A Study Of Parton Dynamics At Low X With Zeus At Hera

Inclusive jet production in neutral current deep inelastic positron-proton scattering has been measured for boson virtualities larger than 25 GeV. The data were taken at the HERA collider with center-of-mass energy 300 GeV using the ZEUS detector and correspond to an integrated luminosity of 38.7 inverse picobarns. Jets were identified using the longitudinally invariant kT-cluster algorithm. Measurements of differential inclusive jet cross sections are presented as functions of jet transverse energy, jet pseudorapidity, boson virtuality and Bjorken x with transverse energy larger than 6 GeV and pseudorapidity between −1 and 3. The data are compared to leading-logarithm parton-shower model predictions and next-to-leading-order QCD calculations using DGLAP evolution and parametrizations of the proton parton distribution functions. Measurements are made in three phase space regions, each one more restrictive, in order to enhance the contribution from events which may be better characterized by BFKL parton evolution. A large discrepancy between data and theory as computed with the NLO calculation at high pseudorapidity and low Bjorken x is seen in the most inclusive measurement. This discrepancy is largely diminished when limiting the phase space, and is, therefore, not attributed to BFKL dynamics. In the most limited region of phase space, a small discrepancy is again seen between data and theory, and may indicate the onset of BFKL dyanamics. However, the theoretical uncertainties are very large, and a definitive statement can only be made once an improved theoretical calculation, perhaps implemented with BFKL parton dyanamics, is made available