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Abramowicz, H.; Aggarwal, R.; Antonov, A.; Ashery, D.; Bachynska, O.; Bamberger, A.; Bartosik, N.; Bindi, M.; Blohm, C.; Brümmer, N.; Bruni, G.; Bussey, P. J.; Chekanov, S.; Chwastowski, J.; Contin, A.; Cooper-Sarkar, A. M.; Dal Corso, F.; Dementiev, R. K.; Derrick, M.; Dobur, D.; Dusini, S.; Eisenberg, Y.; Fang, S.; Ferrando, J.; Garfagnini, A.; Golubkov, Yu. A.; Grabowska-Bołd, I.; Grebenyuk, J.; Grigorescu, G.; Grzelak, G.; Gwenlan, C.; Hart, J. C.; Hilger, E.; Hochman, D.; Horton, K.; Kadenko, I.; Kananov, S.; Kanno, T.; Kim, J. Y.; Korol, Ie; Kuprash, O.; Kuze, M.; Levchenko, B. B.; Libov, V.; Limentani, S.; Ling, T. Y.; Lohmann, W.; Lohrmann, E.; Lontkovskyi, D.; Maeda, J.; Marini, G.; Mastroberardino, A.; Melzer-Pellmann, I.-A.; Mergelmeyer, S.; Miglioranzi, S.; Mohamad Idris, F.; Monaco, V.; Namsoo, T.; Nobe, T.; Notz, D.; Nuncio-Quiroz, A. E.; Okazaki, N.; Onishchuk, Yu; Pawlik, B.; Pelfer, P. G.; Pellegrino, A.; Perlański, W.; Polini, A.; Raval, A.; Reeder, D. D.; Roloff, P.; Ruspa, M.; Sacchi, R.; Savin, A. A.; Schioppa, M.; Schneekloth, U.; Schönberg, V.; Schwartz, J.; Sciulli, F.; Shehzadi, R.; Singh, I.; Son, D.; Stifutkin, A.; Stopa, P.; Szuba, D.; Tapper, A. D.; Tiecke, H.; Tsurugai, T.; Verbytskyi, A.; Viazlo, O.; Volynets, O.; Wan Abdullah, W. A. T.; Wrona, K.; Yamada, S.; Youngman, C.; Żarnecki, A. F.; Zeuner, W.; Zhou, C.; Zolko, M.; Zotkin, D. S.
The European physical journal. C, Particles and fields, 01/2012, Letnik: 72, Številka: 1Journal Article
The exclusive electroproduction of two pions in the mass range 0.4< M ππ <2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb −1 . The analysis was carried out in the kinematic range of 2< Q 2 <80 GeV 2 , 32< W <180 GeV and | t |<0.6 GeV 2 , where Q 2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, | F ( M ππ )|, assuming that the studied mass range includes the contributions of the ρ , ρ ′ and ρ ′′ vector-meson states. The masses and widths of the resonances were obtained and the Q 2 dependence of the cross-section ratios σ ( ρ ′→ ππ )/ σ ( ρ ) and σ ( ρ ′′→ ππ )/ σ ( ρ ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e + e − → π + π − .
