289 research outputs found

### Moments and power corrections of longitudinal and transverse proton structure functions from lattice QCD

We present a simultaneous extraction of the moments of $F_2$ and $F_L$
structure functions of the proton for a range of photon virtuality, $Q^2$. This
is achieved by computing the forward Compton amplitude on the lattice utilizing
the second-order Feynman-Hellmann theorem. Our calculations are performed on
configurations with two different lattice spacings and volumes, all at the
$SU(3)$ symmetric point. We find the moments of $F_{2}$ and $F_{L}$ in good
agreement with experiment. Power corrections turn out to be significant. This
is the first time the $Q^2$ dependence of the lowest moment of $F_2$ has been
quantified.Comment: 14 pages, 11 figures, 2 tables. Version to appear in PR

### TURBOMOLE: Today and Tomorrow

TURBOMOLE is a highly optimized software suite for large-scale quantum-chemical and materials science simulations of molecules, clusters, extended systems, and periodic solids. TURBOMOLE uses Gaussian basis sets and has been designed with robust and fast quantum-chemical applications in mind, ranging from homogeneous and heterogeneous catalysis to inorganic and organic chemistry and various types of spectroscopy, lightâ€“matter interactions, and biochemistry. This Perspective briefly surveys TURBOMOLEâ€™s functionality and highlights recent developments that have taken place between 2020 and 2023, comprising new electronic structure methods for molecules and solids, previously unavailable molecular properties, embedding, and molecular dynamics approaches. Select features under development are reviewed to illustrate the continuous growth of the program suite, including nuclear electronic orbital methods, Hartreeâ€“Fock-based adiabatic connection models, simplified time-dependent density functional theory, relativistic effects and magnetic properties, and multiscale modeling of optical properties

### Quasi-degenerate baryon energy states, the Feynman-Hellmann theorem and transition matrix elements

The standard method for determining matrix elements in lattice QCD requires the computation of three-point correlation functions. This has the disadvantage of requiring two large time separations: one between the hadron source and operator and the other from the operator to the hadron sink. Here we consider an alternative formalism, based on the Dyson expansion leading to the Feynman- Hellmann theorem, which only requires the computation of two-point correlation functions. Both the cases of degenerate energy levels and quasi-degenerate energy levels which correspond to diagonal and transition matrix elements respectively can be considered in this formalism. As an example numerical results for the Sigma to Nucleon vector transition matrix element are presented.M. Batelaan, K. U. Can, R. Horsley, Y. Nakamura, H. Perlt, P. E. L. Rakow, G. Schierholz, H. StÃ¼ben, R. D. Young and J. M. Zanott

### Quasi-degenerate baryon energy states, the Feynman-Hellmann theorem and transition matrix elements

The standard method for determining matrix elements in lattice QCD requires the computation of three-point correlation functions. This has the disadvantage of requiring two large time separations: one between the hadron source and operator and the other from the operator to the hadron sink. Here we consider an alternative formalism, based on the Dyson expansion leading to the Feynman-Hellmann theorem, which only requires the computation of two-point correlation functions. Both the cases of degenerate energy levels and quasi-degenerate energy levels which correspond to diagonal and transition matrix elements respectively can be considered in this formalism. As an example numerical results for the Sigma to Nucleon vector transition matrix element are presented

### Weak decay constants of the pseudoscalar mesons from lattice QCD+QED

With increasing requirements for greater precision, it becomes essential to describe the effects of isospin breaking induced by both quark masses and electro-magnetic effects. In this work we have performed a lattice analysis of the weak decay constants of the pseudoscalar mesons including such isospin breaking effects, with particular consideration being given to the state mixing of the $\pi^0$, $\eta$ and $\eta^\prime$. We also detail extensions to the non-perturbative RI$^\prime$-MOM renormalization scheme for application to non-degenerate flavour-neutral operators which are permitted to mix, and present initial results. Using flavour-breaking expansions in terms of quark masses and charges we reach decay constant determinations at physical quark masses for all but the $\eta^\prime$, demonstrating in principle how precision determinations of all pseudoscalar decay constants could be reached in lattice QCD with QED and strong isospin-breaking

### TURBOMOLE:Today and Tomorrow

TURBOMOLE is a highly optimized software suite for large-scale quantum-chemical and materials science simulations of molecules, clusters, extended systems, and periodic solids. TURBOMOLE uses Gaussian basis sets and has been designed with robust and fast quantum-chemical applications in mind, ranging from homogeneous and heterogeneous catalysis to inorganic and organic chemistry and various types of spectroscopy, light-matter interactions, and biochemistry. This Perspective briefly surveys TURBOMOLE's functionality and highlights recent developments that have taken place between 2020 and 2023, comprising new electronic structure methods for molecules and solids, previously unavailable molecular properties, embedding, and molecular dynamics approaches. Select features under development are reviewed to illustrate the continuous growth of the program suite, including nuclear electronic orbital methods, Hartree-Fock-based adiabatic connection models, simplified time-dependent density functional theory, relativistic effects and magnetic properties, and multiscale modeling of optical properties

### Constraining beyond the Standard Model nucleon isovector charges

At the TeV scale, low-energy precision observations of neutron
characteristics provide unique probes of novel physics. Precision studies of
neutron decay observables are susceptible to beyond the Standard Model (BSM)
tensor and scalar interactions, while the neutron electric dipole moment,
$d_n$, also has high sensitivity to new BSM CP-violating interactions. To fully
utilise the potential of future experimental neutron physics programs, matrix
elements of appropriate low-energy effective operators within neutron states
must be precisely calculated. We present results from the QCDSF/UKQCD/CSSM
collaboration for the isovector charges $g_T,~g_A$ and $g_S$ using lattice QCD
methods and the Feynman-Hellmann theorem. We use a flavour symmetry breaking
method to systematically approach the physical quark mass using ensembles that
span five lattice spacings and multiple volumes. We extend this existing
flavour breaking expansion to also account for lattice spacing and finite
volume effects in order to quantify all systematic uncertainties. Our final
estimates of the isovector charges are
$g_T~=~1.009(20)_{\text{stat}}(03)_{\text{sys}},~g_A=1.246(69)_{\text{stat}}(05)_{\text{sys}}$
and $g_S~=~1.06(10)_{\text{stat}}(03)_{\text{sys}}$ renormalised, where
appropriate, at $\mu=2~\text{GeV}$ in the $\overline{\text{MS}}$ scheme.Comment: 16 pages, 11 figures, 6 table

### Quasi-degenerate baryon energy states, the Feynman-Hellmann theorem and transition matrix elements

The standard method for determining matrix elements in lattice QCD requires the computation of three-point correlation functions. This has the disadvantage of requiring two large time separations: one between the hadron source and operator and the other from the operator to the hadron sink. Here we consider an alternative formalism, based on the Dyson expansion leading to the Feynman-Hellmann theorem, which only requires the computation of two-point correlation functions. Both the cases of degenerate energy levels and quasi-degenerate energy levels which correspond to diagonal and transition matrix elements respectively can be considered in this formalism. As an example numerical results for the Sigma to Nucleon vector transition matrix element are presented

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