Helicity Amplitude Analysis of Z_\rm c(3900)^\pm in e^+e^-\to\pi^+\pi^-J/\psi

It is crucial to determine the spin and parity (J^P) of Z_\rm c(3900)^\pm for understanding its structure. We perform a helicity amplitude analysis on Z_\rm c(3900)^\pm in the process e^+e^-\to\pi^+\pi^-J/\psi with the hypotheses J^P=0^-, 1^+, 1^-, 2^+ and 2^-. To estimate the significance of J^P=1^+ over other hypotheses, we perform a Monte Carlo simulation study, and we also discuss the prospect of measuring the spin parity in the future experiment with a large data sample.