1. 1 Measurements at 8 TeV of TTbar events with additional particles in the final state Boris Mangano (ETH Zürich) on behalf of the CMS collaboration Boris Mangano (ETH Zürich) on behalf of the CMS collaboration

2. Boris ManganoLHCP 2014page 2 Outline TTbar plus what? -TTbar+jets -TTbar+BBbar -TTbar+V: o TTbar+gamma o TTbar+W o TTbar+Z 8TeV results released during the last 12 months Were these processes seen also at 8TeV ? new results PAS TOP-12-041 PAS TOP-13-010 PAS TOP-13-011 8 TeV TOP-12-018 PAS TOP-12-024 TOP-12-014 7 TeV

3. Boris ManganoLHCP 2014page 3 Motivation TTbar plus what? -TTbar+jets -TTbar+BBbar -TTbar+V: o TTbar+gamma o TTbar+W o TTbar+Z About ½ of TTbar events contain extra jets with |  | 30 GeV. Possibility to test higher order QCD calculations. Irreducible non-resonant background for ttH (H->bb) analysis. Potential to verify if couplings to the top quark are compatible with SM or altered by BSM effects.

4. Boris ManganoLHCP 2014page 4 tt+jets @ 8TeV (19.6 /fb) PAS TOP-12-041 Event selection: -Dilepton OS events (el and mu) -For same-flavour pairs, Z-veto and require MET -N-jets >=2 -N-bjets >=1 Unfolding: -cross-section in N-jets bins is presented at particle level Extra jets definition: -Kinematic reconstruction method to identify b-jets from ttbar decay. -Other extra jets are then analysed Main source of uncertainty: Up to 20% uncertainty from jet-energy- scale and signal model uncertainties.

5. Boris ManganoLHCP 2014page 5 The whole is greater than the sum of its parts (Aristotle) MC@NLO + Herwig does not generate sufficiently large jet multiplicities. tt+jets @ 8TeV (19.6 /fb)

6. Boris ManganoLHCP 2014page 6 The whole is greater than the sum of its parts (Aristotle) Leading extra jet p T (GeV) tt+jets @ 8TeV (19.6 /fb) Second Leading extra jet p T (GeV) These distributions are at reconstruction level

7. Boris ManganoLHCP 2014page 7 PAS TOP-13-010 Event selection: -Dilepton OS events (el and mu) -For same-flavour pairs, Z-veto and require MET -N-jets >=4 -N-bjets (tight) >=2 tt+bb@ 8TeV (19.6 /fb) Main source of uncertainty: 20-25% total uncertainty. Mostly from uncertainties in b-tagging discriminator templates. Normalization of simulated samples: -Performed by means of a fit to the measured b-tagging algorithm discriminator. -Templates for different tt+X samples (including tt+bb signal) are taken from simulation.

8. Boris ManganoLHCP 2014page 8 The whole is greater than the sum of its parts (Aristotle) First additional jet Second additional jet Simultaneous template fit of two data distributions tt+bb@ 8TeV (19.6 /fb)

9. Boris ManganoLHCP 2014page 9 The whole is greater than the sum of its parts (Aristotle) Factor 0.38 to account for difference in selection efficiency between ttbb and ttjj (from simulation) Cross-section ratio at particle level: tt+bb@ 8TeV (19.6 /fb) using again selection efficiencies from simulation

10. Boris ManganoLHCP 2014page 10 PAS TOP-13-011 Event selection: -one isolated central  with pT > 26 GeV -Veto on extra leptons -N-jets >=4, with p T > 55, 45, 35, 20 GeV -N-bjets >=1 -One central photon E T > 25 GeV  R (photon,muon) > 0.7 tt+gamma @ 8TeV (19.7 /fb) Main source of uncertainty: 20-25% total uncertainty from modelling of the background template. Signal extraction: -Template fit of charged-hadron- isolation discriminant distribution in data. -Templates for signal and misidentified photons from simulations.

11. Boris ManganoLHCP 2014page 11 tt+gamma @ 8TeV (19.7 /fb) N-1 plots for some of the observables used to select the signal photons.

12. Boris ManganoLHCP 2014page 12 The whole is greater than the sum of its parts (Aristotle) tt+gamma @ 8TeV (19.7 /fb) Fit of distribution of the charged-hadron-isolation discriminant Inclusive ttbar cross section (TOP-12-017)

13. Boris ManganoLHCP 2014page 13 ttW and ttZ @8TeV (19.5 /fb) -Both ttW and ttZ processes are very rare and the measurement of their cross sections can be used to test the internal consistency of SM. TOP-12-036 pre-print to be released in the next days -ttZ production allows the probe of tZ coupling.

14. Boris ManganoLHCP 2014page 14 ttW in same-sign dilepton Signal region definition: - Tight prompt-lepton selection -same-sign dilepton (el or mu) -third lepton vetoed only if it makes a Z-candidate -N-jets >= 3 -N-bjets >=1 -lepton pT>40 GeV and HT > 155 GeV Analysis type: counting experiment Against misidentified prompt leptons and ttbar background Against WZ and other diboson processes. Remove overlap with ttZ analysis. Final optimization against ttbar background

15. Boris ManganoLHCP 2014page 15 ttW in same-sign dilepton Dominant background: -ttbar with misidentified leptons is estimated from data. Uncertainty is about 50%. Other backgrounds: -ttZ, WZ and other rarer processes are estimated from simulations. -Z+jets with mis-measured lepton charge estimated from data Six signal regions to exploit larger S/B in plus-plus channels.

16. Boris ManganoLHCP 2014page 16 ttZ in trilepton Analysis type: counting experiment Signal region definition: -Three tight leptons (el or mu) -Two same-flavour opposite-sign making a Z-candidate -N-jets >= 4 -N-bjets (loose) >=2 & N-bjet (medium) >=1 Against misidentified leptons and ttbar background Against WZ and other diboson processes. Remove overlap with ttW analysis.

17. Boris ManganoLHCP 2014page 17 ttZ in trilepton Dominant background: -non-top-quark background processes with b-jets from ISR. Uncertainty is about 50%. Other backgrounds: -TTbar with misidentified leptons is estimated from data. -Rarer, and irreducible, SM processes estimated from simulation Only one signal region is used for the statistical interpretation of the data

18. Boris ManganoLHCP 2014page 18 ttZ in four-lepton Analysis type: counting experiment Signal regions definition: -Four tight leptons (el or mu) -Two same-flavour opposite-sign making a Z-candidate -Veto on second Z-candidate -N-bjets =1 -N-bjets >1 Against WZ and lepton misidentification Two non-overlapping signal regions Against ZZ background

19. Boris ManganoLHCP 2014page 19 ttZ in four-lepton Backgrounds: -ZZ(*) in four leptons is estimated from MC -Z+X events with misidentified leptons Limits and benefits of this channel: -statistically limited -Large S/B ratio

20. Boris ManganoLHCP 2014page 20 ttV (V = W or Z) Results in agreement with SM predictions: cross section ttW = 206 ± 23 fb cross section ttZ = 197 ± 25 fb Numbers from MG5_aMC@NLO. They are compatible with first NLO calculations from MCFM and PowHel.

21. Boris ManganoLHCP 2014page 21 Summary TTbar plus what? -TTbar+jets -TTbar+BBbar -TTbar+V: o TTbar+gamma o TTbar+W o TTbar+Z 8TeV results released during the last 12 months PAS TOP-12-041 PAS TOP-13-010 PAS TOP-13-011 TOP-12-036 pre-print to be released in the next days New Results

22. Boris ManganoLatsis Symposium 201322 Backup slides

23. Boris ManganoLHCP 2014page 23 ttV (V = W or Z)

24. Boris ManganoLHCP 2014page 24 The whole is greater than the sum of its parts (Aristotle) tt+jets