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Status Update

Status Update. Lindsey Gray University of Wisconsin at Madison Weekly Meeting 21 July, 2009. Action Items. Pythia/MadGraph Analysis See other draft talk for Multiboson group. Still working on s/sqrt(s+b) plots, will send later this week First results of multivariate analysis

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Status Update

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  1. Status Update Lindsey Gray University of Wisconsin at Madison Weekly Meeting 21 July, 2009

  2. Action Items • Pythia/MadGraph Analysis • See other draft talk for Multiboson group. • Still working on s/sqrt(s+b) plots, will send later this week • First results of multivariate analysis • Need access to ECAL/HCAL RecHits – will be in PAT CMSSW_3_1_x • Status of POWHEG adaptation of Baur’s MC Generator • First results & shape comparison of full NLO calculation • Check POWHEG against Tevatron data (next week?) • Started on Muon DPG digi validator • Resurrect and show plots from RCT Calibration Routines • Postponed until Fall Lindsey Gray, UW Madison

  3. What’s Different in POWHEG • Spin dependent calculation in Baur’s MC changed to spin-averaged cross section • Necessary for dipole subtraction • Baur’s cutoff regulator is replaced with Catani-Seymour or FKS regulator (CS Dipole Subtraction in this case) • No jet pt or rapidity cuts, singularities subtracted off • Physical observables must independent of the regulator chosen • Born, virtual, collinear and real contributions will change, total and differential cross sections should be unaffected • Collinear contribution ~ to Born level result • Just “paste” Born level Zγ result into POWHEG’s collinear contribution calculation • Baur’s code uses narrow width approximation, POWHEG code has tunable finite Z width Lindsey Gray, UW Madison

  4. Current Status of Development • All necessary portions of Baur’s NLO calculation have been extracted in POWHEG framework • Charged leptons only, for now • Testing is in progress: • Born matrix element result is fully tested • Normalization and shapes match in limit of zero Z width • Results to be shown • Collinear & Virtual corrections implemented • Numerically stable cross section result • Plots to be Shown • Real matrix element result is implemented • Numerically stable, currently investigating normalization issues • Shape only comparison to be shown Lindsey Gray, UW Madison

  5. Preliminary Full NLO Results • POWHEG normalization is off • Under investigation • SM shapes match well • So its not a problem with the matrix elements • Keep in mind that no jet pt cut was applied to the POWHEG result • Distributions slightly more central • Issues with Anomalous Couplings Baur POWHEG Need more iterations Lindsey Gray, UW Madison

  6. Preliminary Full NLO Results Lindsey Gray, UW Madison

  7. Preliminary Full NLO Results V` Lindsey Gray, UW Madison

  8. Preliminary Full NLO Results:Anomalous Couplings • Anomalous couplings come along for the ride again! • Statistical errors were larger with AC present • 2% instead of .5% • Need to investigate this difference! Lindsey Gray, UW Madison

  9. Conclusions and Next Steps • Determine cause of NLO normalization difference and shape difference for Anomalous Coupling • All necessary components for NLO Zγ cross section calculation are working in POWHEG fwk. • What remains now is to implement the POWHEG Sudakov form factor (independent of process) • Last step before event generation • Once NLO calculation and Sudakov factor are fully tested • Test event generation • Compare unweighted event kinematics distributions to NLO differential cross sections • Run trials interfacing POWHEG lhe-event file to Pythia, Herwig, et al. and cross check results. Lindsey Gray, UW Madison

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