Measurement of the k_T Distribution of Particles in Jets Produced in p anti-p Collisions at s**(1/2) =1.96 TeV

We present a measurement of the transverse momentum with respect to the jet axis (k_T) of particles in jets produced in p anti-p collisions at s**(1/2) =1.96 TeV. Results are obtained for charged particles within a cone of opening angle 0.5 radians around the jet axis in events with dijet invariant masses between 66 and 737 GeV/c2. The experimental data are compared to theoretical predictions obtained for fragmentation partons within the framework of resumed perturbative QCD using the modified leading log and next-to-modified leading log approximations. The comparison shows that trends in data are successfully described by the theoretical predictions, indicating that the perturbative QCD stage of jet fragmentation is dominant in shapi+ng basic jet characteristics.