A hybrid, asymmetric, linear Higgs factory based on plasma-wakefield and radio-frequency acceleration

Abstract

The construction of an electron–positron collider “Higgs factory” has been stalled for a decade, not because of feasibility but because of the cost of conventional radio-frequency (RF) acceleration. Plasma-wakefield acceleration promises to alleviate this problem via significant cost reduction based on its orders-of-magnitude higher accelerating gradients. However, plasma-based acceleration of positrons is much more difficult than for el ectrons. We propose a collider scheme that avoids positron acceleration in plasma, using a mixture of beam-driven plasma-wakefield acceleration to high energy for the electrons and conventional RF acceleration to low energy for the positrons. We emphasise the benefits o f a symmetric e nergies, a symmetric b unch charges a nd a symmetric t ransverse emittances. The implications for luminosity and experimentation at such an asymmetric facility are explored and found to be comparable to conventional facilities; the cost is found to be much lower. Some of the areas in which R&D is necessary to make HALHF a reality are highlighted, including estimates for the improvement required in key technologies. These range from a factor of 10 to a factor of 1000.

R&D for positron sources at high-energy lepton colliders

“…There exists also the possibility to use an undulator-based positron source for CLIC [9]. The implementation of polarized beams at the HALHF concept [10] is currently under development. Alternative designs for generating polarized positrons via Laser-Compton backscattering have been proposed as well but are currently not pursued [11,12].…”

Status of e+e- Higgs factory projects

“…Status of 𝑒 + 𝑒 − Higgs Factory Projects There is even a newer kid on the block: only in spring this year, a Hybrid Asymmetric Linear Higgs Factory, HALHF [20], has been proposed based on colliding a high-energy, plasma-wakefield accelerated electron beam with a lower energy conventional positron beam. This idea motivates a significant plasma acceleration R&D program targeting collider applications, in particular to demonstrate the concatenation of several plasma cells.…”

Narrow bandwidth, low-emittance positron beams from a laser-wakefield accelerator

“…In order to achieve significant beam-loading conditions in the accelerator cavity, it is also necessary to inject significant amount of charge, typically in the region of 10s of pC 13 . For a future particle collider (e.g a Higgs factory) it will also be necessary to provide a higher charge ( nC) at a high energy ( GeV) 14 .…”