Stefan Meinel

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• Meinel, S., & Rendon, G. (2022). $\Lambdac\to\Lambda^*(1520)$ form factors from lattice QCD and improved analysis of the $\Lambda_b \to \Lambda^*(1520)$ and $\Lambdab\to\Lambdac^*(2595,2625)$ form factors. Phys. Rev. D, 105(5), 054511.
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  We present the first lattice-QCD calculation of the form factors governing the charm-baryon semileptonic decays $\Lambda_c \to \Lambda^*(1520)\ell^+\nu_\ell$. As in our previous calculation of the $\Lambda_b \to \Lambda^*(1520)$ form factors, we work in the $\Lambda^*(1520)$ rest frame, but here we use four different heavy-baryon momenta instead of just two. Because of the lower mass of the $\Lambda_c$, the moderately-sized momenta used here are sufficient to determine the form factors in the full kinematic range of the semileptonic decay. We also update the analysis of our lattice results for the $\Lambda_b \to \Lambda^*(1520)$ and $\Lambda_b \to \Lambda_c^*(2595,2625)$ form factors by imposing exact relations among the different form factors at zero recoil that follow from rotational symmetry. Imposing these relations ensures the correct behavior of the angular observables near the endpoint.
• Meinel, S., Meinel, S., Rendon, G., & Rendon, G. (2022). Charm-baryon semileptonic decays and the strange \ensuremath\Lambda* resonances: New insights from lattice QCD. Phys. Rev. D, 105(5), L051505.
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  Understanding the properties of the strange $\Lambda^*$ baryon resonances is a long-standing and fascinating problem. $\Lambda_c$ charm-baryon semileptonic weak decays to these resonances are highly sensitive to their internal structure and can be used to test theoretical models. We have performed the first lattice-QCD computation of the form factors governing $\Lambda_c$ semileptonic decays to a $\Lambda^*$ resonance: the $\Lambda^*(1520)$, which has negative parity and spin $3/2$. Here we present the resulting Standard-Model predictions of the $\Lambda_c\to\Lambda^*(1520)\ell^+\nu_\ell$ differential and integrated decay rates as well as angular observables. Furthermore, by combining the recent BESIII measurement of the $\Lambda_c \to X e^+ \nu_e$ inclusive semipositronic branching fraction [\href{https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.251801}{Phys.~Rev.~Lett.~{\bf 121}, 251801 (2018)}] with lattice-QCD predictions of the $\Lambda_c \to \Lambda e^+ \nu_e$, $\Lambda_c \to n e^+ \nu_e$, and $\Lambda_c \to \Lambda^*(1520) e^+ \nu_e$ decay rates, we obtain an upper limit on the sum of the branching fractions to all other semipositronic final states. In particular, this upper limit constrains the $\Lambda_c\to\Lambda^*(1405)e^+ \nu_e$ branching fraction to be very small, which may be another hint for a molecular structure of the $\Lambda^*(1405)$.
• Meinel, S., & Rendon, G. (2021). $\Lambda_b \to \Lambda^*(1520)\ell^+\ell^-$ form factors from lattice QCD. Physical Review D, 103(074505).
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  We present the first lattice QCD determination of the Λb→Λ∗(1520) vector, axial vector, and tensor form factors that are relevant for the rare decays Λb→Λ∗(1520)ℓ+ℓ−. The lattice calculation is performed in the Λ∗(1520) rest frame with nonzero Λb momenta, and is limited to the high-q2 region. An interpolating field with covariant derivatives is used to obtain good overlap with the Λ∗(1520). The analysis treats the Λ∗(1520) as a stable particle, which is expected to be a reasonable approximation for this narrow resonance. A domain-wall action is used for the light and strange quarks, while the b quark is implemented with an anisotropic clover action with coefficients tuned to produce the correct Bs kinetic mass, rest mass, and hyperfine splitting. We use three different ensembles of lattice gauge-field configurations generated by the RBC and UKQCD collaborations, and perform extrapolations of the form factors to the continuum limit and physical pion mass. We give Standard-Model predictions for the Λb→Λ∗(1520)ℓ+ℓ− differential branching fraction and angular observables in the high-q2 region.
• Meinel, S., & Rendon, G. (2021). $\Lambda_b \to \Lambda_c^*(2595,2625)\ell^-\bar\nu$ form factors from lattice QCD. Physical Review D, 103, 094516. doi:10.1103/PhysRevD.103.094516
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  We present the first lattice-QCD determination of the form factors describing the semileptonic decays Λb→Λ∗c(2595)ℓ−ν¯ and Λb→Λ∗c(2625)ℓ−ν¯, where the Λ∗c(2595) and Λ∗c(2625) are the lightest charm baryons with JP=12− and JP=32−, respectively. These decay modes provide new opportunities to test lepton flavor universality and also play an important role in global analyses of the strong interactions in b→c semileptonic decays. We determine the full set of vector, axial vector, and tensor form factors for both decays, but only in a small kinematic region near the zero-recoil point. The lattice calculation uses three different ensembles of gauge-field configurations with 2+1 flavors of domain-wall fermions, and we perform extrapolations of the form factors to the continuum limit and physical pion mass. We present Standard-Model predictions for the differential decay rates and angular observables. In the kinematic region considered, the differential decay rate for the 12− final state is found to be approximately 2.5 times larger than the rate for the 32− final state. We also test the compatibility of our form-factor results with zero-recoil sum rules.
• Silvi, G., & others, . (2021). P-wave nucleon-pion scattering amplitude in the $\Delta (1232)$ channel from lattice QCD. Physical Review D, 103, 094508. doi:10.1103/PhysRevD.103.094508
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  We determine the Δ(1232) resonance parameters using lattice QCD and the Lüscher method. The resonance occurs in elastic pion-nucleon scattering with JP=3/2+ in the isospin I=3/2, P-wave channel. Our calculation is performed with Nf=2+1 flavors of clover fermions on a lattice with L≈2.8 fm. The pion and nucleon masses are mπ=255.4(1.6) MeV and mN=1073(5) MeV, and the strong decay channel Δ→πN is found to be above the threshold. To thoroughly map out the energy-dependence of the nucleon-pion scattering amplitude, we compute the spectra in all relevant irreducible representations of the lattice symmetry groups for total momenta up to P⃗ =2πL(1,1,1), including irreps that mix S and P waves. We perform global fits of the amplitude parameters to up to 21 energy levels, using a Breit-Wigner model for the P-wave phase shift and the effective-range expansion for the S-wave phase shift. From the location of the pole in the P-wave scattering amplitude, we obtain the resonance mass mΔ=1378(7)(9) MeV and the coupling gΔ-πN=23.8(2.7)(0.9).
• Engelhardt, M., Green, J. R., Hasan, N., Krieg, S., Meinel, S., Negele, J., Pochinsky, A., & Syritsyn, S. (2020). From Ji to Jaffe-Manohar orbital angular momentum in lattice QCD using a direct derivative method. Phys. Rev. D, 102(7), 074505. doi:10.1103/PhysRevD.102.074505
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  A lattice QCD approach to quark orbital angular momentum in the proton based on generalized transverse momentum-dependent parton distributions (GTMDs) is enhanced methodologically by incorporating a direct derivative technique. This improvement removes a significant numerical bias that had been seen to afflict results of a previous study. In particular, the value obtained for Ji quark orbital angular momentum is reconciled with the one obtained independently via Ji’s sum rule, validating the GMTD approach. Since GTMDs simultaneously contain information about the quark impact parameter and transverse momentum, they permit a direct evaluation of the cross product of the latter. They are defined through proton matrix elements of a quark bilocal operator containing a Wilson line; the choice in Wilson line path allows one to continuously interpolate from Ji to Jaffe-Manohar quark orbital angular momentum. The latter is seen to be significantly enhanced in magnitude compared to Ji quark orbital angular momentum, confirming previous results.
• Gambino, P., & others, . (2020). Challenges in semileptonic $B$ decays. Eur. Phys. J. C, 80(10), 966.
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  Two of the elements of the Cabibbo–Kobayashi–Maskawa quark mixing matrix, |Vub| and |Vcb|, are extracted from semileptonic B decays. The results of the B factories, analysed in the light of the most recent theoretical calculations, remain puzzling, because for both |Vub| and |Vcb| the exclusive and inclusive determinations are in clear tension. Further, measurements in the τ channels at Belle, Babar, and LHCb show discrepancies with the Standard Model predictions, pointing to a possible violation of lepton flavor universality. LHCb and Belle II have the potential to resolve these issues in the next few years. This article summarizes the discussions and results obtained at the MITP workshop held on April 9–13, 2018, in Mainz, Germany, with the goal to develop a medium-term strategy of analyses and calculations aimed at solving the puzzles. Lattice and continuum theorists working together with experimentalists have discussed how to reshape the semileptonic analyses in view of the much higher luminosity expected at Belle II, searching for ways to systematically validate the theoretical predictions in both exclusive and inclusive B decays, and to exploit the rich possibilities at LHCb.
