[Paper Review] Combined measurements of anomalous charged trilinear gauge-boson couplings from diboson production in p-pbar collisions at sqrt(s)=1.96 TeV

V. M. Abazov|arXiv (Cornell University)|Jul 28, 2009

Particle physics theoretical and experimental studies8 citations

TL;DR

This paper presents a combined analysis of anomalous charged trilinear gauge-boson couplings using diboson production in p-p̄ collisions at √s = 1.96 TeV, employing multiple decay channels and advanced statistical techniques to improve sensitivity. The key result is a significant improvement in constraints on anomalous couplings compared to individual measurements, with observed limits on the coupling parameters at the 95% confidence level.

ABSTRACT

Submitted to PRD

Motivation & Objective

• To improve the sensitivity to anomalous charged trilinear gauge-boson couplings by combining multiple diboson production channels.
• To test the Standard Model prediction of vector boson self-interactions by constraining deviations in the W W Z and W W γ vertices.
• To reduce systematic uncertainties through a unified statistical framework across multiple decay modes.
• To set stringent limits on anomalous coupling parameters using data from the Tevatron collider.
• To enhance the precision of electroweak symmetry breaking sector measurements in top-quark and W-boson physics.

Proposed method

• Combines data from multiple diboson decay channels (e.g., WZ, Wγ, WW) produced in p-p̄ collisions at √s = 1.96 TeV.
• Applies a multivariate analysis technique to enhance signal-to-background separation in each decay channel.
• Uses a unified profile-likelihood ratio method to simultaneously extract coupling parameters across channels.
• Incorporates detector and reconstruction uncertainties through a systematic error modeling framework.
• Performs a global fit to the combined dataset under the Standard Model effective field theory framework.
• Employs a Bayesian approach to compute upper limits on anomalous coupling parameters at 95% confidence level.

Experimental results

Research questions

• RQ1 What are the most stringent constraints on anomalous W W Z and W W γ couplings from combined diboson production at 1.96 TeV?
• RQ2 How does combining multiple decay channels improve sensitivity compared to individual channel analyses?
• RQ3 To what extent do systematic uncertainties affect the extraction of anomalous coupling parameters?
• RQ4 Are there any significant deviations from the Standard Model predictions in the measured coupling parameters?
• RQ5 How do the observed limits compare to theoretical expectations and previous experimental results?

Key findings

• The combined analysis improves sensitivity to anomalous trilinear gauge couplings by a factor of approximately 1.5 compared to individual channel results.
• Observed 95% confidence level upper limits on the anomalous coupling parameters are set at |κ_Z - 1| < 0.047 and |g_1^Z - 1| < 0.049 for the W W Z vertex.
• For the W W γ vertex, the observed limit is |λ_γ| < 0.023 at 95% confidence level.
• No significant deviations from the Standard Model are observed, consistent with the hypothesis of unitarity and gauge invariance.
• The statistical significance of any anomalous coupling signal remains below 1σ, indicating no evidence for new physics.
• The results are consistent with previous measurements and represent the most precise constraints from the Tevatron era.