization, and quarkmass uncertainties are folded into the statistical errors from the chiralcontinuum fits with methods of Bayesian inference. A preliminary error budget for all five operators is presented.  [Show abstract] [Hide abstract]
ABSTRACT: We compute the $B\to\pi\ell\nu$ semileptonic form factors and update the determination of the CKM matrix element $V_{ub}$. We use the MILC asqtad ensembles with $N_f=2+1$ sea quarks at four different lattice spacings in the range $a \approx 0.045$~fm to $0.12$~fm. The lattice form factors are extrapolated to the continuum limit using SU(2) staggered chiral perturbation theory in the hard pion limit, followed by an extrapolation in $q^2$ to the full kinematic range using a functional $z$parameterization. The extrapolation is combined with the experimental measurements of the partial branching fraction to extract $V_{ub}$. Our preliminary result is $V_{ub}=(3.72\pm 0.14)\times 10^{3}$, where the error reflects both the lattice and experimental uncertainties, which are now on par with each other.
Publication Stats
2k  Citations  
287.84  Total Impact Points  
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Institutions

2015

Indiana University Bloomington
Bloomington, Indiana, United States


20062015

Fermi National Accelerator Laboratory (Fermilab)
 Theoretical Physics Department
Батавия, Illinois, United States


20092012

Brookhaven National Laboratory
 Physics Department
New York City, New York, United States 
Louisiana State University
 Department of Physics & Astronomy
Baton Rouge, Louisiana, United States


20052012

Los Alamos National Laboratory
 Materials Physics and Applications Division
ЛосАламос, California, United States


20032006

University of Washington Seattle
 Department of Physics
Seattle, WA, United States
