Search for excited $\tau$-leptons and leptoquarks in the final state with $\tau$-leptons and jets in pp collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The ATLAS collaboration
JHEP 06 (2023) 199, 2023.

Abstract (data abstract)
A search is reported for excited $\tau$-leptons and leptoquarks in events with two hadronically decaying $\tau$-leptons and two or more jets. The search uses proton-proton collision data at $\sqrt{s} = 13~\mathrm{TeV}$ recorded by the ATLAS experiment during the Run 2 of the Large Hadron Collider in 2015-2018. The total integrated luminosity is 139 fb$^{-1}$. The excited $\tau$-lepton is assumed to be produced and to decay via a four-fermion contact interaction into an ordinary $\tau$-lepton and a quark-antiquark pair. The leptoquarks are assumed to be produced in pairs via the strong interaction, and each leptoquark is assumed to couple to a charm or lighter quark and a $\tau$-lepton. No excess over the background prediction is observed. Excited $\tau$-leptons with masses below 2.8 TeV are excluded at 95% CL in scenarios with the contact interaction scale $\Lambda$ set to 10 TeV. At the extreme limit of model validity where $\Lambda$ is set equal to the excited $\tau$-lepton mass, excited $\tau$-leptons with masses below 4.6 TeV are excluded. Leptoquarks with masses below 1.3 TeV are excluded at 95% CL if their branching ratio to a charm quark and a $\tau$-lepton equals 1. The analysis does not exploit flavour-tagging in the signal region.

  • Limits on the excited tau production cross-section

    Figure 7a

    10.17182/hepdata.141537.v1/t1

    Observed and expected upper 95% CL limit on the $\tau^\ast$ production cross-section as a function of $m_{\tau^\ast}$ for a fixed...

  • Limits on the contact interaction scale $\Lambda$.

    Figure 7b

    10.17182/hepdata.141537.v1/t2

    Observed and expected lower 95% CL limit on the contact interaction scale $\Lambda$ as a function of $m_{\tau^\ast}$.

  • Limits on the LQ production cross-section

    Figure 8

    10.17182/hepdata.141537.v1/t3

    Observed and expected upper 95% CL limit on the LQ production cross-section as a function of $m_\mathrm{LQ}$. The LQ couples...

  • Signal Region Cutflow

    Auxiliary

    10.17182/hepdata.141537.v1/t4

    Cutflow for two representative signal samples used in this analysis. The excited tau mass $m_{\tau^\ast} = 2.75$ TeV and the...

  • Acceptance x efficiency of the $\tau^\ast$ signal SR selection

    Auxiliary Figure 5a

    10.17182/hepdata.141537.v1/t5

    Acceptance x efficiency of the $\tau^\ast$ signal SR selection

  • Acceptance x efficiency of the LQ signal SR selection

    Auxiliary Figure 5b

    10.17182/hepdata.141537.v1/t6

    Acceptance x efficiency of the LQ signal SR selection

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