THETA plotting for Z boson Decay

[hsnrza007]

Hi, I'm plotting z boson decay (z > e+ e-)angle distribution using "plot THETA(e-)200 0 3.1415" but the plot that I'm getting peaks at around 90 degrees and then goes to zero as we move to 0 or Pi. Now in the manual it says that the THETA function computes the angle between beam axis and momentum. And in my case the z boson is at rest so what beam axis MadAnalysis5 takes? if it's arbitrary then why the THETA peaks at 90 degree angle, as it means that the most of the particles decay at 90 degree, wrt to arbitrary beam axis. Which is not making sense. And my PX,PY,PZ all are identical.

[BFuks]

Hello, MadAnalysis only plots what it finds in the input event file. In any given event record, the four momenta of the diferent particles are given (in the lab frame, usually) and this is on this information that the angles are computed. If the plot you obtain seems incorrect, the first thing to check is the input events themselves. Regards, Benjamin

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On 14 Nov 2025, at 10:43, hsnrza007 ***@***.***> wrote: Hi, I'm plotting z boson decay (z > e+ e-)angle distribution using "plot THETA(e-)200 0 3.1415" but the plot that I'm getting peaks at around 90 degrees and then goes to zero as we move to 0 or Pi. Now in the manual it says that the THETA function computes the angle between beam axis and momentum. And in my case the z boson is at rest so what beam axis MadAnalysis5 takes? if it's arbitrary then why the THETA peaks at 90 degree angle, as it means that the most of the particles decay at 90 degree, wrt to arbitrary beam axis. Which is not making sense. And my PX,PY,PZ all are identical. — Reply to this email directly, view it on GitHub <#306>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIWJNJYRRWPWXMPFHGF4UTD34WP4HAVCNFSM6AAAAACMDCSQNWVHI2DSMVQWIX3LMV43ERDJONRXK43TNFXW4OZZGE2DAMZYGA>. You are receiving this because you are subscribed to this thread.