Elastic and proton-dissociative ρ0 photoproduction at HERA

J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, M. C.K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. BruniG. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. de Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari, A. Pesci, A. Polini, F. Ricci, G. Sartorelli, Y. Zamora Garcia, A. Zichichi, C. Amelung, A. Bornheim, I. Brock, K. Coböken, J. Crittenden, R. Deffner, M. Eckert, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H. P. Jakob, U. F. Katz, R. Kerger, E. Paul, M. Pfeiffer, Ch Rembser, J. Stamm, R. Wedemeyer, H. Wieber, D. S. Bailey, S. Campbell-Robson, W. N. Cottingham, B. Foster, R. Hall-Wilton, M. E. Hayes, G. P. Heath, H. F. Heath, J. D. McFall, D. Piccioni, D. G. Roff, R. J. Tapper, M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, J. Y. Kim, J. H. Lee, I. T. Lim, M. Y. Pac, A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, B. Mellado, J. A. Parsons, S. Ritz, S. Sampson, F. Sciulli, P. B. Straub, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, J. Figiel, K. Klimek, M. B. Przybycień, L. Zawiejski, L. Adamczyk, B. Bednarek, M. Bukowy, A. Czermak, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarebska, L. Suszycki, J. Zaja̧c, Z. Dulinński, A. Kotanński, G. Abbiendi, L. A.T. Bauerdick, U. Behrens, H. Beier, J. K. Bienlein, G. Cases, O. Deppe, K. Desler, G. Drews, U. Fricke, D. J. Gilkinson, C. Glasman, P. Göttlicher, T. Haas, W. Hain, D. Hasell, K. F. Johnson, M. Kasemann, W. Koch, U. Kötz, H. Kowalski, J. Labs, L. Lindemann, B. Löhr, M. Löwe, O. Mańczak, J. Milewski, T. Monteiro, J. S.T. Ng, D. Notz, K. Ohrenberg, I. H. Park, A. Pellegrino, F. Pelucchi, K. Piotrzkowski, M. Roco, M. Rohde, J. Roldán, J. J. Ryan, A. A. Savin, U. Schneekloth, O. Schwarzer, F. Selonke, B. Surrow, E. Tassi, T. Voß, D. Westphal, G. Wolf, U. Wollmer, C. Youngman, A. F. Zarnecki, W. Zeuner, B. D. Burow, H. J. Grabosch, A. Meyer, S. Schlenstedt, G. Barbagli, E. Gallo, P. Pelfer, G. Anzivino, G. Maccarrone, L. Votano, A. Bamberger, S. Eisenhardt, P. Markun, T. Trefzger, S. Wölfle, J. T. Bromley, N. H. Brook, P. J. Bussey, A. T. Doyle, N. Macdonald, D. H. Saxon, L. E. Sinclair, E. Strickland, R. Waugh, I. Bohnet, N. Gendner, U. Holm, A. Meyer-Larsen, H. Salehi, K. Wick, L. K. Gladilin, D. Horstmann, D. Kçira, R. Klanner, E. Lohrmann, G. Poelz, W. Schott, F. Zetsche, T. C. Bacon, I. Butterworth, J. E. Cole, G. Howell, B. H.Y. Hung, L. Lamberti, K. R. Long, D. B. Miller, N. Pavel, A. Prinias, J. K. Sedgbeer, D. Sideris, R. Walker, U. Mallik, S. M. Wang, J. T. Wu, P. Cloth, D. Filges, J. I. Fleck, T. Ishii, M. Kuze, I. Suzuki, K. Tokushuku, S. Yamada, K. Yamauchi, Y. Yamazaki, S. J. Hong, S. B. Lee, S. W. Nam, S. K. Park, F. Barreiro, J. P. Fernández, G. García, R. Graciani, J. M. Hernández, L. Hervás, L. Labarga, M. Martínez, J. del Peso, J. Puga, J. Terrón, J. F. de Trocóniz, F. Corriveau, D. S. Hanna, J. Hartmann, L. W. Hung, W. N. Murray, A. Ochs, M. Riveline, D. G. Stairs, M. St-Laurent, R. Ullmann, T. Tsurugai, V. Bashkirov, B. A. Dolgoshein, A. Stifutkin, G. L. Bashindzhagyan, P. F. Ermolov, Y. A. Golubkov, L. A. Khein, N. A. Korotkova, I. A. Korzhavina, V. A. Kuzmin, O. Y. Lukina, A. S. Proskuryakov, L. M. Shcheglova, A. N. Solomin, S. A. Zotkin, C. Bokel, M. Botje, N. Brümmer, F. Chlebana, J. Engelen, E. Koffeman, P. Kooijman, A. van Sighem, H. Tiecke, N. Tuning, W. Verkerke, J. Vossebeld, M. Vreeswijk, L. Wiggers, E. de Wolf, D. Acosta, B. Bylsma, L. S. Durkin, J. Gilmore, C. M. Ginsburg, C. L. Kim, T. Y. Ling, P. Nylander, T. A. Romanowski, H. E. Blaikley, R. J. Cashmore, A. M. Cooper-Sarkar, R. C.E. Devenish, J. K. Edmonds, J. Große-Knetter, N. Harnew, C. Nath, V. A. Noyes, A. Quadt, O. Ruske, J. R. Tickner, H. Uijterwaal, R. Walczak, D. S. Waters, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, J. Bulmahn, B. Y. Oh, J. R. Okrasiński, W. S. Toothacker, J. J. Whitmore, Y. Iga, G. D'Agostini, G. Marini, A. Nigro, M. Raso, J. C. Hart, N. A. McCubbin, T. P. Shah, E. Barberis, D. Epperson, C. Heusch, J. T. Rahn, H. F.W. Sadrozinski, A. Seiden, R. Wichmann, D. C. Williams, H. Abramowicz, G. Briskin, S. Dagan, S. Kananov, A. Levy, T. Abe, T. Fusayasu, M. Inuzuka, K. Nagano, K. Umemori, T. Yamashita, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, T. Matsushita, R. Cirio, M. Costa, M. I. Ferrero, S. Maselli, V. Monaco, C. Peroni, M. C. Petrucci, M. Ruspa, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D. C. Bailey, C. P. Fagerstroem, R. Galea, G. F. Hartner, K. K. Joo, G. M. Levman, J. F. Martin, R. S. Orr, S. Polenz, A. Sabetfakhri, D. Simmons, R. J. Teuscher, J. M. Butterworth, C. D. Catterall, T. W. Jones, J. B. Lane, R. L. Saunders, M. R. Sutton, M. Wing, J. Ciborowski, G. Grzelak, M. Kasprzak, K. Muchorowski, R. J. Nowak, J. M. Pawlak, R. Pawlak, T. Tymieniecka, A. K. Wróblewski, J. A. Zakrzewski, M. Adamus, C. Coldewey, Y. Eisenberg, D. Hochman, U. Karshon, W. F. Badgett, D. Chapin, R. Cross, S. Dasu, C. Foudas, R. J. Loveless, S. Mattingly, D. D. Reeder, W. H. Smith, A. Vaiciulis, M. Wodarczyk, A. Deshpande, S. Dhawan, V. W. Hughes, S. Bhadra, W. R. Frisken, M. Khakzad, W. B. Schmidke

