Polarized same-sign WW: wrong polarization assignment for final states with tau leptons
Dear MadGraph5_aMC@NLO Authors,
I’m generating polarized same-sign WW (using MG5 v2.8.1) with the following commands:
import model sm-no_b_mass
define l+ = e+ mu+ ta+
define vl = ve vm vt
define l- = e- mu- ta-
define vl~ = ve~ vm~ vt~
define p = g u c d s u~ c~ d~ s~ b b~
define j = g u c d s u~ c~ d~ s~ b b~
generate p p > w+{X} w+{Y} j j QED=4 QCD=0, w+ > l+ vl @1
add process p p > w-{X} w-{Y} j j QED=4 QCD=0, w- > l- vl~ @1
where {X,Y} is either {0,T} or {T,0}. (I’ll further refer to these 2 cases as 0T sample and T0 sample.)
Since I am using unordered mode [Ref: https:/
When validating the sample, I apply these 2 selections: n(W)>1 & Ws decay to opposite flavor leptons. Now, amongst the 3 possible cases (e-mu, mu-tau, e-tau), we observe that the 0T and T0 samples agree only in the e-mu channel. In e-tau and mu-tau channels, the W decaying to tau is observed to have polarization preference. In the 0T sample, the transversely polarized W always decays via tau, W{T}>tau nu, while in the T0 sample, the longitudinally polarized W always decays via tau, W{0}>tau nu. This renders a non-closure between the sums 00+0T+TT, 00+T0+TT, and the unpolarized sample, for the cosTheta distribution. Please find attached link to supporting slides with cosTheta plots: https:/
Is there some specific setting that I’m not using, which causes this issue?
I am happy to run further tests you might suggest if that helps.
Thanks in advance!
Cheers,
Prasham
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