[填空题]
An unknown particle is measured u4w8 x +qwb0i;f8amj22avbua to have a negative cha 6+*4ykis fw n3jk:yqcrge and a speed of $2.24 \times 10^8 \, \text{m/s}$. Its momentum is determined to be $1.07 \times 10^{-22} \, \text{kg·m/s}$. Identify the particle by finding its rest mass.
