zz>4l madspin: factor 2 from declaration of same decay for same two particles
Hi experts,
we're generating zz>4l EFT aQGC samples and using madspin- start from
generate p p > j j z z QCD=0 T0==1
then how to define z decays among there two options?:
case1) decay z > l+ l-; decay z > l+ l-
case2) decay z > l+ l-
1) and 2) give the same lepton kinematics and everything the same except in case 1) sum of weights and cross-section is exactly twice larger
cross-section from log file (for FT0 QUAD) before madspin is 0.07496 +- 0.0001524 pb
after madspin
in case1) cross-section (nb)= 6.789e-07
and in case 2) cross-section (nb)= 3.395e-07
estimation starting from production gives
sigma*(
(factor 2 from the indistinguisahble boson)
which is much closer to case1) xsec after decay
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another thing with case2) which is kind strange, when generating 13200 events:
decay z > l+ l-; decay z > l+ l- >>>>> generate 13200 decay event for particle z
decay z > l+ l- >>>>> generate 26400 decay event for particle z
why factor 2 for decay events for case 2) ?
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how to define lepton decays of two Z?
is this factor two coming indistinguishable particles?
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