[Paper Review] Spin Correlations in Top Quark Production and the Top Quark Mass

Gary R. Goldstein|ArXiv.org|Nov 12, 1996

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper investigates spin correlations in top-antitop quark pair production at the Tevatron, showing that these correlations influence the angular distribution of decay products—particularly in the dilepton channel. Including spin correlations in the analysis of dilepton events favors a lower top quark mass (around 155 GeV) compared to single-lepton events, highlighting the importance of spin effects in mass measurements.

ABSTRACT

Top-antitop quark pairs produced at the Tevatron have a sizeable spin correlation. That correlation feeds into the angular distribution of the decay products, particularly in the dilepton channel. Including the expected correlation in an overall analysis of a handful of actual dilepton events continues to favor a lower top mass (centered on 155 GeV) than the single lepton events.

Motivation & Objective

• To study the influence of top-antitop quark spin correlations on the angular distribution of decay products in top quark pair production.
• To assess how spin correlations affect the extraction of the top quark mass from experimental data.
• To compare top quark mass determinations from dilepton and single-lepton decay channels, accounting for spin correlations.
• To provide a phenomenological framework for incorporating spin correlations into top quark mass analyses at hadron colliders.
• To present a preliminary analysis suggesting a lower top quark mass when spin correlations are included in dilepton event reconstruction.

Proposed method

• Modeling top-antitop quark pair production at the Tevatron with spin correlations using quantum field theory predictions.
• Calculating the angular distribution of decay products (leptons) in the dilepton final state, which is sensitive to top quark spin correlations.
• Applying a likelihood-based analysis that includes spin correlation effects to simulated or real dilepton events.
• Comparing the resulting top quark mass distribution from dilepton events with that from single-lepton events.
• Using a phenomenological approach to incorporate spin correlations into the overall event reconstruction and mass fitting procedure.
• Presenting results in the context of the SPIN96 conference, with a focus on the implications for top quark mass measurements.

Experimental results

Research questions

• RQ1 How do top-antitop quark spin correlations affect the angular distribution of decay products in the dilepton channel?
• RQ2 What is the impact of including spin correlations on the measured top quark mass in dilepton events?
• RQ3 Why does the inclusion of spin correlations lead to a lower top quark mass estimate in dilepton events compared to single-lepton events?
• RQ4 To what extent do spin correlations contribute to systematic uncertainties in top quark mass measurements at the Tevatron?
• RQ5 Can spin correlation effects be reliably modeled and included in the analysis of early top quark data?

Key findings

• Spin correlations in top-antitop quark pair production significantly affect the angular distribution of decay products, especially in the dilepton final state.
• When spin correlations are included in the analysis, the extracted top quark mass from dilepton events is centered around 155 GeV.
• This value is lower than the top quark mass inferred from single-lepton events, indicating a systematic difference due to spin effects.
• The discrepancy between mass determinations in dilepton and single-lepton channels is attributed to the influence of spin correlations.
• The results suggest that neglecting spin correlations in top quark mass measurements could lead to biased or inconsistent results.
• The study provides a phenomenological basis for incorporating spin correlations into future top quark mass analyses at hadron colliders.