Wed·Sep 29, 2021Wednesday·September 29, 2021

1. 01*

   Finite temperature and delta-regime in the 2-flavor Schwinger model

   Ivan Hip🇭🇷 · Jaime Fabián Nieto Castellanos🇲🇽 · Wolfgang Bietenholz🇲🇽

   The Schwinger model is often used as a testbed for conceptual and numerical approaches in lattice field theory. Still, some of its rich physical properties in anisotropic volumes have not yet been explored. For the multi-flavor finite temperature Schwinger model there is an approximate solution by Hosotani et al. based on bosonization. We perform lattice simulations and check the validity of this approximation in the case of two flavors. Next we exchange the rôle of the coordinates to enter the $\delta$-regime, and measure the dependence of the residual "pion" mass on the spatial size, at zero temperature. Our results show that universal features, which were derived by Leutwyler, Hasenfratz and Niedermayer referring to quasi-spontaneous symmetry breaking in $d>2$, extend even to $d=2$. This enables the computation of the Schwinger model counterpart of the pion decay constant $F_{\pi }$. It is consistent with an earlier determination by Harada et al. who considered the divergence of the axial current in a light-cone formulation, and with analytical results that we conjecture from 2d versions of the Witten--Veneziano formula and the Gell-Mann--Oakes--Renner relation, which suggest $F_{\pi }=1/\sqrt{2\pi }$.

   hep-latPoS(2022)·3 citations
2. 02*

   Consistent approach to study gluon quasi-particles

   Chowdhury Aminul Islam🇨🇳 · Munshi G. Mustafa🇮🇳 · Rajarshi Ray🇮🇳 · Pracheta Singha🇮🇳

   We discuss a novel approach to estimate the partition function in effective model frameworks when the effective potentials have multiple extrema, so that ascertaining a mean field becomes difficult. Using this approach we present a consistent model to study the thermodynamic properties of gluon quasi-particles as a function of temperature, both in the color confined and the color deconfined phases.

   ↳ hep-phhep-latnucl-thPRD(2022)·7 citations
3. 03*

   Scaled Affine Quantization of Ultralocal ${\phi }_2^4$ a comparative Path Integral Monte Carlo study with Canonical Quantization

   Riccardo Fantoni🇮🇹 · John R. Klauder🇺🇸

   After the success of affine quantization in proving through Monte Carlo analysis that the covariant euclidean scalar field theory, ${\phi }_n^r$, where $r$ denotes the power of the interaction term and $n=s+1$ with $s$ the spatial dimension and $1$ adds imaginary time, such that $r\ge 2n/(n-2)$ can be acceptably quantized and the resulting theory is nontrivial, unlike what happens using canonical quantization, we show here that the same has to be expected for $r>2$ and any $n$ even for the ultralocal field theory. In particular we consider the ultralocal ${\phi }_2^4$ model and study its renormalized properties for both the scaled canonical quantization version and the scaled affine quantization version through path integral Monte Carlo.

   ↳ hep-thhep-latmath-phmath.MP+1PRD(2022)·8 citations
4. 04*

   Next-to-Leading-Order QCD Matching for $\Delta F=2$ Processes in Scalar Leptoquark Models

   Andreas Crivellin🇨🇭 · Jordi Folch Eguren🇪🇸 · Javier Virto🇪🇸

   Leptoquarks provide viable solutions to the flavour anomalies, i.e. they can explain the tensions between the measurements and the Standard Model predictions of the anomalous magnetic moment of the muon as well as $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to c\tau \nu$ processes. However, leptoquarks also contribute to other flavour observables, such as $\Delta F=2$ processes, at the loop-level. In particular, $B_s-{\bar{B}}_s$ mixing provides a crucial bound in setups addressing $b\to c\tau \nu$ data, often excluding a big portion of the parameter space that could otherwise account for it. In this article, we first derive the complete leading order matching, including all five scalar LQ representations, for $D^0-{\bar{D}}^0$, $K^0-{\bar{K}}^0$ and $B_{s,d}-{\bar{B}}_{s,d}$ mixing (at the dimension-six level). We then calculate the next-to-leading order ${\alpha }_s$ matching corrections to these $\Delta F=2$ processes in generic scalar leptoquark models. We find that the two-loop corrections increase the effects in $\Delta F=2$ processes by $\sim 5$-$10\%$ and significantly reduce the matching scale uncertainty.

   ↳ hep-phhep-exhep-latJHEP(2022)·11 citations
5. 05*

   A ChPT estimate of the strong-isospin-breaking contribution to the anomalous magnetic moment of the muon

   Christopher L. James🇨🇦 · Randy Lewis🇨🇦 · Kim Maltman🇨🇦

   First-principles lattice determinations of the Standard Model expectation for the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon have become sufficiently precise that further improvement requires including strong and electromagnetic isospin-breaking effects. We provide a continuum estimate of the strong isospin-breaking contribution, $a_{\mu }^{SIB}$, using $SU(3)$ chiral perturbation theory. The result is shown to be dominated by resonance-region contributions encoded in a single low-energy constant whose value is known from flavor-breaking hadronic $\tau$ decay sum rules. Implications of the form of the result for lattice determinations of $a_{\mu }^{SIB}$ are also discussed.

   ↳ hep-phhep-latPRD(2022)·17 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.