Study of the pion trajectory in the photoproduction of leading neutrons at HERA

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 < x_L <0.925

of the incoming proton energy, and the four-momentum-transfer squared at the proton-neutron vertex is small,

|t|<0.425

GeV

^2

. The

x_L

distribution of the neutrons is measured in bins of

t

. The

(1-x_L)

distributions in the

t

bins studied satisfy a power law

dN/dx_L \propto (1-x_L)^{a(t)}

, with the powers

a(t)

following a linear function of

t

: \mbox{

a(t)=0.88\pm 0.09 ({\rm stat.})^{+0.34}_{-0.39}({\rm syst.})-(2.81\pm 0.42({\rm stat.})^{+1.13}_{-0.62}({\rm syst.}) {\rm Ge V}^{-2})t

.} 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.

Note:

11 pages, 3 figures: revised analysis Report-no: DESY-04-037

electron p: colliding beams
electron p: inclusive reaction
n: photoproduction
n: energy spectrum
momentum transfer dependence
Regge poles
pi: exchange
ZEUS
experimental results
DESY HERA Stor

References(23)

Figures(0)

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