• Larsen, R., Meinel, S., Mukherjee, S., & Petreczky, P. (2020). Bethe-Salpeter amplitudes of Upsilons. Phys. Rev. D, 102, 114508. doi:10.1103/PhysRevD.102.114508
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  Based on lattice nonrelativistic QCD (NRQCD) studies, we present results for Bethe-Salpeter amplitudes for Υ(1S), Υ(2S), and Υ(3S) in vacuum as well as in quark-gluon plasma. Our study is based on 2+1 flavor 483×12 lattices generated using the Highly Improved Staggered Quark action and with a pion mass of 161 MeV. At zero temperature, the Bethe-Salpeter amplitudes follow the expectations based on nonrelativistic potential models. At nonzero temperatures, the interpretation of Bethe-Salpeter amplitudes turns out to be more nuanced but consistent with our previous lattice QCD study of excited Upsilons in quark-gluon plasma.
• Rendon, G., Leskovec, L., Meinel, S., Negele, J., Paul, S., Petschlies, M., Pochinsky, A., Silvi, G., & Syritsyn, S. (2020). $I=1/2$ $S$-wave and $P$-wave $K\pi$ scattering and the $\kappa$ and $K^*$ resonances from lattice QCD. Phys. Rev. D, 102(11), 114520. doi:10.1103/PhysRevD.102.114520
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  We present a lattice-QCD determination of the elastic isospin-1/2 S-wave and P-wave Kπ scattering amplitudes as a function of the center-of-mass energy using Lüscher’s method. We perform global fits of K-matrix parametrizations to the finite-volume energy spectra for all irreducible representations with total momenta up to √32πL; this includes irreducible representations (irreps) that mix the S- and P-waves. Several different parametrizations for the energy dependence of the K-matrix are considered. We also determine the positions of the nearest poles in the scattering amplitudes, which correspond to the broad κ resonance in the S-wave and the narrow K∗(892) resonance in the P-wave. Our calculations are performed with 2+1 dynamical clover fermions for two different pion masses of 317.2(2.2) and 175.9(1.8) MeV. Our preferred S-wave parametrization is based on a conformal map and includes an Adler zero; for the P-wave, we use a standard pole parametrization including Blatt-Weisskopf barrier factors. The S-wave κ-resonance pole positions are found to be [0.86(12)−0.309(50)i]  GeV at the heavier pion mass and [0.499(55)−0.379(66)i]  GeV at the lighter pion mass. The P-wave K∗-resonance pole positions are found to be [0.8951(64)−0.00250(21)i]  GeV at the heavier pion mass and [0.8718(82)−0.0130(11)i]  GeV at the lighter pion mass, which corresponds to couplings of gK∗Kπ=5.02(26) and gK∗Kπ=4.99(22), respectively.
• Detmold, W., Edwards, R. G., Dudek, J. J., Engelhardt, M., Lin, H., Meinel, S., Orginos, K., & Shanahan, P. (2019). Hadrons and nuclei. EUROPEAN PHYSICAL JOURNAL A, 55(11). doi:10.1140/epja/i2019-12902-4
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  This document is one of a series of whitepapers from the USQCD collaboration. Here, we discuss opportunities for lattice QCD calculations related to the structure and spectroscopy of hadrons and nuclei. An overview of recent lattice calculations of the structure of the proton and other hadrons is presented along with prospects for future extensions. Progress and prospects of hadronic spectroscopy and the study of resonances in the light, strange and heavy quark sectors is summarized. Finally, recent advances in the study of light nuclei from lattice QCD are addressed, and the scope of future investigations that are currently envisioned is outlined.
• Green, J. R., Engelhardt, M., Hasan, N., Krieg, S., Meinel, S., Negele, J. W., Pochinsky, A. V., & Syritsyn, S. N. (2019). Excited-state effects in nucleon structure on the lattice using hybrid interpolators. PHYSICAL REVIEW D, 100(7). doi:10.1103/PhysRevD.100.074510
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  It would be very useful to find a way of reducing excited-state effects in lattice QCD calculations of nucleon structure that has a low computational cost. We explore the use of hybrid interpolators, which contain a nontrivial gluonic excitation, in a variational basis together with the standard interpolator with tuned smearing width. Using the clover discretization of the field strength tensor, a calculation using a fixed linear combination of standard and hybrid interpolators can be done using the same number of quark propagators as a standard calculation, making this a cost-effective option. We find that such an interpolator, optimized by solving a generalized eigenvalue problem, reduces excited-state contributions in two-point correlators. However, the effect in three-point correlators, which are needed for computing nucleon matrix elements, is mixed: for some matrix elements such as the tensor charge, excited-state effects are suppressed, whereas for others such as the axial charge, they are enhanced. The results illustrate that the variational method is not guaranteed to reduce the net contribution from excited states except in its asymptotic regime, and suggest that it may be important to use a large basis of interpolators capable of isolating all of the relevant low-lying states.
• Larsen, R., Meinel, S., Mukherjee, S., & Petreczky, P. (2019). Thermal broadening of bottomonia: Lattice nonrelativistic QCD with extended operators. PHYSICAL REVIEW D, 100(7). doi:10.1103/PhysRevD.100.074506
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  We present lattice non-relativistic QCD calculations of bottomonium correlation functions at temperatures T≃150−350 MeV. The correlation functions were computed using extended bottomonium operators, and on background gauge-field configurations for 2+1-flavor QCD having physical kaon and nearly-physical pion masses. We analyzed these correlation functions based on simple theoretically-motivated parameterizations of the corresponding spectral functions. The results of our analyses are compatible with significant in-medium thermal broadening of the ground state S- and P-wave bottomonia.
• Larsen, R., Meinel, S., Mukherjee, S., & Petreczky, P. (2020). Excited bottomonia in quark-gluon plasma from lattice QCD. PHYSICS LETTERS B, 800. doi:10.1016/j.physletb.2019.135119
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  We present the first lattice QCD study of up to 3S and 2P bottomonia at non-zero temperatures. Correlation functions of bottomonia were computed using novel bottomonium operators and a variational technique, within the lattice non-relativistic QCD framework. We analyzed the bottomonium correlation functions based on simple physically-motivated spectral functions. We found evidence of sequential in-medium modifications, in accordance with the sizes of the bottomonium states.
• Lehner, C., Meinel, S., Blum, T., Christ, N. H., El-Khadra, A. X., Hansen, M. T., Kronfeld, A. S., Laiho, J., Neil, E. T., Sharpe, S. R., & Van, d. (2019). Opportunities for Lattice QCD in quark and lepton flavor physics. EUROPEAN PHYSICAL JOURNAL A, 55(11). doi:10.1140/epja/i2019-12891-2
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  This document is one of a series of whitepapers from the USQCD collaboration. Here, we discuss opportunities for lattice QCD in quark and lepton flavor physics. New data generated at Belle II, LHCb, BES III, NA62, KOTO, and Fermilab E989, combined with precise calculations of the relevant hadronic physics, may reveal what lies beyond the Standard Model. We outline a path toward improvements of the precision of existing lattice-QCD calculations and discuss groundbreaking new methods that allow lattice QCD to access new observables.
• Leskovec, L., Meinel, S., Pflaumer, M., & Wagner, M. (2019). Lattice QCD investigation of a doubly-bottom (b)over-bar(b)over-barud tetraquark with quantum numbers I(J(P))=0(1(+)). PHYSICAL REVIEW D, 100(1). doi:10.1103/PhysRevD.100.014503
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  We use lattice QCD to investigate the spectrum of the b¯b¯ud four-quark system with quantum numbers I(JP)=0(1+). We use five different gauge-link ensembles with 2+1 flavors of domain-wall fermions, including one at the physical pion mass, and treat the heavy b¯ quark within the framework of lattice nonrelativistic QCD. Our work improves upon previous similar computations by considering in addition to local four-quark interpolators also nonlocal two-meson interpolators and by performing a Lüscher analysis to extrapolate our results to infinite volume. We obtain a binding energy of (−128±24±10)MeV, corresponding to the mass (10476±24±10)MeV, which confirms the existence of a b¯b¯ud tetraquark that is stable with respect to the strong and electromagnetic interactions.
