paper

Lund and Cambridge multiplicities for precision physics

arXiv:2205.02861 · doi:10.1007/JHEP10(2022)156

Abstract

We revisit the calculation of the average jet multiplicity in high-energy collisions. First, we introduce a new definition of (sub)jet multiplicity based on Lund declusterings obtained using the Cambridge jet algorithm. We develop a new systematic resummation approach. This allows us to compute both the Lund and the Cambridge average multiplicities to next-to-next-to-double (NNDL) logarithmic accuracy in electron-positron annihilation, an order higher in accuracy than previous works in the literature. We match our resummed calculation to the exact NLO () result, showing predictions for the Lund multiplicity at LEP energies with theoretical uncertainties up to smaller than the previous state-of-the-art. Adding hadronisation corrections obtained by Monte Carlo simulations, we also show a good agreement with existing Cambridge multiplicity data. Finally, to highlight the flexibility of our method, we extend the Lund multiplicity calculation to hadronic collisions where we reach next-to-double logarithmic accuracy for colour singlet production.

64 pages, 11 figures, minor clarifications, version to appear in JHEP

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