Hard exclusive electroproduction of π+π- pairs

A. Airapetian, N. Akopov, Z. Akopov, M. Amarian, V. V. Ammosov, A. Andrus, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetissian, P. Bailey, D. Balin, V. Baturin, M. Beckmann, S. Belostotski, S. Bernreuther, N. Bianchi, H. P. Blok, H. BöttcherA. Borissov, A. Borysenko, M. Bouwhuis, J. Brack, A. Brüll, V. Bryzgalov, G. P. Capitani, T. Chen, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, R. de Leo, M. Demey, L. de Nardo, E. de Sanctis, E. Devitsin, P. di Nezza, M. Düren, M. Ehrenfried, A. Elalaoui-Moulay, G. Elbakian, F. Ellinghaus, U. Elschenbroich, R. Fabbri, A. Fantoni, A. Fechtchenko, L. Felawka, S. Frullani, G. Gapienko, V. Gapienko, F. Garibaldi, K. Garrow, E. Garutti, G. Gavrilov, V. Gharibyan, G. Graw, O. Grebeniouk, L. G. Greeniaus, I. M. Gregor, K. A. Griffioen, K. Hafidi, M. Hartig, D. Hasch, D. Heesbeen, M. Henoch, R. Hertenberger, W. H.A. Hesselink, A. Hillenbrand, M. Hoek, Y. Holler, B. Hommez, G. Iarygin, A. Ivanilov, A. Izotov, H. E. Jackson, A. Jgoun, R. Kaiser, E. Kinney, A. Kisselev, M. Kopytin, V. Korotkov, V. Kozlov, B. Krauss, V. G. Krivokhijine, L. Lagamba, L. Lapikás, A. Laziev, P. Lenisa, P. Liebing, L. A. Linden-Levy, K. Lipka, W. Lorenzon, H. Lu, J. Lu, S. Lu, B. Q. Ma, B. Maiheu, N. C.R. Makins, Y. Mao, B. Marianski, H. Marukyan, F. Masoli, V. Mexner, N. Meyners, O. Mikloukho, C. A. Miller, Y. Miyachi, V. Muccifora, A. Nagaitsev, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. D. Nowak, K. Oganessyan, H. Ohsuga, A. Osborne, N. Pickert, S. Potashov, D. H. Potterveld, M. Raithel, D. Reggiani, P. E. Reimer, A. Reischl, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, L. Rubacek, J. Rubin, D. Ryckbosch, Y. Salomatin, I. Sanjiev, I. Savin, A. Schäfer, C. Schill, G. Schnell, K. P. Schüler, J. Seele, R. Seidl, B. Seitz, R. Shanidze, C. Shearer, T. A. Shibata, V. Shutov, K. Sinram, W. Sommer, M. Stancari, M. Statera, E. Steffens, J. J.M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, P. Tail, H. Tanaka, S. Taroian, B. Tchuiko, A. Terkulov, A. Tkabladze, A. Trzcinski, M. Tytgat, A. Vandenbroucke, P. van der Nat, G. van der Steenhoven, Y. van Haarlem, M. C. Vetterli, V. Vikhrov, M. G. Vincter, C. Vogel, M. Vogt, J. Volmer, C. Weiskopf, J. Wendland, J. Wilbert, G. Ybeles Smit, Y. Ye, Z. Ye, S. Yen, B. Zihlmann, P. Zupranski

Research output: Contribution to journalArticlepeer-review

Abstract

Hard exclusive electroproduction of π+π- pairs off hydrogen and deuterium targets has been studied by the HERMES experiment at DESY. Legendre moments 〈P1〉 and 〈P3〉 of the angular distributions of π+ mesons in the center-of-mass frame of the pair have been measured for the first time. Their dependence on the π+π- invariant mass can be understood as being due to the interference between relative P-wave (isovector) and S-, D-wave (isoscalar) states of the two pions. The increase in magnitude of 〈P1〉 as Bjorken x increases is interpreted in the framework of generalized parton distributions as an enhancement of flavour non-singlet qq̄ exchange for larger values of x, which leads to a sizable admixture of isoscalar and isovector pion pairs. In addition, the interference between P-wave and D-wave states separately for transverse and longitudinal pion pairs has been studied. The data indicate that in the f2(1270) region at 〈Q2〉=3 GeV2 higher-twist effects can be as large as the leading-twist longitudinal component.

Original languageEnglish (US)
Pages (from-to)212-222
Number of pages11
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume599
Issue number3-4
DOIs
StatePublished - Oct 14 2004

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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