**Next message:**Vladyslav Shtabovenko: "Re: Question about TID in FC9.2.0"**Previous message:**Xiu-Lei Ren: "Re: Re: Question about TID in FC9.2.0"**Maybe in reply to:**Zhou Yong: "Maybe a error at OneLoop"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Mail actions:**[ respond to this message ] [ mail a new topic ]

This one seems to be the oldest question (16 years old) on this mailing list without a satisfying answer.

I checked the integral with the current dev version and FeynHelpers and agree with the OneLoopFPI output

up to the relative sign in front of the 4:

$LoadAddOns = {"FeynHelpers"};

<< FeynCalc`

SP[p, p] = pp;

int = 1/(I Pi^2) FAD[{p - k}, {k, mW}] GSD[k];

res1 = OneLoop[k, int]

(PaXEvaluate[16 Pi^4 res1, PaXImplicitPrefactor -> 1/(2 Pi)^D,

PaXSeries -> {{pp, 0, 0}}] /. {ScaleMu^2 ->

ScaleMu^2 E^EulerGamma/(4 Pi),

1/Epsilon -> 2/Epsilon}) // Simplify

One should also mention that it is very easy to make a mistake here, if one just naively

puts p^2 to zero in B0:

(PaXEvaluate[

16 Pi^4 res1 /. B0[FCI@SP[p, p], 0, mW^2] -> B0[0, 0, mW^2],

PaXImplicitPrefactor -> 1/(2 Pi)^D,

PaXSeries -> {{pp, 0, 1}}] /. {ScaleMu^2 ->

ScaleMu^2 E^EulerGamma/(4 Pi),

1/Epsilon -> 2/Epsilon}) // Simplify

This is because B0 is multiplied by 1/p^2, so one would loose a finite contribution when doing so.

I guess this is what might have happened to OP.

Cheers,

Vladyslav

*> Dear Rolf Mertig Professor:
*

*>
*

*> I have calculate some feynman diagrams of elecweak model.Compairing
*

*> large gauge boson mass,the light quark momentum can be neglected,so
*

*> analytic results will be gotten.I expand B0,C0,D0 functions when
*

*> neglecting external momentum.But I found the results achieved by using
*

*> OneLoop function are different from the results achieved by hand.
*

*> So I chosed a very simple loop integration to check my results,and find
*

*> maybe OneLoop function is wrong.
*

*> I write a small function "OneLoopFPI" to imitate the processes of
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*> calculations by hand Using feynman parameters method in common.I found
*

*> it give the same results with my previous results gotten by hand.
*

*> I send you a ps file about a very simple question dealing with OneLoop
*

*> and OneLoopFPI function.Maybe you can find where I was wrong.
*

*> Thanks for your attentions.
*

*>
*

*> zhou yong 14,Dec,2000
*

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