Introduction

This page is used for systematics estimation on the CSC analysis

Systematics on b jet energy scale

b jet energy scale: The value of the b jet energy scale is changed from -10 to +10%, and the values obtained for the observables are fitted with a linear function. The systematic error is considered as the effect of a variation of 5% or a more pessimistic estimate of 10% in the b jet energy scale.

  • w_pola_b_e_scale_systematics.gif:
    w_pola_b_e_scale_systematics.gif
  • spin_correlation_b_e_scale_systematics.gif:
    spin_correlation_b_e_scale_systematics.gif
  • refer to he plots taken from note phys-pub-2006-022, "rome" data: w pola and spin correlation

  • According to the plots, the systematics are (considering variation of 5% of b jet energy scale )
F0 FL FR A Ad
0.002 0.02 0.02 0.07 0.015

Systematics on b jet tag efficiency

b jet tag efficiency: The value of the b jet tag efficiency is varied and the values obtained for the observables are studied as a function of the b tag. The systematic error is considered as the effect on the observables of a variation of 5% and 10% in the b jet tagging efficiency, as compared with the standard value.

* btag efficiency vs. cut on weight:
csc_full_btageffi_vs_cutwight.gif

According to the plot above, cut on weight 9.0, 7.9, 6.65, 5.38, 4.05 to get 50%, 55%, 60%, 65%, 70% of b tag efficiency.

  • spin_correlation_A_btag_systematics.gif:
    spin_correlation_A_btag_systematics.gif

  • w_pola_btag_systematics.gif:
    w_pola_btag_systematics.gif

  • According to the plots, the systematics are (considering variation of 5% of b tag efficiency )
F0 FL FR A Ad
0.002 0.007 0.005 0.027 0.07

Systematics on light jet energy scale

Light jet energy scale: The value of the energy scale of the light jets is changed from -15 to +15%, and the values obtained for the observables are fitted with a linear function. The systematic error is considered as the effect of a variation of 5%, or a more pessimistic estimate of 10% in the energy scale of the light jets.

4 points are selected for this purpose, they are light jet energy rescale to 85% 92.5% 107.5% 115%

  • spin_correlation_A_ljet_systematics.gif:
    spin_correlation_A_ljet_systematics.gif

  • According to the plots, the systematics are (considering variation of 5% of light jet energy scale )
A Ad
0.11 0.017

Systematics on pile-up

Pile-up: The effect of pile-up events is studied by comparing the values of the observables obtained with and without adding pile-up events (an average of 4.6 pile-up events per bunch collision).

data sample trig1_pile1sf05_misal1_mc12.005200.T1_McAtNlo_Jimmy.recon.AOD.v12000605_tid009988(although simulated with 120605, has 1mm bug) is fetched for this purpose, but it has only 15%(52k) of statistics of data sample 5200 without pile_up.

Due to the low statistics the events pass selection and reconstruction is quite few (549 events). In order to fit the distribution of cospsi, the bins width are enlarged (34bins to 10 bins). The fitting result is shown as below.

  • 5200_pileup_note7_wpola_results.gif:
    5200_pileup_note7_wpola_results.gif

According to the approach described above, the systematics introduced by pile up is taken as below, which is 10 times larger than the estimation of fast simulation (of course here 4.6 pile up event more than fast simulation, 2.3 events)

F0 FL FR
0.08 0.08 0.16

A noticeable phenomenon is the cut of >4 jets efficiency 43% is much smaller than the standard one, 54%, ?? With this question, this estimation will not replace the fast-simulation one at least now.

Systematics on Background

Background: The cross sections for the backgrounds were varied individually within 1sigma of the expected cross-section. The systematic error was considered as the quadratic sum of all background contributions.

The main background contribution is from ttbar->tau events ~10%, Other background is totally <3%, negligible.

Here the systematics from background is due to the uncertainty on the brand ratio between emu events and tau events (both from ttbar). the S/B is variated by 20% to see the effect on the measurement as in the plot:

  • S_over_B_systematics.gif:
    S_over_B_systematics.gif
  • Systematics related to 20% of variation of S/B is
F0 FL FR A Ad
0.002 0.004 0.001 0.000 0.004

Systematics on top mass dependency

Top mass dependence: Samples corresponding to top masses in the range 160 – 190 GeV are simulated, and the influence of mt on the values obtained for the observables is determined. The systematic error used here is obtained from a linear fit of the values found, corresponding to a top mass uncertainty of 2 GeV.

Top mass selected are 170, 175, 190 GeV. the data with top mass 160 GeV failed in the final measurement, (minimization failed in fit)

  • as in plot w_pola_t_mass_systematics.gif
  • Systematics related to 2GeV of variation of top mass is
F0 FL FR
0.02 0.015 0.006

Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formateps 5200_pileup_note7_wpola_results.eps r1 manage 30.4 K 2008-03-10 - 15:44 ChengguangZhu  
GIFgif 5200_pileup_note7_wpola_results.gif r1 manage 14.9 K 2008-03-10 - 15:45 ChengguangZhu  
GIFgif S_over_B_systematics.gif r1 manage 23.1 K 2008-03-09 - 14:52 ChengguangZhu  
GIFgif csc_full_btageffi_vs_cutwight.gif r1 manage 9.1 K 2008-03-07 - 15:09 ChengguangZhu btag efficiency vs. cut on weight
GIFgif spin_correlation_A_btag_systematics.gif r2 r1 manage 8.1 K 2008-03-11 - 14:01 ChengguangZhu  
GIFgif spin_correlation_A_ljet_systematics.gif r1 manage 9.1 K 2008-03-08 - 16:30 ChengguangZhu  
GIFgif spin_correlation_b_e_scale_systematics.gif r1 manage 9.2 K 2008-03-12 - 22:31 ChengguangZhu  
JPEGjpg sys.jpg r1 manage 37.5 K 2008-03-08 - 16:53 ChengguangZhu  
JPEGjpg sys2.jpg r1 manage 26.0 K 2008-03-08 - 16:53 ChengguangZhu  
Unknown file formatcxx sys_T7CSCnote_et25.cxx r2 r1 manage 23.6 K 2008-03-09 - 15:04 ChengguangZhu  
GIFgif w_pola_b_e_scale_systematics.gif r1 manage 13.9 K 2008-03-12 - 22:31 ChengguangZhu  
GIFgif w_pola_btag_systematics.gif r1 manage 12.4 K 2008-03-08 - 16:30 ChengguangZhu  
GIFgif w_pola_t_mass_systematics.gif r1 manage 11.5 K 2008-03-09 - 16:38 ChengguangZhu  
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Topic revision: r13 - 2008-03-12 - ChengguangZhu
 
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