Hard exclusive electroproduction of pi(+)pi(-) pairs

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, G; Contalbrigo, M; Dalpiaz, Pf; De Leo, Raffaele; 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, R; 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, P; 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, F; 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, D; 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, M; Statera, M; 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; Wendland, J; Wilbert, J; Smit, Gy; Ye, Y; Ye, Z; Yen, S; Zihlmann, B; Zupranski, P.

doi:10.1016/j.physletb.2004.08.059

Hard exclusive electroproduction of pi(+) pi(-) pairs off hydrogen and deuterium targets has been studied by the HERMES experiment at DESY Legendre moments (P-1) and (P-3) of the angular distributions of pi(+) mesons in the center-of-mass frame of the pair have been measured for the first time. Their dependence on the pi(+) pi(-) 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 (P-1) as Bjorken x increases is interpreted in the framework of generalized parton distributions as an enhancement of flavour non-singlet qq 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 f(2)(1270) region at = 3 GeV2 higher-twist effects can be as large as the leading-twist longitudinal component. (C) 2004 Published by Elsevier B.V.

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Titolo:	Hard exclusive electroproduction of pi(+)pi(-) pairs
Autori:	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 G Contalbrigo M Dalpiaz PF DE LEO, Raffaele 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 R 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 P 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 F 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 D 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 M Statera M 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 Wendland J Wilbert J Smit GY Ye Y Ye Z Yen S Zihlmann B Zupranski P. mostra contributor esterni nascondi contributor esterni
Data di pubblicazione:	2004
Rivista:	PHYSICS LETTERS. SECTION B
Abstract:	Hard exclusive electroproduction of pi(+) pi(-) pairs off hydrogen and deuterium targets has been studied by the HERMES experiment at DESY Legendre moments (P-1) and (P-3) of the angular distributions of pi(+) mesons in the center-of-mass frame of the pair have been measured for the first time. Their dependence on the pi(+) pi(-) 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 (P-1) as Bjorken x increases is interpreted in the framework of generalized parton distributions as an enhancement of flavour non-singlet qq 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 f(2)(1270) region at = 3 GeV2 higher-twist effects can be as large as the leading-twist longitudinal component. (C) 2004 Published by Elsevier B.V.
Handle:	http://hdl.handle.net/11586/89698
Appare nelle tipologie:	1.1 Articolo in rivista

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