CDF Logo Search for Technicolor Particles Produced in Association with W Bosons at CDF
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Contents

  1. Technicolor Signal
  2. Event Selection and Search Strategies
  3. Figures
    1. Jet Multiplicity
    2. Signal Acceptance
    3. Reconstructed Mass
    4. Limit
    5. Cross Check
    6. Other Kinematics
  4. Tables


We present a search for technicolor particles decaying into b-bbar and produced in association with W bosons in p-pbar collisions at √s= 1.96 TeV. The search uses approximately 955 pb-1 of the dataset accumulated in the CDF detector at the Fermilab Tevatron. Events with an electron or muon, missing ET and two jets, one of them b-tagged, are selected. In the case of exactly one vertex b-tag we apply a neural network filter to reject contamination from charm and light quark jets. The number of tagged events and the invariant mass distributions of W+2 jets and dijets are consistent with the Standard Model expectations. We set a 95% confidence level upper limit on the production cross section times branching ratio as a function of the technicolor particle masses.



Technicolor Signal and Cross Section in this analysis

Feynman diagram
Signal cross section times Branching ratio

Event selection and search strategies

Basic Event selection
Selection requirement
One tag w/ NNtagDouble tag
Leptoncentral isolated electron or muon (Pt >20 GeV)
Missing Et > 25 GeV > 20 GeV
Jet (require exact two jet event) with
at least one b-tagging with silicon detector
Et > 20 GeV, |&eta| < 2.0
Neural network b-taggingApplyNot apply
Serch strategies
One tag with NN tag events and double tag events are estimated separately due to take advantage of the S/N ratio in double tag. Finally the limit combined with each other is used as final results. The best result is given by combined likelihood because the expected limit between 1 tag and 2 tag are comparable.

Figures:

Jet multiplicity

One tag w/ NN tag
Double tag
Jet multiplicity distributions for each tag stage.
Black point means observed data and different colors show different background components.
Red hash means background uncertainties

Signal Acceptance

Technicolor signal acceptance for one tag w/ NNtag
and double tag.
Blue(Red) point means one tag /w NNtag (double tag) acceptance

Dijet invariant mass and W+2jet invariant mass

One tag w/ NN tag
Double tag
dijet mass(left) and W+2jet mass(right) distributions for each tag stage.
Black point means observed data and different colors show different background components and
cyan means Technicolor signal (&rho(Tc)=200 GeV,&pi(Tc)=115 GeV).
Red hash means background uncertainties

Q value (= m(ρT) - m(πT) - m(W))

One tag w/ NN tag
Double tag
Q value distributions for each tag stage.
Black point means observed data and different colors show different background components and
cyan means Technicolor signal (&rho(Tc)=200 GeV,&pi(Tc)=115 GeV).
Red hash means background uncertainties

2D plot (total background)

One tag w/ NN tag
Double tag
Two dimensinal plots(Q value and dijet mass) of merged total backgrounds for each tag stage

2D plot (data)

One tag w/ NN tag
Double tag
Two dimensinal plots(Q value and dijet mass) of observed data for each tag stage

2D plot (signal m(&rho)=200 GeV, m(&pi)=115 GeV)

One tag w/ NN tag
Double tag
Two dimensinal plots(Q value and dijet mass) of Technicolor signal for each tag stage.
Number of events are normalized by Theoretical cross section.

Expected limit from background-only pseudo-experiments

Comparison of expected limit among one tag w/ NN tag only (blue),
double tag only (cyan) and combined (red)

Observed limit using combined likelihood and pseudo-experiment results

Observed limit using combined likelihood. Black point means observed data and red line means the mean of pseudo experiment.
Yellow(cyan) band shows 1(2) sigma diviation from the mean

Observed limit using double tag and pseudo-experiment results

Observed limit using double tag likelihood. Black point means observed data and red line means the mean of pseudo experiment.
Yellow(cyan) band shows 1(2) sigma diviation from the mean

Observed limit using 1tag w/ NNtag and pseudo-experiment results

Observed limit using 1tag w/ NNtag likelihood. Black point means observed data and red line means the mean of pseudo experiment.
Yellow(cyan) band shows 1(2) sigma diviation from the mean

Cross check of single-tag results: Dijet mass distribution after sliding Q cut

Dijet mass distributions on 1tag /w NN tag events after sliding
Q value cut (<30 GeV, <40 GeV, <50 GeV, <60 GeV).

