Measurement of the Charged-Pion Polarizability
- Adolph, C. et al
- arXiv:1405.6377CERN-PH-EP-2014-109
 | Comparison of the measured (black points with error bars) and simulated (red histograms) kinematic distributions for measurements with pion beam: (a) transverse momentum $p_{T}$ of the scattered pion; (b) energy balance $\Delta E$; (c) $|Q|$ distribution, featuring for the real data at higher values the contribution from strong interaction, which is not contained in the simulation; (d) invariant mass of the $\pi\gamma$ system. Kinematic cuts are indicated by vertical dashed lines. |
 | Comparison of the measured (black points with error bars) and simulated (red histograms) kinematic distributions for measurements with pion beam: (a) transverse momentum $p_{T}$ of the scattered pion; (b) energy balance $\Delta E$; (c) $|Q|$ distribution, featuring for the real data at higher values the contribution from strong interaction, which is not contained in the simulation; (d) invariant mass of the $\pi\gamma$ system. Kinematic cuts are indicated by vertical dashed lines. |
 | Comparison of the measured (black points with error bars) and simulated (red histograms) kinematic distributions for measurements with pion beam: (a) transverse momentum $p_{T}$ of the scattered pion; (b) energy balance $\Delta E$; (c) $|Q|$ distribution, featuring for the real data at higher values the contribution from strong interaction, which is not contained in the simulation; (d) invariant mass of the $\pi\gamma$ system. Kinematic cuts are indicated by vertical dashed lines. |
 | Comparison of the measured (black points with error bars) and simulated (red histograms) kinematic distributions for measurements with pion beam: (a) transverse momentum $p_{T}$ of the scattered pion; (b) energy balance $\Delta E$; (c) $|Q|$ distribution, featuring for the real data at higher values the contribution from strong interaction, which is not contained in the simulation; (d) invariant mass of the $\pi\gamma$ system. Kinematic cuts are indicated by vertical dashed lines. |
 | The measured and simulated $x_\gamma$ distributions for pion (lower curve) and muon (upper curve) beam. The statistical uncertainty of the real data points is indicated by vertical error bars, while the width of the symbols is set arbitrarily to one third of the bin width. The lines connect the simulation results for the same bin centers. The bottom panel shows the $\pi^0$ background fraction $f_{\pi^{0}}$ that was subtracted from the pion data. |
 | The $x_\gamma$ dependence of the ratio of the measured differential cross section $d\sigma/dx_{\gamma}$ over the expected cross section for point-like particles. Top (bottom) panel: measurement with pion (muon) beam. The respective ratios contain the corrections described in the text. The bands denote the respective statistical uncertainties of the fit results shown by the solid lines. Error bars denote statistical uncertainties. The quality of the fits can be characterized by the values $\chi_{\pi}^2/NDF=22.0/18$ and $\chi_{\mu}^2/NDF=19.6/18$, respectively. |