We measure the differential cross sections for W production in association with at least n jets as a function of jet Et, jet-jet delta R and jet-jet invariant mass. This is a hadron level measurement, thus comparisons with W + Jets theory should be made at the hadron level. We show comparisons with W + Jets Monte Carlo samples generated using Leading Order Alpgen (v2) + PYTHIA, where the Monte Carlo samples have been normalised to the inclusive cross section for each jet multiplicity.
The cross sections are defined for a restricted W kinematic phase space as indicated on the plots. This is to reduce the dependance of the measurement on the particular W + Jets Monte Carlo used for the acceptance correction. With this definition the W acceptance is very flat as a function of jet Et, and thus does not alter the shape of the cross sections.
Jets are corrected to the hadron level and we additionally apply an unsmearing
correction to account for the resolution of
the detector. One should notice that no Underlying Event correction has been applied to this measurement,
but that the contribution of the Underlying Event is at most 10% and only important at low Et.
The differential cross sections for the leading jet in >= 1 jet events, second jet in >=2 jets events, third jet in >=3 jets events and fourth jet in >=4 jets events. The W(ev) + 1p LO Alpgenv2+PYTHIA theoretical prediction is compared to the leading jet, W(ev) + 2p to the second jet and so on.
The integrated cross sections from the previous plot. Here the bin is the minimum Et above which the cross section is integrated. Note that the data-theory agreement in the first bin is perfect by construction, since this is how the theory is currently normalised.
The first-second jets delta R differential cross section for W + >=2 jets, where both jets have a minimum jet Et of 15 GeV.
The first-second jets invariant mass differential cross section for W + >=2 jets, where both jets have a minimum jet Et of 15 GeV.
Missing transverse energy in the W + >= 1 jet sample. The missing transverse energy distribution in data is fitted to background and signal templates to extract the background normalization. The blue histogram is the template for the qcd background, extracted with the anti-elctron method. The green histogram is the signal template and the purple one is the template for all the other backgrounds: W->tv, Z->ee, WW, top. The red histogram is the combined template that best fits the data.
Missing transverse energy in the W + >= 2 jets sample. The missing transverse energy distribution in data is fitted to background and signal templates to extract the background normalization. The blue histogram is the template for the qcd background, extracted with the anti-elctron method. The green histogram is the signal template and the purple one is the template for all the other backgrounds: W->tv, Z->ee, WW, top. The red histogram is the combined template that best fits the data.
Missing transverse energy in the W + >= 3 jets sample. The missing transverse energy distribution in data is fitted to background and signal templates to extract the background normalization. The blue histogram is the template for the qcd background, extracted with the anti-elctron method. The green histogram is the signal template and the purple one is the template for all the other backgrounds: W->tv, Z->ee, WW, top. The red histogram is the combined template that best fits the data.
Missing transverse energy in the W + >= 4 jets sample. The missing transverse energy distribution in data is fitted to background and signal templates to extract the background normalization. The blue histogram is the template for the qcd background, extracted with the anti-elctron method. The green histogram is the signal template and the purple one is the template for all the other backgrounds: W->tv, Z->ee, WW, top. The red histogram is the combined template that best fits the data.
Electron transverse energy in the W + >= 1 jet sample. The electron transverse energy distribution in data is compared to the signal and background templates normalized to the fractions extracted from the missing transverse energy fit.
Background fraction as a function of the leading jet minimum transverse energy in the W + >= 1 jet sample.
Background fraction as a function of the second leading jet minimum transverse energy in the W + >= 2 jets sample.
Error breakdown for the differential cross section in the W + >= 1 jet sample.
Error breakdown for the integrated cross section in the W + >= 1 jet sample.
