<t>Hi,I'm also trying to figure out how the Hagan's formula would change when you shift the SABR model. At first sight it seems to me that you can just substitute the F and K by F+theta and K+theta in the original formula, because the function C(f) (see formula A.58 in Managing Sile Risk) changes br...

<t>A (probably very straightforeward) question for you guys,when calibrating a Gaussian short rate model (vasicek/g2++), one would normally search for the parameters that make the model prices as close as possible to the observed market prices. In the literature (Brigo, for example), calibration is ...