The differential cross section d sigma/dt for elastic rho(0) photoproduction, gamma p --> rho(0)p (rho(0) --> pi(+)pi(-)), has been measured in ep interactions at HERA. The squared four-momentum exchanged at the proton vertex, t, has been determined directly by measuring the momentum of the scattered proton using the ZEUS Leading Proton Spectrometer (LPS), a large scale system of silicon micro-strip detectors operating close to the HERA proton beam. The LPS allows the measurement of the momentum of high energy protons scattered at small angles with accuracies of 0.4% for the longitudinal momentum and 5 MeV for the transverse momentum. Photoproduction of rho(0) mesons has been investigated in the interval 0.073 < \t\ < 0.40 GeV2, for photon virtualities Q(2) < 1 GeV2 and photon-proton centre-of-mass energies W between 50 and 100 GeV. In the measured range, the t distribution exhibits an exponential shape with a slope parameter b = 9.8 +/- 0.8 (stat.) +/- 1.1 (syst.) GeV-2. The use of the LPS eliminates the contamination from events with diffractive dissociation of the proton into low mass states.
The ZEUS Leading Proton Spectrometer and its use in the measurement of elastic rho(0) photoproduction at HERA
GARFAGNINI, ALBERTO;BRUGNERA, RICCARDO;CARLIN, ROBERTO;STROILI, ROBERTO;
1997
Abstract
The differential cross section d sigma/dt for elastic rho(0) photoproduction, gamma p --> rho(0)p (rho(0) --> pi(+)pi(-)), has been measured in ep interactions at HERA. The squared four-momentum exchanged at the proton vertex, t, has been determined directly by measuring the momentum of the scattered proton using the ZEUS Leading Proton Spectrometer (LPS), a large scale system of silicon micro-strip detectors operating close to the HERA proton beam. The LPS allows the measurement of the momentum of high energy protons scattered at small angles with accuracies of 0.4% for the longitudinal momentum and 5 MeV for the transverse momentum. Photoproduction of rho(0) mesons has been investigated in the interval 0.073 < \t\ < 0.40 GeV2, for photon virtualities Q(2) < 1 GeV2 and photon-proton centre-of-mass energies W between 50 and 100 GeV. In the measured range, the t distribution exhibits an exponential shape with a slope parameter b = 9.8 +/- 0.8 (stat.) +/- 1.1 (syst.) GeV-2. The use of the LPS eliminates the contamination from events with diffractive dissociation of the proton into low mass states.
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