-- ChengguangZhu - 25 Nov 2007

Useful links : AtlfastProcedure StoregateKeysForAODRelease12


To tune MC with the first data of ATLAS, atlfast is a better selection, which needs short time and less resources for a MC loop. So the performance of atlfast data and full simulation data are compared here.

A comparison with only events passed selection and quality cut, with AcerMC data, can be found at ZhuSelEvnetsCom

Used data ZhuGeneratorWithAcerMC

MCatNLO Data sample: trig1_misal1_mc12.005200.T1_McAtNlo_Jimmy.recon.AOD.v12000601_tid005997: totally 344k weighted events, 182.8k semileptonic e/mu events events are used.

Full simulation with 1mm bug, fixed at AOD level

Atlfast data: The bjet tag in atlfast emulates (code from J.B. Devivie) the b tag of full simulation. In the emulation, weight are set to jets in a specific (pt, eta) window randomly according to weight distribution of full-sim jets in such a window. %h% important: weight is caculated according to jet's specific characteristics, tagged jets should have same characteristics of course, meaning that the randomly set weight may bring bias in measurements.

Both data read out from the same data sample, the jet energy is calibrated to quarks.

Selection efficiencies

Selection Items Efficiency for Atlfast Efficiency for full sim (e.mu ID) Comments
= 1 electron, pt>20GeV, abs(eta)<2.5,(all e events) 70.6% 51.2% atlfast ~90.8% (91.2%abs(eta)<2.5 99.2%pt>5GeV), with reco efficiency 89.5%, finally 81%
90.8%*89.5%*84%(pt>20G)=68.2%, 70.6% due to contamination of non-iso electron
= 1muon, pt>20GeV, abs(eta)<2.5(all muon events) 66.8% 69.1% atlfast: ~89.9% of muon (91.2%abs(eta)<2.5 98.6%pt>6GeV), with reco efficiency, finally 77%
ask pt>20GeV means 86.5%, finally 66.8%
=1 lep (eigher e or muon) (all events) 68.6% 60%  
4+jets, pt>30GeV, abs(eta)<2.5 54.1% 59.3%  
2+jets b taged (in all 4+ jets events) 33.6% 32.3% atlfast has higher btag efficiency
pTmiss>20GeV 90.8% 91.9%  
all kinematic cuts 10.6% 9.8%  
kinematic cuts and quality cuts 3.67% 2.93% (abs(pwhad[4]-80410)<20000. && pt_n/pt_miss>0.99 && abs(ptlep[4]-175000.)<35000. && abs(pthad[4]-175000.)<35000.)


  • Electrons: in full sim, electron->parameter(ElectronParameters::etcone20) same as author()= 1 or 3.
Qalities atlfast full sim (e/mu ID) Comments
b tag efficiency for truth b jets (42% truth b jets) 62.7% 60.8% emulation weight is slightly higher
purity for b tagged jets 93.1% 93.4% atlfast purity even lower, btag increase, c/l jet rejection worse
c jet rejection (10% truth c jets ) 6.6 6.9  
tau jet rejection (truth tau jets,not in signal ) 16.9 20.5  
l jet rejection( 48% truth l jets) 118 131  
electron reconstruction efficiency true pt>20GeV abs(eta)<2.5 89.9% 69.6% artificially set reco effi to 89.5%?
purity of selected electrons 95.4% 98.3% aflfast electron is not isolated, I should use isolation with comparing to jets, jets e/p matched to a ele should be regarded as electron? 68.2%/70.6%=96.6%(purity)
muon reconstruction efficiency 84.4% 91.7% artificially set reco effi to 84.4%?
purity of selected muons 99.4% 98.7% atlfast muon is isolated in AtlfastMuonCollection, unisolated muon is stored in AtlfastNonIsoMuonCollection

Plots (red: atlfast, blue: full simulation)

* comp_fast_full.cxx: code for producing the plots

program flowing

for AcernMC red for atlfast and blue for full sim.: 0 -->1 lepton-->1--> >=4jets --> 2--> >=2bjets and >=2ljets --> 3--> etmiss>20G --> 4-->wln-->5-->wjj and jjb-->7



  • pt, eta and phi distribution of selected elections and resolutions:

electron reco efficiency vs eta phi pt

  • e reconstruction efficiency along eta, pt and phi for truth electron with pt>20GeV |eta|<2.5:

electron reco efficiency vs energy

plot 1: reconstructed coslep with e_pt_cut>25GeV (red) and >60GeV (black) coslep<0 is affected(suppressed) by cut on low pt electron
plot 2: reconstructed electron energy (p) distribution, for atlfast (red) and full sim (blue) full sim reconstructed less high energy electron
plot 3: electron reconstruction efficiency v.s. energy(p) as plot 2

Conclusion: full sim reconstructed less high energy electrons ---> suppress the reconstruction of coslep (>0) as see (blue in plot 1 and 2 at below)

  • fullfast_e_154.gif

electron selection

  • p1:Before selection: aflfast: 17% with no ele at all (88.5%*89.5%+noisolated electron); p2: after selection; p3; after selection, full sim with isEM ID, matched distribution.


  • pt, eta and phi distribution of selected muons and resolutions:

muon reconstruction efficiency

  • muon reconstruction efficiency along eta, pt and phi for truth muonon with pt>20GeV |eta|<2.5:


  • pt, eta and phi distribution of selected jets and multiplicity of l jets, bjets :

  • AcerMC atlfast jet resolution.
    • There was a bug in reading out truth information previously--->the truth b quark readout is not directly from top, being a b after radiating, and the calibration with full sim parameter looks making jet reso shift rightwards. Look at the 7th sub-plot in the plot above, the red one for atlfast is in fact before calibration.
    • but it doesn't affect analysis:
    • Now it's fixed. The pre-calibration with full sim parameter looks working well--->shift being corrected and the shape of the distribution is more reasonable (left tail):

jet weight

  • full sim weight and atlfast emulation weight:
  • do jet pre-calibration should re-valuate etmiss in the same time? No, precalibration and the etmiss artificially shift correction is in the same level, which is called calibration and correlate all objects each other. but in study of the uncertainty of the jet miscalibration, we think about the errors in jet calibration, then other correlated objects, e.g. etmiss should be recalibrated again according to their relation.


  • c/l jet rejection v.s. btag effi:


  • etmiss 1. reco pt 2. reco phi 3. pt resolution 4. phi resolution:
  • artificial etmiss shift 1.042 in the 12.0.6 should be removed? No in CSC 1206 data, the etmiss resolution is -5.5% shifted, in fact need to multiply a larger value for calibrate it.

reconstructed mass of w and t

  • invariant mass

  • Whad atlfast
    Whad fullsim
    thad atlfastthad fullsimtlep atlfasttlep fullsim


  • resolution of cospsi, psi is the angle between the direction of lepton in w rest frame and w direction in t rest frame :
    • use only pure signal (without even cmbk) for full sim:

All angles and angle resolution:

  • first raw, resoluation of reconstructed $cos\Psi$, $cos\Phi$, coslep, coshad_lej, coslep*coshad_lej:
  • second raw: distribution of them. fullfast_angle_and_angle_resolution.gif

Angle distributions with quality cut

  • Distributions are reconstructed angles with cuts: qualitycut*mttbar*ept25. Left-up corner: entries of fast data, right-up entries of full simulaiton
  • for coslep>0, full simulation has lower reconstruction efficiency, see reason
  • for coshad_lej, the reconstruction efficiency for full and fast simulation match better. Because accordingly coshad_lej<0 is slightly suppressed due to correlation with coslep, see left tail of plot 3

coslep (coshad_lej>0) 60-75% more events than right one for fast and coslep (coshad_lej<0)
| coshad_lej (coslep>0) similar events with the right one | and | coshad_lej (coslep<0) |

ttbar mass and resolution:


t and ttbar pt resolution

  • ttbar pt is closer to had top in full than in fast (Used semilep events and quality cut):

semiemu and semitau events

  • Because 3 neutrinos in the semitau events fly in different direction, the measured pt_miss is the sum pt of the 3 neutrinos, but take the pt_miss as their sum energy, it will be low estimated. This affect the reconstruction of w and further t
  • The following are plots of lep_w pt resolution, lep_w eta resolution, lep_w phi resolution and lep_t eta resolution, lep_t mass resolution and lep_t mass distribution. blue for semiemu events and red for the semitau events
  • It means that although the tau decayed leptons fly almost in the direction of tau, but when we want its direction in the w rest frame or t rest frame, the reconstructed one is much worse. :
  • resolution of coslep, cospsi, cosphilep_lej and coslep*coshad_lej, blue for semiemu events and red for semitau events.:

Assigned to Due date Description State Closed Notify  
ChengguangZhu 2007-12-20 plots of jet reconstruction efficiency and purity and fake jets     edit
ChengguangZhu 2007-12-09 atlfast electron muon reconstruction and effieicnys     edit

Topic attachments
I Attachment History Action Size Date Who Comment
GIFgif AcerMC_atlfast_jet_reso.gif r1 manage 11.1 K 2008-01-28 - 10:45 ChengguangZhu  
GIFgif b-tag-weight.gif r2 r1 manage 21.3 K 2007-11-26 - 12:46 ChengguangZhu  
GIFgif biasA_Acmcer_program_flowing.gif r1 manage 2.5 K 2007-12-21 - 11:07 ChengguangZhu program flowing, for AcernMC red for atlfast and blue for full sim.
Unknown file formatcxx comp_acermc_mcnlo.cxx r1 manage 38.4 K 2007-12-18 - 17:48 ChengguangZhu code for producing the plots
Unknown file formatcxx comp_fast_full.cxx r1 manage 63.5 K 2007-12-18 - 17:49 ChengguangZhu code for producing the plots
GIFgif etmiss.gif r1 manage 18.1 K 2007-12-07 - 19:53 ChengguangZhu etmiss 1. reco pt 2. reco phi 3. pt resolution 4. phi resolution
GIFgif fast_full_ele_num_pt.gif r3 r2 r1 manage 15.1 K 2007-11-26 - 20:25 ChengguangZhu  
GIFgif fast_ljrej_btageffi.gif r1 manage 10.7 K 2007-11-27 - 19:30 ChengguangZhu btag
GIFgif fast_semiemu_and_semitau.gif r1 manage 23.6 K 2008-01-16 - 10:06 ChengguangZhu  
GIFgif fast_semiemu_and_semitau2.gif r1 manage 22.9 K 2008-01-16 - 10:25 ChengguangZhu  
GIFgif fastfull_cospsi_reso.gif r1 manage 7.3 K 2007-11-27 - 19:58 ChengguangZhu cospsi
GIFgif fastfull_electron_dist.gif r1 manage 16.6 K 2007-11-27 - 19:43 ChengguangZhu e
GIFgif fastfull_electron_reco_effi.gif r1 manage 18.8 K 2007-11-27 - 18:57 ChengguangZhu e reco
GIFgif fastfull_jet_reso.gif r2 r1 manage 16.8 K 2007-11-27 - 19:54 ChengguangZhu  
GIFgif fastfull_muon_dist.gif r1 manage 16.4 K 2007-11-27 - 19:44 ChengguangZhu mu
GIFgif fastfull_muon_reco_effi.gif r1 manage 18.1 K 2007-11-27 - 18:57 ChengguangZhu muon reco
GIFgif fastfull_ttbar_and_t.gif r2 r1 manage 22.5 K 2008-01-11 - 17:05 ChengguangZhu  
GIFgif fastfull_ttbar_mass_and_reso.gif r1 manage 22.4 K 2008-01-09 - 16:04 ChengguangZhu ttbar mass and resolution
GIFgif fastfull_w_t_mass.gif r1 manage 17.3 K 2007-11-27 - 18:07 ChengguangZhu mass
GIFgif fullfasst_cospsi_full_puresignal_fast_semilep.gif r1 manage 7.7 K 2007-12-03 - 10:44 ChengguangZhu use only pure signal (without even cmbk) for full sim
GIFgif fullfast_153.gif r1 manage 28.0 K 2008-03-24 - 23:18 ChengguangZhu  
GIFgif fullfast_angle_and_angle_resolution.gif r1 manage 32.3 K 2007-12-18 - 17:49 ChengguangZhu measured angle and angle resolution: $cos\Psi$, $cos\Phi$, coslep, coshad_lej, coslep*coshad_lej
GIFgif fullfast_e_154.gif r2 r1 manage 14.7 K 2008-03-25 - 00:38 ChengguangZhu  
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Topic revision: r25 - 2008-03-31 - ChengguangZhu
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