the boosted spinors can be written as u ( s ) ( p → → ) = p / + m 2 m ( E + m ) u ( s ) ( 0 → → ) = E + m 2 m [ ϕ ϕ ( s ) σ σ → → ⋅ ⋅ p → → E + m ϕ ϕ ( s ) ] and v ( s ) ( p → → ) = − − p / + m 2 m ( E + m ) v ( s ) ( 0 → → ) = E + m 2 m [ σ σ → → ⋅ ⋅ p → → E + m χ χ ( s ) χ χ ( s ) ]