Speaker
Description
The leading-order hadronic vacuum polarization (HVP) contribution to the muon
anomalous magnetic moment, $a_\mu = (g-2)_\mu / 2$, can be evaluated either
through $ab\,\, initio$ lattice QCD calculations or via data-driven
dispersive analyses based on low-energy $e^+e^- \to$ hadrons
cross-section measurements. In this framework, the dipion production
channel accounts for approximately $70\%$ of the total HVP contribution.
At present, the predictions obtained from these two approaches show a
significant discrepancy. Resolving this tension, commonly referred to as
the ``new muon $g-2$ puzzle'', is essential for achieving a reliable
comparison between experimental measurements and theoretical predictions.
The process $e^+e^- \to \pi^+\pi^-\gamma$ plays a key role in the
determination of the $\pi^+\pi^-$ production cross section below
$2\,\mathrm{GeV}$ at flavour factories through the radiative return
method. In this context, a precise control of theory-driven systematic
uncertainties in the simulation of the process is essential to ensure
reliable cross-section measurements.
To this aim, we present the first calculation of QED next-to-leading
order (NLO) corrections to radiative pion and muon pair production in
$e^+e^-$ annihilation, matched to a QED Parton Shower (PS) algorithm for the
fully exclusive simulation of multiphoton emission, thereby achieving
NLOPS accuracy.
For pion pair production, we consider two different approaches to the
treatment of the pion form factor in the loop calculation: the purely
factorized approach (FxsQED), in which the point-like amplitude is
multiplied by the pion form factor evaluated at the appropriate
virtuality, and the Generalized Vector Meson Dominance (GVMD) model,
where the pion form factor is incorporated directly in the loop
integration.
We present phenomenological results obtained with a new version of
the BabaYaga@NLO event generator, which includes the radiative
channels $e^+e^- \to X^+X^-\gamma$ ($X=\mu,\pi$) according to the above
theoretical approach.
| Are you an early career researcher? | Yes, a PhD student |
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