• Meinel, S. (2019). Nucleon axial, scalar, and tensor charges using lattice QCD at the physical pion mass. PHYSICAL REVIEW D, 99, 114505. doi:10.1103/PhysRevD.99.114505
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  We report on lattice QCD calculations of the nucleon isovector axial, scalar, and tensor charges. Our calculations are performed on two 2+1-flavor ensembles generated using a 2-HEX-smeared Wilson-clover action at the physical pion mass and lattice spacings $a\approx$ 0.116 and 0.093 fm. We use a wide range of source-sink separations - eight values ranging from roughly 0.4 to 1.4 fm on the coarse ensemble and three values from 0.9 to 1.5 fm on the fine ensemble - which allows us to perform an extensive study of excited-state effects using different analysis and fit strategies. To determine the renormalization factors, we use the nonperturbative Rome-Southampton approach and compare RI'-MOM and RI-SMOM intermediate schemes to estimate the systematic uncertainties. Our final results are computed in the MS-bar scheme at scale 2 GeV. The tensor and axial charges have uncertainties of roughly 4%, $g_T=0.972(41)$ and $g_A=1.265(49)$. The resulting scalar charge, $g_S=0.927(303)$, has a much larger uncertainty due to a stronger dependence on the choice of intermediate renormalization scheme and on the lattice spacing.
• Meinel, S. (2020). Bayesian analysis of $b\to sμ^+μ^-$ Wilson coefficients using the full angular distribution of $Λ_b\to Λ(\to p\, π^-)μ^+μ^-$ decays. PHYSICAL REVIEW D, 101, 035023. doi:10.1103/PhysRevD.101.035023
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  Following updated and extended measurements of the full angular distribution of the decay Λb→Λ(→pπ−)μ+μ− by the LHCb collaborations, as well as a new measurement of the Λ→pπ− decay asymmetry parameter by the BESIII collaboration, we study the impact of these results on searches for non-standard effects in exclusive b→sμ+μ− decays. To this end, we constrain the Wilson coefficients C9 and C10 of the numerically leading dimension-six operators in the weak effective Hamiltonian, in addition to the relevant nuisance parameters. In stark contrast to previous analyses of this decay mode, the changes in the updated experimental results lead us to find very good compatibility with both the Standard Model and with the b→sμ+μ− anomalies observed in rare B-meson decays. We provide a detailed analysis of the impact of the partial angular distribution, the full angular distribution, and the Λb→Λμ+μ− branching fraction on the Wilson coefficients. In this process, we are also able to constrain the size of the production polarization of the Λb baryon at LHCb.
• Alexandrou, C., Leskovec, L., Meinel, S., Negele, J., Paul, S., Petschlies, M., Pochinsky, A., Rendon, G., & Syritsyn, S. (2018). pi gamma -> pi pi transition and the rho radiative decay width from lattice QCD. PHYSICAL REVIEW D, 98(7).
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  We report a lattice QCD determination of the $\pi\gamma \to \pi \pi$ transition amplitude for the $P$-wave, $I=1$ two-pion final state, as a function of the photon virtuality and $\pi\pi$ invariant mass. The calculation was performed with $2+1$ flavors of clover fermions at a pion mass of approximately $320$ MeV, on a $32^3\times96$ lattice with $L\approx 3.6$ fm. We construct the necessary correlation functions using a combination of smeared forward, sequential and stochastic propagators, and determine the finite-volume matrix elements for all $\pi\pi$ momenta up to $|\vec{P}|= \sqrt{3} \frac{2\pi}{L}$ and all associated irreducible representations. In the mapping of the finite-volume to infinite-volume matrix elements using the Lellouch-L\"uscher factor, we consider two different parametrizations of the $\pi\pi$ scattering phase shift. We fit the $q^2$ and $s$ dependence of the infinite-volume transition amplitude in a model-independent way using series expansions, and compare multiple different truncations of this series. Through analytic continuation to the $\rho$ resonance pole, we also determine the $\pi\gamma \to \rho$ resonant transition form factor and the $\rho$ meson photocoupling, and obtain $|G_{\rho\pi\gamma}| = 0.0802(32)(20)$.
• Alexandrou, C., Leskovec, L., Meinel, S., Negele, J., Paul, S., Petschlies, M., Pochinsky, A., Rendon, G., & Syritsyn, S. (2017). P-wave pi pi scattering and the rho resonance from lattice QCD. PHYSICAL REVIEW D, 96(3).
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  We calculate the parameters describing elastic $I=1$, $P$-wave $\pi\pi$ scattering using lattice QCD with $2+1$ flavors of clover fermions. Our calculation is performed with a pion mass of $m_\pi \approx 320\:\:{\rm MeV}$ and a lattice size of $L\approx 3.6$ fm. We construct the two-point correlation matrices with both quark-antiquark and two-hadron interpolating fields using a combination of smeared forward, sequential and stochastic propagators. The spectra in all relevant irreducible representations for total momenta $|\vec{P}| \leq \sqrt{3} \frac{2\pi}{L}$ are extracted with two alternative methods: a variational analysis as well as multi-exponential matrix fits. We perform an analysis using L\"uscher's formalism for the energies below the inelastic thresholds, and investigate several phase shift models, including possible nonresonant contributions. We find that our data are well described by the minimal Breit-Wigner form, with no statistically significant nonresonant component. In determining the $\rho$ resonance mass and coupling we compare two different approaches: fitting the individually extracted phase shifts versus fitting the $t$-matrix model directly to the energy spectrum. We find that both methods give consistent results, and at a pion mass of $am_{\pi}=0.18295(36)_{stat}$ obtain $g_{\rho\pi\pi} = 5.69(13)_{stat}(16)_{sys}$, $am_\rho = 0.4609(16)_{stat}(14)_{sys}$, and $am_{\rho}/am_{N} = 0.7476(38)_{stat}(23)_{sys} $, where the first uncertainty is statistical and the second is the systematic uncertainty due to the choice of fit ranges.
• Datta, A., Kamali, S., Meinel, S., & Rashed, A. (2017). Phenomenology of Lambda(b) ->Lambda(c)tau(nu)over-bar(tau) using lattice QCD calculations. JOURNAL OF HIGH ENERGY PHYSICS.
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  In a recent paper we studied the effect of new-physics operators with different Lorentz structures on the semileptonic $\Lambda_b \to \Lambda_c \tau \bar{\nu}_{\tau}$ decay. This decay is of interest in light of the $R({D^{(*)}})$ puzzle in the semileptonic $\bar{B} \to D^{(*)} \tau {\bar\nu}_\tau$ decays. In this work we add tensor operators to extend our previous results and consider both model-independent new physics (NP) and specific classes of models proposed to address the $R({D^{(*)}})$ puzzle. We show that a measurement of $R(\Lambda_c) = {\cal B}[\Lambda_b \to \Lambda_c \tau \bar{\nu}_{\tau}] / {\cal B}[\Lambda_b \to \Lambda_c \ell \bar{\nu}_{\ell}]$ can strongly constrain the NP parameters of models discussed for the $R({D^{(*)}})$ puzzle. We use form factors from lattice QCD to calculate all $\Lambda_b \to \Lambda_c \tau \bar{\nu}_{\tau}$ observables. The $\Lambda_b \to \Lambda_c$ tensor form factors had not previously been determined in lattice QCD, and we present new lattice results for these form factors here.
• Green, J., Hasan, N., Meinel, S., Engelhardt, M., Krieg, S., Laeuchli, J., Negele, J., Orginos, K., Pochinsky, A., & Syritsyn, S. (2017). Up, down, and strange nucleon axial form factors from lattice QCD. PHYSICAL REVIEW D, 95(11).
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  We report a calculation of the nucleon axial form factors $G_A^q(Q^2)$ and $G_P^q(Q^2)$ for all three light quark flavors $q\in\{u,d,s\}$ in the range $0\leq Q^2\lesssim 1.2\text{ GeV}^2$ using lattice QCD. This work was done using a single ensemble with pion mass 317~MeV and made use of the \emph{hierarchical probing} technique to efficiently evaluate the required disconnected loops. We perform nonperturbative renormalization of the axial current, including a nonperturbative treatment of the mixing between light and strange currents due to the singlet-nonsinglet difference caused by the axial anomaly. The form factor shapes are fit using the model-independent $z$ expansion. From $G_A^q(Q^2)$, we determine the quark contributions to the nucleon spin and axial radii. By extrapolating the isovector $G_P^{u-d}(Q^2)$, we obtain the induced pseudoscalar coupling relevant for ordinary muon capture and the pion-nucleon coupling constant. We find that the disconnected contributions to $G_P$ form factors are large, and give an interpretation based on the dominant influence of the pseudoscalar poles in these form factors.
• Meinel, S. (2018). $Λ_c \to N$ form factors from lattice QCD and phenomenology of $Λ_c \to n \ell^+ ν_\ell$ and $Λ_c \to p μ^+ μ^-$ decays. PHYSICAL REVIEW D.
