2011 QCD and High Energy Interactions - Rencontres de Moriond ...

) [pb]
ν
e
→
B(W’
×
σ
10
1
-1
10
-2
10
-1
CDF Run II Preliminary, 5.3 fb
σ × Br(NNLO)
σ × Br( ± 1σ)
obs. Limit 95 % C.L.
exp. Limit 95 % C.L.
68 % exp. Limit 95 % C.L.
95 % exp. Limit 95 % C.L.
-3
10
500 600 700 800 900 1000 1100 1200 1300
2
[GeV/c ]
mW’
Figure 5: Exclusion plot from CDF search for W ′
decaying to an electron and a neutrino.
tb) [pb]
→
(p p
σ
5
4.5 (a)
-1
DØ 2.3 fb
4
Observed limit
3.5
Expected limit
3
2.5
2
1.5
1
0.5
L R
W’ (a =1, a =0)
0
600 650 700 750 800 850 900 950 1000
M(W’) [GeV]
Figure 6: Exclusion plot from the DØ search for W ′
decaying to a top and bottom quarks.
ET > 20 GeV. Main backgrounds are t¯t + γ and W + γ+jets. No new physics is seen, and this
analysis yields an impressive measurement of SM t¯t + γ cross section of σ = 0.18 ± 0.07(stat.) ±
0.04(sys.) ± 0.01(lum.) pb.
4 Search for Vector-like Quarks
DØ performed a 5.4 fb−1 search for vector-like quarks that would manifest themselves in W/Z +
2 jets 11 . For the Z+jets channel two electrons or muons above 20 GeV with pT (dilepton) > 100
GeV/c, at least two jets above 20 GeV (leading > 100 GeV), ET / < 50 GeV and 70 < Mℓℓ < 110
GeV/c2 are required. Main background comes from SM Z+jets. The mass of the vector-like
quark must be above 430-551 GeV/c2 (depending on the couplings) at 95% CL. For the W +jets
channel one electron or muon is selected with pT > 50 GeV/c, same jet requirement, ET / > 50/40
GeV and (2M W T c2 + ET / ) > 80 GeV. The main backgrounds come from SM W +jets, top quarks,
QCD multijets, Z+jets, and diboson. The mass of the vector-like quark must be above 403-693
GeV/c2 (depending on the couplings) at 95% CL.
References
1. T. Aaltonen et al. (CDF Collaboration), arXiv:1103.4650 [hep-ex] (2011).
2. T. Aaltonen et al. (CDF Collaboration), CDF public note 10479 (2011).
3. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 83, 011102(R) (2011).
4. V. Abazov et al. (D0 Collaboration), Phys. Lett. B 695, 88 (2011).
5. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. Lett. 106, 121801 (2011).
6. T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 83, 031102 (2011).
7. V. Abazov et al. (D0 Collaboration), Phys. Lett. B 699, 145 (2011).
8. V. Abazov et al. (D0 Collaboration), Phys. Rev. Lett. 107, 011801 (2011).
9. T. Aaltonen et al. (CDF Collaboration), CDF public note 10355 (2011).
10. T. Aaltonen et al. (CDF Collaboration), CDF public note 10270 (2011).
11. V. Abazov et al. (D0 Collaboration), Phys. Rev. Lett. 106, 081801 (2011).