Measurements of the inclusive W and Z boson production cross sections and their ratios in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV

Abstract: Measurements are presented of the W and Z boson production cross sections in proton-proton collisions at a center-of-mass energy of 13.6 TeV. Data collected in 2022 and corresponding to an integrated luminosity of 5.01 fb$^{-1}$ with one or two identified muons in the final state are analyzed. The results for the products of total inclusive cross sections and branching fractions for muonic decays of W and Z bosons are 11.93 $\pm$ 0.08 (syst) $\pm$ 0.17 (lumi) $^{+0.07}_{-0.07}$ (acc) nb for W$^+$ boson production, 8.86 $\pm$ 0.06 (syst) $\pm$ 0.12 (lumi) $^{+0.05}_{-0.06}$ (acc) nb for W$^-$ boson production, and 2.021 $\pm$ 0.009 (syst) $\pm$ 0.028 (lumi) $^{+0.011}_{-0.013}$ (acc) nb for the Z boson production in the dimuon mass range of 60-120 GeV, all with negligible statistical uncertainties. Furthermore, the corresponding fiducial cross sections, as well as cross section ratios for both fiducial and total phase space, are provided. The ratios include charge-separated results for W boson production (W$^+$ and W$^-$) and the sum of the two contributions (W$^\pm$), each relative to the measured Z boson production cross section. Additionally, the ratio of the measured cross sections for W$^+$ and W$^-$ boson production is reported. All measurements are in agreement with theoretical predictions, calculated at next-to-next-to-leading order accuracy in quantum chromodynamics.

Precise Measurement of Inclusive (\rm{W}) and (\rm{Z}) Boson Production Cross Sections at (\sqrt{s}=13.6) TeV in Proton-Proton Collisions

This paper presents precise measurements of the inclusive production cross sections of (\rm{W}) and (\rm{Z}) bosons in proton-proton collisions at a center-of-mass energy of 13.6 TeV. Conducted by the CMS Collaboration, the study utilizes the data collected from the Large Hadron Collider (LHC) during its 2022 run, corresponding to an integrated luminosity of 5.01 (\rm{fb}^{-1}). The work primarily focuses on the events where (\rm{W}) and (\rm{Z}) bosons decay into muons, exploiting the excellent performance of the CMS muon detection systems to achieve high-precision results.

Summary of Methodology

The paper details the experimental approach for measuring both the fiducial and total inclusive cross sections, which crucially involves detecting final states with one or two muons. The muonic decay channels of the (\rm{W}) and (\rm{Z}) bosons provide a cleaner signal that can be measured against a backdrop of potential background processes, such as top quark pair production, other electroweak interactions, and QCD multijet events. The geographic coverage and energy reconstruction capabilities of the CMS detector are critical to this effort, especially in areas requiring precise muon momentum measurements and missing transverse energy estimates.

The analysis exploits sophisticated Monte Carlo (MC) simulations to understand detector responses, calculate acceptances, and model the contributions from various background processes. Theoretical predictions at next-to-next-to-leading order (NNLO) QCD, augmented by next-to-next-to-leading logarithmic (NNLL) resummation of transverse momentum distributions, are used to benchmark the experimental outcomes, with parton distribution functions (PDFs) playing a crucial role in these predictions.

Key Results

The paper provides detailed numbers for the total inclusive (\times) branching fractions for (\rm{W^+}), (\rm{W^-}), and (\rm{Z}) productions. They are measured to be (11.93 \, \rm{nb}), (8.86 \, \rm{nb}), and (2.021 \, \rm{nb}) respectively, with systematic uncertainties dominating the precision error considerations. These measurements align well with theoretical predictions, providing a robust validation of the underlying modeling and computation techniques involved.

The study also reports on ratios of cross sections, namely (R_{W^+/Z}), (R_{W^-/Z}), and (R_{W^+/W^-}), where the cancellation of several systematic nuisances in the ratios allows for even smaller uncertainties than the direct cross section measurements. These ratios provide additional insight into the properties of (\rm{W}) and (\rm{Z}) boson productions and serve as a testbed for new physics, such as deviations in electroweak unification or unexpected coupling modifications.

Implications and Future Work

The precise measurement of (\rm{W}) and (\rm{Z}) production cross sections at the unprecedented energy scale of 13.6 TeV represents a critical component of our ongoing exploration of particle physics, reinforcing the predictive power of the Standard Model while searching for potential signals of new physics. The accuracy achieved provides stringent constraints on various theoretical models, particularly those seeking to address the small discrepancies between experiment and existing EWK predictions at lower energy scales.

Moreover, these results help refine global PDF fits, thereby improving our understanding of the proton's substructure—a cornerstone for interpreting collider data across numerous search channels. Future analyses could benefit from this dataset by pursuing more differential studies, such as examining the rapidity and transverse momentum distributions of the (\rm{W}) and (\rm{Z}) bosons, which could unlock further understanding and challenge current theoretical frameworks.

As such, this work sets the stage for further high-precision measurements that could reveal discrepancies indicative of physics beyond the Standard Model, thus widening our grasp of the fundamental forces governing the universe.