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  A lattice QCD determination of the $\Lambda_c \to N$ vector, axial vector,and tensor form factors is reported. The calculation was performed with $2+1$flavors of domain wall fermions at lattice spacings of $a\approx 0.11\:{\rmfm},\:0.085\:{\rm fm}$ and pion masses in the range $230\:{\rm MeV} \lesssimm_\pi \lesssim 350$ MeV. The form factors are extrapolated to the continuumlimit and the physical pion mass using modified $z$ expansions. The rates ofthe charged-current decays $\Lambda_c \to n\, e^+ \nu_e$ and $\Lambda_c \to n\,\mu^+ \nu_\mu$ are predicted to be $\left( 0.405 \pm 0.016_{\,\rm stat} \pm0.020_{\,\rm syst} \right)|V_{cd}|^2 \:{\rm ps}^{-1}$ and $\left( 0.396 \pm0.016_{\,\rm stat} \pm 0.020_{\,\rm syst} \right)|V_{cd}|^2 \:{\rm ps}^{-1}$,respectively. The phenomenology of the rare charm decay $\Lambda_c \to p\,\mu^+ \mu^-$ is also studied. The differential branching fraction, the fractionof longitudinally polarized dimuons, and the forward-backward asymmetry arecalculated in the Standard Model and in an illustrative new-physics scenario.[Journal_ref: ]
• Meinel, S. (2018). Computing the nucleon charge and axial radii directly at $Q^2=0$ in lattice QCD. PHYSICAL REVIEW D, 97, 034504.
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  We describe a procedure for extracting momentum derivatives of nucleon matrixelements on the lattice directly at $Q^2=0$. This is based on the Rome methodfor computing momentum derivatives of quark propagators. We apply thisprocedure to extract the nucleon isovector magnetic moment and charge radius aswell as the isovector induced pseudoscalar form factor at $Q^2=0$ and the axialradius. For comparison, we also determine these quantities with the traditionalapproach of computing the corresponding form factors, i.e. $G^v_E(Q^2)$ and$G_M^v(Q^2)$ for the case of the vector current and $G_P^v(Q^2)$ and$G_A^v(Q^2)$ for the axial current, at multiple $Q^2$ values followed by$z$-expansion fits. We perform our calculations at the physical pion mass usinga 2HEX-smeared Wilson-clover action. To control the effects of excited-statecontamination, the calculations were done at three source-sink separations andthe summation method was used. The derivative method produces resultsconsistent with those from the traditional approach but with larger statisticaluncertainties especially for the isovector charge and axial radii.[Journal_ref: Phys. Rev. D 97, 034504 (2018)]
• Detmold, W., & Meinel, S. (2016). $\Lambda_b to \Lambda \ell^+ \ell^-$ form factors, differential branching fraction, and angular observables from lattice QCD with relativistic $b$ quarks. PHYSICAL REVIEW D, 93, 074501. doi:10.1103/PhysRevD.93.074501
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  Using $(2+1)$-flavor lattice QCD, we compute the 10 form factors describing the $\Lambda_b \to \Lambda$ matrix elements of the $b \to s$ vector, axial vector, and tensor currents. The calculation is based on gauge field ensembles generated by the RBC and UKQCD Collaborations with a domain-wall action for the $u$, $d$, and $s$ quarks and the Iwasaki gauge action. The $b$ quark is implemented using an anisotropic clover action, tuned nonperturbatively to the physical point, and the currents are renormalized with a mostly nonperturbative method. We perform simultaneous chiral, continuum, and kinematic extrapolations of the form factors through modified $z$ expansions. Using our form factor results, we obtain precise predictions for the $\Lambda_b \to \Lambda(\to p^+ \pi^-) \mu^+ \mu^-$ differential branching fraction and angular observables in the Standard Model.
• Meinel, S. (2017). $\Lambda_c to \Lambda \ell^+ \nu_ell$ form factors and decay rates from lattice QCD with physical quark masses. PHYSICAL REVIEW LETTERS, 118, 082001. doi:10.1103/PhysRevLett.118.082001
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  The first lattice QCD calculation of the form factors governing $\Lambda_c \to \Lambda \ell^+ \nu_\ell$ decays is reported. The calculation was performed with two different lattice spacings and includes one ensemble with a pion mass of 139(2) MeV. The resulting predictions for the $\Lambda_c \to \Lambda e^+ \nu_e$ and $\Lambda_c \to \Lambda \mu^+ \nu_\mu$ decay rates divided by $|V_{cs}|^2$ are $0.2007(71)(74)\:{\rm ps}^{-1}$ and $0.1945(69)(72)\:{\rm ps}^{-1}$, respectively, where the two uncertainties are statistical and systematic. Taking the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ from a global fit and the $\Lambda_c$ lifetime from experiments, this translates to branching fractions of $\mathcal{B}(\Lambda_c\to\Lambda e^+\nu_e)=0.0380(19)_{\rm LQCD}(11)_{\tau_{\Lambda_c}}$ and $\mathcal{B}(\Lambda_c\to\Lambda \mu^+\nu_\mu)=0.0369(19)_{\rm LQCD}(11)_{\tau_{\Lambda_c}}$. These results are consistent with, and two times more precise than, the measurements performed recently by the BESIII Collaboration. Using instead the measured branching fractions together with the lattice calculation to determine the CKM matrix element gives $|V_{cs}|= 0.949(24)_{\rm LQCD}(14)_{\tau_{\Lambda_c}}(49)_{\mathcal{B}}$.
• Meinel, S., & Dyk, D. (2016). Using $\Lambda_b \to \Lambda \mu^+ \mu^-$ data within a Bayesian analysis of $|\Delta B| = |\Delta S| = 1$ decays. PHYSICAL REVIEW D, 94, 013007. doi:10.1103/PhysRevD.94.013007
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  We study the impact of including the baryonic decay $\Lambda_b\to \Lambda(\to p\, \pi^-)\mu^+\mu^-$ in a Bayesian analysis of $|\Delta B | = |\Delta S| = 1$ transitions. We perform fits of the Wilson coefficients $\wilson{9}$, $\wilson{9'}$, $\wilson{10}$ and $\wilson{10'}$, in addition to the relevant nuisance parameters. Our analysis combines data for the differential branching fraction and three angular observables of $\Lambda_b\to \Lambda(\to p\, \pi^-)\mu^+\mu^-$ with data for the branching ratios of $B_s \to \mu^+\mu^-$ and inclusive $b \to s\ell^+\ell^-$ decays. Newly available precise lattice QCD results for the full set of $\Lambda_b \to \Lambda$ form factors are used to evaluate the observables of the baryonic decay. Our fits prefer shifts to $\wilson{9}$ that are opposite in sign compared to those found in global fits of only mesonic decays, and the posterior odds show no evidence of physics beyond the Standard Model. We investigate a possible hadronic origin of the observed tensions between theory and experiment.
• Detmold, W., Lehner, C., & Meinel, S. (2015). Lambda(b) -> pl(-)(nu)over-bar(l) and Lambda(b) -> Lambda(c)l(-)(nu)over-bar(l) form factors from lattice QCD with relativistic heavy quarks. PHYSICAL REVIEW D, 92, 034503. doi:10.1103/PhysRevD.92.034503
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  Measurements of the Lambda(b) -> pl(-)(nu) over bar (l) and Lambda(b) ->Lambda(c)l(-)(nu) over bar (l) decay rates can be used to determine the magnitudes of the Cabibbo-Kobayashi-Maskawa matrix elements V-ub and V-cb, provided that the relevant hadronic form factors are known. Here we present a precise calculation of these form factors using lattice QCD with 2 + 1 flavors of dynamical domain-wall fermions. The b and c quarks are implemented with relativistic heavy-quark actions, allowing us to work directly at the physical heavy-quark masses. The lattice computation is performed for six different pion masses and two different lattice spacings, using gauge-field configurations generated by the RBC and UKQCD Collaborations. The b -> u and b -> c currents are renormalized with a mostly nonperturbative method. We extrapolate the form factor results to the physical pion mass and the continuum limit, parametrizing the q(2) dependence using z expansions. The form factors are presented in such a way as to enable the correlated propagation of both statistical and systematic uncertainties into derived quantities such as differential decay rates and asymmetries. Using these form factors, we present predictions for the Lambda(b) -> pl(-)(nu) over bar (l) and Lambda(b) ->Lambda(c)l(-)(nu) over bar (l) differential and integrated decay rates. Combined with experimental data, our results enable determinations of vertical bar V-ub vertical bar, vertical bar V-cb vertical bar, and vertical bar V-ub/V-cb vertical bar with theory uncertainties of 4.4%, 2.2%, and 4.9%, respectively.
