In this work we predict the masses and binding energies of two B_s exotic-meson candidates using Lattice QCD, namely the B_s0^* and B_s1. We use a relativistic heavy-quark action for the valence b-quark in our simulations, tuned fully non-perturbatively by a neural network. This allows us to take the continuum limit and eliminates the largest systematic we attributed to our previous determination of these states using Lattice-NRQCD. This is the first Lattice QCD study to show that these states remain deeply bound in the continuum limit. We thoroughly benchmark our heavy-quark approach by reproducing the experimental values of the 1S hyperfine splittings of B and B_s mesons, as well as the mass splitting between the B and B_s mesons. Our final results yield binding energies with respect to the BK and B^*K thresholds of -65.9(6.0)(3.0)_Iso MeV and -60.6(6.6)(3.0)_Iso(1.0)_GEVP MeV for the B_s0^* and B_s1 respectively.

This work presents technical details of determining the finite-volume energy spectra for the scattering amplitude of the coupled-channel $\pi\Sigma - \bar{K}N$ from lattice QCD data. The importance of reliably extracting such spectra lies in the crucial dependence of the hadronic scattering amplitudes analysis on the energy spectrum when using Lüscher's formalism. Results of the methods used are presented and the final finite-volume spectra are shown. The analysis of the scattering amplitude based on these results, exhibits a two-pole structure for the $\Lambda(1405)$, a virtual bound state below the $\pi\Sigma$ threshold and a resonance pole right below the $\bar{K}N$ threshold.

This report summarizes results of the first lattice QCD calculation of coupled-channel πΣ − K¯N scattering in the Λ(1405) region. This study was carried out using a single CLS ensemble with a heavier-than-physical pion mass mπ ≈ 200 MeV and a lighter-than-physical kaon mass mK ≈ 487 MeV. Once the finite-volume energy spectrum has been reliably extracted, the Lüscher method was employed to obtain scattering amplitudes. Through a variety of parametrizations of the two-channel K-matrix, the final results show a virtual bound state below the πΣ threshold and a resonance right below K¯N.

This letter presents the first lattice QCD computation of the coupled channel $\pi\Sigma-\bar{K}N$ scattering amplitudes at energies near $1405\,{\rm MeV}$. These amplitudes contain the resonance $\Lambda(1405)$ with strangeness $S=-1$ and isospin, spin, and parity quantum numbers $I(J^P)=0(1/2^-)$. However, whether there is a single resonance or two nearby resonance poles in this region is controversial theoretically and experimentally. Using single-baryon and meson-baryon operators to extract the finite-volume stationary-state energies to obtain the scattering amplitudes at slightly unphysical quark masses corresponding to $m_\pi\approx200$ MeV and $m_K\approx487$ MeV, this study finds the amplitudes exhibit a virtual bound state below the $\pi\Sigma$ threshold in addition to the established resonance pole just below the $\bar{K}N$ threshold. Several parametrizations of the two-channel $K$-matrix are employed to fit the lattice QCD results, all of which support the two-pole picture suggested by $SU(3)$ chiral symmetry and unitarity.

A lattice QCD computation of the coupled channel $\pi\Sigma-\bar{K}N$ scattering amplitudes in the $\Lambda(1405)$ region is detailed. Results are obtained using a single ensemble of gauge field configurations with $N_{\rm f} = 2+1$ dynamical quark flavors and $m_{\pi} \approx 200$ MeV and $m_K\approx487$ MeV. Hermitian correlation matrices using both single baryon and meson-baryon interpolating operators for a variety of different total momenta and irreducible representations are used. Several parametrizations of the two-channel scattering $K$-matrix are utilized to obtain the scattering amplitudes from the finite-volume spectrum. The amplitudes, continued to the complex energy plane, exhibit a virtual bound state below the $\pi\Sigma$ threshold and a resonance pole just below the $\bar{K}N$ threshold.

In this paper we determine the masses of I(J^P)=0(3/2^+) and 0(3/2^-) Ω-baryon ground states using lattice QCD. We utilise Wilson-clover ensembles with 2+1 dynamical quark flavours generated by the CLS consortium along a trajectory with a constant trace of the quark-mass matrix. We show that N^3LO SU(3)_f chiral perturbation theory expressions describe the ground-state masses with positive-parity well, and we use them to set the lattice scale. Methodologically, our combination of gauge-fixed wall sources and the generalized Pencil of Functions allows for high-precision determinations of the lattice spacing at a relative error of around 0.3% with controlled excited-state contamination. The fit we perform allows for the continuum value of t_0 to vary, thereby determining this quantity with a comparable level of precision to that of the lattice scale. Using the resulting scales our measurement of the negative-parity Ω^3/2^- state is found to be consistent with the recently-discovered Ω(2012)^-, which can therefore be assigned the quantum numbers I(J^P)=0(3/2^-).

