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Marc Wagner

Publications and source records attributed to Marc Wagner.

At least 19 recordsLinked to original sources
arXiv2026

Long-distance hybrid spin-dependent and hybrid-quarkonium mixing potentials from lattice gauge theory

We present $SU(3)$ lattice gauge theory results for the $\mathcal{O}(1/m_Q)$ hybrid spin-dependent and hybrid-quarkonium mixing potentials. The only existing lattice computation of these potentials is limited to quark-antiquark separations smaller than approximately $0.5\,\text{fm}$. In this work, we extend the lattice results up to around $1.25 \, \text{fm}$ using large-volume, high-statistics simulations at several lattice spacings and gradient flow times, providing the first lattice data in this previously unexplored regime.

hep-lat↗
arXiv2025

$\bar{b}\bar{b}ud$ Tetraquarks with $I(J^P)=0(1^-)$ and $\bar{b}\bar{c}ud$ Tetraquarks with $I(J^P)=0(0^+)$ and $I(J^P)=0(1^+)$ from Lattice QCD Antistatic-Antistatic Potentials

We study heavy spin effects in $\bar{b}\bar{b}ud$ and $\bar{b}\bar{c}ud$ four-quark systems using the Born-Oppenheimer approximation and existing antistatic-antistatic potentials computed with lattice QCD. We report about a recent refined investigation of the $\bar{b}\bar{b}ud$ system with $I(J^P)=0(1^-)$, where we predicted a tetraquark resonance slightly above the $B^{*}B^{*}$ threshold. Furthermore, we extend our Born-Oppenheimer approach to $\bar{b}\bar{c}ud$ four-quark systems. For quantum numbers $I(J^P)=0(0^+)$ as well as $I(J^P)=0(1^+)$ we find virtual bound states rather far away from the lowest meson-meson thresholds.

hep-lat↗
arXiv2025

Hybrid spin-dependent and hybrid-quarkonium mixing potentials at order $(1 /m_Q)^1$ from SU(3) lattice gauge theory

We present the first lattice gauge theory results for hybrid spin-dependent and hybrid-quarkonium mixing potentials appearing at order $(1 /m_Q)^1$ in the Born-Oppenheimer Effective Field theory for hybrid mesons with gluon spin $\kappa^{PC} = 1^{+-}$. Specifically, we compute the four unknown potentials $V^{sa}_{11}(r)$, $V^{sb}_{10}(r)$, which are relevant for the hyperfine splitting in heavy hybrid meson spectra, as well as $V^\text{mix}_{\Sigma_u^-}(r)$ and $V^\text{mix}_{\Pi_u}(r)$, which describe the mixing of heavy hybrid mesons with ordinary quarkonium. We relate these potentials to matrix elements, which we extract from generalized Wilson loops with a chromomagnetic field insertion along one of the temporal lines and suitable hybrid creation operators replacing the spatial lines. We use gradient flow, which facilitates the renormalization of the matrix elements and has the additional benefit of significantly reducing statistical noise. We present results for gauge group SU(3) and lattice spacing $a=0.060$ fm. Our results demonstrate that a future combined continuum and zero-flow time extrapolation is possible within our setup, which will be necessary to reliably predict the hyperfine splitting of heavy hybrid mesons as well as their mixing with ordinary quarkonium through coupled channel Schr\"odinger equations.

hep-lat↗
arXiv2024

Prediction of an $I(J^{P})=0(1^{-})$ $\bar{b}\bar{b}ud$ Tetraquark Resonance Close to the $B^\ast B^\ast$ Threshold Using Lattice QCD Potentials

