Speaker
Description
In the summer of 2014, HADES conducted measurements with secondary pion-beam using different targets. The program is devoted to measure dielepton radiation from baryonic resonances. In particular we investigated a sub-threshold coupling of rho to baryonic resonances in the second resonance region, specially N(1520). Most of the beam time was dedicated to measurement of $e^{+}e^{-}$ production from PolyEthylene target at pion beam momentum of 690 $MeV/c$. Combining these data with carbon data it is possible to extract pion-proton interactions. Therefore it was possible to measure at the same time exclusive $\pi^{-}p \rightarrow e^{+}e^{-}$ and inclusive $e^{+}e^{-}$ production. The normalization of spectra has been done using elastic scattering of pion on proton. The identification of $e^{+}e^{-}$ is was performed through appropriate cuts on time-of-flight, energy loss, shower signal and RICH (Ring Imaging Cherenkov) observables. Exclusive and inclusive invariant mass spectra is compared with the different channel contributions simulated with a dedicated Monte Carlo simulation tool for hadronic physics (PLUTO). Using missing mass cuts it was possible to identified the events from the reaction $\pi^{-}p \rightarrow n e^{+}e^{-}$ which shows that the $e^{+}e^{-}$ yield of invariant mass above 250 $MeV/c^{2}$ is consisted with $N(1520)\rightarrow n\rho\rightarrow ne^{+}e^{-}$. Models associate the excess of dilepton measured in heavy ions reactions with the excitation and decay of baryonic resonances of dileptons via intermediate $\rho$ meson
| Content type | Experiment |
|---|---|
| Collaboration | HADES |
| Centralised submission by Collaboration | Presenter name already specified |
