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. Böttcher; A. 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

doi:10.1016/S0370-2693(04)01248-1

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

Physics

Research output: Contribution to journal › Article › peer-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 language	English (US)
Pages (from-to)	212-222
Number of pages	11
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	599
Issue number	3-4
DOIs	https://doi.org/10.1016/S0370-2693(04)01248-1
State	Published - Oct 14 2004

ASJC Scopus subject areas

Nuclear and High Energy Physics

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10.1016/S0370-2693(04)01248-1

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Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V. V., Andrus, A., Aschenauer, E. C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Balin, D., Baturin, V., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H. P., ... Zupranski, P. (2004). Hard exclusive electroproduction of π⁺π^- pairs. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 599(3-4), 212-222. https://doi.org/10.1016/S0370-2693(04)01248-1

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, Böttcher, H, Borissov, A, Borysenko, A, Bouwhuis, M, Brack, J, Brüll, A, Bryzgalov, V, Capitani, GP, Chen, T, Ciullo, G, Contalbrigo, M, Dalpiaz, PF, de Leo, R, Demey, M, de Nardo, L, de Sanctis, E, Devitsin, E, di Nezza, P, Düren, 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, Lapikás, 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, Schäfer, A, Schill, C, Schnell, G, Schüler, 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, Tail, 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, Ybeles Smit, G, Ye, Y, Ye, Z, Yen, S, Zihlmann, B & Zupranski, P 2004, 'Hard exclusive electroproduction of π⁺π^- pairs', Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, vol. 599, no. 3-4, pp. 212-222. https://doi.org/10.1016/S0370-2693(04)01248-1

@article{09d7eeabe4fb4f4885bf295d32843ee1,

title = "Hard exclusive electroproduction of π+π- pairs",

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 q{\=q} 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.",

author = "A. Airapetian and N. Akopov and Z. Akopov and M. Amarian and Ammosov, {V. V.} and A. Andrus and Aschenauer, {E. C.} and W. Augustyniak and R. Avakian and A. Avetissian and E. Avetissian and P. Bailey and D. Balin and V. Baturin and M. Beckmann and S. Belostotski and S. Bernreuther and N. Bianchi and Blok, {H. P.} and H. B{\"o}ttcher and A. Borissov and A. Borysenko and M. Bouwhuis and J. Brack and A. Br{\"u}ll and V. Bryzgalov and Capitani, {G. P.} and T. Chen and G. Ciullo and M. Contalbrigo and Dalpiaz, {P. F.} and {de Leo}, R. and M. Demey and {de Nardo}, L. and {de Sanctis}, E. and E. Devitsin and {di Nezza}, P. and M. D{\"u}ren and M. Ehrenfried and A. Elalaoui-Moulay and G. Elbakian and F. Ellinghaus and U. Elschenbroich and R. Fabbri and A. Fantoni and A. Fechtchenko and L. Felawka and S. Frullani and G. Gapienko and V. Gapienko and F. Garibaldi and K. Garrow and E. Garutti and G. Gavrilov and V. Gharibyan and G. Graw and O. Grebeniouk and Greeniaus, {L. G.} and Gregor, {I. M.} and Griffioen, {K. A.} and K. Hafidi and M. Hartig and D. Hasch and D. Heesbeen and M. Henoch and R. Hertenberger and Hesselink, {W. H.A.} and A. Hillenbrand and M. Hoek and Y. Holler and B. Hommez and G. Iarygin and A. Ivanilov and A. Izotov and Jackson, {H. E.} and A. Jgoun and R. Kaiser and E. Kinney and A. Kisselev and M. Kopytin and V. Korotkov and V. Kozlov and B. Krauss and Krivokhijine, {V. G.} and L. Lagamba and L. Lapik{\'a}s and A. Laziev and P. Lenisa and P. Liebing and Linden-Levy, {L. A.} and K. Lipka and W. Lorenzon and H. Lu and J. Lu and S. Lu and Ma, {B. Q.} and B. Maiheu and Makins, {N. C.R.} and Y. Mao and B. Marianski and H. Marukyan and F. Masoli and V. Mexner and N. Meyners and O. Mikloukho and Miller, {C. A.} and Y. Miyachi and V. Muccifora and A. Nagaitsev and E. Nappi and Y. Naryshkin and A. Nass and M. Negodaev and Nowak, {W. D.} and K. Oganessyan and H. Ohsuga and A. Osborne and N. Pickert and S. Potashov and Potterveld, {D. H.} and M. Raithel and D. Reggiani and Reimer, {P. E.} and A. Reischl and Reolon, {A. R.} and C. Riedl and K. Rith and G. Rosner and A. Rostomyan and L. Rubacek and J. Rubin and D. Ryckbosch and Y. Salomatin and I. Sanjiev and I. Savin and A. Sch{\"a}fer and C. Schill and G. Schnell and Sch{\"u}ler, {K. P.} and J. Seele and R. Seidl and B. Seitz and R. Shanidze and C. Shearer and Shibata, {T. A.} and V. Shutov and K. Sinram and W. Sommer and M. Stancari and M. Statera and E. Steffens and Steijger, {J. J.M.} and H. Stenzel and J. Stewart and F. Stinzing and P. Tail and H. Tanaka and S. Taroian and B. Tchuiko and A. Terkulov and A. Tkabladze and A. Trzcinski and M. Tytgat and A. Vandenbroucke and {van der Nat}, P. and {van der Steenhoven}, G. and {van Haarlem}, Y. and Vetterli, {M. C.} and V. Vikhrov and Vincter, {M. G.} and C. Vogel and M. Vogt and J. Volmer and C. Weiskopf and J. Wendland and J. Wilbert and {Ybeles Smit}, G. and Y. Ye and Z. Ye and S. Yen and B. Zihlmann and P. Zupranski",

