The Brownian loop soup by Gregory F. Lawler and Wendelin Werner (2004, 10.1007/s00440-003-0319-6)

By Gregory F. Lawler, Wendelin Werner. Probability Theory and Related Fields 128, 565–588.

Author preprint: arxiv.org/abs/math/0304419

Section 4.1, equation (15), defines loop measure by normalized planar Brownian bridges with density 1/(2 pi t squared); Proposition 6 proves conformal invariance. The introduction defines loop soups as Poisson samples of this measure. The arXiv PDF date displayed by the current rendering is not used as the journal publication date.