# The transverse momentum distribution of hadrons within jets

## TL;DR

This paper investigates the transverse momentum distribution of hadrons within jets in proton-proton collisions, offering a new way to study poorly constrained TMD fragmentation functions, especially for gluons, using SCET-based factorization.

## Contribution

It introduces a novel observable for in-jet fragmentation that isolates TMDFFs without dependence on TMD PDFs, enabling cleaner experimental constraints.

## Key findings

- Demonstrated factorization within SCET for the observable.
- Showed the observable's independence from TMD PDFs.
- Compared numerical results with LHC data.

## Abstract

We study the transverse momentum distribution of hadrons within jets, where the transverse momentum is defined with respect to the standard jet axis. We consider the case where the jet substructure measurement is performed for an inclusive jet sample $pp\to\text{jet}+X$. We demonstrate that this observable provides new opportunities to study transverse momentum dependent fragmentation functions (TMDFFs) which are currently poorly constrained from data, especially for gluons. The factorization of the cross section is obtained within Soft Collinear Effective Theory (SCET), and we show that the relevant TMDFFs are the same as for the more traditional processes semi-inclusive deep inelastic scattering (SIDIS) and electron-positron annihilation. Different than in SIDIS, the observable for the in-jet fragmentation does not depend on TMD parton distribution functions which allows for a cleaner and more direct probe of TMDFFs. We present numerical results and compare to available data from the LHC.