bad events passing MinSelector
Dear Sherpa experts,
We're using Sherpa 2.2.1 (and also testing with 2.2.2) to generate an ATLAS sample for what we call "very-low-mass Drell-Yan", to model very soft dilepton pairs with very low dilepton masses. These samples are meant to complement other (Sherpa) samples which model on-shell Z+jets events as well as off-shell dilepton+jets (with dilepton masses down to 10 GeV). The configuration is:
(run){
%scales, tags for scale variations
FSF:=1.; RSF:=1.; QSF:=1.;
SCALES STRICT_METS{FSF*MU_F2}{RSF*MU_R2}{QSF*MU_Q2};
%tags for process setup
NJET:=3; LJET:=2,3; QCUT:=20.;
%me generator settings
ME_SIGNAL_GENERATOR Comix Amegic LOOPGEN;
LOOPGEN:=OpenLoops
%settings for MAX(HT,PTV) slicing
SHERPA_LDADD=SherpaFastjetMAXHTPTV
HTMIN:=70
HTMAX:=140
}(run)
(processes){
Process 93 93 -> 13 -13 93 93{NJET};
Order (*,2); CKKW sqr(QCUT/E_CMS);
Cut_Core 1;
NLO_QCD_Mode MC@NLO {LJET};
ME_Generator Amegic {LJET};
RS_ME_Generator Comix {LJET};
Loop_Generator LOOPGEN {LJET};
Max_N_Quarks 4 {6,7,8};
Max_Epsilon 0.01 {6,7,8};
Integration_Error 0.99 {3,4,5,6,7,8};
End process;
}(processes)
(selector){
# mll > 2*ml+250 MeV
Mass 13 -13 0.4614 E_CMS
# pT_lep1>2 GeV, pT_lep2>2 GeV
"PT" 90 2.0,E_CMS:2.0,E_CMS [PT_UP]
# either (mll < 10 GeV) or (pT_lep2 < 5 GeV)
# to make it complementary to the 10<mll<40 samples
MinSelector {
Mass 13 -13 0.0 10.0
"PT" 90 0.0,E_CMS:0.0,5.0 [PT_UP]
}
# 70 GeV < max(HT,pTV) < 140 GeV
FastjetMAXHTPTV HTMIN HTMAX antikt 20.0 0.0 0.4
}(selector)
The part that we're worried about is the MinSelector
piece, which is intended to enforce the complementarity of these samples with our on-shell Z+jets and low-mass DY samples. Our goal is to keep events with either dilepton mass between 0 and 10 GeV, or subleading lepton pT below 5 GeV, or both. However, when inspecting the resulting leptons (status==20
when available, or status==3
if no status==20
leptons are present) we see the following:
Note the small (but nonzero) number of events with both pT(l2)>5 GeV
and m(ll)>10 GeV
. Our understanding is that these events should be rejected by the MinSelector
filter, but somehow they have survived. Any help you can offer in understanding whether these events are features or bugs would be appreciated.
Thanks!
-Mike