New clustering algorithm for multijet cross sections in e +e − annihilation

Abstract

Cross sections for e +e − → n- jets, as functions of the jet resolution parameter y cut, are computed according to a new clustering algorithm. The jet multiplicity n is defined in such a way that jets i and j with energies E i and E j at relative angle angle θ ij are resolved if y ij = 2(1− cosθ ij) min (E i 2, E j 2) s>y cut , where s is the centre-of-mass energy squared. Using this algorithm, large higher-order corrections at small values of y cut can easily be evaluated. Our calculations include resummation of leading and next-to-leading logarithms of y cut to all orders in QCD perturbation theory. This enables us to predict the jet cross sections at small y cut for arbitrary n. Simple analytical results for n⩽5 are presented.