  We investigate theoretically the relative time delay of photoelectrons
originating from different atomic subshells of noble gases. This quantity was
measured via attosecond streaking and studied theoretically by Schultze et al.
[Science 328, 1658 (2010)] for neon. A substantial discrepancy was found
between the measured and the calculated values of the relative time delay.
Several theoretical studies were put forward to resolve this issue, e.g., by
including correlation effects. In the present paper we explore a further
aspect, namely the directional dependence of time delay. In contrast to neon,
for argon target a strong angular dependence of time delay is found near a
Cooper minimum.
