Stefan Leupold
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View article: Electromagnetic isovector form factors of the transition from the $N^*(1520)$ to the nucleon
Electromagnetic isovector form factors of the transition from the $N^*(1520)$ to the nucleon Open
Dispersion theory is used to provide a model-independent low-energy representation of the three electromagnetic isovector transition form factors $N^{*}(1520)\to N$. At low energies the virtual photon couples dominantly to a pion pair. Tak…
View article: Goldberger-Treiman relation and Wu-type experiment in the decuplet sector
Goldberger-Treiman relation and Wu-type experiment in the decuplet sector Open
The leading-order chiral Lagrangian for the baryon octet and decuplet states coupled to Goldstone bosons and external sources contains six low-energy constants. Five of them are fairly well-known from phenomenology, but the sixth one is pr…
View article: Electromagnetic form factors of the transition from the Delta to the nucleon
Electromagnetic form factors of the transition from the Delta to the nucleon Open
The low-energy electromagnetic form factors of the $Δ$(1232)-to-nucleon transition are derived combining dispersion theory techniques and chiral perturbation theory. The form factors are expressed in terms of the well-understood pion vecto…
View article: Light quark mass dependence of nucleon electromagnetic form factors in dispersively modified chiral perturbation theory
Light quark mass dependence of nucleon electromagnetic form factors in dispersively modified chiral perturbation theory Open
The nucleon isovector electromagnetic form factors are calculated up to next-to-next-to-leading order by combining relativistic chiral perturbation theory (ChPT) of pion, nucleon, and Δ(1232) with dispersion theory. We specifically address…
View article: Goldberger-Treiman relation and Wu-type experiment in the decuplet sector
Goldberger-Treiman relation and Wu-type experiment in the decuplet sector Open
The leading-order chiral Lagrangian for the baryon octet and decuplet states coupled to Goldstone bosons and external sources contains six low-energy constants. Five of them are fairly well known from phenomenology, but the sixth one is pr…
View article: Pixel State Value Network for Combined Prediction and Planning in Interactive Environments
Pixel State Value Network for Combined Prediction and Planning in Interactive Environments Open
Automated vehicles operating in urban environments have to reliably interact with other traffic participants. Planning algorithms often utilize separate prediction modules forecasting probabilistic, multi-modal, and interactive behaviors o…
View article: Light quark mass dependence of nucleon electromagnetic form factors in dispersively modified chiral perturbation theory
Light quark mass dependence of nucleon electromagnetic form factors in dispersively modified chiral perturbation theory Open
The nucleon isovector electromagnetic form factors are calculated up to next-to-next-to-leading order by combining relativistic chiral perturbation theory (ChPT) of pion, nucleon, and $Δ$(1232) with dispersion theory. We specifically addre…
View article: Estimates for rare three-body decays of the Omega baryon using chiral symmetry and the $ΔI = 1/2$ rule
Estimates for rare three-body decays of the Omega baryon using chiral symmetry and the $ΔI = 1/2$ rule Open
We study rare three-body decays of the Omega baryon using SU(3) chiral perturbation theory, the successful effective field theory of quantum chromodynamics at low energies. At leading order, we calculate the branching fractions of the deca…
View article: Study of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math> violation in hyperon decays at super-charm-tau factories with a polarized electron beam
Study of violation in hyperon decays at super-charm-tau factories with a polarized electron beam Open
Nonleptonic two-body weak decays of baryons are an important tool to probe the combined charge conjugation--parity symmetry ($CP$) violation. We explain why the decays of strange baryons provide complementary information to the decays of k…
View article: Study of CP violation in hyperon decays at Super Charm-Tau Factories with a polarized electron beam
Study of CP violation in hyperon decays at Super Charm-Tau Factories with a polarized electron beam Open
Non-leptonic two-body weak decays of baryons are an important tool to probe the combined charge-conjugation--parity symmetry (CP) violation. We explain why the decays of strange baryons provide complementary information to the decays of ka…
View article: Spacelike zero crossings and timelike phases in the electromagnetic form factors of vector mesons
Spacelike zero crossings and timelike phases in the electromagnetic form factors of vector mesons Open
Some form factors of ground-state hadrons with spin might show a zero crossing at spacelike momenta of electron-hadron scattering. In the timelike region of hadron-antihadron production by electron-positron collisions the form factors beco…
View article: Sum rule for the partial decay rates of bottom hadrons based on the dynamical supersymmetry of the $\bar s$ quark and the $ud$ diquark
