  Let $v \ne 0$ be a vector in $\R^n$.
  Consider the Laplacian on $\R^n$ with drift $\Delta_{v} = \Delta + 2v\cdot
\nabla$ and the measure $d\mu(x) = e^{2 \langle v, x \rangle} dx$, with respect
to which $\Delta_{v}$ is self-adjoint. This measure has exponential growth with
respect to the Euclidean distance. We study weak type $(1, 1)$ and other sharp
endpoint estimates for the Riesz transforms of any order, and also for the
vertical and horizontal Littlewood-Paley-Stein functions associated with the
heat and the Poisson semigroups.
