[Fix] WakePotential.reference_loss sign for dipolar wake

Fix TD calculation for transverse dipolar wakes due to sign change in the 31/08/2021 commit.

tracking/wakepotential.py

@@ -507,12 +507,14 @@ class WakePotential(Element):
         for wake_type in self.types:
             tau0, Wp = self.get_wakepotential(bunch, wake_type)
             profile0 = getattr(self, "profile0_" + wake_type)
-            factorTD = -1*np.trapz(Wp*profile0, tau0)
+            factorTD = np.trapz(Wp*profile0, tau0)
             
+            if wake_type == "Wlong":
+                factorTD *= -1
             if wake_type == "Wxdip":
-                factorTD = factorTD / bunch["x"].mean()
+                factorTD /= bunch["x"].mean()
             if wake_type == "Wydip":
-                factorTD = factorTD / bunch["y"].mean()
+                factorTD /= bunch["y"].mean()
             
             Z = getattr(self.wakefield, "Z" + wake_type[1:])
             sigma = bunch['tau'].std()