Cronin effect from backward to forward rapidity. A tale of two misteries

I discuss recent experimental data on the Cronin effect in deuteron old collisions at the top RHIC energy, in a pseudorapidity range η ε [-2,3]. Two theoretical approaches are compared and contrasted: the pQCD-based Glauber-Eikonal model and Colour Glass Condensate models. Neither can describe the Cronin effect over the whole pseudorapidity interval up to now explored experimentally, its most mysterious and intriguing part being at negative rapidity. (author)