1. W and Z+ Jets Comparing event generators for Vector Boson events
Jennifer Thompson,
Bergische Univerität Wuppertal

2. Introduction
This compares different event generators for vector boson decays and jets.
Ratios are also presented to show the different physics of W and Z decays
For electron distributions, the e- was always used in the case of the Z, and whichever of the e+/e- existed in the case of the W
Look at systematics of W+ jet/Z+jet ratio
Plots are normalised to 1. This suppresses σ(W)TOT/σ(Z)TOT
Wuppertal interested in studying ratio to understand Beyond Standard Model Physics

3. Implemented Cuts 3 different sets of cuts were implemented Phase space
pT minimum of 20 GeV/c for electrons and jets
η maximum of 2.47 for electrons
η maximum of 2.8 for jets
Neutrino
All phase space cuts
For W, neutrino was treated as a second electron
All cuts
For W, minimum missing ET of 25 GeV
For W, minimum transverse mass of 40 GeV/c2
For W, exactly one electron
For Z, invariant mass between 71 GeV/c2 and 110 GeV/c2
This is the default used

4. Agreement of Generators: Ratios of Vector Boson
Ratios for all cuts including global cuts on W and Z bosons
Good agreement between all generators

5. Agreement of Generators: Electron pT
Again, all cuts including those on W and Z boson
Wider distribution for Z boson case than W boson

6. Electron pT Ratio Plots for all cuts with Sherpa generator
Histogram shows shift by a couple of GeV of distribution between W and Z
This is why the ratio jumps from around 1.5 to around 0.5

7. Behaviour of all Generators: Electron pT and η
These are for all generators, which have a good agreement

8. Systematics: Electron η Distributions
These are the plots for the experimental phase space cuts, without cuts on W or Z boson masses
W and Z are treated differently due to the cuts on the electrons
This biases the results

9. Systematics: Electron η Distributions
Here the neutrino in the case of the W boson was treated as a second electron
The W and Z bosons are treated the same and so have the same distributions

10. Comparing Generators: pT 1st Jet
Good agreement between AlpGen and Sherpa
Pythia falls off slightly faster
For W boson Sherpa is above AlpGen

11. Comparing Generators: pT 1st Jet Ratio
Sherpa and AlpGen disagree at high pT
Good agreement at low pT

12. Comparing Generators: Jet Multiplicity Ratios
Good agreement between AlpGen and Sherpa
Pythia falls off faster for higher numbers of jets

13. Conclusions Sherpa and AlpGen show good agreement
Cuts on the phase space make a difference to the observed Physics, treatment of the neutrino is very important to understand the systematics
Continue project by using Sherpa 1.2.2

14. Backup

15. W bosons- pT and η

16. Z bosons- pT and η

17. Electron for phase cuts