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Search for a heavy gauge boson decaying to a charged lepton and a neutrino in 1 fb-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

ATLAS Collaboration

TL;DR

This ATLAS study searches for heavy charged gauge bosons $W'$ decaying to a lepton and a neutrino in 7 TeV $pp$ collisions using 1.04 fb$^{-1}$. The analysis leverages the transverse mass $m_T$ in both electron and muon channels, employs a Bayesian limit-setting framework with NNLO cross sections and Horace electroweak corrections, and uses data-driven methods to constrain QCD backgrounds. No signal is observed, and a combined limit excludes $m_{W'}$ up to 2.15 TeV for Sequential Standard Model couplings, representing the strongest constraint in this mass range from the 7 TeV run. The results significantly improve prior bounds and validate the leptonic $W'$ search strategy for high-mass resonances at the LHC.

Abstract

The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb^-1. No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV.

Search for a heavy gauge boson decaying to a charged lepton and a neutrino in 1 fb-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

TL;DR

This ATLAS study searches for heavy charged gauge bosons decaying to a lepton and a neutrino in 7 TeV collisions using 1.04 fb. The analysis leverages the transverse mass in both electron and muon channels, employs a Bayesian limit-setting framework with NNLO cross sections and Horace electroweak corrections, and uses data-driven methods to constrain QCD backgrounds. No signal is observed, and a combined limit excludes up to 2.15 TeV for Sequential Standard Model couplings, representing the strongest constraint in this mass range from the 7 TeV run. The results significantly improve prior bounds and validate the leptonic search strategy for high-mass resonances at the LHC.

Abstract

The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb^-1. No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV.

Paper Structure

This paper contains 8 sections, 7 equations, 3 figures, 6 tables.

Table of Contents

  1. Introduction
  2. Data
  3. Simulation
  4. Event selection
  5. Statistical analysis
  6. Parameter estimation and systematics
  7. Results
  8. Conclusions

Figures (3)

  • Figure 1: Spectra of $p_{\mathrm{T}}$ (top), missing $E_{\mathrm{T}}$ (center) and $m_{\mathrm T}$ (bottom) for the electron (left) and muon (right) channels after event selection. The points represent data and the filled histograms show the stacked backgrounds. Open histograms are $W'\rightarrow \ell \nu$ signals added to the background with masses in Ge V indicated in parentheses in the legend. The QCD backgrounds estimated from data are also shown. The signal and other background samples are normalized using the integrated luminosity of the data and the NNLO (approximate-NNLO for $t\bar{t}$) cross sections listed in Table \ref{['tab:xsec']}.
  • Figure 2: Expected and observed limits on $\sigma B$ for $W'\rightarrow e \nu$ (top), $W'\rightarrow \mu \nu$ (center), and the combination (bottom) assuming the same branching fraction for both channels. The NNLO calculated cross section and its uncertainty are also shown.
  • Figure 3: Normalized cross section limits ($\sigma_{\rm limit}/\sigma_{\rm SSM}$) for $W'\rightarrow \ell \nu$ as a function of mass for this measurement and from CDF cdf:Wprime2010, CMS cms:wpmu2011mar and the previous ATLAS search atlas:wprime_2010_pub. The cross section calculations assume the $W'$ has the same couplings as the standard model $W$ boson. The region above each curve is excluded at the 95% CL.