Using 1-Jettiness to Measure 2 Jets in DIS 3 Ways

TL;DR

This paper develops a theoretical framework using soft collinear effective theory to predict two-jet production cross sections in deep inelastic scattering, incorporating fixed order and resummed corrections, and explores different event shape definitions.

Contribution

It introduces three variants of 1-jettiness in DIS, derives their factorization theorems, and demonstrates a universal nonperturbative correction parameter across these variants.

Findings

Predictions for HERA kinematic ranges.

Different 1-jettiness definitions affect factorization structures.

Universal nonperturbative correction parameter Omega1.

Abstract

We predict cross sections in deep inelastic scattering (DIS) for the production of two jets---one along the proton beam direction created by initial state radiation (ISR) and another created by final state radiation after the hard collision. Our results include fixed order corrections and a summation of large logarithms up to next-to-next-to-leading logarithmic (NNLL) accuracy in resummed perturbation theory. We make predictions for three versions of a DIS event shape 1-jettiness, each of which constrains hadronic final states to be well collimated into two jets along the beam and final-state jet directions, but which differ in their sensitivity to the transverse momentum of the ISR from the proton beam. We use the tools of soft collinear effective theory (SCET) to derive factorization theorems for these three versions of 1-jettiness. The sensitivity to the ISR gives rise to significantly different structures in the corresponding factorization theorems---for example, dependence on either the ordinary or the generalized kperp-dependent beam function. Despite the differences among 1-jettiness definitions, we show that the leading nonperturbative correction that shifts the tail region of their distributions is given by a single universal nonperturbative parameter Omega1, even accounting for hadron mass effects. Finally, we give numerical results for Q^2 and x values explored at the HERA collider, emphasizing that the target of our factorization-based analyses is to open the door for higher-precision jet phenomenology in DIS.