arXiv subjects

Cristiane Y. London

Publications and source records attributed to Cristiane Y. London.

6 recordsLinked to original sources

arXiv2026

Estimate of $Γ(H \to gg)$ at $O(α_s^7)$ from Padé approximants with constraints from large-$n_f$

In this work we estimate the first unknown QCD correction to the decay of the Higgs boson into gluons, $H\to gg$, in the heavy-top limit using Padé approximants built to the perturbative series and to its Borel transform. In the process, we also obtain estimates for the first unknown coefficients of the QCD $β$ function, of the QCD decoupling relation, and of the gluonium correlator. We also provide an updated prediction for the first unknown coefficient of $Γ(H\to b\bar{b})$. We determine the polynomial dependence of the perturbative coefficients on the number of quark flavors, $n_f$. We point out that the large-$n_f$ result for $H\to gg$ can be obtained from results for the gluonium correlator already available in the literature. The coefficient of the highest power of $n_f$ is then imposed as a constraint and is also used as a new test to discard unreliable approximants. The method is validated through the postdiction of the last known coefficient of the series. Our model-independent estimate for the yet unknown coefficient of order $α_s^7$ of $Γ(H\to gg)$ is $-312\pm 15$ (in the $\overline{\mathrm{MS}}$ scheme with $μ=m_H$, where $m_H$ is the Higgs mass). With our estimate the residual renormalization-scale dependence of $Γ(H\to gg)$ is reduced by a factor of almost 1.5.

hep-ph↗

arXiv2024

The role of Padé and D-Log Padé approximants in the context of the MUonE Experiment

In the context of the anomalous magnetic moment of the muon, the hadronic contribution plays a crucial role, especially given its large contribution to the final error. Currently, lattice QCD simulations are in disagreement with dispersive calculations based on $e^+e^-$ hadronic cross sections. The new MUonE experiment intends to shed light on this situation extracting the hadronic contribution to the running of the electromagnetic coupling in the space-like region, $Δα_{\rm had}(t)$, from elastic $eμ$ scattering. Still, due to the limited kinematic range that can be covered by the experiment, a powerful method must be devised to accurately extract the desired hadronic contribution from a new experiment of this type. In this work, we show how Padé and D-Log Padé approximants profiting from the analyticity of the correlator governing the hadronic contribution can be a powerful tool in reaching the required precision.

hep-ph↗

arXiv2024

Model-independent extrapolation of MUonE data with Padé and D-Log approximants

The MUonE experiment is designed to extract the hadronic contribution to the electromagnetic coupling in the space-like region, $Δα_{\rm had}(t)$, from elastic $eμ$ scattering. The leading order hadronic vacuum polarization contribution to the muon $g-2$, $a_μ^{\mathrm{HVP, \,LO}}$, can then be obtained from a weighted integral over $Δα_{\rm had}(t)$. This, however, requires knowledge of $Δα_{\rm had}(t)$ in the whole domain of integration, which cannot be achieved by experiment. In this work, we propose to use Padé and D-Log Padé approximants as a systematic and model-independent method to fit and reliably extrapolate the future MUonE experimental data, extracting $a_μ^{\mathrm{HVP,\,LO}}$ with a conservative but competitive uncertainty, using no, or very limited, external information. The method relies on fundamental analytic properties of the two-point correlator underlying $a_μ^{\mathrm{HVP,\,LO}}$ and provides lower and upper bounds for the result for $a_μ^{\mathrm{HVP,\,LO}}$. We demonstrate the reliability of the method using toy data sets generated from a model for $Δα_{\rm had}(t)$ reflecting the expected statistics of the MUonE experiment.

hep-ph↗

arXiv2023

Probing the singularities of the Landau-gauge gluon and ghost propagators with rational approximants

We employ Padé approximants in the study of the analytic structure of the four-dimensional $SU(2)$ Landau-gauge gluon and ghost propagators in the infrared regime. The approximants, which are model independent, serve as fitting functions for the lattice data. We carefully propagate the uncertainties due to the fitting procedure, taking into account all possible correlations. For the gluon-propagator data, we confirm the presence of a pair of complex poles at $p_{\rm pole}^2 = \left[(-0.37 \,\pm\, 0.05_{\rm stat}\,\pm\, 0.08_{\rm sys}) \pm i\,(0.66\, \pm\, 0.03_{\rm stat}\, \pm\, 0.02_{\rm sys})\right]\, \mathrm{GeV}^2$, where the first error is statistical and the second systematic. The existence of this pair of complex poles, already hinted upon in previous works, is thus put onto a firmer basis, thanks to the model independence and to the careful error propagation of our analysis. For the ghost propagator, the Padés indicate the existence of a single pole at $p^2 = 0$, as expected. In this case, our results also show evidence of a branch cut along the negative real axis of $p^2$. This is corroborated with another type of approximant, the D-Log Padés, which are better suited to studying functions with a branch cut and are applied here for the first time in this context. Due to particular features and limited statistics of the gluon-propagator data, our analysis is inconclusive regarding the presence of a branch cut in the gluon case.

hep-lat↗

arXiv2022

Probing singularities of Landau-gauge propagators with Padé approximants

Padé approximants are employed in order to study the analytic structure of the four-dimensional SU(2) Landau-gauge gluon and ghost propagators in the infrared regime. The approximants, which are model independent, are used as fitting functions to lattice data for the propagators, carefully propagating uncertainties due to the fit procedure and taking into account all possible correlations. Applying this procedure systematically to the gluon-propagator data, we observe the presence of a pair of complex poles at $p^2_{\mathrm{pole}} = (-0.37 \pm 0.05_{\mathrm{stat}} \pm 0.08_{\mathrm{sys}}) \pm \, i\, (0.66 \pm 0.03_{\mathrm{stat}} \pm 0.02_{\mathrm{sys}}) \, \mathrm{GeV}^2$, where ``stat'' represents the statistical error and ``sys'' the systematic one. We also find a zero on the negative real axis of $p^2$, at $p^2_{\mathrm{zero}} = (-2.9 \pm 0.4_{\mathrm{stat}} \pm 0.9_{\mathrm{sys}}) \, \mathrm{GeV}^2$. We thus note that our procedure -- which is based on a model-independent approach and includes careful error propagation -- confirms the presence of a pair of complex poles in the gluon propagator, in agreement with previous works. For the ghost propagator, the Padés indicate the existence of the single pole at $p^2 = 0$, as expected. We also find evidence of a branch cut on the negative real axis. Through the use of the so-called D-Log Padé method, which is designed to approximate functions with cuts, we corroborate the existence of this cut for the ghost propagator.

hep-lat↗

arXiv2022

Higher-order QCD corrections to $H\to b\bar b$ from rational approximants

We use rational approximants to study missing higher orders in the massless scalar-current quark correlator. We predict the yet unknown six-loop coefficient of its imaginary part, related to $Γ(H\to b \bar b)$, to be $c_5=-6900\pm 1400$. With this result, the perturbative series becomes almost insensitive to renormalization scale variations and the intrinsic QCD truncation uncertainty is tiny. This confirms the expectation that higher-order loop computations for this quantity will not be required in the foreseeable future, as the uncertainty in $Γ(H\to b \bar b)$ will remain largely dominated by the Standard Model parameters.

hep-ph↗