Measurement of $W^{\pm}Z$ production cross sections and gauge boson polarisation in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The ATLAS collaboration
Eur.Phys.J. C79 (2019) 535, 2019

Abstract (data abstract)
CERN-LHC. This paper presents measurements of $W^{\pm}Z$ production in $pp$ collisions at a center-of-mass energy of $13$ TeV. The data were collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider, and correspond to an integrated luminosity of 36.1 fb$^{-1}$. The $W^{\pm}Z$ candidate events are reconstructed using leptonic decay modes into electrons and muons of the gauge bosons. The measured inclusive cross section in the detector fiducial region for leptonic decay modes is $\sigma_{W^\pm Z \rightarrow \ell^{'} \nu \ell \ell}^{\textrm{fid.}} = 63.7 \, \pm~1.0~\textrm{(stat.)} \, \pm~2.3~\textrm{(sys.)} \, \pm~0.3~\textrm{(mod.)} \, \pm~1.5~\textrm{(lumi.)}$ fb, in agreement with the next-to-next-to-leading-order Standard Model prediction of $61.5^{+1.4}_{-1.3}$ fb. Cross sections for $W^+Z$ and $W^-Z$ production and their ratio are presented as well as differential cross sections for several kinematic observables. An analysis of angular distributions of lepton decays of $W$ and $Z$ bosons is performed and integrated helicity fractions in the detector fiducial region are measured for each of the $W$ and $Z$ bosons. The longitudinal polarisation of pair-produced vector bosons is measured for the first time in $pp$ collisions. The cross sections are measured in a fiducial phase space reflecting the detector acceptance, defined by: - $p_{\mathrm{T}}$ of electrons and muons from Z0 decays > 15 GeV - $p_{\mathrm{T}}$ of electrons and muons from the $W^{\pm}$ decays > 20 GeV - $|\eta|$ of muons and electrons < 2.5 - Leptons from the Z0 boson are separated by $\Delta R(\ell,\ell) > 0.2$ from each other - Leptons from the Z0 and W bosons are separated by $\Delta R(\ell,\ell) > 0.3$ from each other - |dilepton mass - Z0 mass| < 10 GeV - $m_{\mathrm{T}}$ of $W^{\pm}$ > 30 GeV. At particle level, the kinematics of final-state prompt electrons and muons is computed including the contributions from final-state radiated photons within a distance in the ($\eta,\phi$) plane of $\Delta R = \sqrt{(\Delta\eta)^2 + (\Delta\phi)^2} = 0.1$ around the direction of the charged lepton. These dressed leptons and the final-state neutrinos that do not originate from hadron or $\tau$ decays are associated with the $W$ and $Z$ boson decay products with an algorithmic approach, called ``resonant shape''. This algorithm is based on the value of an estimator expressing the product of the nominal line shapes of the $W$ and $Z$ resonances $P = \left| \frac{1}{ m^2_{(\ell^+,\ell^-)} - \left(m_Z^{\textrm{PDG}}\right)^2 + i \; \Gamma_Z^{\textrm{PDG}} \; m_Z^{\textrm{PDG}} } \right|^2 \times \; \left| \frac {1} { m^2_{(\ell',\nu_{\ell'})} - \left(m_W^{\textrm{PDG}}\right)^2 + i \; \Gamma_W^{\textrm{PDG}} \; m_W^{\textrm{PDG}} } \right|^2$ where $m_Z^{\textrm{PDG}}$ ($m_W^{\textrm{PDG}}$) and $\Gamma_Z^{\textrm{PDG}}$ ($\Gamma_W^{\textrm{PDG}}$) are the world average mass and total width of the $Z$ ($W$) boson, respectively, as reported by the Particle Data Group. The input to the estimator is the invariant mass $m$ of all possible pairs ($\ell^+,\ell^-$) and ($\ell',\nu_{\ell'}$) satisfying the fiducial selection requirements. The final choice of which leptons are assigned to the $W$ or $Z$ bosons corresponds to the configuration exhibiting the highest value of the estimator.

  • Table 1

    Data from Table 4 of the paper

    10.17182/hepdata.83701.v1/t1

    The measured $W^{\pm}Z$ fiducial cross section in the four channels and their combination. The first systematic uncertainty is the combined...

  • Table 2

    Data from Table 4 of the paper

    10.17182/hepdata.83701.v1/t2

    The measured $W^{+}Z$ fiducial cross section in the four channels and their combination. The first systematic uncertainty is the combined...

  • Table 3

    Data from Table 4 of the paper

    10.17182/hepdata.83701.v1/t3

    The measured $W^{-}Z$ fiducial cross section in the four channels and their combination. The first systematic uncertainty is the combined...

  • Table 4

    Data from Auxilliary table 1

    10.17182/hepdata.83701.v1/t4

    The measured fiducial cross sections are corrected to the dressed level. The ratio of $C_{WZ}^{\textrm{dressed}}/C_{WZ}^{\textrm{Born}}$ factors presented in this table...

  • Table 5

    Data from Page 16 of the paper

    10.17182/hepdata.83701.v1/t5

    Ratio of fiducial cross sections measured for $W^{+} Z$ and $W^{-} Z$ production.

  • Table 6

    Data from Page 16 of the paper

    10.17182/hepdata.83701.v1/t6

    Cross section extrapolated to total phase space and all W and Z boson decays. The first systematic uncertainty is the...

  • Table 7

    Data from Auxillary material

    10.17182/hepdata.83701.v1/t7

    The total cross section is measured at dressed level and can also be corrected to Born level use this acceptance...

  • Table 8

    Data from Figure 4 of the paper, Auxiliary Table 6

    10.17182/hepdata.83701.v1/t8

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 9

    Data from Auxiliary Table 7

    10.17182/hepdata.83701.v1/t9

    Correlation matrix for the unfolded cross section.

  • Table 10

    Data from Figure 4 of the paper, Auxiliary Table 2

    10.17182/hepdata.83701.v1/t10

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 11

    Data from Auxiliary Table 3

    10.17182/hepdata.83701.v1/t11

    Correlation matrix for the unfolded cross section.

  • Table 12

    Data from Figure 4 of the paper, Auxiliary Table 4

    10.17182/hepdata.83701.v1/t12

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 13

    Data from Auxiliary Table 5

    10.17182/hepdata.83701.v1/t13

    Correlation matrix for the unfolded cross section.

  • Table 14

    Data from Figure 4 of the paper, Auxiliary Table 10

    10.17182/hepdata.83701.v1/t14

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 15

    Data from Auxiliary Table 11

    10.17182/hepdata.83701.v1/t15

    Correlation matrix for the unfolded cross section.

  • Table 16

    Data from Figure 5 of the paper, Auxiliary Table 8

    10.17182/hepdata.83701.v1/t16

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 17

    Data from Auxiliary Table 9

    10.17182/hepdata.83701.v1/t17

    Correlation matrix for the unfolded cross section.

  • Table 18

    Data from Figure 5 of the paper, Auxiliary Table 12

    10.17182/hepdata.83701.v1/t18

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 19

    Data from Auxiliary Table 13

    10.17182/hepdata.83701.v1/t19

    Correlation matrix for the unfolded cross section.

  • Table 20

    Data from Figure 6 of the paper, Auxiliary Table 14

    10.17182/hepdata.83701.v1/t20

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 21

    Data from Auxiliary Table 15

    10.17182/hepdata.83701.v1/t21

    Correlation matrix for the unfolded cross section.

  • Table 22

    Data from Figure 6 of the paper, Auxiliary Table 16

    10.17182/hepdata.83701.v1/t22

    Measured fiducial cross section for a single leptonic decay channel $\ell'^\pm \nu \ell^+ \ell'^-$ of the $W The relative uncertainties...

  • Table 23

    Data from Auxiliary Table 17

    10.17182/hepdata.83701.v1/t23

    Correlation matrix for the unfolded cross section.

  • Table 24

    Data from Table 5 of the paper

    10.17182/hepdata.83701.v1/t24

    5: Measured helicity fractions in the fiducial phase space with Born level leptons, for $W^-$, $W^+Z$ and $W^{\pm}Z$ events. The...

Loading Data...