Smallest p-value anywhere in the 2-D plane (m(πT) vs.m(ρT))

The distributions of smallest p-value into all mass sample for one
pseudo experiment.
This plots shows the results of one thousand pseudo experiments.
Red arrow means the smallest observed p-value
(&rho(Tc)=210 GeV,&pi(Tc)=105 GeV)

Kinematics distributions for selected events

Lepton

One tag w/ NN tag
Double tag

Missing Transverse Energy

One tag w/ NN tag
Double tag

Jet1 (higher ET jet)

One tag w/ NN tag
Double tag

Jet2 (second-highest ET jet)

One tag w/ NN tag
Double tag

W Transverse mass and Ht

One tag w/ NN tag
Double tag

minimum Δφ between met and lepton or jet

One tag w/ NN tag
Double tag

&Delta &phi between MET and closest jet, &Delta &phi between MET and lepton, &largest eta of two jets

One tag w/ NN tag
Double tag

&Delta R between jets, &Delta R between lepton and closest jet

One tag w/ NN tag
Double tag

Pt(dijet), &Delta &phi between jets, Q+Mjj

One tag w/ NN tag
Double tag

Event Display of candidate event: run 184377, event 13093573


Tables:

- Background summary (one tag w/ NNtag)
Tex format
---------------------------------------- Total background table---------------------------------
                Njet               1jet               2jet               3jet             >=4jet
-------------------------------------------------------------------------------------------------
       Pretag Events              80361              13246               2111                573
-------------------------------------------------------------------------------------------------
              Mistag     124.5 +/- 24.4      47.7 +/- 9.6       14.2 +/- 2.9        3.9 +/- 1.1
           Wb#bar{b}     269.6 +/- 94.5     132.3 +/- 44.8      26.2 +/- 8.1        4.7 +/- 1.5
           Wc#bar{c}      54.8 +/- 18.0      39.3 +/- 13.5       7.6 +/- 2.6        1.4 +/- 0.5
                  Wc     161.6 +/- 40.7      31.4 +/- 8.3        3.0 +/- 0.7        0.4 +/- 0.1
               Z +jet     15.0 +/- 6.1       10.8 +/- 4.3        4.0 +/- 1.5        0.9 +/- 0.4
     t#bar{t}(6.7pb)       6.6 +/- 1.1       40.2 +/- 6.2       80.7 +/- 12.1      93.0 +/- 13.4
          Single top      17.1 +/- 1.7       24.2 +/- 2.1        5.0 +/- 0.4        0.8 +/- 0.1
 Diboson/Z->#tau#tau       8.8 +/- 1.5       14.4 +/- 2.4        3.8 +/- 0.6        0.9 +/- 0.2
            nonW QCD      28.4 +/- 5.3       16.8 +/- 3.1        5.8 +/- 1.2        4.4 +/- 1.2
-------------------------------------------------------------------------------------------------
           Total Bkg     686.5 +/- 126.0    357.0 +/- 63.6     150.4 +/- 19.0     110.5 +/- 14.4
-------------------------------------------------------------------------------------------------
     Observed Events                712                341                156                129
- Background summary (double tag)
Tex format
----------------------------------------- Total background table---------------------------------
                Njet               2jet               3jet             >=4jet
-------------------------------------------------------------------------------------------------
       Pretag Events              14604               2362                646
-------------------------------------------------------------------------------------------------
              Mistag        3.2 +/- 0.5       1.5 +/- 0.3        1.1 +/- 0.2
           Wb#bar{b}       19.2 +/- 6.5       5.1 +/- 1.6        0.8 +/- 0.3
           Wc#bar{c}        3.0 +/- 1.1       0.4 +/- 0.1        0.1 +/- 0.03
                  Wc        0.0 +/- 0.0       0.0 +/- 0.0        0.0 +/- 0.0
     t#bar{t}(6.7pb)       10.5 +/- 2.3      29.8 +/- 6.5       46.2 +/- 10.0
          Single top        4.7 +/- 0.8       1.5 +/- 0.3        0.3 +/- 0.1
               Z+jet        1.9 +/- 0.8       0.8 +/- 0.3        0.2 +/- 0.06
 Diboson/Z->#tau#tau        1.2 +/- 0.2       0.3 +/- 0.05       0.3 +/- 0.04
            nonW QCD        1.5 +/- 0.3       1.0 +/- 0.2        0.5 +/- 0.1 
-------------------------------------------------------------------------------------------------
           Total Bkg       45.2 +/- 8.4      40.4 +/- 7.0       49.5 +/- 10.1 
-------------------------------------------------------------------------------------------------
     Observed Events                 39                 44                 65
- Signal systematics
Tex format
1tag w/ NNtagdouble tag
Lepton ID~2%~2%
Trigger<1%<1%
ISR/FSR6.7%14%
PDF1.7%2.6%
JES2.8%3.9%
b-tagging5.3%16%
Total9%22%

Tatsuya Masubuchi
Last modified: Thu Nov 9 11:48:35 CST 2006