# Quark Fragmentation within an Identified Jet - High Energy Physics - Phenomenology

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Abstract: We derive a factorization theorem that describes an energetic hadron hfragmenting from a jet produced by a parton i, where the jet invariant mass ismeasured. The analysis yields a -fragmenting jet function- G i^hs,z thatdepends on the jet invariant mass s, and on the energy fraction z of thefragmentation hadron. We show that G^h i can be computed in terms ofperturbatively calculable coefficients, J {ij}s,z-x, integrated againststandard non-perturbative fragmentation functions, D j^{h}x. We also showthat the sum over h of the integral over z of z G i^hs,z is given by thestandard inclusive jet function J is which is perturbatively calculable inQCD. We use Soft-Collinear Effective Theory and for simplicity carry out ourderivation for a process with a single jet, B -> X h l nu, with invariant massm {X h}^2 >> Lambda QCD^2. Our analysis yields a simple replacement rule thatallows any factorization theorem depending on an inclusive jet function J i tobe converted to a semi-inclusive process with a fragmenting hadron h. We applythis rule to derive factorization theorems for B -> X K gamma which is thefragmentation to a Kaon in b -> s gamma, and for e^+e^-> dijets+h withmeasured hemisphere dijet invariant masses.

Author: ** Massimiliano Procura, Iain W. Stewart**

Source: https://arxiv.org/