Z+Jets Cross Section Analysis
IFAE-Barcelona
IFAE-Barcelona


Authors

Stefano Camarda (camarda@fnal.gov)

Mario Martínez (mmp@fnal.gov)

Lorenzo Ortolan (loreorto@ifae.es)

Veronica Sorin (vsorin@fnal.gov)

CDF, FNAL, M.S. 318
P.0. Box 500
Batavia, Illinois 60510
USA


Differential cross sections measurement in Z*(→l+l-)+jets final state
L = 9.4 fb-1



We present results on Z*(→l+l-)+jets production (with l=e,μ) in p-pbar collisions at √s = 1.96 TeV using data collected with the upgraded Collider Detector at Fermilab in Run II corresponding to an integrated luminosity of 9.4 fb-1. Jets are reconstructed using the Midpoint algorithm with R=0.7 and are required to have pTjet>30 GeV/c and |yjet|<2.1. The measured cross sections are unfolded to hadron level and compared to several theoretical predictions. Fixed order pQCD predictions include additional correction for parton-to-hadron non-pQCD effects.



  • Results with 9.4 fb-1 of integrated luminosity

  • The cross sections are measured in the following kinematic range:
    • Two central muons or electrons with |ηl| < 1.0 and PT > 25 GeV
    • Z mass window: 66 < Mll < 116 GeV/c2
    • ΔR(l,jet) > 0.7

    Differential cross sections are measured independently in the electron and the muon channel, and combined using a modified BLUE algorithm that take into account asymmetric errors. For information on each particular channel please refer to the public web page for muons and for electrons .
    Jets are reconstructed using the MidPoint algorithm with R=0.7.
    Measured cross sections are unfolded to hadron level jets in the kinematic range pTjet > 30 GeV/c and |yjet| < 2.1. Systematic uncertainties on data and theoretical predictions are shown in the plots, except an additional 6% luminosity uncertainty.



  • Mee mass distribution
    Mee invariant mass distribution reconstructed in data compared to the SM prediction in events with at least one jet. Only the statistical uncertainty is shown.


  • M μμ mass distribution
    Mμ μ invariant mass distribution reconstructed in data compared to the SM prediction in events with at least one jet. Only the statistical uncertainty is shown.



  • Comparison in Z*+≥1 jet final state
    Measured cross sections are compared to the following theoretical predictions: approximate nNLO LOOPSIM+MCFM, LO and NLO MCFM, LO and NLO BLACKHAT+SHERPA, ME+PS ALPGEN+PYTHIA, NLO+PS POWHEG+PYTHIA. The fixed order pQCD predictions LOOPSIM, MCFM and BLACKHAT include an additional Chad correction that accounts for non-pQCD contributions.


    Comparison in Z*+≥2 jets final state
    Measured cross sections are compared to NLO MCFM and ME+PS ALPGEN+PYTHIA. Scale variations, PDF variations and different PYTHIA Tunes are shown.


    Comparison in Z*+≥N jets final state
    Measured cross sections as a function of jet multiplicity is compared to approximate nNLO LOOPSIM+MCFM, LO and NLO BLACKHAT+SHERPA, ME+PS ALPGEN+PYTHIA, and NLO+PS POWHEG+PYTHIA predictions.


    LOOPSIM+MCFM: Comparison with approximate nNLO in Z*+≥1 jet final state
    Measured cross sections are compared to approximate nNLO LOOPSIM+MCFM. The theoretical prediction include an additional Chad correction that accounts for non-pQCD contributions.


    BLACKHAT+SHERPA: Comparison with NLO pQCD in Z*+≥3 jets final state
    Measured cross sections are compared to LO and NLO BLACKHAT+SHERPA. The theoretical prediction include an additional Chad correction that accounts for non-pQCD contributions.


    ALPGEN+PYTHIA: Comparison with ME+PS
    Measured cross sections are compared to ME+PS ALPGEN+PYTHIA. The central value of theoretical prediction is the αs-matched Tune Perugia 2011. Scale variation uncertainties, PDF variations and different PYTHIA Tunes are shown.


    POWHEG+PYTHIA: Comparison with NLO+PS
    Measured cross sections are compared to NLO+PS POWHEG+PYTHIA. Scale variation uncertainties, PDF variations and different PYTHIA Tunes are shown.


            Last modified by Stefano Camarda (camarda@fnal.gov) on March 22, 2012