[填空题]
The lifetimes listed in Table 32-2 are ia1slrwh6acv-m1 l uf,+ b1,i mn :bd9ntpj2n x3 terms of proper time, measured in a reference frame where the particle istj pdn:9x2n3b at rest. If a tau lepton is created with a kinetic energy of 450 MeV, how long would its track be as measured in the lab, on average, ignoring any collisions? $\Delta x_{\text{lab}} = $ $ \times 10^{-5}\ \text{m}$
