The Subjet Multiplicity in Quark and Gluon Jets
Abstract
We calculate the mean number of subjets in quark and gluon jets in the final state of e+e- annihilation. Since `quark' and `gluon' jets are scheme-dependent objects, we stress the importance of using the same definition as in experimental analyses. We define the jets using the kperp algorithm at a coarse scale y1, and the subjets using a finer scale y0, in the same algorithm. Gluon jets are anti-tagged by the presence of heavy quarks in both other jets. Our result is exact to leading order in alphas, and resums leading and next-to-leading logarithmic terms in the ratio y1/y0 to all orders in alphas.
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