  We address the multi-node failure repair challenges for MDS array codes.
Presently, two primary models are employed for multi-node repairs: the
centralized model where all failed nodes are restored in a singular data
center, and the cooperative model where failed nodes acquire data from
auxiliary nodes and collaborate amongst themselves for the repair process.This
paper focuses on the cooperative model, and we provide explicit constructions
of optimal MDS array codes with $d$ helper nodes under this model. The
sub-packetization level of our new codes is $(d-k+h)(d-k+1)^{\lceil n/2
\rceil}$ where $h$ is the number of failed nodes, $k$ the number of information
nodes and $n$ the code length. This improves upon recent constructions given by
Liu \emph{et al.} (IEEE Transactions on Information Theory, Vol. 69, 2023).
