IRIDE: Interdisciplinary research infrastructure based on dual electron linacs and lasers

This paper describes the scientific aims and potentials as well as the preliminary technical design of RUDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity "particles factory", based on a combination of high duty cycle radio-frequency superconducting electron linacs and of high energy lasers. Conceived to provide unique research possibilities for particle physics, for condensed matter physics, chemistry and material science, for structural biology and industrial applications, IRIDE will open completely new research possibilities and advance our knowledge in many branches of sci…

Charm quark mass with calibrated uncertainty

We determine the charm quark mass ${\hat m}_c({\hat m}_c)$ from QCD sum rules of moments of the vector current correlator calculated in perturbative QCD. Only experimental data for the charm resonances below the continuum threshold are needed in our approach, while the continuum contribution is determined by requiring self-consistency between various sum rules, including the one for the zeroth moment. Existing data from the continuum region can then be used to bound the theoretical error. Our result is ${\hat m}_c({\hat m}_c) = 1272 \pm 8$ MeV for $\hat\alpha_s(M_Z) = 0.1182$. Special attention is given to the question how to quantify and justify the uncertainty.

Pseudoscalar decays into lepton pairs from rational approximants

The pseudoscalar decays into lepton pairs P! ‘‘ are analyzed with the machinery of Canterbury approximants, an extension of Pade 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 p 0 ! e + e and h! m + m channels…

$\eta$-$\eta\prime$ mixing in Large-Nc ChPT: discussion, phenomenology, and prospects

A systematic study of the η-η ′ mixing in Large-Nc chiral perturbation theory is presented [1] with special emphasis on the role of the next-to-next-to-leading-order contributions in the combined momentum, quark-mass, and 1/Nc expansions. At this order, loop corrections as well as OZIrule-violating pieces need to be included. Mixing angles as well as pseudoscalar decay constants are discussed within this framework. The results are compared with recent phenomenological approaches.

New determination of theηtransition form factor in the Dalitz decayη→e+e−γwith the Crystal Ball/TAPS detectors at the Mainz Microtron

The Dalitz decay eta -> e(+) e(-) gamma has been measured in the gamma p -> eta p reaction with the Crystal Ball and TAPS multiphoton spectrometers, together with the photon-tagging facility at the Mainz Microtron MAMI. The experimental statistic used in this work is one order of magnitude greater than in any previous measurement of eta -> e(+) e(-) gamma. The value obtained for the slope parameter Lambda(-2) of the eta transition form factor, Lambda(-2) = (1.95 +/- 0.15(stat) +/- 0.10(syst)) GeV-2, is in good agreement with recent measurements conducted in eta -> e(+) e(-) gamma and eta -> mu(+) mu(-) gamma decays, as well as with recent form-factor calculations. The uncertainty obtained i…

ηandη′transition form factors from rational approximants

The $\ensuremath{\eta}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}$ transition form factors in the spacelike region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. The slope and curvature parameters of the form factors as well as their values at zero and infinity are extracted from experimental data. The impact of these results on the mixing parameters of the $\ensuremath{\eta}$-${\ensuremath{\eta}}^{\ensuremath{'}}$ system and the pseudoscalar-exchange contributions to the hadronic light-by-light scattering part of the anomalous magnetic moment ${a}_{\ensuremath{\mu}}$ are also discussed.

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.

η′transition form factor from space- and timelike experimental data

The ${\ensuremath{\eta}}^{\ensuremath{'}}$ transition form factor is reanalyzed in view of the recent first observation by BESIII of the Dalitz decay ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\gamma}{e}^{+}{e}^{\ensuremath{-}}$ in both space- and timelike regions at low and intermediate energies using the Pad\'e approximants method. The present analysis provides a suitable parametrization for reproducing the measured form factor in the whole energy region and allows one to extract the corresponding low-energy parameters together with a prediction of their values at the origin, related to ${\mathrm{\ensuremath{\Gamma}}}_{{\ensuremath{\eta}}^{\ensuremath{'}}\ens…

Precise determination of resonance pole parameters through Pad\'e approximants

In this work, we present a precise and model--independent method to extract resonance pole parameters from phase-shift scattering data. These parameters are defined from the associated poles in the second Riemann sheet, unfolded by the analytic continuation to the complex pole using Pad\'e approximants. Precise theoretical parameterizations of pion-pion scattering phase shifts based on once-- and twice-- subtracted dispersion relations are used as input, whose functional form allows us to show the benefit and accuracy of the method. In particular, we extract from these parametrization the pole positions of the $f_0(500)$ at $\sqrt{s}=(453\pm 15) - i(297 \pm 15)$ MeV, the $\rho(770)$ at $\sq…

Overview of the hadronic light-by-light contribution to the muon (g−2)

In this talk I review the recent progress on the numerical evaluation of the Hadronic Light-by-Light contribution to the anomalous magnetic moment of the muon and I discuss the role of experimental data on the accuracy of its determination.

