Thu·Oct 21, 2021Thursday·October 21, 2021

1. 01*

   Approaching the Chiral and Continuum Limit of Large-N QCD

   Evan Wickenden🇺🇸 · Thomas DeGrand🇺🇸

   We present preliminary results from our calculation of the low energy constants (LECs) of the chiral effective theory for 3, 4 and 5 color QCD with $N_f=2$ dynamical fermion flavors. We simulate with clover fermions over a range of lattice couplings and quark masses. We observe the expected $N_c$ scaling for the LECs appropriate to the condensate $B$ and pseudoscalar decay constant $F$. The range of quark masses over which leading order chiral perturbation theory describes the data grows as $N_c$ rises.

   hep-latPoS(2022)·0 citations
2. 02*

   Improved analysis of nucleon isovector charges and twist-2 matrix elements on CLS $N_f=2+1$ ensembles

   Konstantin Ottnad🇩🇪 · Dalibor Djukanovic🇩🇪 · Tim Harris🇬🇧 · Harvey B. Meyer🇩🇪 · Georg von Hippel🇩🇪 · Hartmut Wittig🇩🇪

   Preliminary results are presented for nucleon isovector charges and twist-2 matrix elements which have been obtained employing an improved analysis strategy to deal with excited-state contamination. The set of CLS $N_f=2+1$ gauge ensembles in this study has been extended compared to our 2018 calculation, including an ensemble at physical quark masses. Besides the addition of new ensembles, the number of gauge configurations and measurements has been increased on several of the existing ensembles and the analysis has been extended to include additional source-sink separations. The ensembles cover a range of the light quark mass corresponding to $M_{\pi }\approx 0.130\mathrm{MeV}\dots 350\mathrm{MeV}$, four values of the lattice spacing $a\approx 0.05\mathrm{fm}\dots 0.09\mathrm{fm}$ and a large range of volumes. Results at the physical point are computed for each observable from a combined chiral, continuum and finite-volume extrapolation.

   hep-latPoS(2022)·7 citations
3. 03*

   Isoscalar electromagnetic form factors of the nucleon in $N_{\mathrm{f}}=2+1$ lattice QCD

   Dalibor Djukanovic🇩🇪 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Konstantin Ottnad🇩🇪 · Miguel Salg🇩🇪 · Jonas Wilhelm🇩🇪 · Hartmut Wittig🇩🇪

   We present results for the isoscalar electromagnetic form factors of the nucleon computed on the Coordinated Lattice Simulations (CLS) ensembles with $N_{\mathrm{f}}=2+1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved conserved vector current. In order to estimate the excited-state contamination, we employ several source-sink separations and apply the summation method. For the computation of the quark-disconnected diagrams, a stochastic estimation based on the one-end trick is performed, in combination with a frequency-splitting technique and the hopping parameter expansion. By these means, we obtain a clear signal for the form factors including the quark-disconnected contributions, which have a statistically significant effect on our results.

   hep-latPoS(2022)·2 citations
4. 04*

   First global QCD analysis of the TMD ${\mathbf{g}}_{1\mathbf{T}}$ from semi-inclusive DIS data

   Shohini Bhattacharya🇺🇸 · Zhong-Bo Kang🇺🇸 · Andreas Metz🇺🇸 · Gregory Penn🇺🇸 · Daniel Pitonyak🇺🇸

   The worm-gear transverse momentum dependent (TMD) function $g_{1T}$ is one of the eight leading-twist TMDs and has the probabilistic interpretation of finding a longitudinally polarized quark inside a transversely polarized hadron. In this work, we present the first simultaneous extraction of $g_{1T}$ from all the available experimental measurements. The study involves the analysis of COMPASS, HERMES, and Jefferson Lab data on semi-inclusive deep-inelastic scattering using Monte Carlo techniques. We also compare $g_{1T}$ obtained from this experimental data with different theoretical approaches, such as the large-$N_c$ approximation, the Wandzura-Wilczek-type approximation, and lattice QCD.

   ↳ hep-phhep-exhep-latPRD(2022)·34 citations
5. 05*

   Axial inverse magnetic catalysis

   Yuanyuan Wang🇨🇳 · Shinya Matsuzaki🇨🇳

   We find that the inverse magnetic catalysis for $U(1)$ axial symmetry (AIMC: axial inverse magnetic catalysis) can emerge around the chiral crossover regime in the thermomagnetic QCD with 2 + 1 flavors at physical point. This phenomenon can be correlated with the IMC for the chiral $SU(2{)}_L\times SU(2{)}_R$ symmetry (CIMC: chiral IMC). We explicitly observe the AIMC based on a Nambu-Jona-Lasinio model with 2 + 1 quark flavors, where introduced anomalous magnetic moments of the quarks play the essential role to drive both the CIMC and AIMC. Our finding is shortly testable on lattices. Possible phenomenological and cosmological implications are also briefly addressed.

   ↳ hep-phhep-latnucl-thPRD(2022)·6 citations
6. 06*

   Two-Fermion Bound and Scattering States in a Finite Volume including QED in P-Wave and Beyond

   Gianluca Stellin🇩🇪

   Introducing a short range force coupling the spinless fermions to one unit of angular momentum in the framework of pionless EFT, we first report the two-body scattering amplitudes with Coulomb corrections, extended to two fermions of opposite charge in refs. [1,2]. Motivated by the growing interest in lattice approaches, we immerse the system into a cubic box with periodic boundary conditions and display the finite-volume corrections to the energy of the lowest bound and unbound $T_1^{-}$ eigenstates. The latter turn out to consist of power law terms proportional to the fine-structure constant. In the calculations, quadratic and higher order contributions in $\alpha$ are discarded, on the grounds that the gapped nature of the momentum operator in the finite-volume environment allows for a perturbative treatment of the QED interactions. An outlook on the extension of the analysis to D-wave short-range interactions is eventually given.

   ↳ nucl-thhep-latPoS(2022)·0 citations
7. 07*

   Lefschetz Thimble Quantum Monte Carlo for Spin Systems

   T. C. Mooney🇺🇸 · Jacob Bringewatt🇺🇸 · Neill C. Warrington🇺🇸 · Lucas T. Brady🇺🇸

   Monte Carlo simulations are useful tools for modeling quantum systems, but in some cases they suffer from a sign problem, leading to an exponential slow down in their convergence to a value. While solving the sign problem is generically NP-hard, many techniques exist for mitigating the sign problem in specific cases; in particular, the technique of deforming the Monte Carlo simulation's plane of integration onto Lefschetz thimbles (complex hypersurfaces of stationary phase) has seen significant success in the context of quantum field theories. We extend this methodology to spin systems by utilizing spin coherent state path integrals to re-express the spin system's partition function in terms of continuous variables. Using some toy systems, we demonstrate its effectiveness at lessening the sign problem in this setting, despite the fact that the initial mapping to spin coherent states introduces its own sign problem. The standard formulation of the spin coherent path integral is known to make use of uncontrolled approximations; despite this, for large spins they are typically considered to yield accurate results, so it is somewhat surprising that our results show significant systematic errors. Therefore, possibly of independent interest, our use of Lefschetz thimbles to overcome the intrinsic sign problem in spin coherent state path integral Monte Carlo enables a novel numerical demonstration of a breakdown in the spin coherent path integral.

   ↳ quant-phhep-latPRB(2022)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.