r jet =0.5 midpoint algorithm

• The following slides for D0 were taken from a thesis (Sept 2010) looking for WH(->jj) with 5.4 fb-1 of data

• Shannon Zelitch from University of Virginia

Rjet=0.5 Midpoint algorithm

CDF analyses• Require electron/muon ET> 20 GeV and ||<1.0

• Missing ET > 25 GeV and MTW>30 GeV

• Jets using JetClu R=0.4, ET>20 GeV and ||<2.4 (for WW/WZ search)– increase to 30 GeV (a priori) for bump measurement

• Require pTjj>40 GeV/c

• The following slides are from Pierliugi’s talk at CERN last week

• analysis website: http://www-cdf.fnal.gov/physics/ewk/2011/wjj/

Summary• So both CDF and D0 seem to use ALPGEN+Pythia with mlm matching for

calculation of the W/Z+jets background• Both CDF and D0 appear to see bumps at the same place/about the same

size– Tilman and Zack not withstanding, the bump does not appear to be

caused by tT or single top production• There are residual differences in the Rjj distribution

– which are reweighted out by D0– which are pointed out by CDF as residual systematics, without clear

indication of how/whether to correct using sidebands• there is still a bump with the correction, but of a smaller

significance• So clearly we need to understand the origin of those residual differences; I

believe John Campbell has distributions at NLO, but it would be useful to check with Blackhat+Sherpa, and Sherpa, for the Rjj distribution for W + 2 jets (exclusive), W + 2 jets (inclusive; Rjj between the lead jets), W + 2 jets (inclusive; all Rjj)

• This is a major phenomenology weakness, the idea that a major discovery may be either hidden or created by a problem in QCD modelling