Data di Pubblicazione:
1998
Abstract:
Elastic and proton-dissociative p(o) photoproduction (gamma p --> rho(o)p, gamma p --> rho(o)N, respectively, with rho(o) --> pi(+)pi(-)) 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 M-N(2) < 0.1W(2). For the elastic process, the pi(+)pi(-) invariant mass spectrum has been investigated as a function of t. As in fixed target experiments, the rho(o) 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 pi(+)pi(-) production. The cross section has been studied as a function of W; a fit to the resonant part with the form W-a gives a = 0.16 +/- 0.06 (stat.)(-0.15)(+0.11) (syst.). The resonant part of the gamma p --> pi(+)pi(-) p cross section is 11.2 +/- 0.1 (stat.)(-1.2)(+1.1)(syst.) mu b at [W] = 71.7 GeV. The t dependence of the cross section can be described by a function of the type A(rho) exp (-b(rho)\t\ + c(p)t(2)) with b(rho) = 10.9 +/- 0.3 (stat.)(-0.5)(+1.0) (syst.) GeV-2 and c(rho) = 2.7 +/- 0.9 (stat.)(-1.7)(+1.9) (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 alpha(IP)' = 0.23 +/- 0.15 (stat.)(-0.07)(+0.10), (syst.) GeV-2 has been deduced. The rho(o) spin density matrix elements r(00)(04), r(1-1)(04) and Re[r(10)(04)] have been measured and found to be consistent with expectations based on s-channel helicity conservation. For proton-dissociative pi(+)pi(-) photoproduction in the rho(o) mass range, the distributions of the two-pion invariant mass, Wi 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 rho(o) photoproduction cross section is 2.0 +/- 0.2 (stat.) +/- 0.7 (syst.).
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
ZEUS; DOUBLE DIFFRACTION DISSOCIATION; CENTRAL TRACKING DETECTOR; ZEUS BARREL CALORIMETER; CERN SPS COLLIDER; OF-MASS ENERGY; CROSS-SECTIONS; SCATTERING; ISR
Elenco autori:
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.;F. Anselmo;P. Antonioli;G. Bari;M. Basile;L. Bellagamba;D. Boscherini;A. Bruni;G. Bruni;G. C. Romeo;G. Castellini;M. Chiarini;L. Cifarelli;F. Cindolo;A. Contin;M. Corradi;S. D. 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. Z. Garcia;A. Zichichi;C. Amelung;A. Bornheim;I. Brock;K. Coboken;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;C. Rembser;J. Stamm;R. Wedemeyer;H. Wieber;D. S. Bailey;S. Campbell-Robson;W. N. Cottingham;R. Hall-Wilton;M. E. Hayes;G. P. Heath;G. P. 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. Przybycien;L. Zawiejski;L. Adamczyk;B. Bednarek;M. Bukowy;A. Czermak;K. Jelen;D. Kisielewska;T. Kowalski;M. Przybycien;E. Rulikowska-Zarebska;L. Suszycki;J. Zajac;Z. Dulinski;A. Kotanski;G. Abbiendi;L. A. T.;U. Behrens;H. Beier;J. K. Bienlein;G. Cases;O. Deppe;K. Desler;G. Drews;U. Fricke;D. J. Gilkinson;C. Glasman;P. Gottlicher;T. Haas;W. Hain;D. Hasell;K. F. Johnson;M. Kasemann;W. Koch;U. Kotz;H. Kowalski;J. Labs;L. Lindemann;B. Lohr;M. Lowe;O. Manczak;J. Milewski;T. Monteiro;J. S. T.;D. Notz;K. Ohrenberg;I. H. Park;A. Pellegrino;F. Pelucchi;K. Piotrzkowski;M. Roco;M. Rohde;J. Roldan;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. Wolfle;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. Kcira;R. Klanner;E. Lohrmann;G. Poelz;W. Schott;F. Zetsche;T. C. Bacon;I. Butterworth;J. E. Cole;G. Howell;B. H. Y.;L. Lamberti;K. R. Long;D. B. Miiller;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. Fernandez;G. Garcia;R. Graciani;J. M. Hernandez;L. Hervas;L. Labarga;M. Martinez;J. d. Peso;J. Puga;J. Terron;J. F. de;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. Brummer;F. Chlebana;J. Engelen;E. Koffeman;P. Kooijman;A. v. Sighem;H. Tiecke;N. Tuning;W. Verkerke;J. Vossebeld;M. Vreeswijk;L. Wiggers;E. d. 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.;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
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