Name: Michael Park (email_not_shown)
Date: 12/19/16-05:48:18 AM Z

Hi. I have been having a lot of trouble trying to compute the scalar C0 integral for general masses using the Package-X routines.

Using the FeynCalc interface

in: PaXEvaluate[C0[0,0,mH^2,ma^2,ma^2,ma^2]]

out: log^2((-mH^2+Sqrt[mH^4-4 mH^2 MT3^2]+2 MT3^2)/(2 MT3^2))/(2 mH^2)

...however, when I try more general masses it seems to give up

in: PaXEvaluate[C0[0,0,mH^2,ma^2,mb^2,ma^2]]
out: C0[0,0,mH^2,ma^2,mb^2,ma^2]

Similarly, if I use the straight Package-X routines it gives me a reasonable answer for massless final states and one flavor in the loop

in: LoopIntegrate[Spur[\[DoubleStruckOne]],
     q, {q - k1, ma}, {q + k2, ma}, {q, ma}] /. {k1.k1 -> 0,
     k2.k2 -> 0, q.q -> mH^2, q -> k1 + k2,
     k1.k2 -> (mH^2 - 2 mW^2)/2} /. {LTensor[k1, \[Mu]] -> 0,
    LTensor[k2, \[Nu]] -> 0} // LoopRefine // Simplify
out: (2 Log[(2 ma^2 - mH^2 + 2 mW^2 +
   Sqrt[(mH^2 - 2 mW^2) (-4 ma^2 + mH^2 - 2 mW^2)])/(
  2 ma^2)]^2)/(mH^2 - 2 mW^2)

..however if I make the final state particles massive or if I enter more general loop masses, the computation seems to quit

I was wondering if there was any way to handle these more complicated C0 integrals? Thanks very much!

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