The photoproduction reaction gamma p --> mu(+)mu(-) p has been studied in ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of 43.2 pb(-1). The Upsilon meson has been observed in photoproduction for the first time. The sum of the products of the elastic Upsilon(1S),Upsilon(2S),Upsilon(3S) photoproduction cross sections with their respective branching ratios is determined to be 13.3 +/- 6.0(stat.)(-2.3)(+2.7)(syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model. (C) 1998 Elsevier Science B.V. All rights reserved.
The photoproduction reaction gamma p --> mu(+)mu(-) p has been studied in ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of 43.2 pb(-1). The Upsilon meson has been observed in photoproduction for the first time. The sum of the products of the elastic Upsilon(1S),Upsilon(2S),Upsilon(3S) photoproduction cross sections with their respective branching ratios is determined to be 13.3 +/- 6.0(stat.)(-2.3)(+2.7)(syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model. (C) 1998 Elsevier Science B.V. All rights reserved.
Measurement of elastic Upsilon photoproduction at HERA
CAPUA, Marcella;MASTROBERARDINO, Anna;Schioppa M;TASSI, Enrico;
1998-01-01
Abstract
The photoproduction reaction gamma p --> mu(+)mu(-) p has been studied in ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of 43.2 pb(-1). The Upsilon meson has been observed in photoproduction for the first time. The sum of the products of the elastic Upsilon(1S),Upsilon(2S),Upsilon(3S) photoproduction cross sections with their respective branching ratios is determined to be 13.3 +/- 6.0(stat.)(-2.3)(+2.7)(syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model. (C) 1998 Elsevier Science B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.