We use antistatic-antistatic potentials computed with lattice QCD and a coupled-channel Born-Oppenheimer approach to explore the existence of a $\bar{b} \bar{b} u d$ tetraquark resonance with quantum numbers $I(J^P) = 0(1^-)$. A pole in the $\mbox{T}$ matrix signals a resonance with mass $m = 2 m_B + 94.0^{+1.3}_{-5.4} \, \text{MeV}$ and decay width $\Gamma = 140^{+86}_{-66} \, \text{MeV}$, i.e. very close to the $B^\ast B^\ast$ threshold. We also compute branching ratios, which clearly indicate that this resonance is mainly composed of a $B^\ast B^\ast$ meson pair with a significantly smaller $B B$ contribution. By varying the potential matrix responsible for the coupling of the $B B$ and the $B^\ast B^\ast$ channel as well as the $b$ quark mass, we provide additional insights and understanding concerning the formation and existence of the resonance. We also comment on the importance of our findings and the main takeaways for a possible future full lattice QCD investigation of this $I(J^P) = 0(1^-)$ $\bar{b} \bar{b} u d$ tetraquark resonance.

hep-lat↗
arXiv2024

Computing $1/m_Q$ and $1/m_Q^2$ corrections to the static potential with lattice gauge theory using gradient flow

We present selected preliminary lattice gauge theory results for $O(1/m_Q)$ and $O(1/m_Q^2)$ corrections to the static potential. These results are based on Wilson loops with two field strength insertions, which we renormalize using gradient flow. We explore tree level improvement to reduce systematic errors in the Wilson loops due to the finite lattice spacing and flow time, in particular at small temporal and spatial separations.

hep-lat↗
arXiv2024

Antistatic-antistatic $\bar Q \bar Q qq$ potentials for $u$, $d$ and $s$ light quarks from lattice QCD

We report on our ongoing lattice QCD computation of antistatic-antistatic potentials in the presence of two light quarks using the CLS $N_f=2$ gauge configurations and the OpenQ*D codebase. We utilize a set of 16 creation operators, corresponding to 8 sectors characterized by angular momentum and parity quantum numbers for light quarks $qq = (ud - du) / \sqrt{2}$ (isospin $0$), $qq \in \{ uu , (ud + du) / \sqrt{2}, dd \}$ (isospin $1$) and $qq \in \{ us , ds \}$ (isospin $1/2$ and strangeness $-1$). We improve on previous work by considering a large number of off-axis separations of the static antiquarks and by using tree-level improvement. The resulting potentials provide vague indication for one-pion exchange at $\bar Q \bar Q$ separations $r \gtrapprox$ 0.5 fm.

hep-lat↗
arXiv2024

Regularization effects in the Nambu-Jona-Lasinio model: Strong scheme dependence of inhomogeneous phases and persistence of the moat regime

This work investigates the phase structure of the non-renormalizable (3+1)-dimensional Nambu-Jona-Lasinio (NJL) model with particular focus on inhomogeneous phases (IPs), where the chiral condensate is non-uniform in space, and the closely related moat regimes, where mesonic dispersion relations favor non-vanishing momenta. We use the mean-field approximation and consider five different regularization schemes including three lattice discretizations. The results within the different regularization schemes are systematically analyzed in order to study the dependence of the IP on the choice of regulatization scheme and regulator value. The IP exhibits a drastic dependence on the chosen regularization scheme rendering any physical interpretation of results on inhomogeneous phases in this model doubtful. In contrast, we find only a mild scheme dependence of the moat regime suggesting that its existence is a consequence of the action of the NJL model and its symmetries and, thus, that it might also exist in QCD.

hep-ph↗
arXiv2024

$\bar b \bar b u d$ and $\bar b \bar b u s$ tetraquarks from lattice QCD using symmetric correlation matrices with both local and scattering interpolating operators

We study the $\bar b \bar b u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$ as well as the $\bar b \bar b u s$ tetraquark with quantum numbers $J^P = 1^+$ using lattice QCD. We improve on existing work by including both local and scattering interpolating operators on both sides of the correlation functions and use symmetric correlation matrices. This allows not only a reliable determination of the energies of QCD-stable tetraquark ground states, but also of low-lying excited states, which are meson-meson scattering states. The latter is particularly important for future finite-volume scattering analyses. Here, we perform chiral and continuum extrapolations of just the ground-state energies, for which finite-volume effects are expected to be small. Our resulting tetraquark binding energies, $-100 \pm 10\:^{+36}_{-51}\:\:{\rm MeV}$ for $\bar b \bar b u d$ and $-30 \pm 3\:^{+11}_{-31}\:\:{\rm MeV}$ for $\bar b \bar b u s$, are consistent with other recent lattice-QCD predictions.

