How to determine nucleon polarization at existing collider experiments?

We propose a novel approach to measure the spin polarization of protons produced in electron-positron collisions. Using existing tracking devices and supporting structure material, general-purpose spectrometers can be utilized as a large-acceptance polarimeter without a hardware upgrade. With the proposed approach, the spin polarization of protons can be revealed, providing a complementary and accurate description of the final-state particles. This could have far-reaching implications, such as enabling the complete determination of the nucleon timelike electromagnetic form factors.