How is the particle spin in the LHE file related to the helicity in HELAS

For the case where such information is not lorentz invariant (i.e. for massive particle), the
important point is that those helicity information are given in the partonic center of mass of the collision.

But yes those are the same definition as the one for helas.

> I would like to know this since I am interested in validating the Madgraph reweighting tool by computing the matrix element ratios by hand, using the full helicity information

Note that you can compare both reweighting method (per helicity or on average on helicity ) within MG5aMC.

Cheers,

Olivier

> On 22 Dec 2022, at 16:55, akash <email address hidden> wrote:
>
> New question #704190 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/704190
>
> Hello Madgraph authors,
>
> How do I interpret the particle spins written in the LHE file as helicity eigenvalues used by HELAS during computation of matrix elements?
>
> Are they exactly the same?
> Are they related by sign flips? For ex. flipping the spin of particles with negative longitudinal momentum gives the helicity, or something like this?
>
> I would like to know this since I am interested in validating the Madgraph reweighting tool by computing the matrix element ratios by hand, using the full helicity information
>
> Thanks
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.