hep-lat↗
arXiv2023

Antistatic-antistatic-light-light potentials from lattice QCD

We present results for tetraquark potentials of two static anti-quarks $\bar b \bar b$ in the presence of two light quarks $u$ and/or $d$. We improve on existing results by computing the static potential also for off-axis separations, which increases the number of data points significantly. Moreover, we compute for the first time $\bar b \bar b u s$ potentials.

hep-lat↗
arXiv2023

Shallow Bound States and Hints for Broad Resonances with Quark Content $\bar{b}\bar{c}ud$ in $B$-$\bar{D}$ and $B^*$-$\bar{D}$ Scattering from Lattice QCD

We present the first determination of the energy dependence of the $B$-$\bar{D}$ and $B^*$-$\bar{D}$ isospin-0, $S$-wave scattering amplitudes both below and above the thresholds using lattice QCD, which allows us to investigate rigorously whether mixed bottom-charm $\bar{b}\bar{c}ud$ tetraquarks exist as bound states or resonances. The scattering phase shifts are obtained using L\"uscher's method from the energy spectra in two different volumes. To ensure that no relevant energy level is missed, we use large, symmetric $7 \times 7$ and $8 \times 8$ correlation matrices that include, at both source and sink, $B^{(*)}$-$\bar{D}$ scattering operators with the lowest three or four possible back-to-back momenta in addition to local $\bar{b}\bar{c}ud$ operators. We fit the energy dependence of the extracted scattering phase shifts using effective-range expansions. We observe sharp peaks in the $B^{(*)}$-$\bar{D}$ scattering rates close to the thresholds, which are associated with shallow bound states, either genuine or virtual, a few MeV or less below the $B^{(*)}$-$\bar{D}$ thresholds. In addition, we find hints for resonances with masses of order $100$ MeV above the thresholds and decay widths of order $200$ MeV.

hep-lat↗
arXiv2023

Relativistic corrections to the static potential from generalized Wilson loops at finite flow time

We present results from an ongoing project concerned with the computation of $\mathcal{O}(1/m_Q)$ and $\mathcal{O}(1/m_Q^2)$ relativistic corrections to the static potential. These corrections are extracted from Wilson loops with two chromo-field insertions. We use gradient flow, which allows to renormalize the inserted fields and leads to a significantly improved signal-to-noise ratio, providing access to loops with large spatial and temporal extents.

hep-lat↗
arXiv2023

Gluelump masses and mass splittings from SU(3) lattice gauge theory

We compute gluelump masses and mass differences using SU(3) lattice gauge theory. We study states with total angular momentum up to $J = 3$, parity $P = +,-$ and charge conjugation $C = +,-$. Computations on four ensembles with rather fine lattice spacings in the range $0.040 \, \text{fm} \ldots 0.093 \, \text{fm}$ allow continuum extrapolations of gluelump mass differences. We complement existing results on hybrid static potentials with the obtained gluelump masses, which represent the limit of vanishing quark-antiquark separation. We also discuss the conversion of lattice gluelump masses to the Renormalon Subtracted scheme, which is e.g. important for studies of heavy hybrid mesons in the Born-Oppenheimer approximation.

hep-lat↗
arXiv2022

Inhomogeneous phases in the 3+1-dimensional Nambu-Jona-Lasinio model and their dependence on the regularization scheme

