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In the following table are briefly described the most recent EWK public results based on data and Monte-Carlo studies.
Date |
Analysis |
Main Results |
Documentation |
July 2010 |
Data: Measurement of the W and Z inclusive production cross sections at sqrt(s)=7 TeV with the CMS experiment at the LHC |
We present the first measurements of inclusive W and Z production cross sections in muon and electron decay channels at sqrt(s)=7 TeV , obtained using 198 nb-1 of pp collisions in the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The measured inclusive cross sections are sigma(pp -> W+X -> lnu+X)=9.22 +/- 0.24(stat) +/- 0.47(syst) +/- 1.01(lumi) nb, and sigma(pp -> Z+X -> lnu+X)=0.882 +0.077 -0.073(stat) +0.042 -0.036(syst) +/- 0.097(lumi) nb, limited to the di-lepton invariant mass range [60 - 120] GeV |
PAS EWK-010-002 |
Sept 2010 |
Data: Study of tau reconstruction algorithms using pp collisions data collected at sqrt(s) = 7 TeV |
Proton–proton collision events collected with the CMS experiment at LHC at a center–of–mass energy of sqrt(s) = 7 TeV in 2010 are used to commission the algorithms for reconstruction and identification of tau lepton hadronic decays. Four different types of algorithms are considered: three based on particle–flow event reconstruction and one based on combinations of tracks and calorimeter clusters. Probabilities for quark and gluon jets to pass the tau identification criteria of the different algorithms are measured in data dominated by QCD multi–jet events and compared to predictions of Monte Carlo simulations. |
PAS PFT-10-004 |
March 2009 |
Monte Carlo: Measurement of the W and Z cross sections with muons at 10 TeV |
We discuss and develop methods for the measurement of the cross sections pp ->W+X -> μn + X and pp -> Z + X -> μ+μ− + X with the CMS detector at the LHC, at a center-of-mass energy of 10 TeV. We assume an integrated luminosity of 10 pb−1. For the Z measurement, both the event yield and the average trigger, isolation, and reconstruction efficiencies can be extracted simultaneously from fits of the invariant mass spectrum. For the W measurement, we update results shown in the 2007/002 Physics Analysis Summary note. |
PAS EWK-09-001 |
June 2009 |
Monte Carlo: Muon differential cross section and charge asymmetry in inclusive pp to W(mu-nu) + X production at 10 TeV |
Inclusive pp to W(mu-nu) +X production at the LHC has a large cross section, of the order of ten nanobarns. Studies of the lepton pseudorapidity distribution can provide constraints on the Parton Distribution Functions (PDFs). The differential cross section results at 10 TeV are given for an integrated luminosity of 10 pb-1. The resulting W muon charge asymmetry, at an integrated luminosity of 100 pb-1, is determined to be in the range 0.004 to 0.006 statistical accuracy in 6 measurements of asymmetry as a function of muon pseudorapidity. This is comparable to the PDF uncertainties and can be used to constrain PDF models once the systematic errors are under control. |
PAS EWK-09-003 |
June 2009 |
Monte Carlo: Prospects for measuring the WW production cross section at 10 TeV |
Analysis strategy for measuring the WW production cross section in 100 pb-1 of pp collision data at sqrt(s) = 10 TeV. Based on Monte Carlo simulations of WW and the major background processes, we explore suitable background reduction cuts and develop data-driven methods to estimate those backgrounds. We present the event yields and statistical and systematic uncertainties that we expect to achieve with this analysis strategy. We estimate a total uncertainty on the cross-section of 30% or better. |
PAS EWK-09-002 |
July 2009 |
Monte Carlo: Study of the ratio of W+jets to Z+jets at 10 TeV |
Simulation study of the ratio of W+jets to Z+jets in pp collisions at sqrt(s) = 10 TeV and feasibility of measurements of the ratio up to four inclusive jets with O(100) pb-1 of early CMS data at the LHC. These measurements allow early understanding of W+jets and Z+jets production at the LHC, since several detector effects and theoretical uncertainties cancel out. They also provide means of implementing a data-driven normalization of the W+jets and Z+jets backgrounds important to Standard Model processes (e.g. top quark) and new physics searches. |
PAS EWK-09-006 |
July 2009 |
Monte Carlo: Study of the Z to ee differential cross section as a function of Z rapidity at 10 TeV |
Estimates for measurement of the shape of the rapidity distribution for Z bosons produced in proton-proton collisions with the CMS detector at sqrt(s)=10 TeV. We consider integrated luminosity scenarios from 10 to 100 pb-1. The results of this measurement will provide input to constrain the parton density function of the proton at the LHC for many measurements and searches. |
PAS EWK-09-005 |
July 2009 |
Monte Carlo: Study of Z production in association with jets at 10 TeV |
Simulation study of Z boson production in association with jets in pp collisions at sqrt(s)= 10 TeV and feasibility of significant measurements up to four inclusive jets with O(100) pb-1 of early CMS data at the LHC. QCD predicts a constant ratio of Z+n jets over Z+(n+1) jets yields while several new physics models are expected to produce an excess of events at high jet multiplicity. We present the measurement of this ratio in the dielectron+jets and dimuon+jets final states using tracker-based, calorimetry-based, and Particle Flow jet definitions. We discuss the Z+jets sample as a ’candle’ for both physics and detector commissioning. |
PAS EWK-08-006 |
July 2009 |
Monte Carlo: Towards a Measurement of the Inclusive W to enu and γ*/Z->e+e cross sections at 10 TeV |
Methods for an early measurement of the inclusive W and γ*/Z production cross sections in the electron decay channel, assuming 10 pb-1 of pp collision data at sqrt(s) = 10 TeV. A simple and robust electron selection is used. This selection is intended to anticipate imperfections in calibration and alignment of the CMS detector in early data. Data driven methods have been used to measure the selection efficiencies, to tune the selection cuts, and to subtract the background in the W case. The electroweak boson signal yields can be measured with a statistical precision of less than 2.0% in each case, while the systematic biases in our methods have been estimated from simulation studies to be 4.0% and 2.4% for W and Z, respectively. Initial precision in the integrated luminosity measurement of 10% is expected to dominate the precision of the cross section measurements. |
PAS EWK-09-004 |