Inclusive W and Z production in the forward region at √s=7 TeV

The preprint is available here.

J. High Energy Phys. 06 (2012) 058

arXiv:1204.1620

More detailed information: ANA note 2011-091

Abstract

Measurements of inclusive W and Z boson production cross-sections in pp collisions at s√=7 TeV using final states containing muons are presented. The data sample corresponds to an integrated luminosity of 37 pb−1 collected with the LHCb detector. The W and Z bosons are reconstructed from muons with a transverse momentum above 20 GeV/c and pseudorapidity between 2.0 and 4.5, and, in the case of the Z cross-section, a dimuon invariant mass between 60 and 120 GeV/c2. The cross-sections are measured to be {831񸙦729 pb} for W+, {656񸅹923 pb} for W− and {76.71.73.32.7 pb} for Z, where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity. Differential cross-sections, W and Z cross-section ratios and the lepton charge asymmetry are also measured in the same kinematic region. The ratios are determined to be σW+→μ+ν/σW−→μ−νˉ={1.270.020.01}, and σW+→μ+ν+σW−→μ−νˉ)/σZ→μμ={19.40.50.9}. The results are in general agreement with theoretical predictions, performed at next-to-next-to-leading order in QCD using recently calculated parton distribution functions.

Figures

(Note, eps versions are available under attachments).

