Plotting mass recoil from radiative return process

[nyckxxstark]

Question

Dead MadAnalysis5 team,

I am working on the reconstructed level mode feature of ma5 but using the normal mode to generate plots. My signal is mu- mu+ > Z_D photon, Z_D > e- e+ which is a radiative return process. Is there a way to plot the mass recoil as defined by the equation (19) below? Thanks a lot!

[BFuks]

Hi,

Can't you use, for instance, plot RECOIL(zd, a) where the recoil is defined in tools/SampleAnalyzer/Commons/DataFormat/ParticleBaseFormat.h.

Cheers,

Benjamin

[nyckxxstark]

Hi! Can I use plot RECOIL(e[1] e[2], a) assuming that Z_D decays to e[1] and e[2]? Thanks!

[BFuks]

Of course.

Cheers,

Benjamin

[nyckxxstark]

Hi! The definition of RECOIL in tools/SampleAnalyzer/Commons/DataFormat/ParticleBaseFormat.h. is given by this

/// Accessor to the recoil class (computed wrt another particle)
const MAfloat32 recoil(const ParticleBaseFormat* p) const
{ return std::abs((momentum_ - p->momentum()).M()); }

So, if I plot RECOIL(e[1] e[2], a), does this mean I am plotting m_recoil = sqrt((p_e[1] + p_e[1] - p_photon)^2)? If this is the case, I am not plotting equation (19) since p_1 and p_2 correspond to momenta of the beam (which are the muons). Thanks for your prompt response!

[BFuks]

Hi,

In this case you should combine the initial-state particles in the first argument of the method (and indicate the [allstate] option to make sure both final-state and initial-state particles are considered by the code)

Cheers,

Benjamin

[nyckxxstark]

Hi! I did plot RECOIL(mu- mu+, a) [allstate] instead of plot RECOIL(e[1] e[2], a) but the histogram is empty. How to fix this?

[BFuks]

Hi, Yes, precisely. Cheers, Benjamin

…

On 14 Nov 2025, at 07:40, nyckxxstark ***@***.***> wrote: nyckxxstark left a comment (MadAnalysis/madanalysis5#305) <#305 (comment)> Hi! So instead of plot RECOIL(e[1] e[2], a) should I do plot RECOIL(e[1] e[2], a) [allstate]? — Reply to this email directly, view it on GitHub <#305 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIWJNJ732CB447JTPEKJ3WL34V2OBAVCNFSM6AAAAACMCG56WWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTKMZRGEZTMMBUGY>. You are receiving this because you commented.