| Abstract ||Exclusive production of four charged pions at the ep collider HERA is studied at small photon virtualities Q^2 < 2 GeV^2.
The data were taken with the H1 detector in the years 2006 and 2007 at a centre-of-mass energies of 319 GeV and 225 GeV
and correspond to an integrated luminosity of 7.6 pb-1 and 1.7 pb-1 respectively.
The cross section of the reaction gamma p -> (2pi+2pi-)Y is determined in the phase space of 35 < W < 100 GeV, |t| < 1 GeV2
and M_Y < 1.6 GeV. The 4pi mass spectra indicate that the reaction proceeds predominantly via production and decay of
rho-prime resonances. The fit however does not allow yet to distinguish unambiguously between the hypothesis
of one or two broad and overlapping rho-prime resonances.|