Critical Issues in Linear Colliders

TL;DR

This paper reviews the current state, challenges, and future prospects of linear colliders in particle physics, discussing technological limitations, potential high-energy advancements, and the feasibility of emerging acceleration methods.

Contribution

It provides a comprehensive analysis of linear collider parameters, evaluates advanced plasma and laser acceleration techniques, and critically assesses their viability for future high-energy colliders.

Findings

Current technologies can reach about 5 TeV energies with sufficient luminosity.

Laser and plasma acceleration methods face significant conceptual and practical challenges at high energies.

Linear colliders above 10 TeV are difficult with existing and emerging technologies.

Abstract

Linear colliders (LC) on the energy 0.5-1 TeV are considered as the next step in the particle physics. High acceleration gradients, small beam sizes, precision tolerances, beam collision effects are main problems for linear colliders. In this paper we discuss physics motivation, parameters and status of current LC projects, e+e-, gamma-gamma and gamma-electron modes of operation, physical limitations on the energy and luminosity. Present technologies allow to reach energies about 5 TeV with adequate luminosities. Advanced technique based on plasma and laser method of acceleration can provide much higher accelerating gradients, however, perspectives of these methods for high energy colliders are still under big question. Linear colliders with energies above 10 TeV are hard for any acceleration technology. Speculations on possibility of PeV linear colliders based on ponderomotive laser acceleration are just not serious and contain several mistakes on conceptual level. It is shown that due to radiation in the transverse laser field, methods of acceleration based on laser bunch ``pressure'' do not work at high energies.