A study of the $Z$ production cross-section in $pp$ collisions at $\sqrt{s} = 7$ TeV using tau final states

TL;DR

This paper reports a measurement of the Z boson production cross-section in proton-proton collisions at 7 TeV using tau final states, providing insights into electroweak processes and tau lepton behavior.

Contribution

It presents the first measurement of the Z to tau tau cross-section at 7 TeV with the LHCb detector, including the ratio to Z to mu mu decays, with detailed uncertainty analysis.

Findings

Measured Z to tau tau cross-section: 71.4 pb with uncertainties.

Determined the ratio of Z to tau tau to Z to mu mu cross-sections as 0.93.

Provided systematic and statistical uncertainties for the measurement.

Abstract

A measurement of the inclusive $Z \to \tau\tau$ cross-section in $pp$ collisions at $\sqrt{s} = 7$ TeV is presented based on a dataset of 1.0 fb$^{-1}$ collected by the LHCb detector. Candidates for $Z \to \tau\tau$ decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for $Z$ bosons, with invariant mass between 60 and 120 GeV/$c^2$, which decay to $\tau$ leptons with transverse momenta greater than 20 GeV/$c$ and pseudorapidities between 2.0 and 4.5, is measured to be $\sigma_{pp \to Z \to \tau\tau} = 71.4 \pm 3.5 \pm 2.8 \pm 2.5$ pb; the first uncertainty is statistical, the second uncertainty is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for $Z \to \tau\tau$ to $Z \to \mu\mu$ is determined to be $0.93 \pm 0.09$, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements.