processes with high multiplicity of b-jets in ME level

[alexandra.oliveira@cern.ch]

Dear developers

I am trying to generate processes with high multiplicity of b-quarks in final state, for instance

b bar{b} b bar{b} j j

and

Z(b bar{b}) b bar{b} j j

the configuration files I am using are bellow

in the run however I am mostly having these kind of warnings

################################################ Poincare::Poincare(): Inaccurate rotation {

a = (-0.0672029,0.906422,0.416993) b = (0,0,1) a' = (0.878832,0.433463,0.199411) -> rel. dev. (inf,inf,-0.800589) m_ct = 0.416993 m_st = -0.90891 m_n = (0,1.16895e-07,-2.54096e-07)

} ###############################################

I am not sure which physics is behind it, and if an smart cut would help

do you have any idea?

thanks Alexandra

bellow the Run.dat's

#################################### to bbbbjj

(run){

EVENTS 10; BEAM_1 = 2212; BEAM_ENERGY_1 = 6500; BEAM_2 = 2212; BEAM_ENERGY_2 = 6500;

% tags and settings for ME-level cuts J1CUT:=20.; J2CUT:=20.;

EVENT_OUTPUT=HepMC_Short[bbbbjj];

}(run)

(processes){

Process 93 93 -> 5 -5 93 93 Order_EW 0; CKKW sqr(20/E_CMS) Integration_Error 0.10; Selector_File *|(coresel){|}(coresel) {2}; End process;

}(processes)

(coresel){

NJetFinder 2 20.0 0.0 0.4 -1

}(coresel)

##############################################

to Z(bb)bbjj

(run){

EVENTS 20000; NJET:=2; QCUT:=20; BEAM_1 2212; BEAM_ENERGY_1 6500; BEAM_2 2212; BEAM_ENERGY_2 6500; WIDTH[6] 0; STABLE[6] 0; WIDTH[24] 0; STABLE[24] 0; HARD_DECAYS 1; HARD_SPIN_CORRELATIONS 1; CORE_SCALE QCD; EVENT_OUTPUT=HepMC_Short[ttjj]

}(run);

(processes){

Process 93 93 -> 23[a] 5 -5 93{NJET}; Decay 23[a] -> 5 -5; Order_EW 2; CKKW sqr(QCUT/E_CMS); End process;

}(processes);

[Jan Winter]

Dear Alexandra,

thanks for contacting us. Can I ask you to provide a few more details regarding your analysis, apparently you are interested in final states with at least 4 b-jets and 2 additional jets? Is that correct? Your first run card doesn't do that for you and the way your final state is regularized doesn't reflect your needs either. The problems you see arise from improperly regularized final states. Can you please specify what lowest-order final state you're interested in and what jet / b-jet cuts you're using in your analysis.

Do you see the same type of error messages with both run cards?

Best, jan.

Replying to alexandra.oliveira@…:

Dear developers

I am trying to generate processes with high multiplicity of b-quarks in final state, for instance

b bar{b} b bar{b} j j

and

Z(b bar{b}) b bar{b} j j

the configuration files I am using are bellow

in the run however I am mostly having these kind of warnings

################################################ Poincare::Poincare(): Inaccurate rotation {

a = (-0.0672029,0.906422,0.416993) b = (0,0,1) a' = (0.878832,0.433463,0.199411) -> rel. dev. (inf,inf,-0.800589) m_ct = 0.416993 m_st = -0.90891 m_n = (0,1.16895e-07,-2.54096e-07)

} ###############################################

I am not sure which physics is behind it, and if an smart cut would help

do you have any idea?

thanks Alexandra

bellow the Run.dat's

#################################### to bbbbjj

(run){

EVENTS 10; BEAM_1 = 2212; BEAM_ENERGY_1 = 6500; BEAM_2 = 2212; BEAM_ENERGY_2 = 6500;

% tags and settings for ME-level cuts J1CUT:=20.; J2CUT:=20.;

EVENT_OUTPUT=HepMC_Short[bbbbjj];

}(run)

(processes){

Process 93 93 -> 5 -5 93 93 Order_EW 0; CKKW sqr(20/E_CMS) Integration_Error 0.10; Selector_File *|(coresel){|}(coresel) {2}; End process;

}(processes)

(coresel){

NJetFinder 2 20.0 0.0 0.4 -1

}(coresel)

##############################################

to Z(bb)bbjj

(run){

EVENTS 20000; NJET:=2; QCUT:=20; BEAM_1 2212; BEAM_ENERGY_1 6500; BEAM_2 2212; BEAM_ENERGY_2 6500; WIDTH[6] 0; STABLE[6] 0; WIDTH[24] 0; STABLE[24] 0; HARD_DECAYS 1; HARD_SPIN_CORRELATIONS 1; CORE_SCALE QCD; EVENT_OUTPUT=HepMC_Short[ttjj]

}(run);

(processes){

Process 93 93 -> 23[a] 5 -5 93{NJET}; Decay 23[a] -> 5 -5; Order_EW 2; CKKW sqr(QCUT/E_CMS); End process;

}(processes);

[Jan Winter]

run card for b bbar + 2jets

[Jan Winter]

run card for b bbar + b bbar + 2jets

[Jan Winter]

Dear Alexandra,

please find two run cards (producing stable results) in the attachment to help you get started with your first background scenario (where you don't look at b bbar pairs from Z resonances), Run6.dat has the process you're mainly interested in, Run4.dat is the version with only one b bbar pair in the final state. Things to notice are: (1) the simulation uses massive b quarks right from the hardest level, ie in the MEs, (2) for testing purposes, hadronization (FRAGMENTATION=Off;) and underlying event (MI_HANDLER=None;) are switched off (once you convinced yourself that everything is going fine, you can remove these commands, also only then it makes sense to start playing with event output) and (3) the cards are set such that cross section integration will be optimized, so the 6-particle FS require some good CPU time (if you want quick tests in the beginning I suggest to use FINISH_OPTIMIZATION=Off and adjust the "Integration_Error" settings accordingly). I would also recommend thinking about your selection cuts. As set now they are very loose, so as a result you get large cross sections. If your selection in the end is more restrictive then it'd be more efficient to have more cuts already applied at the generation level.

Any question, please let me know. Best wishes, jan.

ps The adjusted cards regarding the Z resonance case will be added in the next few days.