https://arxiv.org/pdf/1501.02382.pdf
Page 30 Lemma 7.6, there is written something like $O_P(\cdot)$ - it looks like the Landau notation, that the right term doesn't grow faster than $c \cdot \sqrt{\frac{log(d)}{T}}$ for some constant $c$.
But is this what is meant here? What is the $P$ standing for?