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<p>The study of leptoquarks and their couplings to fermions with different chiralities provides a powerful tool for distinguishing among different leptoquark models. As a case study, we focus on two specific third-generation scalar leptoquark models, <i>S</i><sub>3</sub> and <i>R</i><sub>2</sub>, which differ in their electroweak quantum numbers and chiral structures of couplings to the top quark, leading to distinct top-quark polarization states. To enhance the efficacy of the analysis, we employ jet substructure techniques like Soft Drop, <i>N</i>-subjettiness, and our custom <i>b</i>-tagging method, along with other event variables. The analysis has been performed using both fixed radius and dynamic radius jet clustering algorithms. A multivariate analysis using a boosted decision tree (BDT) is performed to isolate signal from the Standard Model background. For a leptoquark mass of 1250 GeV, the analysis achieves a signal significance of up to 5<i>.</i>3 <i>σ</i> at the 14 TeV HL-LHC. Furthermore, a <i>CL</i><sub><i>s</i></sub>-based profile likelihood estimator is applied to polarization-sensitive variables to discriminate between the two models. To enhance separation between the two models, an additional BDT classifier score is obtained by training a BDT network to distinguish between the <i>S</i><sub>3</sub> and <i>R</i><sub>2</sub> models. In the chosen signal region, the BDT classifier score provides a separation score of up to 3<i>.</i>2 <i>σ</i>, outperforming traditional variables such as <i>E</i><sub><i>b</i></sub>/<i>E</i><sub><i>t</i></sub> and cos <i>θ</i><sub><i>b</i></sub>.</p>

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Jet substructure probe on scalar leptoquark models via top polarization

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月11日

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  • Anupam Ghosh,
  • Partha Konar,
  • Tousik Samui,
  • Ritesh K. Singh

摘要

The study of leptoquarks and their couplings to fermions with different chiralities provides a powerful tool for distinguishing among different leptoquark models. As a case study, we focus on two specific third-generation scalar leptoquark models, S3 and R2, which differ in their electroweak quantum numbers and chiral structures of couplings to the top quark, leading to distinct top-quark polarization states. To enhance the efficacy of the analysis, we employ jet substructure techniques like Soft Drop, N-subjettiness, and our custom b-tagging method, along with other event variables. The analysis has been performed using both fixed radius and dynamic radius jet clustering algorithms. A multivariate analysis using a boosted decision tree (BDT) is performed to isolate signal from the Standard Model background. For a leptoquark mass of 1250 GeV, the analysis achieves a signal significance of up to 5.3 σ at the 14 TeV HL-LHC. Furthermore, a CLs-based profile likelihood estimator is applied to polarization-sensitive variables to discriminate between the two models. To enhance separation between the two models, an additional BDT classifier score is obtained by training a BDT network to distinguish between the S3 and R2 models. In the chosen signal region, the BDT classifier score provides a separation score of up to 3.2 σ, outperforming traditional variables such as Eb/Et and cos θb.