NULL Wilson coefficient for Z-Up-Up quark penguin operator

[User001]

Dear Florian,

I obtained Null results in FlavorKit for Wilson coefficients for Z-Up-Up quark penguin operators. The Photon and Gluon penguin have non-zero normal results.

Do you have any idea of the possible reason?

Here are PreSARAH code for Z2U.m, modified from default Z2l.m. I also attached the FlavorKit output screenshot.

I tried "UpQuark -> TopQuark " as indicated in default TopPhotonQ.m, and also multi-choices of FermionOrderExternal and/or CombinationGenerations. But they all got the same NULL results for Z-Up-Up.

Many thanks.

***** Z2U.m *****
NameProcess="Z2U";

ConsideredProcess = "2Fermion1Vector";
FermionOrderExternal={1,2};
NeglectMasses={};

ExternalFields= {UpQuark,bar[UpQuark],Zboson};
CombinationGenerations = {{1,2},{1,3},{2,3}};

AllOperators={
{OZ2USL,Op[7] Pair[ec[3],k[1]]},
{OZ2USR,Op[6] Pair[ec[3],k[1]]},
{OZ2UVL,Op[7,ec[3]]},
{OZ2UVR,Op[6,ec[3]]}
};

OutputFile = "Z2U.m";

Filters = {};

***** Z2U.m *****

Best regards
Peiwen

——————————————————
Peiwen Wu (吴 培文)
Research Fellow
Korea Institute for Advanced Study (KIAS)
Email (KIAS): pwwu@kias.re.kr
Email (Personal): peiwen.wu123@gmail.com
——————————————————

[Avelino]

Hi, it would be useful to know the model for which you are doing this calculation. Is it a model that comes with the SARAH package or a model implemented by yourself? Are there new particles?

[User001]

Hi, it would be useful to know the model for which you are doing this calculation. Is it a model that comes with the SARAH package or a model implemented by yourself? Are there new particles?

Dear Avelino,

Two models I tested both give NULL results for Z-up-up penguin, including the default SM and another one of my current project.

Let me attach some screenshots for Z-Up-Up and Photon-Up-Up, since the attachment does not accept PDF file.

Best regards
Peiwen

——————————————————
Peiwen Wu (吴 培文)
Research Fellow
Korea Institute for Advanced Study (KIAS)
Email (KIAS): pwwu@kias.re.kr
Email (Personal): peiwen.wu123@gmail.com
——————————————————

[User001]

Hi, it would be useful to know the model for which you are doing this calculation. Is it a model that comes with the SARAH package or a model implemented by yourself? Are there new particles?

BTW, everything works normally with non-zero outputs for the Z-Down-Down quarks, i.e. the default Z2l.m.

Best regards
Peiwen

——————————————————
Peiwen Wu (吴 培文)
Research Fellow
Korea Institute for Advanced Study (KIAS)
Email (KIAS): pwwu@kias.re.kr
Email (Personal): peiwen.wu123@gmail.com
——————————————————