Sum rule for the partial decay rates of bottom hadrons based on the dynamical supersymmetry of the $\bar s$ quark and the $ud$ diquark Open
We investigate the weak decays of $\bar B_{s}^{0}$ and $Λ_{b}$ to charm hadrons based on the dynamical supersymmetry between the $\bar s$ quark and the $ud$ diquark. We derive a new sum rule relating the decay rates of the processes $\bar …
View article: Electromagnetic transition form factors and Dalitz decays of hyperons
Electromagnetic transition form factors and Dalitz decays of hyperons Open
Dalitz decays of a hyperon resonance to a ground-state hyperon and an electron-positron pair can give access to some information about the composite structure of hyperons. We present expressions for the multi-differential decay rates in te…
View article: Electromagnetic transition form factors and Dalitz decays of hyperons
Electromagnetic transition form factors and Dalitz decays of hyperons Open
Dalitz decays of a hyperon resonance to a ground-state hyperon and an electron-positron pair can give access to some information about the composite structure of hyperons. We present expressions for the multi-differential decay rates in te…
View article: Pion-pole contribution to hadronic light-by-light scattering
Pion-pole contribution to hadronic light-by-light scattering Open
We report on the first dispersive calculation of the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon $(g-2)_\mu$. It is unambiguously defined in terms of the doubly-virtual pion tra…
View article: Dynamics of critical fluctuations: Theory -- phenomenology -- heavy-ion collisions
Dynamics of critical fluctuations: Theory -- phenomenology -- heavy-ion collisions Open
This report summarizes the presentations and discussions during the Rapid Reaction Task Force "Dynamics of critical fluctuations: Theory -- phenomenology -- heavy-ion collisions", which was organized by the ExtreMe Matter Institute EMMI an…
View article: Low-energy axial-vector transitions from decuplet to octet baryons
Low-energy axial-vector transitions from decuplet to octet baryons Open
Axial-vector transitions of decuplet to octet baryons are parametrized at low energies guided by a complete and minimal chiral Lagrangian up to next-to-leading order. It is pointed out that beyond the well-known leading-order term, there i…
View article: Nucleon parton distributions from hadronic quantum fluctuations
Nucleon parton distributions from hadronic quantum fluctuations Open
A physical model is presented for the non-perturbative parton distributions\nin the nucleon. This is based on quantum fluctuations of the nucleon into\nbaryon-meson pairs convoluted with Gaussian momentum distributions of partons\nin hadro…
View article: Constraining P and CP violation in the main decay of the neutral Sigma hyperon
Constraining P and CP violation in the main decay of the neutral Sigma hyperon Open
On general grounds based on quantum field theory the decay amplitude for Σ0→Λγ consists of a parity conserving magnetic and a parity violating electric dipole transition moment. Because of the subsequent self-analyzing weak decay of the Λ …
View article: Pion-Pole Contribution to Hadronic Light-By-Light Scattering in the Anomalous Magnetic Moment of the Muon
Pion-Pole Contribution to Hadronic Light-By-Light Scattering in the Anomalous Magnetic Moment of the Muon Open
The π^{0} pole constitutes the lowest-lying singularity of the hadronic light-by-light (HLBL) tensor, and thus, it provides the leading contribution in a dispersive approach to HLBL scattering in the anomalous magnetic moment of the muon (…
View article: Towards solving the proton spin puzzle
Towards solving the proton spin puzzle Open
The fact that the spins of the quarks in the proton, as measured in deep inelastic lepton scattering, only add up to about 30$\%$ of the spin of the proton is still not understood after 30 years. We show that our newly developed model for …
View article: Chiral-partner D mesons in a heat bath within QCD sum rules
Chiral-partner D mesons in a heat bath within QCD sum rules Open
Utilizing QCD sum rules, we extract the temperature dependences of the spectral properties of the pseudo-scalar and scalar D mesons regarded as chiral partners. Besides the masses also decay constants are analyzed as the D meson yields in …
View article: Towards a dispersive determination of the pion transition form factor
Towards a dispersive determination of the pion transition form factor Open
We start with a brief motivation why the pion transition form factor is interesting and, in particular, how it is related to the high-precision standard-model calculation of the gyromagnetic ratio of the muon. Then we report on the current…
View article: Renormalization of the low-energy constants of chiral perturbation theory from loops with dynamical vector mesons
Renormalization of the low-energy constants of chiral perturbation theory from loops with dynamical vector mesons Open
Starting from a relativistic Lagrangian for pseudoscalar Goldstone bosons and\nvector mesons in the antisymmetric tensor representation, a one-loop\ncalculation is performed to pin down the divergent structures that appear for\nthe effecti…