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Pablo Sanchez-Puertas

Publications and source records attributed to Pablo Sanchez-Puertas.

31 records · Page 2Linked to original sources
arXiv2018

A revision of radiative corrections to double-Dalitz decays

The radiative corrections to double-Dalitz ($P\to\bar{\ell}\ell\bar{\ell'}\ell'$) decays are revisited and completed up to next-to-leading order in QED, finding mild differences with respect to previous studies. These might be relevant for extracting information about the mesons transition form factors, which play an important role in determining the hadronic light-by-light contribution to the anomalous magnetic moment of the muon.

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arXiv2018

A theoretical study of meson transition form factors

In this thesis we discuss a rational and data-based description of the single- and double-virutal transition form factors of the lightest pseudoscalar mesons. We obtain an accurate description of these in the spacelike and low-energy timelike regions. The phenomenological applications are wide. Among them, we discuss, the eta-eta' mixing, the rare pseudoscalar decays into a lepton pair and the pseudoscalar-pole contribution to the hadronic light-by-light part of the anomalous magnetic moment of the muon. In all these cases we discuss and illustrate the relevance of employing a data-based approach in order not to incur in potential systematic errors.

hep-ph↗
arXiv2018

Insisting on the role of experimental data: the pseudoscalar-pole piece to the $(g_μ-2)$ and the $|V_{ub}|$ from $B \to π\ell ν_{\ell}$ differential branching ratio

We employ a mathematical framework based on rational approximants in order to calculate meson form factors. The method profits from unitary, is systematic and data based, and is able to ascribe a systematic uncertainty which provides for the desired model independence. Two examples are discussed: the transition form factor entering the pseudoscalar-pole piece of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon, and the $B \to π$ form factor participating the $B\toπ\ellν_{\ell}$ differential branching ratios which allows to determine the $|V_{ub}|$ CKM parameter.

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arXiv2017

Pseudoscalar-pole contribution to the $(g_μ-2)$: a rational approach

We employ a mathematical framework based on rational approximants in order to calculate the pseudoscalar-pole piece of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon, $a_μ^{\textrm{HLbL};P}$. The method is systematic and data based, profiting from over 13 different collaborations, and able to ascribe, for the first time, a systematic uncertainty which provides for the model independence. As a result, we obtain $a_μ^{\textrm{HLbL};P}=94.3(5.3) \times10^{-11}$, which uncertainty is well below the one foreseen at future experiments measuring the $(g_μ-2)$.

hep-ph↗
arXiv2016

$η$ and $η'$ decays into lepton pairs

In this work, we calculate the branching ratios for the $η(η')\rightarrow\bar{\ell}\ell$ decays, where $\ell = e,μ$. These processes have tiny rates in the standard model due to spin flip, loop, and electromagnetic suppression, for what they could be sensitive to New Physics effects. In order to provide a reliable input for the Standard Model, we exploit the general analytical properties of the amplitude. For that purpose, we invoke the machinery of Canterbury approximants, which provides a systematic description of the underlying hadronic physics in a data-driven fashion. Given the current experimental discrepancies, we discuss in detail the role of the resonant region and comment on the reliability of $χ$PT calculations. Finally, we discuss the kind of new physics which we think would be relevant to account for them.

hep-ph↗
arXiv2016

Updated pseudoscalar contributions to the hadronic light-by-light of the muon (g-2)

In this work, we present our recent results on a new and alternative data-driven determination for the hadronic light-by-light pseudoscalar-pole contribution to the muon $(g-2)$. Our approach is based on Canterbury approximants, a rational approach to describe the required transition form factors, which provides a systematic and model-independent framework beyond traditional large-$N_c$ approaches. As a result, we obtain a competitive determination with errors according to future $(g-2)$ experiments including, for the first time, a well-defined systematic uncertainty.

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arXiv2016

The $η^\prime$ transition form factor from space- and time-like experimental data

The $η^\prime$ transition form factor is reanalyzed in view of the recent BESIII first observation of the Dalitz decay $η^\prime\toγe^+e^-$ in both space- and time-like regions at low and intermediate energies using the Padé approximants method. The present analysis provides a suitable parameterization for reproducing the measured form factor in the whole energy region and allows to extract the corresponding low-energy parameters together with a prediction of its values at the origin, related to $Γ_{η^\prime\toγγ}$, and the asymptotic limit. The $η$-$η^\prime$ mixing is reassessed within a mixing scheme compatible with the large-$N_c$ chiral perturbation theory at next-to-leading order, with particular attention to the OZI-rule--violating parameters. The $J/ψ$, $Z\toη^{(\prime)}γ$ decays are also considered and predictions reported.

