High Energy Polarized e+e− Beams

Yu Shatunov,A Otboev,I Koop,S Mane

doi:10.1142/s2010194516600892

Abstract

Recently, the wide discussion about Higgs-factory design again returns to problem of high energy polarized electrons and positrons. It’s good known the radiative beam polarization at LEP-collider. It was obtained after spin resonance suppression at [Formula: see text] pick, but didn’t appear at energies above 70 GeV due to an enhancement of unavoidable depolarization effects. We examine in this paper various ideas for radiative polarization at TLEP/FCC-ee and formulate some estimates for the polarization buildup time and the asymptotic polarization. Using wigglers, a useful degree of polarization (for energy calibration), with a time constant of about 1 h, may be possible up to the threshold of W pair production. At higher energies such as the threshold of Higgs production, attaining a useful level of polarization may be difficult in a planar ring. With Siberian Snakes, wigglers and some imagination, polarization of reasonable magnitude, with a reasonable time constant (of not more than about 1 h), may be achievable at very high energies.

Highlights

IntroductionThere are four operating energies of principal interest, viz. the Z0 pole (45 GeV), W -pair production threshold (80 GeV), Higgs production (technically ee− → HZ, 120 GeV) and t+t− pair production (175 GeV)
There are four operating energies of principal interest, viz. the Z0 pole (45 GeV), W -pair production threshold (80 GeV), Higgs production and t+t− pair production (175 GeV)
The main reason is a need to minimize the vertical emittance excitation by quantum fluctuations of synchrotron radiation (SR) in the bending magnets of the snake. Another unpleasant features of the bending snake: unavoidable orbit excursion during beam acceleration and considerable SR power produced by its bends

Summary

Introduction

There are four operating energies of principal interest, viz. the Z0 pole (45 GeV), W -pair production threshold (80 GeV), Higgs production (technically ee− → HZ, 120 GeV) and t+t− pair production (175 GeV). All mention experiments require extremely high luminosity. The first two experiments should be performed with high precision energy calibration.That’s why, we does not consider a linear e+e− collider as a candidate to the Higgs-factory. High energy circular e+e− collider to both for the luminosity and for longitudinal polarization is able. This is an Open Access article published by World Scientific Publishing Company. 1660089-1 provide the precise beam energy calibration. We shall discuss both polarization topics below. Later this machine has been renamed FCC-ee, but for contact with work by others we shall continue to use ‘TLEP’ occasionally

Radiative Polarization

Siberian Snake

Ring with odd number of snakes

Ring with even number of snakes

Conclusion