Fri·Dec 17, 2021Friday·December 17, 2021

1. 01*

   Status on Lattice Calculations of the Proton Spin Decomposition

   Keh-Fei Liu🇺🇸

   Lattice calculations of the proton spin components is reviewed. The lattice results of the quark spin from the axial-vector current matrix element at $\sim 0.3-0.4$ is smaller than those from the constituent quark models. This is largely due to the fact that the vacuum polarization contribution from the disconnected insertion is negative. Its connection with the anomalous Ward identity is clarified and verified numerically. This resolves the contentious issue in the `proton spin crisis'. The glue spin and angular momentum are found to be large and there is notable contribution from the quark orbital angular momentum. Renormalization, mixing and normalization of the quark and glue angular momenta are discussed. With sufficient precision, they can be compared with more precise experimental measurements when the electron-ion collider facility is available.

   hep-lathep-phAAPPS Bull.(2022)·23 citations
2. 02*

   The spectrum of qubitized QCD: glueballs in a $S(1080)$ gauge theory

   Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Ruairí Brett🇺🇸 · Henry Lamm🇺🇸

   Quantum simulations of QCD require digitization of the infinite-dimensional gluon field. Schemes for doing this with the minimum amount of qubits are desirable. We present a practical digitization for $SU(3)$ gauge theories via its discrete subgroup $S(1080)$. Using a modified action that allows classical simulations down to $a\approx 0.08$ fm, the low-lying glueball spectrum is computed with percent-level precision at multiple lattice spacings and shown to extrapolate to the continuum limit $SU(3)$ results. This suggests that this digitization scheme is sufficient for precision quantum simulations of QCD.

   hep-lathep-phquant-phPRD(2022)·55 citations
3. 03*

   The QCD Deconfinement Critical Point for $N_{\text{f}}=2$ Flavors of Staggered Fermions

   Reinhold Kaiser🇩🇪 · Owe Philipsen🇩🇪 · Alessandro Sciarra🇩🇪

   Quenched QCD at zero baryonic chemical potential undergoes a first-order deconfinement phase transition at a critical temperature $T_c$, which is related to the spontaneous breaking of the global center symmetry. Including heavy, dynamical quarks breaks the center symmetry explicitly and weakens the first-order phase transition. For decreasing quark masses the first-order phase transition turns into a smooth crossover at a $Z_2$-critical point. The critical quark mass corresponding to this point has been examined with $N_{\text{f}}=2$ Wilson fermions for several $N_{\tau }$ in a recent study within our group. For comparison, we also locate the critical point with $N_{\text{f}}=2$ staggered fermions on $N_{\tau }=8$ lattices. For this purpose we perform Monte Carlo simulations for several quark mass values and various aspect ratios in order to extrapolate to the thermodynamic limit. The critical mass is obtained by fitting to a finite size scaling formula of the kurtosis of the Polyakov loop. Our results indicate large discretization effects, requiring simulations on lattices with $N_{\tau }>8$.

   hep-latPoS(2022)·3 citations
4. 04*

   Hadron spin structure from lattice QCD

   Constantia Alexandrou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾

   We present results on the spin carried by quarks and gluons in the nucleon using lattice QCD simulations with physical values of the light, strange and charm quark masses. We also discuss selective results on the x-dependence of parton distribution functions computed in lattice QCD employing the quasi-parton distribution approach and the large momentum effective theory.

   hep-lathep-phnucl-th1 citation
5. 05*

   A variance reduction technique for hadronic correlators with partially twisted boundary conditions

   Nils Asmussen🇬🇧 · Alessandro Barone🇬🇧 · Andreas Jüttner🇬🇧

   Partially twisted boundary conditions are widely used for improving the momentum resolution in lattice computations of hadronic correlation functions. The method is however expensive since every additional twist requires computing additional propagators. We propose a novel variance reduction technique that exploits statistical correlations to reduce the overall cost for computing correlators with additional twist angles. We explain and demonstrate the method for meson 2pt and 3pt functions.

   hep-latPoS(2022)·0 citations
6. 06*

   Thermal interquark potentials for bottomonium using NRQCD from the HAL QCD method

   Thomas Spriggs🇬🇧 · Chris Allton🇬🇧 · Timothy Burns🇬🇧 · Seyong Kim🇰🇷

   We report our preliminary progress in the calculation of the interquark potential of bottomonium at non-zero temperature using the HAL QCD method. We use NRQCD correlation functions of non-local mesonic S-wave states to obtain the central potential as a function of temperature. These results have been obtained using our anisotropic 2+1 flavour "Generation 2" FASTSUM ensembles.

   hep-latPoS(2022)·4 citations
7. 07*

   New puzzle in charmonium decays

   Hongpeng Wang🇨🇳 · Chang-Zheng Yuan🇨🇳

   By analyzing existing data on pseudoscalar charmonium decays, we obtain the ratio of the branching fractions of ${\eta }_c(2S)$ and ${\eta }_c$ decays into ten different final states with light hadrons. For the first time, we test the two existing theoretical predictions of these decays, and find that the experimental data are significantly different from both of them. The lack of observation of any decay mode with higher rate in ${\eta }_c(2S)$ than in ${\eta }_c$ decays suggests very unusual decay dynamics in pseudoscalar charmonium decays to be identified. We also report the first model-independent evaluation of the partial width of ${\eta }_c(2S)\to \gamma \gamma$ ($2.21_{-0.64}^{+0.88}$ keV) and improved determination of that of ${\eta }_c\to \gamma \gamma$ ($5.43_{-0.38}^{+0.41}$ keV). The latter shows a tension with the most recent lattice QCD calculation.