• Green, J., Meinel, S., Engelhardt, M., Krieg, S., Laeuchli, J., Negele, J., Orginos, K., Pochinsky, A., & Syritsyn, S. (2015). High-precision calculation of the strange nucleon electromagnetic form factors. PHYSICAL REVIEW D RAPID COMMUNICATIONS, 92(3), 031501. doi:10.1103/PhysRevD.92.031501
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  We report a direct lattice QCD calculation of the strange nucleon electromagnetic form factors G(E)(s) and G(M)(s) in the kinematic range 0
• Brown, Z. S., Detmold, W., Meinel, S., & Orginos, K. (2014). Charmed bottom baryon spectroscopy from lattice QCD. PHYSICAL REVIEW D, 90(9).
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  We calculate the masses of baryons containing one, two, or three heavy quarks using lattice QCD. We consider all possible combinations of charmand bottom quarks, and compute a total of 36 different states with J(P) = 1/2+ and J(P) =3/2+ . We use domain-wall fermions for the up, down, and strange quarks, a relativistic heavy-quark action for the charm quarks, and nonrelativistic QCD for the bottom quarks. Our analysis includes results from two different lattice spacings and seven different pion masses. We perform extrapolations of the baryon masses to the continuum limit and to the physical pion mass using SU(4 vertical bar 2) heavy-hadron chiral perturbation theory including 1=m(Q) and finite-volume effects. For the 14 singly heavy baryons that have already been observed, our results agree with the experimental values within the uncertainties. We compare our predictions for the hitherto unobserved states with other lattice calculations and quark-model studies.
• Horgan, R. R., Liu, Z., Meinel, S., & Wingate, M. (2014). Calculation of B-0 -> K*(0)mu(+)mu(-) and B-s(0) -> phi mu(+)mu(-) Observables Using Form Factors from Lattice QCD. PHYSICAL REVIEW LETTERS, 112(21).
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  We calculate the differential branching fractions and angular distributions of the rare decays B-0 -> K*(0)mu(+)mu(-) and B-s(0) -> phi mu(+)mu(-), using for the first time form factors from unquenched lattice QCD. We focus on the kinematic region where the K* or phi recoils softly; there, the newly available form factors are most precise and the nonlocal matrix elements can be included via an operator product expansion. Our results for the differential branching fractions calculated in the standard model are higher than the experimental data. We consider the possibility that the deviations are caused by new physics and perform a fit of theWilson coefficients C-9 and C-9' to the experimental data for multiple B-0 -> K*(0)mu(+)mu(-) and B-s(0) -> phi mu(+)mu(-) observables. In agreement with recent results from complementary studies, we obtain C-9 - C-9(SM) = -1.0 +/- 0.6 and C-9' = 1.2 +/- 1.0, whose deviations from zero would indicate the presence of nonstandard fundamental interactions.
• Horgan, R. R., Liu, Z., Meinel, S., & Wingate, M. (2014). Lattice QCD calculation of form factors describing the rare decays B -> K *l(+)l(-) and B-s -> phi l(+)l(-). PHYSICAL REVIEW D, 89(9).
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  The rare decays B-0 -> K-*0 mu(+)mu(-) and B-s -> phi mu(+)mu(-) are now being observed with enough precision to test Standard Model predictions. A full understanding of these decays requires accurate determinations of the corresponding hadronic form factors. Here we present results of lattice QCD calculations of the B -> K-* and B-s -> phi form factors. We also determine the form factors relevant for the decays B-s -> K*l nu and B-s -> (K) over bar (*0)l(+)l(-). We use full-QCD configurations including 2 + 1 flavors of sea quarks using an improved staggered action, and we employ lattice nonrelativistic QCD to describe the bottom quark.
• Detmold, W., Lin, C. -., Meinel, S., & Wingate, M. (2013). Lambda(b) -> Lambda l(+)l(-) form factors and differential branching fraction from lattice QCD. PHYSICAL REVIEW D, 87(7).
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  We present the first lattice QCD determination of the Lambda(b) -> Lambda transition form factors that govern the rare baryonic decays Lambda(b) -> Lambda l(+)l(-) at leading order in heavy-quark effective theory. Our calculations are performed with 2 + 1 flavors of domain-wall fermions, at two lattice spacings and with pion masses down to 227 MeV. Three-point functions with a wide range of source-sink separations are used to extract the ground-state contributions. The form factors are extrapolated to the physical values of the light-quark masses and to the continuum limit. We use our results to calculate the differential branching fractions for Lambda(b) -> Lambda l(+)l(-) with l = e, mu, tau within the standard model. We find agreement with a recent CDF measurement of the Lambda(b) -> Lambda mu(+)mu(-) differential branching fraction. DOI: 10.1103/PhysRevD.87.074502
• Detmold, W., Lin, C. D., Meinel, S., & Wingate, M. (2013). Lambda(b) -> pl(-)(v)over-bar(l) form factors from lattice QCD with static b quarks. PHYSICAL REVIEW D, 88(1).
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  We present a lattice QCD calculation of form factors for the decay Lambda(b) -> p mu(-)(v) over bar (mu), which is a promising channel for determining the Cabibbo- Kobayashi-Maskawa matrix element vertical bar V-ub vertical bar at the Large Hadron Collider. In this initial study we work in the limit of static b quarks, where the number of independent form factors reduces to two. We use dynamical domain-wall fermions for the light quarks, and perform the calculation at two different lattice spacings and at multiple values of the light-quark masses in a single large volume. Using our form factor results, we calculate the Lambda(b) -> p mu-(v) over bar (mu) differential decay rate in the range 14 GeV2
• Detmold, W., Meinel, S., & Shi, Z. (2013). Quarkonium at nonzero isospin density. PHYSICAL REVIEW D, 87(9).
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  We calculate the energies of quarkonium bound states in the presence of a medium of nonzero isospin density using lattice QCD. The medium, created using a canonical (fixed isospin charge) approach, induces a reduction of the quarkonium energies. As the isospin density increases, the energy shifts first increase and then saturate. The saturation occurs at an isospin density close to that where previously a qualitative change in the behavior of the energy density of the medium has been observed, which was conjectured to correspond to a transition from a pion gas to a Bose-Einstein condensed phase. The reduction of the quarkonium energies becomes more pronounced as the heavy-quark mass is decreased, similar to the behavior seen in two-color QCD at nonzero quark chemical potential. In the process of our analysis, the eta(b)-pi and Upsilon-pi scattering phase shifts are determined at low momentum. An interpolation of the scattering lengths to the physical pion mass gives a(eta b,pi) = 0: 0025(8)(6) fm and a(Upsilon,pi) = 0.0030(9)(7) fm.
• Detmold, W., Lin, C. -., & Meinel, S. (2012). Calculation of the heavy-hadron axial couplings g(1), g(2), and g(3) using lattice QCD. PHYSICAL REVIEW D, 85(11).
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  In a recent letter [Phys. Rev. Lett. 108, 172003 (2012)] we have reported on a lattice QCD calculation of the heavy-hadron axial couplings g(1), g(2), and g(3). These quantities are low-energy constants of heavy-hadron chiral perturbation theory (HH chi PT) and are related to the B*B pi, Sigma(b)*Sigma(b)pi, and Sigma(b)(*)Lambda(b)pi couplings. In the following, we discuss important details of the calculation and give further results. To determine the axial couplings, we explicitly match the matrix elements of the axial current in QCD with the corresponding matrix elements in HH chi PT. We construct the ratios of correlation functions used to calculate the matrix elements in lattice QCD, and study the contributions from excited states. We present the complete numerical results and discuss the data analysis in depth. In particular, we demonstrate the convergence of SU(4 vertical bar 2) HH chi PT for the axial-current matrix elements at pion masses up to about 400 MeV and show the impact of the nonanalytic loop contributions. Finally, we present additional predictions for strong and radiative decay widths of charm and bottom baryons.
• Detmold, W., Lin, C. D., & Meinel, S. (2012). Axial Couplings and Strong Decay Widths of Heavy Hadrons. PHYSICAL REVIEW LETTERS, 108(17).
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  We calculate the axial couplings of mesons and baryons containing a heavy quark in the static limit using lattice QCD. These couplings determine the leading interactions in heavy hadron chiral perturbation theory and are central quantities in heavy quark physics, as they control strong decay widths and the light quark mass dependence of heavy hadron observables. Our analysis makes use of lattice data at six different pion masses, 227 MeV < m(pi) < 352 MeV, two lattice spacings, a = 0.085, 0.112 fm, and a volume of (2.7 fm)(3). Our results for the axial couplings are g(1) = 0.449(51), g(2) = 0.84(20), and g(3) = 0.71(13), where g(1) governs the interaction between heavy-light mesons and pions and g(2,3) are similar couplings between heavy-light baryons and pions. Using our lattice result for g(3), and constraining 1/m(Q) corrections in the strong decay widths with experimental data for Sigma((*))(c) decays, we obtain Gamma[Sigma((*))(b) -> Lambda(b)pi(+/-)] = 4.2(1.0), 4.8(1.1), 7.3(1.6), 7.8(1.8) MeV for the Sigma(+)(b), Sigma(-)(b), Sigma(b)*(+), Sigma(b)*(-) initial states, respectively. We also derive upper bounds on the widths of the Xi'(()(b)*()) baryons.
• Stefan, M. (2012). Excited-state spectroscopy of triply bottom baryons from lattice QCD. PHYSICAL REVIEW D, 85(11).
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  The spectrum of baryons containing three b quarks is calculated in nonperturbative QCD, using the lattice regularization. The energies of ten excited bbb states with J(P) = 1/2(+), 3/2(+), 5/2(+), 7/2(+), 1/2(-), and 3/2(-) are determined with high precision. A domain-wall action is used for the up, down, and strange quarks, and the bottom quarks are implemented with nonrelativistic QCD. The computations are done at lattice spacings of a approximate to 0.11 fm and a approximate to 0.08 fm, and the results demonstrate the improvement of rotational symmetry as a is reduced. A large lattice volume of (2.7 fm)(3) is used, and extrapolations of the bbb spectrum to realistic values of the light sea-quark masses are performed. All spin-dependent energy splittings are resolved with total uncertainties of order 1 MeV, and the dependence of these splittings on the couplings in the nonrelativistic QCD action is analyzed.
• Detmold, W., Lin, C. -., & Meinel, S. (2011). Axial couplings in heavy-hadron chiral perturbation theory at the next-to-leading order. PHYSICAL REVIEW D, 84(9).
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  We present calculations of axial-current matrix elements between various heavy-meson and heavy-baryon states to the next-to-leading order in heavy-hadron chiral perturbation theory in the p-regime. When compared with data from lattice computations or experiments, these results can be used to determine the axial couplings in the chiral Lagrangian. Our calculation is performed in partially quenched chiral perturbation theory for both SU(4 vertical bar 2) and SU(6 vertical bar 3). We incorporate finite-size effects arising from a single Goldstone meson wrapping around the spatial volume. Results for full QCD with two and three flavors can be obtained straightforwardly by taking the sea-quark masses to be equal to the valence-quark masses. To illustrate the impact of our chiral perturbation theory calculation on lattice computations, we analyze the SU(2) full-QCD results in detail. We also study one-loop contributions relevant to the heavy-hadron strong-decay amplitudes involving final-state Goldstone bosons, and demonstrate that the quark-mass dependence of these amplitudes can be significantly different from that of the axial-current matrix elements containing only single-hadron external states.
• Meinel, S. (2010). Bottomonium spectrum at order v(6) from domain-wall lattice QCD: Precise results for hyperfine splittings. PHYSICAL REVIEW D, 82(11).
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  The bottomonium spectrum is computed in dynamical 2 + 1 flavor lattice QCD, using nonrelativistic QCD for the b quarks. The main calculations in this work are based on gauge field ensembles generated by the RBC and UKQCD Collaborations with the Iwasaki action for the gluons and a domain-wall action for the sea quarks. Lattice spacing values of approximately 0.08 fm and 0.11 fm are used, and simultaneous chiral extrapolations to the physical pion mass are performed. As a test for gluon-discretization errors, the calculations are repeated on two ensembles generated by the MILC Collaboration with the Luscher-Weisz gauge action. Gluon-discretization errors are also studied in a lattice potential model using perturbation theory for four different gauge actions. The nonperturbative lattice QCD results for the radial and orbital bottomonium energy splittings obtained from the RBC/UKQCD ensembles are found to be in excellent agreement with experiment. To get accurate results for spin splittings, the spin-dependent order-v(6) terms are included in the nonrelativistic QCD action, and suitable ratios are calculated such that most of the unknown radiative corrections cancel. The cancellation of radiative corrections is verified explicitly by repeating the calculations with different values of the couplings in the nonrelativistic QCD action. Using the lattice ratios of the S-wave hyperfine and the 1P tensor splitting, and the experimental result for the 1P tensor splitting, the 1S hyperfine splitting is found to be 60.3 +/- 5.5(stat) +/- 5.0(syst) +/- 2.1(exp) MeV, and the 2S hyperfine splitting is predicted to be 23.5 +/- 4.1(stat) +/- 2.1(syst) +/- 0.8(exp) MeV.
• Meinel, S. (2010). Prediction of the Omega(bbb) mass from lattice QCD. PHYSICAL REVIEW D, 82(11).
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  The mass of the triply-heavy baryon Omega(bbb) is calculated in lattice QCD with 2 + 1 flavors of light sea quarks. The b quark is implemented with improved lattice nonrelativistic QCD. Gauge field ensembles from both the RBC/UKQCD and MILC collaborations with lattice spacings in the range from 0.08 fm to 0.12 fm are used. The final result for the Omega(bbb) mass, which includes an electrostatic correction, is 14.371 +/- 0.004(stat) +/- 0.011(syst) +/- 0.001(exp) GeV. The hyperfine splitting between the physical J = 3/2 state and a fictitious J = 1/2 state is also calculated.
• Horgan, R. R., Khomskii, L., Meinel, S., Wingate, M., Foley, K. M., Lepage, G. P., von Hippel, G. M., Hart, A., Mueller, E. H., Davies, C. T., Dougall, A., & Wong, K. Y. (2009). Moving nonrelativistic QCD for heavy-to-light form factors on the lattice. PHYSICAL REVIEW D, 80(7).
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  We formulate nonrelativistic quantum chromodynamics (NRQCD) on a lattice which is boosted relative to the usual discretization frame. Moving NRQCD allows us to treat the momentum for the heavy quark arising from the frame choice exactly. We derive moving NRQCD through O(1/m(2); v(rel)(4) ), as accurate as the NRQCD action in present use, both in the continuum and on the lattice with O(a(4)) improvements. We have carried out extensive tests of the formalism through calculations of two-point correlators for both heavy-heavy (bottomonium) and heavy-light (B(s)) mesons in 2 + 1 flavor lattice QCD and obtained nonperturbative determinations of energy shift and external momentum renormalization. Comparison to perturbation theory at O(alpha(s)) is also made. The results demonstrate the effectiveness of moving NRQCD. In particular we show that the decay constants of heavy-light and heavy-heavy mesons can be calculated with small systematic errors up to much larger momenta than with standard NRQCD.
• Meinel, S. (2009). Bottomonium spectrum from lattice QCD with 2+1 flavors of domain wall fermions. PHYSICAL REVIEW D, 79(9).
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  Recently, realistic lattice QCD calculations with 2+1 flavors of domain wall fermions and the Iwasaki gauge action have been performed by the RBC and UKQCD Collaborations. Here, results for the bottomonium spectrum computed on their gauge configurations of size 24(3)x64 with a lattice spacing of approximately 0.11 fm and four different values for the light quark mass are presented. Improved lattice nonrelativistic QCD is used to treat the b quarks inside the bottomonium. The results for the radial and orbital energy splittings are found to be in good agreement with experimental measurements, indicating that systematic errors are small. The calculation of the Upsilon(2S)-Upsilon(1S) energy splitting provides an independent determination of the lattice spacing. For the most physical ensemble it is found to be a(-1)=1.740(25)(19) GeV, where the first error is statistical/fitting and the second error is an estimate of the systematic errors due to the lattice nonrelativistic QCD action.

Proceedings Publications

• Petschlies, M., Alexandrou, C., Leskovec, L., Meinel, S., Rendon, G., Pochinsky, A., Paul, S., Syritsyn, S., & Negele, J. W. (2020). The rho radiative decay width from lattice QCD. In Proceedings of The 9th International workshop on Chiral Dynamics — PoS(CD2018), 317.
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  Pion photoproduction constitutes a prototype process, which allows for the study of the electro-weak decay of a QCD-unstable state, the $\rho$ resonance. It is also the most straightforward process to investigate such ( resonant ) transition matrix elements in lattice QCD. We performed a lattice calculation of the process $\pi\pi \to \rho \to \pi\gamma$, at presently the lightest pion mass of 317 MeV and in a large box of size (3.6 fm)$^3$. In addition to outlining the method for our calculation, we give account of our analysis of systematic uncertainties, with focus on parametrization dependence of the $P-$wave phase shift and the analytic continuation of our lattice data to the $\rho$ resonance pole to extract the coupling $|G_{\rho \pi \gamma} | = 0.0802\,(38)$.
• Pflaumer, M., Leskovec, L., Meinel, S., & Wagner, M. (2020, 9). Investigation of Doubly Heavy Tetraquark Systems using Lattice QCD. In Asia-Pacific Symposium for Lattice Field Theory.
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  We search for possibly existent bound states in the heavy-light tetraquark channels with quark content b¯b¯ud, b¯b¯us and b¯c¯ud using lattice QCD. We carry out calculations on several gauge link ensembles with Nf=2+1 flavours of domain-wall fermions and consider a basis of local and non-local interpolators. Besides extracting the energy spectrum from the correlation matrices, we also perform a Lüscher analysis to extrapolate our results to infinite volume.
