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

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

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

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

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

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

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

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

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

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

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

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

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

Backup

W bosons- pT and η

Z bosons- pT and η

Electron for phase cuts