   ↳ hep-phhep-exhep-latCPC(2022)·18 citations
8. 08*

   Hamiltonian Truncation with Larger Dimensions

   Joan Elias Miro🇮🇹 · James Ingoldby🇮🇹

   Hamiltonian Truncation (HT) is a numerical approach for calculating observables in a Quantum Field Theory non-perturbatively. This approach can be applied to theories constructed by deforming a conformal field theory with a relevant operator of scaling dimension $\Delta$. UV divergences arise when $\Delta$ is larger than half of the spacetime dimension $d$. These divergences can be regulated by HT or by using a more conventional local regulator. In this work we show that extra UV divergences appear when using HT rather than a local regulator for $\Delta \ge d/2+1/4$, revealing a striking breakdown of locality. Our claim is based on the analysis of conformal perturbation theory up to fourth order. As an example we compute the Casimir energy of $d=2$ Minimal Models perturbed by operators whose dimensions take values on either side of the threshold $d/2+1/4$.

   ↳ hep-thcond-mat.stat-mechhep-lathep-phJHEP(2022)·13 citations
9. 09*

   Preparation of the SU(3) Lattice Yang-Mills Vacuum with Variational Quantum Methods

   Anthony N Ciavarella🇺🇸 · Ivan A Chernyshev🇺🇸

   Studying QCD and other gauge theories on quantum hardware requires the preparation of physically interesting states. The Variational Quantum Eigensolver (VQE) provides a way of performing vacuum state preparation on quantum hardware. In this work, VQE is applied to pure SU(3) lattice Yang-Mills on a single plaquette and one dimensional plaquette chains. Bayesian optimization and gradient descent were investigated for performing the classical optimization. Ansatz states for plaquette chains are constructed in a scalable manner from smaller systems using domain decomposition and a stitching procedure analogous to the Density Matrix Renormalization Group (DMRG). Small examples are performed on IBM's superconducting Manila processor.

   ↳ quant-phhep-lathep-phnucl-thPRD(2022)·120 citations
10. 10*

    The muon g-2 anomaly confronts new physics in $e^{\pm }$ and ${\mu }^{\pm }$ final states scattering

    Luc Darmé🇫🇷 · Giovanni Grilli di Cortona🇮🇹 · Enrico Nardi🇮🇹

    The 4.2$\sigma$ discrepancy between the standard model prediction for the muon anomalous magnetic moment $a_{\mu }$ and the experimental result is accompanied by other anomalies. A crucial input for the prediction is the hadronic vacuum polarization $a_{\mu }^{\mathrm{HVP}}$ inferred from ${\sigma }_{\mathrm{had}}=\sigma (e^{+}{e}^{-}\to$hadrons) data. However, the two most accurate determinations of ${\sigma }_{\mathrm{had}}$ from KLOE and BaBar disagree by almost 3$\sigma$. Additionally, the combined data-driven result disagrees with the most precise lattice determination of $a_{\mu }^{\mathrm{HVP}}$ by $2.1\sigma$. We show that all these discrepancies could be accounted for by a new boson produced resonantly around the KLOE centre of mass energy and decaying promptly yielding $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ pairs in the final states. This gives rise to three different effects: (i) the additional $e^{+}{e}^{-}$ events will affect the KLOE luminosity determination based on measurements of the Bhabha cross section, and in turn the inferred value of ${\sigma }_{\mathrm{had}}$; (ii) the additional ${\mu }^{+}{\mu }^{-}$ events will affect the determination of ${\sigma }_{\mathrm{had}}$ via the (luminosity independent) measurement of the ratio of ${\pi }^{+}{\pi }^{-}\gamma$ versus ${\mu }^{+}{\mu }^{-}\gamma$ events; (iii) loops involving the new boson would contribute directly to the prediction for $a_{\mu }$. We discuss in detail this possibility, and we present a simple model that can reconcile the KLOE and BaBar results for ${\sigma }_{\mathrm{had}}$, the data-driven and the lattice determinations of $a_{\mu }^{\mathrm{HVP}}$, the predicted and measured values of $a_{\mu }$, while complying with all phenomenological constraints.

    ↳ hep-phhep-exhep-latJHEP(2022)·22 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.