Relativistic free-motion time-of-arrival operator for massive spin-0 particles with positive energy

A relativistic version of the Aharonov-Bohm time-of-arrival operator for spin-0 particles was constructed by Razavi [Il Nuovo Cimento B 63, 271 (1969)]. We study in detail taking its rigged Hilbert space extension. It is shown that extension provides more insights into problem goes beyond Razavi's original results. This allows us to use eigenfunctions exhibit unitary arrival construct distributions. The expectation value also calculated and can arrive earlier or later than expected classically. Last, distribution are be consistent with special relativity.