A lattice QCD computation of the coupled channel πΣ–K¯N scattering amplitudes in the Λ(1405) region is detailed. Results are obtained using a single ensemble of gauge field configurations with Nf=2+1 dynamical quark flavors and mπ≈200 MeV and mK≈487 MeV. Hermitian correlation matrices using both single baryon and meson-baryon interpolating operators for a variety of different total momenta and irreducible representations are used. Several parametrizations of the two-channel scattering K-matrix are utilized to obtain the scattering amplitudes from the finite-volume spectrum. The amplitudes, continued to the complex energy plane, exhibit a virtual bound state below the πΣ threshold and a resonance pole just below the K¯N threshold.4 MoreReceived 28 July 2023Accepted 16 November 2023DOI:https://doi.org/10.1103/PhysRevD.109.014511Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLattice QCDQuantum chromodynamicsScattering amplitudesPhysical SystemsBaryonsParticles & FieldsNuclear Physics

This report summarizes results of the first lattice QCD calculation of coupled-channel pi Sigma - (K) over barN scattering in the Lambda(1405) region. This study was carried out using a single CLS ensemble with a heavier-than-physical pion mass m(pi) approximate to 200 MeV and a lighter-than-physical kaon mass m(K) approximate to 487 MeV. Once the finite-volume energy spectrum has been reliably extracted, the Luscher method was employed to obtain scattering amplitudes. Through a variety of parametrizations of the two-channel K-matrix, the final results show a virtual bound state below the pi Sigma threshold and a resonance right below (K) over barN.

Recent results studying the masses and widths of low-lying baryon resonances in lattice QCD are presented. The $S$-wave $N\pi$ scattering lengths for both total isospins $I = 1/2$ and $I = 3/2$ are inferred from the finite-volume spectrum below the inelastic threshold together with the $I = 3/2$ $P$-wave containing the $\Delta(1232)$ resonance. A lattice QCD computation employing a combined basis of three-quark and meson-baryon interpolating operators with definite momentum to determine the coupled channel $\Sigma\pi$-$N\overline{K}$ scattering amplitude in the $\Lambda(1405)$ region is also presented. Our results support the picture of a two-pole structure suggested by theoretical approaches based on $SU(3)$ chiral symmetry and unitarity.

We present the estimation of the long distance behaviour of the vector-vector correlator computed on a lattice QCD ensemble generated with 2 + 1 flavour physical Wilson clover quarks. The long distance regime of the correlator is dominated by multi-hadronic scattering states. We reconstruct the correlator in this regime using the 𝜋𝜋 scattering states in the 𝐼 = 1 channel. The vector-vector correlator appears in the integrand to estimate the hadronic vacuum polarization contributions to the anomalous magnetic moment of the muon. Therefore, an improved estimation of the correlator will help resolve the tension between (𝑔 − 2)𝜇 experiment and theory.

We use $n_f=2+1$ Wilson-clover gauge-field ensembles from the CLS consortium in a Lattice NRQCD setup to predict the binding energy of a $I(J^P)=0(1^+)$ $ud\bar{b}\bar{b}$ tetraquark and a $\frac{1}{2}(1^+)$ $\ell s\bar{b}\bar{b}$ tetraquark. We determine the binding energies with respect to the relevant $BB^*$ and $B_sB^*$ thresholds respectively to be $112.0(13.2)$ MeV for the $ud\bar{b}\bar{b}$, and $46.4(12.3)$ MeV for the $\ell s\bar{b}\bar{b}$. We also determine the ground-state $J^P=0^+$ $B_{s0}^*$ and $1^+$ $B_{s1}$ mesons to lie $75.4(14.0)$ and $78.7(13.9)$ MeV below the $BK$ and $B^*K$ thresholds respectively. Our errors are entirely dominated by systematics due to discretisation effects. To achieve these measurements, we performed a neural network based nonperturbative tuning of the Lattice NRQCD Hamiltonian's parameters against the basic bottomonium spectrum. For all lattice spacings considered we can reproduce the continuum splittings of low-lying bottomonia. It is worth remarking that our nonperturbative tuning parameters deviate from 1 by significant amounts, particularly the term $c_2$.

We use n(f) = 2 + 1 Wilson-clover gauge-field ensembles from the Coordinated Lattice Simulations (CLS) Consortium in a lattice nonrelativistic QCD (NRQCD) setup to predict the binding energy of an I(J(P)) = 0(1(+)) ud (bb) over bar tetraquark and a 1/2 (1(+))ls (bb) over bar tetraquark. We determine the binding energies with respect to the relevant BB* and BsB* thresholds, respectively, to be 112.0(13.2) MeV for the ud (bb) over bar, and 46.4(12.3) MeV for the ls (bb) over bar. We also determine the ground-state J(P) = 0(+) B-s0* and 1(+) B-s1 mesons to lie 75.4(14.0) and 78.7(13.9) MeV below the BK and B*K thresholds, respectively. Our errors are entirely dominated by systematics due to discretization effects. To achieve these measurements, we performed a neural network based nonperturbative tuning of the lattice NRQCD Hamiltonian's parameters against the basic bottomonium spectrum. For all lattice spacings considered we can reproduce the continuum splittings of low-lying bottomonia. It is worth remarking that our nonperturbative tuning parameters deviate from 1 by significant amounts, particularly the term c(2).

