# Collinear Drop

## TL;DR

This paper introduces collinear drop jet substructure observables that are unaffected by collinear radiation, enabling detailed study of soft radiation within jets for various applications in particle physics.

## Contribution

The paper systematically develops and analyzes collinear drop observables, deriving factorization formulas and resummation techniques using soft-collinear effective theory, including novel classes with no leading double logs.

## Key findings

- Derived factorization formulas for collinear drop observables.
- Performed next-to-leading-logarithmic resummation of soft radiation effects.
- Identified classes of observables with no leading double logarithms.

## Abstract

We introduce collinear drop jet substructure observables, which are unaffected by contributions from collinear radiation, and systematically probe soft radiation within jets. These observables can be designed to be either sensitive or insensitive to process-dependent soft radiation originating from outside the jet. Such collinear drop observables can be exploited as variables to distinguish quark, gluon, and color neutral initiated jets, for testing predictions for perturbative soft radiation in Monte Carlo simulations, for assessing models and universality for hadronization corrections, for examining the efficiency of pileup subtraction methods, and for any other application that leaves an imprint on soft radiation. We discuss examples of collinear drop observables that are based both on clustering and on jet shapes. Using the soft-collinear effective theory we derive factorization expressions for collinear drop observables from QCD jets, and carry out a resummation of logarithmically enhanced contributions at next-to-leading-logarithmic order. We also identify an infinite class of collinear drop observables for which the leading double logarithms are absent.