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Search for High-Mass Resonances Decaying to $\tau\nu$ in pp Collisions at $\sqrt{s}$=13 TeV with the ATLAS Detector

The ATLAS collaboration
Phys.Rev.Lett. 120 (2018) 161802, 2018.

Abstract (data abstract)
CERN-LHC. A search for high-mass resonances decaying to $\tau\nu$ in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector. Units of GeV and pb are used for all data in this entry, which may be different to those used in the publication. Fiducial region: - No electrons or muons - $p_{\rm T}$(e) > 20 GeV, |$\eta$(e)| < 2.47 - $p_{\rm T}$($\mu$) > 20 GeV, |$\eta$($\mu$)| < 2.5 - At least one hadronic tau decay ($\tau_{\rm had-vis}$) - $p_{\rm T}$($\tau_{\rm had-vis}$) > 50 GeV, |$\eta$($\tau_{\rm had-vis}$)| < 2.4 - Choose $\tau_{\rm had-vis}$ with highest $p_{\rm T}$ - $E_{\rm T}^{\rm miss}$ > 150 GeV - 0.7 < $p_{\rm T}$($\tau_{\rm had-vis}$) / $E_{\rm T}^{\rm miss}$ < 1.3 - $\Delta\phi$($\tau_{\rm had-vis}$, $E_{\rm T}^{\rm miss}$) > 2.4 rad - $m_{\rm T}$($\tau_{\rm had-vis}$, $E_{\rm T}^{\rm miss}$) > threshold - Choose threshold in range 250-1800 GeV in 50 GeV steps Note: significant activity near the chosen $\tau_{\rm had-vis}$ would reduce its identification efficiency. If signals with a busy final state are considered we suggest to reject events if the scalar sum $p_{\rm T}$ of stable charged particles within $\Delta R$ = 0.4 or neutral particles within $\Delta R$ = 0.2 of the chosen $\tau_{\rm had-vis}$ is larger than a few GeV (not including pileup or decay products of the chosen $\tau_{\rm had-vis}$) These results can be reinterpreted for alternate signal models using the limits on the visible $\tau\nu$ production cross section ($\sigma_{\rm vis} = \sigma \times \mathcal{A} \times \varepsilon$) provided in Table 2. Reinterpretation requires calculation of: - $\sigma$: signal cross section including production and decay - $\mathcal{A}$: acceptance of fiducial selection at generator level - $\varepsilon$: reconstruction efficiency First, calculate the visible cross section for each $m_{\rm T}$ threshold at a single parameter-space point of the signal model is question. The parameter-space point is excluded if the visible cross section is larger than the limit at any $m_{\rm T}$ threshold. Repeat the process for all parameter-space points and models to determine the excluded regions. The reconstruction efficiency is dependent on $m_{\rm T}$, and therefore on the $m_{\rm T}$ distribution of the signal model. It can be incorporated by weighting generated events by the parameterized efficiency: $\varepsilon$($m_{\rm T}$ [TeV]) = 0.633 - 0.313$m_{\rm T}$ + 0.0688$m_{\rm T}^2$ - 0.00575$m_{\rm T}^3$ For reference, the optimal $m_{\rm T}$ thresholds for the SSM and NU models are given in Table 5, the acceptance and acceptance times efficiency for the SSM model can be found in Tables 6 and 7 and the model independent reconstruction efficiency can be found in Table 8.

  • Table 1

    Data from Figure 1


    Observed and predicted $m_{\rm T}$ distributions including SSM and NU (cot$\phi$ = 5.5) $W^{\prime}$ signals with masses of 3 TeV....

  • Table 2

    Data from Auxiliary Table 3


    Number of expected Standard Model background events including total statistical and systematic uncertainty added in quadrature (calculated before applying the...

  • Table 3

    Data from Figure 4A


    Observed and expected 95% CL upper limits on cross section times $\tau\nu$ branching fraction for $W^{\prime}_{\rm SSM}$.

  • Table 4

    Data from Figure 4B


    Regions of the non-universal G(221) parameter space excluded at 95% CL.

  • Table 5

    Data from Auxiliary Table 2


    Number of expected $W^{\prime}_{\rm SSM}$, $W^{\prime}_{\rm NU}$, Standard Model background and observed events passing the optimal $m_{\rm T}$ threshold for...

  • Table 6

    Data from Auxiliary Figure 1


    Acceptance for $W^{\prime}_{\rm SSM}$ as a function of the $W^{\prime}_{\rm SSM}$ mass, shown after successively applying selection at generator-level. The...

  • Table 7

    Data from Auxiliary Figure 2


    Acceptance times efficiency for $W^{\prime}_{\rm SSM}$ as a function of the $W^{\prime}_{\rm SSM}$ mass, shown after successively applying selection at...

  • Table 8

    Data from Auxiliary Figure 3


    Reconstruction efficiency as a function of $m_{\rm T}$ (see HepData abstract for parameterization), defined as the ratio of the number...

Version 3 modifications: Table 1 now also contains each background contribution to the Standard Model expectation separately with their statistical uncertainties.

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