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Abstract

Elastic and proton-dissociative ρ0 photoproduction (γp → p0p, γp → ρ0N, respectively, with p0 → π+π-) has been studied in ep interactions at HERA for photon-proton centre-of-mass energies in the range 50 < W < 100 GeV and for |t| < 0.5 GeV2, where t is the square of the four-momentum transfer at the proton vertex; the results on the proton-dissociative reaction are presented for masses of the dissociated proton system in the range M2N < 0.1W2. For the elastic process, the π+π- invariant mass spectrum has been investigated as a function of t. As in fixed target experiments, the ρ0 resonance shape is asymmetric; this asymmetry decreases with increasing |t|, as expected in models in which the asymmetry is ascribed to the interference of resonant and non-resonant π+π- production. The cross section has been studied as a function of W; a fit to the resonant part with the form Wa gives a = 0.16 ± 0.06 (stat.) +0.11-0.15 (syst.). The resonant part of the γp → π+π-p cross section is 11.2 ± 0.1 (stat.) +1.1-1.2 (syst.) μb at 〈W〉 = 71.7 GeV. The t dependence of the cross section can be described by a function of the type Aρ exp (-bρ|t| + cρt2) with bρ = 10.9 ± 0.3 (stat.) +1.0-0.5 (syst.) GeV-2 and cρ = 2.7 ± 0.9 (stat.) +1.9-1.7 (syst.) GeV-4. The t dependence has also been studied as a function of W and a value of the slope of the pomeron trajectory α IP′ = 0.23 ± 0.15 (stat.) +0.10-0.07 (syst.) GeV-2 has been deduced. The ρ0 spin density matrix elements r0400 r041-1 and ℜe[r0410] have been measured and found to be consistent with expectations based on s-channel helicity conservation. For proton-dissociative π+π- photoproduction in the ρ0 mass range, the distributions of the two-pion invariant mass, W and the polar and azimuthal angles of the pions in the helicity frame are the same within errors as those for the elastic process. The t distribution has been fitted to an exponential function with a slope parameter 5.8 ± 0.3 (stat.) ± 0.5 (syst.) GeV-2. The ratio of the elastic to proton-dissociative ρ0 photoproduction cross section is 2.0 ± 0.2 (stat.) ± 0.7 (syst.).

Original languageEnglish
Pages (from-to)247-267
Number of pages21
JournalEuropean Physical Journal C
Volume2
Issue number2
DOIs
Publication statusPublished - 1998

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Physics and Astronomy (miscellaneous)

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    Breitweg, J., Derrick, M., Krakauer, D., Magill, S., Mikunas, D., Musgrave, B., Repond, J., Stanek, R., Talaga, R. L., Yoshida, R., Zhang, H., Mattingly, M. C. K., Anselmo, F., Antonioli, P., Bari, G., Basile, M., Bellagamba, L., Boscherini, D., Bruni, A., ... Schmidke, W. B. (1998). Elastic and proton-dissociative ρ0 photoproduction at HERA. European Physical Journal C, 2(2), 247-267. https://doi.org/10.1007/s100529800834