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Measurements of the production of W$^{\pm}$ and Z$^0$ bosons in pp collisions at $\sqrt{s} = 13$ TeV

ALICE Collaboration

Abstract

Measurements of the production of the W$^{\pm}$ and Z$^0$ bosons at midrapidity in pp collisions at $\sqrt{s} = 13$ TeV with ALICE at the Large Hadron Collider (LHC) are presented. The W$^{\pm}$ and Z$^0$ bosons are detected via their (di)electronic decay channels, with the electron reconstruction performed in the midrapidity region ($|y|< 0.6$). The $p_{\rm T}$-integrated and $p_{\rm T}$-differential production cross sections of electrons from W$^{\pm}$ decays in the interval $30 < p_{\rm T} < 60$ GeV/$c$, as well as the $p_{\rm T}$-integrated production cross section of Z$^0$ bosons, are measured. The results are described by perturbative QCD calculations using different sets of parton distribution functions. The production of W$^{\pm}$ bosons and azimuthally correlated associated hadrons is also measured as a function of the charged-particle multiplicity for the first time at the LHC. The former increases approximately linearly with the charged-particle multiplicity, while for the latter, there are hints of a faster-than-linear increase. These observations are compared with theoretical calculations.

Measurements of the production of W$^{\pm}$ and Z$^0$ bosons in pp collisions at $\sqrt{s} = 13$ TeV

Abstract

Measurements of the production of the W and Z bosons at midrapidity in pp collisions at TeV with ALICE at the Large Hadron Collider (LHC) are presented. The W and Z bosons are detected via their (di)electronic decay channels, with the electron reconstruction performed in the midrapidity region (). The -integrated and -differential production cross sections of electrons from W decays in the interval GeV/, as well as the -integrated production cross section of Z bosons, are measured. The results are described by perturbative QCD calculations using different sets of parton distribution functions. The production of W bosons and azimuthally correlated associated hadrons is also measured as a function of the charged-particle multiplicity for the first time at the LHC. The former increases approximately linearly with the charged-particle multiplicity, while for the latter, there are hints of a faster-than-linear increase. These observations are compared with theoretical calculations.
Paper Structure (13 sections, 8 equations, 9 figures, 2 tables)

This paper contains 13 sections, 8 equations, 9 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Experimental apparatus and data--taking conditions
  3. W$^\pm$- and Z$^0$-boson reconstruction
  4. Systematic uncertainties
  5. Systematic uncertainties on ${\rm Z^0}\rightarrow \textrm{e}^{+}\textrm{e}^{-}$
  6. Systematic uncertainties on e$^{\pm} \leftarrow \textrm{W}^{\pm}$
  7. Results
  8. Z$^0$-boson production
  9. W$^{\pm}$-boson production
  10. Production cross section of e$^{\pm} \leftarrow \textrm{W}^{\pm}$
  11. Multiplicity dependence of W${^\pm}$-boson and associated hadron production
  12. Summary
  13. The ALICE Collaboration

Figures (9)

  • Figure 1: Invariant-mass distribution of ${\rm e^{+}e^{-}}$ after background subtraction in pp collisions at $\sqrt s = 13$ TeV. The like-sign (open squares) and unlike-sign (open circles) distributions are also shown. The dashed lines indicate the fiducial mass interval used in this analysis. The vertical lines on the data points are the statistical uncertainties.
  • Figure 2: Raw $p_{\textrm{T}}$ distribution for e$^{-} \leftarrow \textrm{W}^{-}$ (left) and e$^{+} \leftarrow \textrm{W}^{+}$ (right) candidates after the isolation conditions together with the estimated background from heavy-flavour hadron decays and Z$^0$ decays in pp collisions at $\sqrt{s}=$ 13 TeV. The symbols are placed at the centre of the $p_{\rm T}$ interval. The statistical uncertainties are represented by vertical bars.
  • Figure 3: Production cross section of $Z^{0}$ bosons in pp collisions at $\sqrt{s}=$ 13 TeemV within the acceptance of the ALICE central barrel, compared with POWHEG calculations Alioli:2008gx performed with the CT14NNLO Dulat:2015mca, NNPDF40 NNPDF:2021njg and CT18NLO Yan:2022pzl PDF sets. Statistical and systematic uncertainties of the measurement are shown as a vertical line and an open box, respectively.
  • Figure 4: Production cross section of electrons from W$^{-}$ decays as a function of $p_{\rm T}$ at midrapidity in pp collisions at $\sqrt{s}=$13 TeemV compared with POWHEG calculations Alioli:2008gx using the CT14NNLO Dulat:2015mca (left), CT18NLO Yan:2022pzl (middle) and NNPDF4.0 NNPDF:2021njg (right) PDF sets. The symbols are placed at the centre of the $p_{\rm T}$ interval. The statistical and systematic uncertainties of the measurement are shown as vertical lines and open boxes, respectively. The uncertainties of the theoretical calculations are shown as shaded bands. The ratio of the data to the POWHEG calculations is shown in the lower panels.
  • Figure 5: Production cross section of positrons from W$^{+}$decays as a function of $p_{\rm T}$ at midrapidity in pp collisions at $\sqrt{s}=$13 TeemV compared with POWHEG calculations Alioli:2008gx using the CT14NNLO Dulat:2015mca (left), CT18NLO Yan:2022pzl (middle) and NNPDF4.0 NNPDF:2021njg (right) PDF sets. The symbols are placed at the centre of the $p_{\rm T}$ interval. The statistical and systematic uncertainties of the measurement are shown as vertical lines and open boxes, respectively. The uncertainties of the theoretical calculations are shown as shaded bands. The ratio of the data to the POWHEG calculations is shown in the lower panels.
  • ...and 4 more figures