Caption Figure
Invariant mass of the selected muon pairs. The fitted distribution to the data is shown as a solid line and the contribution from background and off-resonance Drell-Yan production as a dashed line. ZmassAll.png
Distributions for pcone. The points are for muons TT from pseudo-W data, the yellow (shaded) histograms are for W -MC simulation, while the open histograms are for muons from QCD background with IP > 80 μm from data. All distributions are normalised to unity. IsoCh.png
Distributions for Econe. The points are for muons TT from pseudo-W data, the yellow (shaded) histograms are for W -MC simulation, while the open histograms are for muons from QCD background with IP > 80 μm from data. All distributions are normalised to unity. IsoNt.png
Muon IP distribution for pseudo-W events as points, W-MC as a yellow (shaded) histogram, and muons from simulated semi-leptonic decays of hadrons contain- ing a b quark in the full open histogram or a c quark in the dashed open histogram. All distributions are normalised to unity. IP.png
E/pc for pseudo-W events as points, W-MC as a yellow (shaded) histogram, and for hadrons from randomly triggered events in the open histogram. The energy E is the sum of the energies in the electromagnetic and hadronic calorimeter associated with the particle. All distributions are normalised to unity. EoP.png
Distribution of muon pT for positively (left panel) and negatively (right panel) charged muons in W candidate events, for the total fiducial cross-section. The data (points) are compared to the fitted contributions from W− and W+ (light shaded). The background contributions are, from top to bottom in the legend: decay-in-flight, Z → μμ, τ decays of W and Z, and heavy flavour decays. TFF0.png
Distribution of muon pT for positively (left panel) and negatively (right panel) charged muons in W candidate events, for the ημ bin 2 - 2.5. The data (points) are compared to the fitted contributions from W− and W+ (light shaded). The background contributions are, from top to bottom in the legend: decay-in-flight, Z → μμ, τ decays of W and Z, and heavy flavour decays. TFF1.png
Distribution of muon pT for positively (left panel) and negatively (right panel) charged muons in W candidate events, for the ημ bin 2.5 - 3. The data (points) are compared to the fitted contributions from W− and W+ (light shaded). The background contributions are, from top to bottom in the legend: decay-in-flight, Z → μμ, τ decays of W and Z, and heavy flavour decays. TFF2.png
Distribution of muon pT for positively (left panel) and negatively (right panel) charged muons in W candidate events, for the ημ bin 3 - 3.5. The data (points) are compared to the fitted contributions from W− and W+ (light shaded). The background contributions are, from top to bottom in the legend: decay-in-flight, Z → μμ, τ decays of W and Z, and heavy flavour decays. TFF3.png
Distribution of muon pT for positively (left panel) and negatively (right panel) charged muons in W candidate events, for the ημ bin 3.5 - 4. The data (points) are compared to the fitted contributions from W− and W+ (light shaded). The background contributions are, from top to bottom in the legend: decay-in-flight, Z → μμ, τ decays of W and Z, and heavy flavour decays. TFF4.png
Distribution of muon pT for positively (left panel) and negatively (right panel) charged muons in W candidate events, for the ημ bin 4 - 4.5. The data (points) are compared to the fitted contributions from W− and W+ (light shaded). The background contributions are, from top to bottom in the legend: decay-in-flight, Z → μμ, τ decays of W and Z, and heavy flavour decays. TFF5.png
Measurements of the Z , W + and W − cross-section and ratios, data are shown as bands which the statistical (dark shaded/orange) and total (light hatched/yellow) errors. The measurements are compared to NNLO and NLO predictions with different PDF sets for the proton, shown as points with error bars. The PDF uncertainty, evaluated at the 68% confidence level, and the theoretical uncertainties are added in quadrature to obtain the uncertainties of the predictions. Summary1.png
Differential cross-section for Z → μμ as a function of yZ. The dark shaded (orange) bands correspond to the statistical uncertainties, the light hatched (yellow) band to the statistical and systematic uncertainties added in quadrature. Superimposed are NNLO (NLO) predictions with different parametrisations for the PDF as points with error bars; they are displaced horizontally for presentation. CSZ.png
Differential W cross-section in bins of muon pseudorapidity. The dark shaded (orange) bands correspond to the statistical uncertainties, the light hatched (yellow) band to the statistical and systematic uncertainties added in quadrature. Superimposed are NNLO (NLO) predictions as described before. CSW20.png
Lepton charge asymmetry Aμ = (σW +→μ+ν − σW −→μ−ν ̄)/(σW +→μ+ν + σW −→μ−ν ̄) in bins of muon pseudorapidity. The dark shaded (orange) bands correspond to the sta- tistical uncertainties, the light hatched (yellow) band to the statistical and systematic uncertainties added in quadrature. Superimposed are NNLO (NLO) predictions as described before. The MSTW08 values for ημ < 2 represent the central value of the prediction. CSWA20.png
RW = σW + →μ+ ν /σW − →μ− ν ̄ in bins of muon pseudorapidity. The dark shaded (orange) bands correspond to the statistical uncertainties, the light hatched (yellow) band to the statistical and systematic uncertainties added in quadrature. Superimposed are NNLO (NLO) predictions with different parametrisations as described before. The MSTW08 values for ημ < 2 represent the central value of the prediction. CSWR.png
Lepton charge asymmetry Aμ = (σW +→μ+ν −σW −→μ−ν ̄)/(σW +→μ+ν +σW −→μ−ν ̄) for muons with pμT >25, respectively in bins of muon pseu- dorapidity. The dark shaded (orange) bands correspond to the statistical uncertainties, the light hatched (yellow) band to the statistical and systematic uncertainties added in quadrature. The statistical uncertainty is undistinguishable from the total uncertainty. Superimposed are the NNLO predictions with the MSTW08 parametrisation for the PDF. CSWA25.png
Lepton charge asymmetry Aμ = (σW +→μ+ν −σW −→μ−ν ̄)/(σW +→μ+ν +σW −→μ−ν ̄) for muons with pμT >30 GeV/c, respectively in bins of muon pseu- dorapidity. The dark shaded (orange) bands correspond to the statistical uncertainties, the light hatched (yellow) band to the statistical and systematic uncertainties added in quadrature. The statistical uncertainty is undistinguishable from the total uncertainty. Superimposed are the NNLO predictions with the MSTW08 parametrisation for the PDF. CSWA30.png

-- TaraShears - 18-Sep-2012

Topic attachments
I Attachment History Action Size Date Who Comment
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