• Kane, C., Lehner, C., Meinel, S., & Soni, A. (2019, July 2019). Radiative leptonic decays on the lattice. In Proceedings of Science, LATTICE2019.
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  Adding a hard photon to the final state of a leptonic pseudoscalar-meson decay lifts the helicity suppression and can provide sensitivity to a larger set of operators in the weak effective Hamiltonian. Furthermore, radiative leptonic B decays at high photon energy are well suited to constrain the first inverse moment of the B-meson light-cone distribution amplitude, an important parameter in the theory of nonleptonic B decays. We demonstrate that the calculation of radiative leptonic decays is possible using Euclidean lattice QCD, and present preliminary numerical results for D+s→ℓ+νγ and K−→ℓ−ν¯γ.
• Meinel, S. (2018, December). Quark orbital angular momentum in the proton evaluated using a direct derivative method. In Proceedings of Science, SPIN2018, 47.
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  Quark orbital angular momentum (OAM) in the proton can be calculated directlygiven a Wigner function encoding the simultaneous distribution of quarktransverse positions and momenta. This distribution can be accessed via protonmatrix elements of a quark bilocal operator (the separation in which is Fourierconjugate to the quark momentum) featuring a momentum transfer (which isFourier conjugate to the quark position). To generate the weighting by quarktransverse position needed to calculate OAM, a derivative with respect tomomentum transfer is consequently required. This derivative is evaluated usinga direct derivative method, i.e., a method in which the momentum derivative ofa correlator is directly sampled in the lattice calculation, as opposed toextracting it a posteriori from the numerical correlator data. The methodremoves the bias stemming from estimating the derivative a posteriori that wasseen to afflict a previous exploratory calculation. Data for Ji OAM generatedon a clover ensemble at pion mass $m_{\pi } = 317\, \mbox{MeV} $ are seen toagree with the result obtained via the traditional Ji sum rule method. Byvarying the gauge connection in the quark bilocal operator, also Jaffe-ManoharOAM is extracted, and seen to be enhanced significantly compared to Ji OAM.
• Meinel, S. (2018, December). Towards the P-wave nucleon-pion scattering amplitude in the $\Delta(1232)$ channel. In Proceedings of Science, LATTICE2018, 89.
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  We use lattice QCD and the L\"uscher method to study elastic pion-nucleonscattering in the isospin $I = 3/2$ channel, which couples to the$\Delta(1232)$ resonance. Our $N_f=2+1$ flavor lattice setup features a pionmass of $m_\pi \approx 250$ MeV, such that the strong decay channel $\Delta\rightarrow \pi N$ is close to the threshold. We present our method forconstructing the required lattice correlation functions from single- andtwo-hadron interpolating fields and their projection to irreduciblerepresentations of the relevant symmetry group of the lattice. We showpreliminary results for the energy spectra in selected moving frames andirreducible representations, and extract the scattering phase shifts. Using aBreit-Wigner fit, we also determine the resonance mass $m_\Delta$ and the$g_{\Delta-\pi N}$ coupling.
• Meinel, S. (2018, November). $K π$ scattering and the $K^*(892)$ resonance in 2+1 flavor QCD. In Proceedings of Science, LATTICE2018, 73.
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  In this project, we will compute the form factors relevant for $B \to K^*(\toK \pi)\ell^+\ell^-$ decays. To map the finite-volume matrix elements computedon the lattice to the infinite-volume $B \to K \pi$ matrix elements, the $K\pi$ scattering amplitude needs to be determined using L\"uscher's method. Herewe present preliminary results from our calculations with $2+1$ flavors ofdynamical clover fermions. We extract the $P$-wave scattering phase shifts anddetermine the $K^*$ resonance mass and the $K^* K \pi$ coupling for twodifferent ensembles with pion masses of $317(2)$ and $178(2)$ MeV.
• Meinel, S. (2018, November). Calculating the $ρ$ radiative decay width with lattice QCD. In Proceedings of Science, LATTICE2018, 65.
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  We present the results of our lattice QCD study of the $\pi\gamma\to\pi\pi$process, where the $\rho$ resonance appears as an enhancement in the transitionamplitude. We use $N_f=2+1$ clover fermions on a lattice of $L=3.6$ fm and apion mass of $320$ MeV. Using a combination of forward, stochastic, andsequential propagators, we calculate the two-point and three-point functionsthat allow us to determine the $\pi\gamma\to\pi\pi$ matrix elements for severalvalues of the invariant mass $s$ and momentum transfer $q^2$. To fit the $q^2$and $s$ dependence of the $\pi\gamma\to\pi\pi$ amplitude, we explore a set ofgeneral parametrizations based on a Taylor expansion. By analytic continuationto the complex pole corresponding to the $\rho$ resonance, we determine theresonant form factors and calculate the radiative decay width of the $\rho$.
• Meinel, S. (2018, October). A Lattice QCD study of the $ρ$ resonance. In Electronic Conference Proceedings Archive.
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  We present a lattice QCD study of the $\rho$ resonance with $N_f=2+1$ cloverfermions at a pion mass of approximately $320$ MeV and lattice size $3.6$ fm.We consider two processes involving the $\rho$. The first process is elasticscattering of two pions in P-wave with isospin $1$. Using the L\"uscher methodwe determine the scattering phase shift, from which we obtain the $\rho$resonance mass and decay width $\Gamma(\rho\to\pi\pi)$. The second process isthe radiative transition $\pi\gamma\to\pi\pi$, where we follow theBrice\~no-Hansen-Walker-Loud approach to determine the transition amplitude inthe invariant mass region near the $\rho$ resonance and for both space- andtime-like photon momentum. This allows us to determine the coupling between the$\rho$, the pion and the photon, and the resulting $\rho$ radiative decaywidth.
• Meinel, S. (2018, October). Nucleon electromagnetic form factors at high $Q^2$ from Wilson-clover fermions. In Proceedings of Science, LATTICE2018, 115.
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  We present results on the nucleon electromagnetic form factors from LatticeQCD at momentum transfer up to about $12$~GeV$^2$. We analyze two gaugeensembles with the Wilson-clover fermion action, a lattice spacing of $a\approx0.09$~fm and pion masses $m_\pi\approx 170$~MeV and $m_\pi\approx 280$~MeV. Inour analysis we employ momentum smearing as well as a set of techniques toinvestigate excited state effects. Good agreement with experiment andphenomenology is found for the ratios $G_E/G_M$ and $F_2/F_1$, whereasdiscrepancies are observed for the individual form factors $F_1$ and $F_2$. Wediscuss various systematics that may affect our calculation.
• Paul, S., Alexandrou, C., Leskovec, L., Meinel, S., Negele, J., Petschlies, M., Pochinsky, A., Rendon, G., & Syritsyn, S. (2018, February). pi pi P-wave resonant scattering from lattice QCD. In EPJ Web of Conferences.
• Hasan, N., Engelhardt, M., Green, J., Krieg, S., Meinel, S., Negele, J., Pochinsky, A., & Syritsyn, S. (2016, November). Computing the nucleon Dirac radius directly at $Q^2=0$. In Proceedings of Science, LATTICE2016, 147.
• Leskovec, L., Alexandrou, C., Koutsou, G., Meinel, S., Negele, J. W., Paul, S., Petschlies, M., Pochinsky, A., Rendon, G., & Syritsyn, S. (2016, November). A study of the radiative transition $\pi \pi \to \pi \gamma^*$ with lattice QCD. In Proceedings of Science, LATTICE2016, 159.
• Meinel, S., & Rendon, G. (2016, August). Lattice QCD calculation of form factors for $\Lambda_b to \Lambda(1520) ell^+ ell^-$ decays. In Proceedings of Science, LATTICE2016, 299.
• Peters, A., Bicudo, P., Leskovec, L., Meinel, S., & Wagner, M. (2016, September). Lattice QCD study of heavy-heavy-light-light tetraquark candidates. In Proceedings of Science, LATTICE2016, 104.
• Horgan, R., Liu, Z., Meinel, S., & Wingate, M. (2015, January). Rare B decays using lattice QCD form factors. In Proceedings of Science, LATTICE2014, 372.
• Brown, Z. S., Detmold, W., Meinel, S., & Orginos, K. (2014, November). Charmed Bottom Baryon Spectroscopy. In Proceedings of Science, LATTICE2013, 248.
• Meinel, S. (2014, January). Flavor physics with $\Lambda_b$ baryons. In Proceedings of Science, LATTICE2013, 024.
• Syritsyn, S., Blum, T., Engelhardt, M., Green, J., Izubuchi, T., & others, . (2014, December). Initial nucleon structure results with chiral quarks at the physical point. In Proceedings of Science.
