Updated baseline design for HALHF: the hybrid, asymmetric, linear Higgs factory

TL;DR

This paper presents an updated design for HALHF, a cost-effective Higgs factory using plasma-wakefield acceleration for electrons and RF for positrons, addressing previous challenges and optimizing parameters.

Contribution

It introduces an improved baseline design for HALHF that overcomes earlier technical challenges through parameter and cost optimization.

Findings

Updated baseline design addresses previous challenges.

Parameter- and cost-optimization process detailed.

Design achieves high-gradient electron acceleration with asymmetry.

Abstract

Particle physicists aim to construct a electron-positron Higgs factory as the next major particle collider. However, the high associated costs motivate the development of more affordable collider designs. Plasma-wakefield acceleration is a promising technology to this end. HALHF is a proposal for a Higgs factory that utilizes beam-driven plasma-wakefield acceleration to accelerate electrons to high energy with high gradient, while using radio-frequency acceleration to accelerate positrons to a lower energy. This asymmetry sidesteps a major difficulty in plasma acceleration: that of accelerating positrons with high efficiency and quality. Since publication, several challenges were identified in the original baseline design. We summarize the updated baseline design, which addresses these challenges, and describe the parameter- and cost-optimization process used to arrive at this design.