Phenomenological applications of rational approximants

We illustrate the powerfulness of Padé approximants (PAs) as a summation method and explore one of their extensions, the so-called quadratic approximant (QAs), to access both space- and (low-energy) time-like (TL) regions. As an introductory and pedagogical exercise, the function [Formula: see text] is approximated by both kind of approximants. Then, PAs are applied to predict pseudoscalar meson Dalitz decays and to extract [Formula: see text] from the semileptonic [Formula: see text] decays. Finally, the [Formula: see text] vector form factor in the TL region is explored using QAs.

Meson dominance of hadron form factors and large-Ncphenomenology

We discuss the pion and nucleon form factors and generalized form factors within the large-Nc approach in the space-like region. We estimate their theoretical uncertainties through the use of the half-width rule, amounting to taking the half-width of the resonances as the deviation of their mass parameters. The approach embodies the meson dominance of form factors and the high-energy constraints from perturbative QCD. We compare the results with the available experimental data and lattice simulations. The meson-dominance form factors are generally comparable to the available experimental data within the half-width-rule uncertainties. Our errors are comparable to the experimental uncertainti…

A new determination of the mass of the c quark from non-analytic reconstruction

Hadron form factors and large-Nc phenomenology

The half width rule provides a way to consider 1/Nc corrections to hadronic models containing resonances. Consequences of such ideas for hadron form factors and Regge trajectories are explored, with special emphasis on the possibility to describe the spectrum of light and heavy unflavored vector mesons in a universal way.

$\eta$ and $\eta'$ transition form factors from Pad\'e approximants

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

Pseudoscalar Transition Form Factors from Rational Approximants

The $\pi^0$, $\eta$, and $\eta^\prime$ transition form factors in the space-like region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. Slope and curvature parameters as well as their values at infinity are extracted from experimental data. These results are suited for constraining hadronic models such as the ones used for the hadronic light-by-light scattering piece of the anomalous magnetic moment of the muon, and for the mixing parameters of the $\eta - \eta^\prime$ system.

Charm quark mass determined from a pair of sum rules

In this paper, we present preliminary results of the determination of the charm quark mass $\hat{m}_c$ from QCD sum rules of moments of the vector current correlator calculated in perturbative QCD at ${\cal O} (\hat \alpha_s^3)$. Self-consistency between two different sum rules allow to determine the continuum contribution to the moments without requiring experimental input, except for the charm resonances below the continuum threshold. The existing experimental data from the continuum region is used, then, to confront the theoretical determination and reassess the theoretic uncertainty.

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

The current 3$\sigma$ discrepancy between experiment and Standard Model predictions for $\pi^0 \to e^+e^-$ is reconsidered using the Pad\'e 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 $\pi^0$ 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$(\pi^0 \to e^+e^-)=6.23(5)\times 10^{-8}$, still represents a discrepancy larger than $2\sigma$, unsurmountable with o…

$\eta$-$\eta'$ mixing in large-$N_c$ chiral perturbation theory: discussion, phenomenology, and prospects

A systematic study of the $\eta$-$\eta'$ mixing in Large-$N_c$ chiral perturbation theory is presented with special emphasis on the role of the next-to-next-to-leading-order contributions in the combined momentum, quark-mass, and $1/N_c$ expansions. At this order, loop corrections as well as OZI-rule-violating pieces need to be included. Mixing angles as well as pseudoscalar decay constants are discussed within this framework. The results are compared with recent phenomenological approaches.

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 …

Reply to "Comment on 'Systematics of radial and angular-momentum Regge trajectories of light non-strange qqbar-states' "

In his Comment, D. Bugg argues against our usage of the PDG collection of light non-strange states together with the half-width rule to analyze the linearity of radial and angular-moment Regge trajectories in the large-N_c limit. After taking into account his observations on our choice of data, the radial Regge trajectories are again analyzed. We still find that our conclusion on the lack of universality between radial- and angular-momentum Regge trajectories is valid.

The anomalous magnetic moment of the muon in the Standard Model

We are very grateful to the Fermilab Directorate and the Fermilab Theoretical Physics Department for their financial and logistical support of the first workshop of the Muon g -2 Theory Initiative (held near Fermilab in June 2017) [123], which was crucial for its success, and indeed for the successful start of the Initiative. Financial support for this workshop was also provided by the Fermilab Distinguished Scholars program, the Universities Research Association through a URA Visiting Scholar award, the Riken Brookhaven Research Center, and the Japan Society for the Promotion of Science under Grant No. KAKEHNHI-17H02906. We thank Shoji Hashimoto, Toru Iijima, Takashi Kaneko, and Shohei Nis…

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 Γη→γγ 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.