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 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.

Hard exclusive electroproduction of π+π− pairs

CIULLO, Giuseppe;CONTALBRIGO, Marco;FERRETTI, Paola;FABBRI, Riccardo;LENISA, Paolo;MASOLI, Francesco Antonio;REGGIANI, DAVIDE;STANCARI, Michelle Dawn;STATERA, Marco;
2004

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 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.
Airapetian, A; Akopov, N; Akopov, Z; Amarian, M; Ammosov, Vv; Andrus, A; Aschenauer, Ec; Augustyniak, W; Avakian, R; Avetissian, A; Avetissian, E; Bailey, P; Balin, D; Baturin, V; Beckmann, M; Belostotski, S; Bernreuther, S; Bianchi, N; Blok, Hp; Bottcher, H; Borissov, A; Borysenko, A; Bouwhuis, M; Brack, J; Brull, A; Bryzgalov, V; Capitani, Gp; Chen, T; Ciullo, Giuseppe; Contalbrigo, Marco; Ferretti, Paola; DE LEO, R; Demey, M; DE NARDO, L; DE SANCTIS, E; Devitsin, E; DI NEZZA, P; Duren, M; Ehrenfried, M; ELALAOUI MOULAY, A; Elbakian, G; Ellinghaus, F; Elschenbroich, U; Fabbri, Riccardo; Fantoni, A; Fechtchenko, A; Felawka, L; Frullani, S; Gapienko, G; Gapienko, V; Garibaldi, F; Garrow, K; Garutti, E; Gavrilov, G; Gharibyan, V; Graw, G; Grebeniouk, O; Greeniaus, Lg; Gregor, Im; Griffioen, Ka; Hafidi, K; Hartig, M; Hasch, D; Heesbeen, D; Henoch, M; Hertenberger, R; Hesselink, Wha; Hillenbrand, A; Hoek, M; Holler, Y; Hommez, B; Iarygin, G; Ivanilov, A; Izotov, A; Jackson, He; Jgoun, A; Kaiser, R; Kinney, E; Kisselev, A; Kopytin, M; Korotkov, V; Kozlov, V; Krauss, B; Krivokhijine, Vg; Lagamba, L; Lapikas, L; Laziev, A; Lenisa, Paolo; Liebing, P; LINDEN LEVY, La; Lipka, K; Lorenzon, W; Lu, H; Lu, J; Lu, S; Ma, Bq; Maiheu, B; Makins, Ncr; Mao, Y; Marianski, B; Marukyan, H; Masoli, Francesco Antonio; Mexner, V; Meyners, N; Mikloukho, O; Miller, Ca; Miyachi, Y; Muccifora, V; Nagaitsev, A; Nappi, E; Naryshkin, Y; Nass, A; Negodaev, M; Nowak, Wd; Oganessyan, K; Ohsuga, H; Osborne, A; Pickert, N; Potashov, S; Potterveld, Dh; Raithel, M; Reggiani, Davide; Reimer, Pe; Reischl, A; Reolon, Ar; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubacek, L; Rubin, J; Ryckbosch, D; Salomatin, Y; Sanjiev, I; Savin, I; Schafer, A; Schill, C; Schnell, G; Schuler, Kp; Seele, J; Seidl, R; Seitz, B; Shanidze, R; Shearer, C; Shibata, Ta; Shutov, V; Sinram, K; Sommer, W; Stancari, Michelle Dawn; Statera, Marco; Steffens, E; Steijger, Jjm; Stenzel, H; Stewart, J; Stinzing, F; Tait, P; Tanaka, H; Taroian, S; Tchuiko, B; Terkulov, A; Tkabladze, A; Trzcinski, A; Tytgat, M; Vandenbroucke, A; VAN DER NAT, P; VAN DER STEENHOVEN, G; VAN HAARLEM, Y; Vetterli, Mc; Vikhrov, V; Vincter, Mg; Vogel, C; Vogt, M; Volmer, J; Weiskopf, C; W. E. N. D. L. A. N. D., .
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/516697
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