In this work we study the $3+1$-dimensional Nambu-Jona-Lasinio (NJL) model in the mean field-approximation. We carry out calculations using five different regularization schemes (two continuum and three lattice regularization schemes) with particular focus on inhomogeneous phases and condensates. The regularization schemes lead to drastically different inhomogeneous regions. We provide evidence that inhomogeneous condensates appear for all regularization schemes almost exclusively at values of the chemical potential and with wave numbers, which are of the order of or even larger than the corresponding regulators. This can be interpreted as indication that inhomogeneous phases in the $3+1$-dimensional NJL model are rather artifacts of the regularization and not a consequence of the NJL Lagrangian and its symmetries.

hep-lat↗
arXiv2022

Inclusion of heavy spin effects in the $u d \bar{b} \bar{b}$ $I(J^{P})=0(1^{-})$ four-quark channel in the Born-Oppenheimer approximation

We refine our previous study of a $u d \bar{b} \bar{b}$ tetraquark resonance with quantum numbers $I(J^{P})=0(1^{-})$, which is based on antiheavy-antiheavy lattice QCD potentials, by including heavy quark spin effects via the mass difference of the $B$ and the $B^{*}$ meson. This leads to a coupled channel Schr\"odinger equation, where the two channels correspond to $BB$ and $B^{*}B^{*}$, respectively. We search for $\mbox{T}$ matrix poles in the complex energy plane, but do not find any indication for the existence of a tetraquark resonance in this refined coupled channel approach. We also vary the antiheavy-antiheavy potentials as well as the $b$ quark mass to further understand the dynamics of this four-quark system.

hep-lat↗
arXiv2022

Antiheavy-Antiheavy-Light-Light Four-Quark Bound States

We present our recent results on antiheavy-antiheavy-light-light tetraquark systems using lattice QCD. Our study of the $ \bar{b}\bar{b}us $ four-quark system with quantum numbers $ J^P=1^+ $ and the $ \bar{b}\bar{c}ud $ four-quark systems with $ I(J^P)=0(0^+) $ and $ I(J^P)=0(1^+) $ utilizes scattering operators at the sink to improve the extraction of the low-lying energy levels. We found a bound state for $ \bar{b}\bar{b}us $ with $ E_{\textrm{bind},\bar{b}\bar{b}us} = (-86 \pm 22 \pm 10)\,\textrm{MeV} $, but no indication for a bound state in both $ \bar{b}\bar{c}ud $ channels. Moreover, we show preliminary results for $ \bar{b}\bar{b}ud $ with $ I(J^P)=0(1^+) $, where we used scattering operators both at the sink and the source. We found a bound state and determined its infinite-volume binding energy with a scattering analysis, resulting in $ E_{\textrm{bind},\bar{b}\bar{b}ud} =(-103 \pm 8 )\,\textrm{MeV} $.

hep-lat↗
arXiv2022

Lattice field theory results for hybrid static potentials at short quark-antiquark separations and their parametrization

We present SU(3) lattice Yang-Mills data for hybrid static potentials from five ensembles with different small lattice spacings and the corresponding parametrizations for quark-antiquark separations $0.08\,\text{fm} \le r \le 1.12\,\text{fm}$. We remove lattice discretization errors at tree level of perturbation theory and partly at order $a^2$ as well as the $a$-dependent self energy. In particular the tree-level improvement of static potentials is discussed in detail and two methods are compared. The resulting parametrizations are expected to represent continuum limit results for hybrid static potentials within statistical errors.

hep-lat↗
arXiv2022

Study of $I=0$ bottomonium bound states and resonances based on lattice QCD static potentials

We investigate $I = 0$ bottomonium bound states and resonances in S, P, D and F waves using lattice QCD static-static-light-light potentials. We consider five coupled channels, one confined quarkonium and four open $B^{(*)}\bar{B}^{(*)}$ and $B^{(*)}_s\bar{B}^{(*)}_s$ meson-meson channels and use the Born-Oppenheimer approximation and the emergent wave method to compute poles of the T matrix. We discuss results for masses and decay widths and compare them to existing experimental results. Moreover, we determine the quarkonium and meson-meson composition of these states to clarify, whether they are ordinary quarkonium or should rather be interpreted as tetraquarks.

hep-lat↗