Radiative Return Capabilities of a High-Energy, High-Luminosity $e^+e^-$ Collider

TL;DR

This paper investigates the potential of a proposed high-luminosity electron-positron collider at 90 or 250 GeV to perform radiative return studies, enabling exploration of lower-energy phenomena and complementing existing colliders.

Contribution

It analyzes the radiative return capabilities of a new high-energy collider, comparing its potential with past and current colliders for various physics studies.

Findings

High-luminosity collider can access lower-energy events via initial-state radiation.

Potential to improve dark photon searches and heavy flavor spectroscopy.

Complementary to existing colliders like LEP, LHC, and Tevatron.

Abstract

An electron-positron collider operating at a center-of-mass energy $E_{CM}$ can collect events at all lower energies through initial-state radiation (ISR or radiative return). We explore the capabilities for radiative return studies by a proposed high-luminosity collider at $E_{CM}$ = 250 or 90 GeV, to fill in gaps left by lower-energy colliders such as PEP, PETRA, TRISTAN, and LEP. These capabilities are compared with those of the lower-energy $e^+e^-$ colliders as well as hadron colliders such as the Tevatron and the CERN Large Hadron Collider (LHC). Some examples of accessible questions in dark photon searches and heavy flavor spectroscopy are given.