note = "Funding Information: We are grateful for inspiring and helpful discussions with M. Diehl, B. Lehmann-Dronke, B. Pire and M.V. Polyakov. We gratefully acknowledge the DESY management for its support, the staff at DESY, and the collaborating institutions for their significant effort. This work was supported by the FWO-Flanders, Belgium; the Natural Sciences and Engineering Research Council of Canada; the ESOP, INTAS and TMR network contributions from the European Union; the German Bundesministerium f{\"u}r Bildung und Forschung; the Italian Instituto Nazionale di Fisica Nucleare (INFN); Monbusho International Scientific Research Program, JSPS and Toray Science Foundation of Japan; the Dutch Foundation for Fundamenteel Onderzoek der Materie (FOM); the UK Particle Physics and Astronomy Research Council; and the US Department of Energy and National Science Foundation.",

year = "2004",

month = oct,

day = "14",

doi = "10.1016/S0370-2693(04)01248-1",

language = "English (US)",

volume = "599",

pages = "212--222",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

publisher = "Elsevier",

number = "3-4",

}

TY - JOUR

T1 - Hard exclusive electroproduction of π+π- pairs

AU - Airapetian, A.

AU - Akopov, N.

AU - Akopov, Z.

AU - Amarian, M.

AU - Ammosov, V. V.

AU - Andrus, A.

AU - Aschenauer, E. C.

AU - Augustyniak, W.

AU - Avakian, R.

AU - Avetissian, A.

AU - Avetissian, E.

AU - Bailey, P.

AU - Balin, D.

AU - Baturin, V.

AU - Beckmann, M.

AU - Belostotski, S.

AU - Bernreuther, S.

AU - Bianchi, N.

AU - Blok, H. P.

AU - Böttcher, H.

AU - Borissov, A.

AU - Borysenko, A.

AU - Bouwhuis, M.

AU - Brack, J.

AU - Brüll, A.

AU - Bryzgalov, V.

AU - Capitani, G. P.

AU - Chen, T.

AU - Ciullo, G.

AU - Contalbrigo, M.

AU - Dalpiaz, P. F.

AU - de Leo, R.

AU - Demey, M.

AU - de Nardo, L.

AU - de Sanctis, E.

AU - Devitsin, E.

AU - di Nezza, P.

AU - Düren, M.

AU - Ehrenfried, M.

AU - Elalaoui-Moulay, A.

AU - Elbakian, G.

AU - Ellinghaus, F.

AU - Elschenbroich, U.

AU - Fabbri, R.

AU - Fantoni, A.

AU - Fechtchenko, A.

AU - Felawka, L.

AU - Frullani, S.

AU - Gapienko, G.

AU - Gapienko, V.

AU - Garibaldi, F.

AU - Garrow, K.

AU - Garutti, E.

AU - Gavrilov, G.

AU - Gharibyan, V.

AU - Graw, G.

AU - Grebeniouk, O.

AU - Greeniaus, L. G.

AU - Gregor, I. M.

AU - Griffioen, K. A.

AU - Hafidi, K.

AU - Hartig, M.

AU - Hasch, D.

AU - Heesbeen, D.

AU - Henoch, M.

AU - Hertenberger, R.

AU - Hesselink, W. H.A.

AU - Hillenbrand, A.

AU - Hoek, M.

AU - Holler, Y.

