(color online) The energy gap as a function of the in-plane magnetic field. For the 1/3 state, the gap always decreases as increasing ω_x for ω = 5.0 (a) and ω = 2.0 (b). However, the gap for the 7/3 state has different behaviors at different ω₀s. For ω₀ = 5.0 (c), we find the energy gap for 9 and 10 electrons still monotonically decreases as increasing ω_x (we assume that the increments for small systems are due to the finite size effect). When ω₀ = 2.0 (d), the gap increases for small tilting and decreases for large tilting.