Bug fix to 9c4dad45 missing escape in tools/vegas.mm

vegas.mm

@@ -53,7 +53,7 @@ Begin["`Private`"];
 BuildPattern[whichpiece_,flavour_,folder_String]:=RegularExpression[folder<>"/"<>whichpiece<>"_"<>flavour<>"_S\\d*X([\\d\\.]*.)D([\\d\\.]*).*"]->"{$1,$2}"
 BuildPattern[whichpiece_,flavour_,opts___Rule]:=Module[{folder, obs},
     folder = Folder/.{opts}; If[folder === Folder, folder=".*"];
-    obs = Observable/.{opts}; If[obs === Observable, obs=".*", obs="O"<>obs<>"\.vegas"];
+    obs = Observable/.{opts}; If[obs === Observable, obs=".*", obs="O"<>obs<>"\\.vegas"];
     RegularExpression[folder<>"/"<>whichpiece<>"_"<>flavour<>"_S\\d*X([\\d\\.]*.)D([\\d\\.]*)_.*"<>obs]->"{$1,$2}"
 ]
 sigmasign = ToExpression@If[MemberQ[Contexts[], "X`"], "X`DiracS", "Global`\[Sigma]"]