We report progress on finite-volume determinations of heavylight-meson – Goldstone boson scattering phase shifts using the Luescher method on CLS 2+1 flavor gauge field ensembles. In a first iteration we will focus on D-meson – pion scattering in the elastic scattering region at various pion masses using ensembles with three lattice spacings. We employ ensembles on the CLS quark-mass trajectory with a fixed trace of the quark-mass matrix as well as ensembles with a strange-quark mass fixed close to its physical value, which will allow us to study both the light and the strange quark-mass dependence of positive parity heavy-light hadrons close to threshold.

We use $n_f=2+1$ Wilson-clover gauge-field ensembles from the CLS consortium in a Lattice NRQCD setup to predict the binding energy of a $I(J^P)=0(1^+)$ $ud\bar{b}\bar{b}$ tetraquark and a $\frac{1}{2}(1^+)$ $\ell s\bar{b}\bar{b}$ tetraquark. We determine the binding energies with respect to the relevant $BB^*$ and $B_sB^*$ thresholds respectively to be $112.0(13.2)$ MeV for the $ud\bar{b}\bar{b}$, and $46.4(12.3)$ MeV for the $\ell s\bar{b}\bar{b}$. We also determine the ground-state $J^P=0^+$ $B_{s0}^*$ and $1^+$ $B_{s1}$ mesons to lie $75.4(14.0)$ and $78.7(13.9)$ MeV below the $BK$ and $B^*K$ thresholds respectively. Our errors are entirely dominated by systematics due to discretisation effects. To achieve these measurements, we performed a neural network based nonperturbative tuning of the Lattice NRQCD Hamiltonian's parameters against the basic bottomonium spectrum. For all lattice spacings considered we can reproduce the continuum splittings of low-lying bottomonia. It is worth remarking that our nonperturbative tuning parameters deviate from 1 by significant amounts, particularly the term $c_2$.

Following the publication of the new measurement of the anomalous magnetic moment of the muon, the discrepancy between experiment and the theory prediction from the g-2 theory initiative has increased to 4.2 σ. Recent lattice QCD calculations predict values for the hadronic vacuum polarization contribution that are larger than the data-driven estimates, bringing the Standard Model prediction closer to the experimental measurement. Euclidean time windows in the time-momentum representation of the hadronic vacuum polarization contribution to the muon g-2 can help clarify the discrepancy between the phenomenological and lattice predictions. We present our calculation of the intermediate distance window contribution using N_f=2+1 flavors of O(a) improved Wilson quarks. We employ ensembles at six lattice spacings below 0.1fm and pion masses down to the physical value. We present a detailed study of the continuum limit, using two discretizations of the vector current and two independent sets of improvement coefficients. Our result at the physical point displays a tension of 3.9 σ with a recent evaluation of the intermediate window based on the data-driven method.

We present a fully non-perturbative determination of a relativistic heavy quark action's parameters on the CLS = 2 + 1 Wilson-clover ensembles using neural networks.We then further illustrate the applicability of such an approach for lattice NRQCD bottom quarks, and finally investigate some physics quantities under our tuning.In particular, we look at the excited spectrum of bottomonia, a popular b b tetraquark candidate, and the not-yet observed bottom-strange cousins of the exotic = 0 + * 0 (2317) and = 1 + 1 (2460) mesons.

We present a preliminary analysis of I = 1 $\pi$ $\pi$ scattering at the physical point. We make use of the stochastic variant of the distillation framework (also known as sLapH) to compute the relevant two-point correlation matrices using a basis of single and multihadron interpolating operators to estimate the low energy spectra. We perform the Lüscher analysis to determine the scattering phase shift which is finding good agreement with the experimentally obtained phase shifts.

Progress in computing various meson-baryon scattering amplitudes is presented on a single ensemble from the Coordinated Lattice Simulations (CLS) consortium with $m_\pi=200$ MeV and $N_f=2+1$ dynamical fermions. The finite-volume L\"uscher approach is employed to determine the lowest few partial waves from ground- and excited-state energies computed from correlation matrices rotated in a single pivot using a generalized eigenvector solution. This analysis requires evaluating matrices of correlation functions between single- and two-hadron interpolating operators which are projected onto definite spatial momenta and finite-volume irreducible representations. The stochastic LapH method is used to estimate all needed quark propagators. Preliminary results are presented for $I=\frac{1}{2}, \frac{3}{2}$ $N\pi$ amplitudes including the $\Delta(1232)$ resonance and the $I=0$ $S$-wave amplitude with unit strangeness relevant for the $\Lambda(1405)$.