AU - Hommez, B.

AU - Iarygin, G.

AU - Ivanilov, A.

AU - Izotov, A.

AU - Jackson, H. E.

AU - Jgoun, A.

AU - Kaiser, R.

AU - Kinney, E.

AU - Kisselev, A.

AU - Kopytin, M.

AU - Korotkov, V.

AU - Kozlov, V.

AU - Krauss, B.

AU - Krivokhijine, V. G.

AU - Lagamba, L.

AU - Lapikás, L.

AU - Laziev, A.

AU - Lenisa, P.

AU - Liebing, P.

AU - Linden-Levy, L. A.

AU - Lipka, K.

AU - Lorenzon, W.

AU - Lu, H.

AU - Lu, J.

AU - Lu, S.

AU - Ma, B. Q.

AU - Maiheu, B.

AU - Makins, N. C.R.

AU - Mao, Y.

AU - Marianski, B.

AU - Marukyan, H.

AU - Masoli, F.

AU - Mexner, V.

AU - Meyners, N.

AU - Mikloukho, O.

AU - Miller, C. A.

AU - Miyachi, Y.

AU - Muccifora, V.

AU - Nagaitsev, A.

AU - Nappi, E.

AU - Naryshkin, Y.

AU - Nass, A.

AU - Negodaev, M.

AU - Nowak, W. D.

AU - Oganessyan, K.

AU - Ohsuga, H.

AU - Osborne, A.

AU - Pickert, N.

AU - Potashov, S.

AU - Potterveld, D. H.

AU - Raithel, M.

AU - Reggiani, D.

AU - Reimer, P. E.

AU - Reischl, A.

AU - Reolon, A. R.

AU - Riedl, C.

AU - Rith, K.

AU - Rosner, G.

AU - Rostomyan, A.

AU - Rubacek, L.

AU - Rubin, J.

AU - Ryckbosch, D.

AU - Salomatin, Y.

AU - Sanjiev, I.

AU - Savin, I.

AU - Schäfer, A.

AU - Schill, C.

AU - Schnell, G.

AU - Schüler, K. P.

AU - Seele, J.

AU - Seidl, R.

AU - Seitz, B.

AU - Shanidze, R.

AU - Shearer, C.

AU - Shibata, T. A.

AU - Shutov, V.

AU - Sinram, K.

AU - Sommer, W.

AU - Stancari, M.

AU - Statera, M.

AU - Steffens, E.

AU - Steijger, J. J.M.

AU - Stenzel, H.

AU - Stewart, J.

AU - Stinzing, F.

AU - Tail, P.

AU - Tanaka, H.

AU - Taroian, S.

AU - Tchuiko, B.

AU - Terkulov, A.

AU - Tkabladze, A.

AU - Trzcinski, A.

AU - Tytgat, M.

AU - Vandenbroucke, A.

AU - van der Nat, P.

AU - van der Steenhoven, G.

AU - van Haarlem, Y.

AU - Vetterli, M. C.

AU - Vikhrov, V.

AU - Vincter, M. G.

AU - Vogel, C.

AU - Vogt, M.

AU - Volmer, J.

AU - Weiskopf, C.

AU - Wendland, J.

AU - Wilbert, J.

AU - Ybeles Smit, G.

AU - Ye, Y.

AU - Ye, Z.

AU - Yen, S.

AU - Zihlmann, B.

AU - Zupranski, P.

N1 - Funding Information: We are grateful for inspiring and helpful discussions with M. Diehl, B. Lehmann-Dronke, B. Pire and M.V. Polyakov. We gratefully acknowledge the DESY management for its support, the staff at DESY, and the collaborating institutions for their significant effort. This work was supported by the FWO-Flanders, Belgium; the Natural Sciences and Engineering Research Council of Canada; the ESOP, INTAS and TMR network contributions from the European Union; the German Bundesministerium für Bildung und Forschung; the Italian Instituto Nazionale di Fisica Nucleare (INFN); Monbusho International Scientific Research Program, JSPS and Toray Science Foundation of Japan; the Dutch Foundation for Fundamenteel Onderzoek der Materie (FOM); the UK Particle Physics and Astronomy Research Council; and the US Department of Energy and National Science Foundation.

PY - 2004/10/14

Y1 - 2004/10/14

N2 - 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.

AB - 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.

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U2 - 10.1016/S0370-2693(04)01248-1

DO - 10.1016/S0370-2693(04)01248-1

M3 - Article

AN - SCOPUS:4544369185

SN - 0370-2693

VL - 599

SP - 212

EP - 222

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

IS - 3-4

ER -