Parton fragmentation within an identified jet at NNLL

  • Ambar Jain
  • Massimiliano Procura
  • Wouter J. Waalewijn


The fragmentation of a light parton i to a jet containing a light energetic hadron h, where the momentum fraction of this hadron as well as the invariant mass of the jet is measured, is described by “fragmenting jet functions”. We calculate the oneloop matching coefficients \( {\mathcal{J}_{ij}} \) that relate the fragmenting jet functions \( \mathcal{G}_i^h \) to the standard, unpolarized fragmentation functions D h j for quark and gluon jets. We perform this calculation using various IR regulators and show explicitly how the IR divergences cancel in the matching. We derive the relationship between the coefficients \( {\mathcal{J}_{ij}} \) and the quark and gluon jet functions. This provides a cross-check of our results. As an application we study the process e + e -Xπ+ on the Υ(4S) resonance where we measure the momentum fraction of the π+ and restrict to the dijet limit by imposing a cut on thrust T. In our analysis we sum the logarithms of τ = 1-T in the cross section to next-to-next-to-leading-logarithmic accuracy (NNLL). We find that including contributions up to NNLL (or NLO) can have a large impact on extracting fragmentation functions from e + e - → dijet + h.


Jets QCD 


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Copyright information

© SISSA, Trieste, Italy 2011

Authors and Affiliations

  • Ambar Jain
    • 1
  • Massimiliano Procura
    • 2
    • 3
  • Wouter J. Waalewijn
    • 4
  1. 1.Department of PhysicsCarnegie Mellon UniversityPittsburghU.S.A.
  2. 2.Physik-DepartmentTechnische Universität MünchenGarchingGermany
  3. 3.Albert Einstein Center for Fundamental Physics, Institute for Theoretical PhysicsUniversity of BernBernSwitzerland
  4. 4.Department of PhysicsUniversity of California at San DiegoLa JollaU.S.A.

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