HEP Lattice·hep-lat

Thu·Oct 15, 2026Thursday·October 15, 2026

5 papers—1 primary·4 cross-listed

01
Excited-State Effects in Nucleon Sigma Terms from a Variational Analysis
Constantia Alexandrou · Giannis Koutsou · Yan Li · Srijit Paul · Ferenc Pittler
We investigate excited-state effects in nucleon sigma-terms in lattice QCD using twisted-mass clover-improved fermion ensembles. We study correlation functions with nucleon and multihadron nucleon- $σ$ -meson interpolating operators. The analysis is performed using three gauge ensembles, including one ensemble simulated with two degenerate light, a strange, and a charm quark with quark masses tuned to approximately their physical value. We solve the generalized eigenvalue problem that arises from the matrix of correlators and show that the three-point function for the light sigma-term obtained using the optimal linear combination of interpolating operators has substantially reduced time dependence without loss of statistical precision. We apply Laplace filtering and investigate residual excited-state contributions in the extraction of $σ_{π N}$ . Using the same optimal linear combination of correlators as for $σ_{π N}$ for the strange sigma-term we also observe suppressed excited state contributions over an extended range of source--sink time separations. For the charm sigma-term, we observe negligible time dependence within the large statistical uncertainties, and these improvements show no significant effect.
hep-lathep-phnucl-th
02
Born-Oppenheimer chiral effective field theory and its application to $X_{b}$
Yu Zhang · Feng-Kun Guo · Christoph Hanhart · Alexey Nefediev · Paul Pütz
Following the discovery of the exotic state $X (3872)$ in the charmonium spectrum, the possible existence of an analogous state, $X_{b}$ , in the bottomonium sector has attracted considerable attention of the hadronic physics community. In this work, we lay the ground for the development of Born-Oppenheimer chiral effective field theory (BO $χ$ EFT), that allows us to include both quark and hadron degrees of freedom as well as the full complexity of the meson-exchange potential in a systematic way. For illustration, the formalism to leading order (LO) is applied to the system of $χ_{b 1}$ states and in particular the $X_{b}$ . The two parameters that are present at this order are constrained using experimental information on the bottomonium spectrum together with lattice input on static quark-antiquark potentials, including string breaking effects. The framework identifies the observed $1^{++}$ state at 10.513 GeV with a predominantly molecular $X_{b}$ , the bottom counterpart of the $X (3872)$ , and predicts an additional predominantly compact bottomonium state at 10.544 GeV, about 60 MeV below the $B B ˉ^{*}$ threshold.
↳ hep-phhep-exhep-lat
03
A Nontrivial Lattice Scalar Quantum Field Model
P.A. Faria da Veiga · R. Mistry · M. O'Carroll
We introduce a new Euclidean quantum model with zero-spin scaled scalar fields on a spacetime hypercubic lattice, which we refer to as the hybrid model. The model coupling parameters are the hopping parameter $κ^{2} > 0$ and the field interaction coupling $α > 0$ . Using the technique of lattice scaled fields, with a noncanonical scaling that corresponds to a partial renormalization (wave function renormalization), we show that the partition function of this model satisfies both thermodynamic and ultraviolet stability bounds, with constants which are uniform in the lattice volume $Λ_{s}$ and the lattice spacing $a \in (0, 1]$ . As a consequence, the model has a finite free energy per degree of freedom in the thermodynamic limit $Λ_{s} ↗ \infty$ , at least in the subsequential sense. Subsequently, we can also take the ultraviolet or continuum limit $a ↘ 0$ . Besides the finiteness property of the free energy, for sufficiently small values of the model coupling parameters $κ^{2}$ and $α$ , we show the model satisfies Osterwalder-Schrader positivity and construct the underlying physical quantum mechanical Hilbert space, and, using a polymer expansion, we show correlations also remain bounded in the thermodynamic limit. Finally, we perturbatively compute an infinite volume truncated four-point correlation showing it is nonzero. Noting that, for fixed $a$ , perturbation series in $κ^{2}$ and $α$ converges, these results are sufficient to show that our hybrid model makes sense as a lattice quantum field theory in spacetime dimension $d = 3, 4$ , with possible extensions to other higher values of $d$ .
↳ math-phhep-latmath.MP
04
Gauge-invariant nonperturbative Wilson action in quantum electrodynamics II
Sorato Nagao · Hiroshi Suzuki
The gradient flow exact renormalization group (GFERG) is a formulation of the exact renormalization group for gauge theories that provides a renormalization group flow preserving the gauge Ward--Takahashi identity exactly. In this paper, we nonperturbatively solve the GFERG flow equation for the simplest nontrivial gauge-invariant Wilson action, introduced in a previous paper, for $D$ -dimensional quantum electrodynamics with~ $N_{f}$ flavors (for all~ $D$ , flavors are counted in units of four-component spinors). For $D = 3$ and~ $D = 2$ , a nontrivial infrared fixed point exists even for~ $N_{f} = 1$ , and the structure of the critical exponents at the fixed point is qualitatively the same as that in the large- $N_{f}$ limit. We also obtain the gauge-field propagator in the continuum limit; for~ $D = 2$ , it reproduces the dynamical mass of the Schwinger model within a few percent. To the best of our knowledge, apart from the large- $N_{f}$ approximation, this is the first example in which the Wilson renormalization group in a gauge theory is solved nonperturbatively while manifestly preserving gauge symmetry.
↳ hep-thhep-lat
05
Constraining three-nucleon forces in nuclear lattice effective field theory
Serdar Elhatisari · Ulf-G. Meißner · Zhengxue Ren · Shuang Zhang
We study short-range three-nucleon forces (3NFs) in nuclear lattice effective field theory with a chiral two-nucleon interaction at N $^{3}$ LO. The one-pion-exchange ( $c_{D}$ ) and contact ( $c_{E}$ ) terms of the leading 3NF are decomposed into locally and non-locally smeared components and supplemented by partial-wave-resolved pair contacts coupled to the density of a third nucleon. We determine their coefficients from nuclear binding energies for nuclei in the mass range from $A = 3$ to $A = 40$ and neutron--alpha finite-volume energies. This allows to work out the minimal three-nucleon force that can be used for future precision studies in NLEFT.
↳ nucl-thhep-latnucl-ex

Excited-State Effects in Nucleon Sigma Terms from a Variational Analysis

Born-Oppenheimer chiral effective field theory and its application to Xb​

A Nontrivial Lattice Scalar Quantum Field Model

Gauge-invariant nonperturbative Wilson action in quantum electrodynamics II

Constraining three-nucleon forces in nuclear lattice effective field theory

Born-Oppenheimer chiral effective field theory and its application to $X_{b}$