Orateur
Description
Pion production in NN collisions is one of the sources of information on the NN interaction and on the contribution of nucleon resonances. In particular, two-pion production in the few energy range, carries information both on single and double baryon excitation and on $\pi\pi$ dynamics, which are also useful for the interpretation of dielectron production. Baryonic resonances indeed contribute to the dielectron spectra via their Dalitz decay ($R\rightarrow Ne^+e^-$) and indirectly as intermediate states for neutral meson Dalitz decays. In addition, the $\pi^+\pi^-$ production channel gives access to the $\rho$ contribution, which, due to its coupling to the baryonic resonances, is a crucial ingredient of calculations of the $e^+e^-$ emissivity in hadronic matter. The possibility to measure simultaneously with HADES pion and $e^+e^-$ production is therefore a great advantage.
Recently, differential and integrated cross sections for the reactions $pp\rightarrow pp\pi^0$, $pp\rightarrow pn\pi^+$ $[1]$, $[2]$, $pp\rightarrow pp\pi^+\pi^-$, $pn\rightarrow pn\pi^+\pi^-$ $[3]$, $pn\rightarrow d\pi^+\pi^-$ $[4]$ have been investigated with HADES at kinetic energies 1.25, 2.2 and 3.5 GeV. We focus here on the analysis of the $pp\rightarrow pp\pi^+\pi^-$ channel at 3,5 GeV, using results from $pp\rightarrow pp\pi^0$, $pp\rightarrow pn\pi^+$ and $pp\rightarrow pK\Lambda$ $[3]$ measured at the same energy by HADES.
$[1]$ G. Agakishiev et al., Eur. Phys. J. A41, 243-277 (2009).
$[2]$ G. Agakishiev et al. Eur.Phys.J. A48 (2012) 74.
$[3]$ G. Agakishiev et al. Eur.Phys.J. A50 (2014) 82.
$[4]$ G. Agakishiev et al. , Eur.Phys.J. A51 (2015), 137.
$[5]$ G. Agakishiev et al., Phys.Lett. B750 (2015) 184.
$[6]$ G. Agakishiev et al. Phys.Lett. B742 (2015) 242-248.
