Probing Transverse-Momentum Dependent Evolution With Groomed Jets

Yiannis Makris; Duff Neill; Varun Vaidya

doi:10.1007/JHEP07(2018)167

paper

Probing Transverse-Momentum Dependent Evolution With Groomed Jets

arXiv:1712.07653 · doi:10.1007/JHEP07(2018)167

Abstract

We propose an observable which involves measuring the properties (transverse momentum $p_{h ⊥}$ and energy fraction $z_{h}$ ) of an identified hadron inside a groomed jet. The jet is identified with an anti-kT/CA algorithm and is groomed by implementing the modified mass drop procedure with an energy cut-off parameter $z_{c u t}$ . The transverse momentum of the hadron inside the jet is measured with respect to the groomed jet axis. We obtain a factorization theorem in the framework of Soft Collinear Effective Theory (SCET), to define a Transverse Momentum Dependent Fragmenting Jet Function (TMDFJF). The TMDFJF is factorized into collinear and collinear soft modes by matching onto SCET $_{+}$ . We resum large logarithms in $E_{J} / p_{h ⊥}$ , where $E_{J}$ is the ungroomed jet energy, to NLL accuracy and apply this formalism for computing the shape of the $p_{h ⊥}$ distribution of a pion produced in an $e^{+} + e^{-}$ collision. We observe that the introduction of grooming makes this observable insensitive to non-global logarithms and particularly sensitive to non-perturbative physics of the transverse momentum dependent evolution at low values of $p_{h ⊥}$ , which can be probed in the variation of the cut-off parameter $z_{c u t}$ of the groomer. We discuss how this observable can be used to distinguish between non-perturbative models that describe universal TMD evolution and provide a window into the three dimensional structure of hadrons.

23 pages, 4 figures

Probing Transverse-Momentum Dependent Evolution With Groomed Jets

Abstract

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