AtlasMeeting_29_10_08


Some information on the top meeting...

Table of Sherpa numbers for fully leptonic ttbar cross-section:

CoM energy ttbar (ratio to 14TeV) ttbar + 1jet (ratio to 14TeV)
14TeV 138.22 0.16% 233.81 1.0%
12TeV 98.18 0.15% (0.74) 154.23 0.99% (0.66)
10TeV 64.29 0.16% (0.47) 92.09 0.94% (0.39)
1.96TeV (LHC pp) 0.37 0.13% 0.15 0.32%
1.96TeV (TeV ppbar) 1.47 0.14% 0.44 0.34%

Problems I can think of so far with the analysis.

*charge veto implimented in AOD too soon.

*muon isolation implimented in AOD too soon before electron definition.

-- KennyWraight - 29 Oct 2008


CDF Note on dilepton analysis. Cross sections on page 10.
Modesigma x Br (Pb)
K Factor
FilterEffic
Wgamma->e nu Gamma 13.6 x 1.36
1.36 1
Wgamma->mu nu Gamma 13.6 x 1.36
1.36 1
Wgamma->tau nu Gamma
13.6x1.36
136 1
WW 1.27 1.0 1
WW@NLO 1.27 1.0 1
WZ0.365
1.0 0.76
ZZ
1.511 1.0 0.23
ttbar 6.7x0.1026 1.0 1
Z->ee355
1.4 1
Z->mumu 355 1.41
Z->tautau (mll>10)
1272 1.4 0.00713
Z->ee (mll<20)

920

1.4 0.0156
Z->ee(mll<20)
920 1.4 0.0156

For WZ the W decays inclusively and the simluation is filtered for at least 2 leptons.For ZZ the Z's decay inclusively and the sample is filtered for at least 2 leptons. The reason for this is that WZ and ZZ produce dileptons through inefficiencies in the detector where 1 or 2 leptons are lost. For WZ one lepton may come from W and one from Z with a lepton from Z lost.

Wgamma produces a lepton plus a conversion lepton and the third lepton in the conversion is lost. This has a rapidity dependence since material increases with increasing |eta|. Same sign leptons are a good monitor of this background.

The Drell Yan has a section below mll< 20 added to the mll>20 to get reasonable statistics for the spectrum down to mll of order 10-12 GeV. This is relevant for Higgs but perhaps not top.

Cross sections taken at NLO are just given and those at LO with a k factor are indicated.

Section 11 has top analysis, with yields in table 31 on page 74. Here they are reproduced:

ttbar 70+-13
DY 28+-6
WW 16+-2
WZ 3+-0.5
ZZ 1.4+-0.2
W+jet 8.4+-2
Wgamma 1.8+-.5
Total 130+-15
Data 139

It is interesting to compare the 70 ttbar events in 3fb-1 at 1960 GeV to the 140 that Kenny has in his talk with 14000 GeV. It will be interesting to compare the background to those shown above.

The W+jet background is estimated from the data by taking dijet events, identifying one jet and asking how often the other passes loose lepton cuts compared to how often it passes full lepton id. This defines the fake probability. The single lepton sample is then searched and events with jets that are found to pass the loose lepton cuts are given a weight according to the measured probability. The kinematics and numbers of these events are then used in the analysis.

Topic attachments
I Attachment History Action SizeSorted ascending Date Who Comment
PowerPointppt AOD_analysis.ppt r2 r1 manage 997.0 K 2008-10-29 - 18:38 KennyWraight Kenny's talk in powerpoint format (should work on Linux)
PowerPointppt AOD_best.ppt r1 manage 1094.0 K 2008-11-11 - 14:37 KennyWraight better triggers and selection (but not right yet)
PDFpdf cdf9402_HWW_30_V2.pdf r1 manage 5189.2 K 2008-10-29 - 16:26 RichardStDenis CDF 3.0 fb dilepton higgs WW analysis
Topic revision: r8 - 2008-11-11 - KennyWraight
 
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