ATC: ATLAS Center at ANL

Low-pT ttbar with pileup

Here are the links to the existing Monte Carlo samples for top-quark studies generated for the 14 TeV center-of-mass energy (pp collisions). Events were generated with the HERWIG++ model, and processed using the Delphes 3.05 fast detector simulation.

All data are stored in the ROOT format using the standard Delphes 3.05 output. Therefore, it is recommended to install Delphes 3.0.5 and look at the example explaining how to read such ROOT files (see the directory “Examples” inside the Delphes package).

The samples use the ATLAS detector geometry located in “examples/delphes_card_ATLAS.tcl” of the Delphes 3.05 installation. There is only one difference: Jets are reconstructed using AntiKT jets with the cone 0.5.

How to download

Please read the Section How to download

Signal ttbar

This is a ttbar fully inclusive sample without any cut on hard processes and without pileup. As before, sqrt(s)=14 TeV, The included processes are:

g g -> t tbar
q qbar -> t tbar

Here is the log file for 200 events (one ROOT file).

Click to display ⇲

Click to hide ⇱

Statistics for the UE process:
                                       generated    number of    Cross-section
                                          events     attempts             (nb)
==============================================================================
Total:                                    102341       102341      2.31448e+08
==============================================================================
Per matrix element breakdown:
MEQCD2to2Fast                             102341       102341      2.31448e+08
==============================================================================

==============================================================================
Eikonalized and soft cross sections:

Model parameters:                    ptmin:   3.5973 GeV, mu2: 0.81 GeV2
                                     DL mode: 2, CMenergy: 14000 GeV
hard inclusive cross section (mb):   231.488
soft inclusive cross section (mb):   27.1639
total cross section (mb):            113.95
inelastic cross section (mb):        78.5382
soft inv radius (GeV2):              0.304411
slope of soft pt spectrum (1/GeV2):  -0.901857
Average hard multiplicity:           5.47435
Average soft multiplicity:           0.359462
==============================================================================

==============================================================================
Statistics for event handler 'LHCHandler':
                                       generated    number of    Cross-section
                                          events     attempts             (nb)
==============================================================================
Total (from   weighted events): including vetoed events            0.62(2)e+00
==============================================================================
Total (from unweighted events):              200          200      0.62(5)e+00
==============================================================================
Per matrix element breakdown:
MEHeavyQuark                                 200          200      0.62(5)e+00
==============================================================================

If you need complete log files for a single ROOT file, take it from

LHC_signal.log.gz HERWIG++ log file
Analysis.log.gz Delphes3 log file

Get the Delphes3 ROOT files from this download link In total, there are 96 files, with 200 ttbar events in each. Thus the total number of events is 19200 signal events. The total luminosity is 31 pb-1

Here is an example for downloading 5 files:

python download.py 5  delphes3/ttbar/signal  herwigpp_ttbar_sig

(set 5 to 96 to download all)

Signal plus pileup

The truth information from the signal MC shown above was used to overlay with 140 pile up events (fixed number, not “Poisson” case!) The events were overplayed at the HEPMC true level (thanks to Andy Buckley for his help and http://pilemc.hepforge.org/ tool), and then were processed using Delphes3.04 (thanks to Dephes3 team which helped to solve technical issues).

Here is the log file for 11000 UE events (which were used as a pool of events for 200 signal events)).

Click to display ⇲

Click to hide ⇱

Statistics for the UE process:
                                       generated    number of    Cross-section
                                          events     attempts             (nb)
==============================================================================
Total:                                    248527       248527      2.31723e+08
==============================================================================
Per matrix element breakdown:
MEQCD2to2Fast                             248527       248527      2.31723e+08
==============================================================================

==============================================================================
Eikonalized and soft cross sections:

Model parameters:                    ptmin:   3.5973 GeV, mu2: 1.11 GeV2
                                     DL mode: 2, CMenergy: 14000 GeV
hard inclusive cross section (mb):   231.454
soft inclusive cross section (mb):   68.5499
total cross section (mb):            113.95
inelastic cross section (mb):        77.963
soft inv radius (GeV2):              0.382009
slope of soft pt spectrum (1/GeV2):  -0.338063
Average hard multiplicity:           2.96865
Average soft multiplicity:           0.871836
==============================================================================

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>> ThePEG - Toolkit for HEP Event Generation - version 1.8.1 <<<<<<<<<<
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

==============================================================================
Statistics for event handler 'LHCHandler':
                                       generated    number of    Cross-section
                                          events     attempts             (nb)
==============================================================================
Total (from   weighted events): including vetoed events            84.6(3)e+00
==============================================================================
Total (from unweighted events):            30000        38053      66.7(5)e+00
==============================================================================
Per matrix element breakdown:
MEMinBias                                  30000        38053      66.7(5)e+00
==============================================================================

If you need complete log file for a single ROOT file, take it from

LHC_pileup.log.gz HERWIG++ log file
Analysis.log.gz Delphes3 log file

Get the ROOT files grouped from this download link In total, there are 96 files, with 200 ttbar events in each. Thus the total number of events is 19200 signal events. The total size of the files is 48 GB.

Each file corresponds exactly to the signal file. For example:

herwigpp_ttbar_sig_[N].root (signal) corresponds herwigpp_ttbar_sig_50mu_[N].root (signal+50 pileups)

where [N] is a number from 1- 96.

Here is an example for downloading 5 files:

python download.py 5 delphes3/ttbar/mu50/signal_pileup  herwigpp_ttbar_sig_50mu

Only pile up events without the signal

Here are pileup events used to mix with the signal events Look at the this download link

python download.py 5 delphes3/ttbar/mu50/pileup  herwigpp_pileup50f

Info about true particle record

To reduce ROOT file size, truth information in these ROOT files was slimmed. Please read here.

How to analyze

If you need to find the effect of pileup on top reconstruction or a jet measurement, you need to run the analysis code over signal MC and then over the signal+pileup MC files.

Read analyse_d3

— Sergei Chekanov 2013/03/06 20:47

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