  A new method for analyzing complex superhump light curves for the 2001
outburst of WZ Sagittae is proposed. The complexity arises because
intrinsically time-varying and non-axisymmetric distributions of superhump
light sources are coupled with the aspect effects around the binary orbital
phase because of its high orbital inclination. The new method can disentangle
these complexities by separating the non-axisymmetric spatial distribution in
the disk from the time variation with the superhump period. It may be called a
helical tomography of an accretion disk because it can reconstruct a series of
disk images (i.e., disk's azimuthal structures) at different superhump phases.
The power spectral data of superhump light curves of the 2001 outburst of WZ
Sge by Patterson et al.(2002,PASP,114,721) are now interpreted under a new
light based on the concept of helical tomography, and the azimuthal wave
numbers of various frequency modes are identified. In particular, a frequency
component, $n\omega_0-\Omega$, where $\omega_0$ and $\Omega$ are the orbital
frequency and a low frequency of the apsidal precession of the eccentric disk,
is understood as an $(n-1)$-armed traveling wave in the disk. A vigorous
excitation of a wave component of $\cos(2\Theta-3\omega_0 t)$ in the first week
of the superhump era of WZ Sge, where $\Theta$ is the azimuthal angle, supports
Lubow's (1991) theory of non-linear wave coupling of the eccentric Lindblad
resonance for the superhump phenomenon. This method can in principle be applied
to other SU UMa stars with high orbital inclination if light curves are fully
covered over the beat cycle.
