Speaker
Description
The pion QCD form factor encodes the effects of the strong interaction in processes involving pions and provides a fundamental probe of non-perturbative and asymptotic Quantum Chromodynamics (QCD).
Because first-principles calculations of non-trivial QCD interactions are challenging, empirically measured form factors play a crucial role in data-driven approaches. In particular, they can be used to improve hadronic modeling in event generators such as Pythia, leading to more accurate simulations of hadronic final states. Measurements of the pion form factor at high energies test the asymptotic behavior predicted by different QCD models, providing valuable benchmarks for theoretical calculations and computational techniques.
The $e^+e^- \rightarrow \pi^+ \pi^-$ process is studied without initial-state radiation using data collected at a center-of-mass energy of 10.58 GeV by the SuperKEKB collider, the world’s highest-luminosity electron--positron collider. The final-state pions are reconstructed with the Belle II detector, a multipurpose detector located at the interaction point of the SuperKEKB beams.
Signal events are selected using multivariate analysis (MVA) techniques and optimized using Monte Carlo simulations of the signal and dominant background processes. Systematic effects associated with the selection are evaluated using a control sample of $\tau^\pm \rightarrow (\rho^\pm \rightarrow \pi^\pm \pi^0)\nu_\tau$ decays, tagged with $\tau^\pm \rightarrow \ell^\pm \nu_\ell \nu_\tau$ ($\ell = e, \mu$), which provides a high-purity source of pions in data for validation and calibration.
| Keyword-1 | Belle II |
|---|---|
| Keyword-2 | QCD |
| Keyword-3 | SuperKEKB |