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Reconstructing Toponium using Recursive Jigsaw Reconstruction

Aman Desai, Amelia Lovison, Paul Jackson

TL;DR

This work addresses the search for a spin-0 toponium state near the $t\bar{t}$ threshold in dileptonic decays at the LHC, where two escaping neutrinos complicate reconstruction. It deploys Recursive Jigsaw Reconstruction within the RestFrames framework to reconstruct the $t\bar{t}$ system, and introduces two discriminants, $\Delta\phi(t\bar{t})$ and $N_{c,\mathrm{hel}}$, to separate signal from the $t\bar{t}$ background. Using Run 3 kinematics at $\sqrt{s}=13.6$ TeV with NRQCD-reweighted toponium samples, the analysis shows that the optimal phase-space region—$\Delta\phi(t\bar{t})\in[-2,2]$ and $N_{c,\mathrm{hel}}\in[0.4,1]$—produces a reconstructed $M_{t\bar{t}}$ with a significance of $15.3\sigma$. The results demonstrate improved sensitivity to the toponium signal and offer a path toward deeper phenomenological understanding of the $t\bar{t}$ threshold region.

Abstract

The results from the ATLAS and CMS experiment at the Large Hadron Collider indicate the existence of a top-quark pair bound state near the $\ttbar$ threshold region. We present a method relying on Recursive Jigsaw Reconstruction to reconstruct the toponium bound state at the $\ttbar$ threshold region. We propose incorporating two variables in the analysis that can improve sensitivity to the toponium signal. Our results indicate that this method may be useful to gain additional insights into the physics phenomenology of the $\ttbar$ threshold region.

Reconstructing Toponium using Recursive Jigsaw Reconstruction

TL;DR

This work addresses the search for a spin-0 toponium state near the threshold in dileptonic decays at the LHC, where two escaping neutrinos complicate reconstruction. It deploys Recursive Jigsaw Reconstruction within the RestFrames framework to reconstruct the system, and introduces two discriminants, and , to separate signal from the background. Using Run 3 kinematics at TeV with NRQCD-reweighted toponium samples, the analysis shows that the optimal phase-space region— and —produces a reconstructed with a significance of . The results demonstrate improved sensitivity to the toponium signal and offer a path toward deeper phenomenological understanding of the threshold region.

Abstract

The results from the ATLAS and CMS experiment at the Large Hadron Collider indicate the existence of a top-quark pair bound state near the threshold region. We present a method relying on Recursive Jigsaw Reconstruction to reconstruct the toponium bound state at the threshold region. We propose incorporating two variables in the analysis that can improve sensitivity to the toponium signal. Our results indicate that this method may be useful to gain additional insights into the physics phenomenology of the threshold region.
Paper Structure (5 sections, 1 equation, 5 figures, 1 table)

This paper contains 5 sections, 1 equation, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Monte Carlo Simulation and Event Preselection
  3. Reconstruction Method for $t\bar{t}$ in Dilepton Final States
  4. Analysis
  5. Conclusion

Figures (5)

  • Figure 1: Example decay tree diagram of the process $t\Bar{t} \rightarrow b\Bar{b} W ( l \nu_l) W ( l \Bar{\nu_l})$
  • Figure 2: Invariant mass distributions of the top-quark pair as evaluated by the reconstruction algorithms.
  • Figure 3: Truth level distributions for $\Delta \phi(t\Bar{t})$ and $N_{chel}$ variables.
  • Figure 4: Correlation between the $\Delta \phi(t\Bar{t})$ and $N_{chel}$ variables for Toponium sample (left) and $t\bar{t}$ sample (right).
  • Figure 5: Results after pre-selections. (a) Significance obtained in the nine analysis regions. (b) Reconstructed $t\bar{t}$ invariant mass in the optimal region.