Exact Heavy To Light Meson Form Factors In The Chiral Limit Of Planar   1+1 QCD
  The form factors of the flavor changing vector current between a $\bar q Q$-meson and the lightest $\bar q q$ (pseudoscalar-)meson are computed exactly and explicitly in the 't~Hooft model (planar QCD in $1+1$ dimensions) in the limit that the mass of $q$-quark vanishes. 
Benjamin Grinstein