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arXiv2016

Phenomenology of bivariate approximants: the pi0 to e+e- case and its impact on the electron and muon g-2

The current 3$σ$ discrepancy between experiment and Standard Model predictions for $π^0 \to e^+e^-$ is reconsidered using the Padé Theory for bivariate functions, the Canterbury approximants. This method provides a model-independent data-driven approximation to the decay as soon as experimental data for the doubly virtual $π^0$ transition form factor are available. It also implements the correct QCD constraints of the form factor both at low- and high-energies. We reassess the Standard Model result including, for the first time, a systematic error. Our result, BR$(π^0 \to e^+e^-)=6.23(5)\times 10^{-8}$, still represents a discrepancy larger than $2σ$, unsurmountable with our present knowledge of the Standard Model, and would claim New Physics if the experimental result is confirmed by a new measurement. Our method also provides the adequate tool to extract the doubly virtual form factor from experimental data in a straightforward manner. This measurement would further shrink our error and establish once and for all the New Physics nature of the discrepancy. In addition, we remark the challenge this discrepancy poses in the evaluation of the hadronic light-by-light scattering contribution to the $(g-2)_μ$, specially confronted with the foreseen accuracy of the forthcoming $(g-2)_μ$ experiments.

hep-ph↗
arXiv2015

Pseudoscalar transition form factors: $(g-2)$ of the muon, pseudoscalar decays into lepton pairs, and the $η-η'$ mixing

We present our model-independent and data-driven method to describe pseudoscalar meson transition form factors in the space- and (low-energy) time-like regions. The method is general and conforms a toolkit applicable to any other form factor, of one and two variables, with the potential to include both high- and low-energy QCD constraints altogether. The method makes use of analyticity and unitary properties of form factors, it is simple, systematic and can be improved upon by including new data. In the present discussion, the method is used to show the impact of experimental data for precision calculations in the low-energy sector of the Standard Model. In particular, due to its relevance for New Physics searches, we have considered the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon (the pseudoscalar exchange contribution), the pseudoscalar decays into lepton pairs, and the determination of the mixing parameters of the $η$ and $η'$ system. For all of them we provide the most updated results in a data-driven manner.

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arXiv2015

Pseudoscalar decays into lepton pairs from rational approximants

The pseudoscalar decays into lepton pairs $P\rightarrow\overline{\ell}\ell$ are analyzed with the machinery of Canterbury approximants, an extension of Padé approximants to bivariate functions. This framework provides an ideal model-independent approach to implement all our knowledge of the pseudoscalar transition form factors driving these decays, can be used for data analysis, and allows to include experimental data and theoretical constraints in an easy way, and determine a systematic error. We find that previous theoretical estimates for these branching ratios have underestimated their theoretical uncertainties. From our updated results, the existing experimental discrepancies for $π^0\rightarrow e^+e^-$ and $η\rightarrow μ^+μ^-$ channels cannot be explained unless the doubly-virtual transition form factors behavior -not yet measured- are out of theoretical expectations, which is an interesting result both for anomalous magnetic moments of leptons, and for physics beyond the standard model.

hep-ph↗
arXiv2015

Pseudoscalar-exchange contribution to $(g-2)_μ$ from rational approximants

We present our recent results on the hadronic light-by-light pseudoscalar-exchange contribution to the anomalous magnetic moment of the muon using rational approximants. Our work provides a generalization of Padé approximants to the bivariate case to describe the most general doubly-virtual transition form factor, which is required in the calculation. This method provides a powerful tool to systematically implement the known experimental data on transition form factors in the space-like region and low energies in a model-independent way. Given the lack of experimental data on the doubly-virtual transition form factor, we make use of the pseduoscalar decays into lepton pairs. We find an interesting and puzzling situation which calls for new experimental measurements to clarify the present state.

hep-ph↗
arXiv2014

$η$ and $η'$ transition form factors from Padé approximants

We employ a systematic and model-independent method to extract, from space- and time-like data, the $η$ and $η'$ transition form factors (TFFs) obtaining the most precise determination for their low-energy parameters and discuss the $Γ_{η\rightarrowγγ}$ impact on them. Using TFF data alone, we also extract the $η-η'$ mixing parameters, which are compatible to those obtained from more sophisticated and input-demanding procedures.

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