Incoherent horizontal emittance growth due to the interplay of beam-beam and longitudinal wakefield in crab-waist colliders

TL;DR

This paper analyzes how beam-beam interactions and longitudinal wakefields cause incoherent horizontal emittance growth in crab-waist colliders, combining theoretical insights with simulations to understand and mitigate the effects.

Contribution

It extends the theory of sychrobetatron resonances to crab-waist colliders and demonstrates their impact on emittance growth through simulations and case studies.

Findings

Interplay of beam-beam and wakefields causes horizontal blowup.

Horizontal-longitudinal dynamics can be studied independently.

Strategies are proposed to mitigate emittance growth.

Abstract

In this paper, we investigate quadrupolar sychrobetatron resonances caused by beam-beam collisions and their interplay with longitudinal wakefields in the context of crab-waist colliders. We present a comprehensive theoretical review of the established theory of sychrobetatron resonances and extend the formalism to explore horizontal sychrobetatron resonances specific to crab-waist colliders. As a case study, we examine incoherent horizontal emittance growth at the SuperKEKB and demonstrate through simulations that the interplay between beam-beam and longitudinal wakefields leads to a horizontal blowup of the bunch size and that the study of the dynamics can be reduced to the horizontal-longitudinal plane, independent of the motion in the vertical dimension. We present extensive simulation results using the codes BBWS, PyHEADTAIL and Xsuite, connect our analytical findings with these findings, and propose strategies to mitigate horizontal blowup.