Particle Multiplicity in Jets and Sub-jets with Jet Axis from Color Current
We study the particle multiplicity in a jet or sub-jet as derived from an energy-multiplicity 2-particle correlation. This definition avoids the notion of a globally fixed jet axis and allows for the study of smaller jet cone openings in a more stable way. The results are sensitive to the mean color current $ _{A_0} $ in the jet from primary parton $A_0$ which takes into account intermediate partonic processes in the sub-jet production where $C_F< < C >_{A_0} < N_c$ at high energies. We generalize previous calculations in Leading Logarithmic Approximation (LLA). The size of the effects related to this jet axis definition are computed for multiplicities in sub-jets with different opening angles and energies by including contributions from the Modified LLA (MLLA) and Next-to-MLLA to the leading order QCD results.