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Nikitenko (IC ) for 7 TeV Analysis Team March, 2013

First measurement of EWK Z+2j production cross section and hadronic activity in rapidity gap in CMS. Nikitenko (IC ) for 7 TeV Analysis Team March, 2013. Public PAS. Paper is under CWR. EWK Z + 2 jet production. Bremsstrahlung VBF multiperipheral

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Nikitenko (IC ) for 7 TeV Analysis Team March, 2013

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  1. First measurement of EWK Z+2j production cross section andhadronic activity in rapidity gap in CMS Nikitenko (IC) for 7 TeV Analysis Team March,2013

  2. Public PAS. Paper is under CWR

  3. EWK Z + 2 jet production Bremsstrahlung VBF multiperipheral Large, negative interference between VBF and others two processes s EWK mmjj = 255 fb, mll > 50 GeV, pTj > 10 GeV, |hj|< 7.0, mjj > 120 GeV s VBF H->tt = 80 fb for mH=125 GeV

  4. Backgrounds • Dominant: • high order as corrections to DY production: • “QCD Z+jets” • 2. Small:tt~ production • 3. Small:diboson production:

  5. Analysis strategy • Signal is very small (S/B ~ 0.1 after optimized selections), therefore • Use different methods to extract signal • Confirm signal in mm and ee modes • Use different methods of jet reconstruction • JPT jets • PF jets

  6. Event selection cut flow table Uncertainty on the dominant background QCD Z+jets due to JES , +13%, -9% is comparable with the signal. The signal must be extracted from the distributions, most sensitive to the presence of the signal

  7. Signal is extracted by two methods • from fit of mjj • from fit of BDT output

  8. mjj fit; mm mode

  9. Signal extraction from fit of BDTD output Variables for BDTD Pre-selections for 1. pTJ1BDTD: 2. pTJ2 3. |hJ1-hJ2| 4. mjj 5. pTZ 6. y* = yZ – (yJ1 + yJ2)/2 7. hJ1+hJ2 8. yZ 9. |fJ1-fZ| 10. |fJ2-fZ| 11. |fJ1-fJ2| |hj| < 3.6

  10. BDTD output fit; mm and ee modes

  11. measured cross sections agrees with NLO prediction (VBFNLO): 166 fb at mll > 50 GeV, pTj > 25 GeV, |hj|< 4.0, mjj > 120 GeV

  12. Section: Hadronic activity in rapidity gap

  13. Check theory expectations with data • Jet activity in rapidity gap for QCD Z/W+jets: • the larger Dhj1j2, the bigger probability to have additional jet in h region between j1 and j2 • the larger pT of tagging jets, the bigger probability to have additional jet in h region between j1 and j2

  14. <Njets> vsDhjj

  15. Conclusions • First measurement of EWK Z+2j process demonstrates the CMS detector and analysis capability to extract a process which is topologically similar to VBF Higgs production and has a cross section comparable to that in the standard model. • First analysis of hadronic activity in the rapidity interval between forward and backward jets in Z+jets process shows good agreement with MadGraph predictions

  16. Difference in kinematics for EWK Z+jets, VBF H and QCD Z+jets

  17. Expected Feature 1 • the larger pT of tagging jets, the bigger probability to have additional jet(s) between them • data confirms simulation predictions

  18. Expected feature 2 • The larger rapidity separation between tagging jets, • the bigger probability to have additional jet(s). data confirms simulation predictions

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