Energetic neutrons produced in ep collisions at HERA have been studied with the ZEUS detector in the photoproduction regime at a mean photon–proton center-of-mass energy of 220 GeV. The neutrons carry a large fraction 0.64<0.925 of the incoming proton energy, and the four-momentum transfer squared at the proton–neutron vertex is small, |t|<0.425 GeV2. The xL distribution of the neutrons is measured in bins of t. The (1−xL) distributions in the t bins studied satisfy a power law dN/dxL∝(1−xL)a(t), with the powers a(t) following a linear function of t: View the MathML source. This result is consistent with the expectations of pion-exchange models, in which the incoming proton fluctuates to a neutron–pion state, and the electron interacts with the pion.
Study of the pion trajectory in the photoproduction of leading neutrons at HERA
COSTA, Marco;MONACO, Vincenzo;SACCHI, Roberto;SOLANO, Ada Maria;
2005-01-01
Abstract
Energetic neutrons produced in ep collisions at HERA have been studied with the ZEUS detector in the photoproduction regime at a mean photon–proton center-of-mass energy of 220 GeV. The neutrons carry a large fraction 0.64<0.925 of the incoming proton energy, and the four-momentum transfer squared at the proton–neutron vertex is small, |t|<0.425 GeV2. The xL distribution of the neutrons is measured in bins of t. The (1−xL) distributions in the t bins studied satisfy a power law dN/dxL∝(1−xL)a(t), with the powers a(t) following a linear function of t: View the MathML source. This result is consistent with the expectations of pion-exchange models, in which the incoming proton fluctuates to a neutron–pion state, and the electron interacts with the pion.File | Dimensione | Formato | |
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