MP thermal masses (#318)

* W thermal mass to match MP

* Commenting on the thermal masses

* modified W mass in the SM model file as well. Also modified comment

---------

Co-authored-by: Joonas Hirvonen <joonas.hirvonen@nottingham.ac.uk>
Co-authored-by: Jorinde van de Vis <jorindevandevis@outlook.com>

Author: 3 people

Models/StandardModel/exampleCollisionDefs.py

@@ -51,6 +51,9 @@ def setupCollisionModel_QCDEW(
     # Define mass helper functions. We need the mass-squares in units of temperature, ie. m^2 / T^2.
     # These should take in a WallGoCollision.ModelParameters object and return a floating-point value
 
+    # Note that the particular values of masses here are for a comparison with arXiv:hep-ph/9506475.
+    # Doubly weak diagrams have been neglected as subleading in the comparison.
+    # For proceeding beyond the leading-log approximation one should use the asymptotic masses.
     # For quarks we include the thermal mass only
     def quarkThermalMassSquared(p: WallGoCollision.ModelParameters) -> float:
         gs = p["gs"]  # this is equivalent to: gs = p.getParameterValue("gs")
@@ -60,7 +63,7 @@ def gluonThermalMassSquared(p: WallGoCollision.ModelParameters) -> float:
         return 2.0 * p["gs"] ** 2
 
     def wBosonThermalMassSquared(p: WallGoCollision.ModelParameters) -> float:
-        return 11.0 * p["gw"] ** 2 / 6.0
+        return 3.0 * p["gw"] ** 2 / 5.0
 
     def HiggsBosonThermalMassSquared(p: WallGoCollision.ModelParameters) -> float:
         return (9 * p["gw"] ** 2 / 4 + 3 * p["yt"]) / 12.0

Models/StandardModel/standardModel.py

@@ -426,6 +426,11 @@ def updateCollisionModel(
 
         gs = inWallGoModel.modelParameters["g3"]  # names differ for historical reasons
         gw = inWallGoModel.modelParameters["g2"]  # names differ for historical reasons
+        
+        
+        # Note that the particular values of masses here are for a comparison with arXiv:hep-ph/9506475.
+        # For proceeding beyond the leading-log approximation one should use the asymptotic masses.
+        # For quarks we include the thermal mass only
         changedParams.addOrModifyParameter("gs", gs)
         changedParams.addOrModifyParameter("gw", gw)
         changedParams.addOrModifyParameter(
@@ -435,7 +440,7 @@ def updateCollisionModel(
             "mg2", 2.0 * gs**2
         )  # gluon thermal mass^2 in units of T
         changedParams.addOrModifyParameter(
-            "mw2", 11.0 * gw**2 / 6.0
+            "mw2", 3.0 * gw**2 / 5.0
         )  # W boson thermal mass^2 in units of T
 
         inOutCollisionModel.updateParameters(changedParams)