• Green, J., Engelhardt, M., Krieg, S., Meinel, S., Negele, J., & others, . (2013, October). Nucleon form factors with light Wilson quarks. In Proceedings of Science, LATTICE2013, 276.
• Brown, Z. S., Detmold, W., Meinel, S., & Orginos, K. (2012, June). Charm-bottom baryon spectroscopy. In Proceedings of Science, QNP2012, 107.
• Detmold, W., Lin, C. D., & Meinel, S. (2012, March). Axial couplings of heavy hadrons from domain-wall lattice QCD. In Proceedings of Science, LATTICE2011, 166.
• Detmold, W., Lin, C. D., Meinel, S., & Wingate, M. (2012, November). Form factors for $\Lambda_b \to \Lambda$ transitions from lattice QCD. In Proceedings of Science, LATTICE2012, 123.
• Meinel, S. (2012, February). Omega_bbb excited-state spectroscopy from lattice QCD. In Proceedings of Science, ConfinementX, 140.
• Liu, Z., Meinel, S., Hart, A., Horgan, R. R., Muller, E. H., & others, . (2011, January). A Lattice calculation of $B -> K^(*)$ form factors. In CKM 2010.
• Liu, Z., Meinel, S., Hart, A., Horgan, R. R., Muller, E. H., & others, . (2009, November). Form factors for rare B decays: Strategy, methodology, and numerical study. In Proceedings of Science, LAT2009, 242.
• Meinel, S., Detmold, W., Lin, C. D., & Wingate, M. (2009, September). Bottom hadrons from lattice QCD with domain wall and NRQCD fermions. In Proceedings of Science, LAT2009, 105.
• Muller, E. H., Davies, C. T., Hart, A., Hippel, G. M., Horgan, R. R., & others, . (2009, September). Radiative corrections to the m(oving)NRQCD action and heavy-light operators. In Proceedings of Science, LAT2009, 241.
• Meinel, S., Muller, E. H., Khomskii, L., Hart, A., Horgan, R. R., & others, . (2008, October). Rare B decays with moving NRQCD and improved staggered quarks. In Proceedings of Science, LATTICE2008, 280.
• Meinel, S., Horgan, R., Khomskii, L., Storoni, L. C., & Wingate, M. (2007, October). Moving NRQCD and B ---> K* gamma. In Proceedings of Science, LAT2007, 377.

Presentations

• Meinel, S. (2021, July). Semileptonic decays of heavy baryons to negative-parity baryons. The 38th International Symposium on Lattice Field Theory (Lattice 2022). Zoom/Gather@Massachusetts Institute of Technology.
• Meinel, S. (2021, November). Progress in Lattice QCD for CKM Physics. 11th International Workshop on the CKM Unitarity Triangle (CKM 2021). Zoom@University of Melbourne, Australia.
• Meinel, S., & Marin-Benito, C. (2021). $\Lambda_Q \to \Lambda^{(*)}$ form factors. IPPP Workshop "Beyond the Flavour Anomalies II".
• Meinel, S. (2020, August). Rare Processes and Precision Measurements. Snowmass 2021 Computational Frontier WorkshopAPS DPF.
• Meinel, S. (2020, July). Weak decays of b and c quarks. Snowmass 2021 Frontier for Rare Processes and Precision Measurements Kickoff MeetingAPS DPF.
• Meinel, S. (2020, November). Λb → Λ* and Λb → Λc* form factors from lattice QCD. b-baryon FestIJCLab, Universite Paris Saclay, GDR-Inf.
• Meinel, S. (2020, October). Lattice QCD for Flavor Physics. Snowmass 2021 Community Planning MeetingAPS DPF.
• Meinel, S. (2019, April). Theory of heavy-quark spectroscopy. APS April Meeting. Denver.
• Meinel, S. (2019, February). 1 -> 2 transition form factors from lattice QCD. 6th KEK Flavor Factory Workshop. KEK, Tsukuba, Japan.
• Meinel, S. (2019, July). Progress in lattice QCD for b physics. APS DPF Meeting. Boston.
• Meinel, S. (2019, June). Radiative leptonic decays on the lattice. 37th International Symposium on Lattice Field Theory. Wuhan, China.
• Meinel, S. (2019, June). Rare b decays and lattice QCD. Summer school on "Frontiers in Lattice QCD". Peking University, Beijing, China.
• Meinel, S. (2019, March). 1 -> 2 transition amplitudes from lattice QCD. MIT Nuclear Theory Seminar. Massachusetts Institute of Technology.
• Meinel, S. (2019, March). Lattice QCD for B physics. 2019 Lattice Workshop for US - Japan Intensity Frontier Incubation. Brookhaven National Laboratory.
• Meinel, S. (2019, October). Challenging the Standard Model of Particle Physics with Bottom Quarks. Physics Department Colloquium. University of Arizona.
• Meinel, S. (2018, April). $\Lambda_b \to \Lambda_c^{(*)}$ form factors from lattice QCD. MITP Workshop "Challenges in Semileptonic B Decays". University of Mainz, Germany.
• Meinel, S. (2018, April). Opportunities for lattice QCD in quark and lepton flavor physics. USQCD All Hands Meeting. Fermilab.
• Meinel, S. (2018, May). Flavor physics with charm and bottom baryons. ASU Cosmology Seminar. Arizona State University.
• Meinel, S. (2018, May). Form factors for b hadron decays from lattice QCD. Frontiers in Lattice Quantum Field Theory, IFT Madrid, 2018.
• Meinel, S. (2018, September). Exclusive semileptonic b baryon decays from lattice QCD. 10th International Workshop on the CKM Unitarity Triangle.
• Meinel, S. (2017, August). Weak decays of heavy mesons to multi-hadron final states. Santa Fe Lattice QCD Workshop 2017.
• Meinel, S. (2017, June). Charm baryon semileptonic decays with lattice QCD. 35th International Symposium on Lattice Field Theory.
• Meinel, S. (2017, September). Flavor physics with charm and bottom baryons. Jefferson Lab Theory Seminar.
• Meinel, S. (2017, September). Heavy baryon decay form factors from Lattice QCD. Lattice Meets Continuum 2017. Siegen, Germany.
• Meinel, S. (2017, September). Hints for physics beyond the Standard Model in decays of beauty quarks. Old Dominion University Physics Colloquium.
• Meinel, S. (2016, April). Lattice results and outlook. Prospects and challenges for semitauonic decays at LHCb. CERN, Geneva.
• Meinel, S. (2016, August). Flavor physics with $\Lambda_b$ baryons. 38th International Conference on High Energy Physics. Chicago.
• Meinel, S. (2016, July). Lattice QCD calculation of form factors for $\Lambda_b \to \Lambda(1520) \ell^+ \ell^-$ decays. 34th International Symposium on Lattice Field Theory. Southampton, UK.
• Meinel, S. (2016, June). Flavor physics with $\Lambda_b$ baryons. Fermilab Theory Seminar. Fermilab.
• Meinel, S. (2016, May). Heavy Baryons on the Lattice. International Conference on the Structure of Baryons. Florida State University, Tallahassee.
• Meinel, S. (2016, September). Heavy baryon decay form factors from lattice QCD. International Workshop on Hadronic Contributions to New Physics Searches. Puerto de la Cruz, Spain.
• Meinel, S. (2015, July). Determination of $|V_{ub}/V_{cb}|$ using baryonic decays. 33rd International Symposium on Lattice Field Theory (Lattice 2015). Kobe, Japan.
• Meinel, S. (2015, July). Rare b decays. 5th International Workshop on Lattice Hadron Physics (LHP V). Cairns, Australia.
• Meinel, S. (2015, May). Rare b decays and lattice QCD. Twelfth Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2015). Vail, Colorado.
• Meinel, S. (2015, November). Flavor physics with $\Lambda_b$ baryons. High-Energy Physics & RIKEN Theory Seminar, BNL. Brookhaven National Laboratory, Upton, NY.
• Meinel, S. (2015, November). Hints for physics beyond the Standard Model in decays of beauty quarks. University of Utah Physics Colloqium. Salt Lake City, Utah: University of Utah.
• Meinel, S. (2015, November). Lattice progress for semileptonic b decays. Implications of LHCb measurements and future prospects. CERN, Geneva, Switzerland: LHCb Collaboration.
• Meinel, S. (2015, October). Determination of $|V_{ub}/V_{cb}|$ using baryonic decays. Brookhaven Forum 2015. Upton, New York: Brookhaven National Laboratory.
• Meinel, S. (2014, October). Heavy baryons in lattice QCD. RIKEN BNL Research Center.
• Meinel, S. (2014, October). Lattice QCD and the search for new physics using beauty quarks. APS Four Corners Section Meeting. Utah Valley University.