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Search for new phenomena in events with three or more charged leptons in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

The ATLAS collaboration
JHEP 1508 (2015) 138, 2015

Abstract (data abstract)
CERN-LHC. A generic search for anomalous production of events with at least three charged leptons is presented. The data sample consists of $pp$ collisions at $\sqrt{s}=8$ TeV collected in 2012 by the ATLAS experiment at the CERN Large Hadron Collider, and corresponds to an integrated luminosity of 20.3 fb$^{-1}$. Events are required to have at least three selected lepton candidates, at least two of which must be electrons or muons, while the third may be a hadronically decaying tau. Selected events are categorized based on their lepton flavour content and signal regions are constructed using several kinematic variables of interest. No significant deviations from Standard Model predictions are observed. Model-independent upper limits on contributions from beyond the Standard Model phenomena are provided for each signal region, along with prescription to re-interpret the limits for any model. Constraints are also placed on models predicting doubly charged Higgs bosons and excited leptons. For doubly charged Higgs bosons decaying to $e\tau$ or $\mu\tau$, lower limits on the mass are set at 400 GeV at 95% confidence level. For excited leptons, constraints are provided as functions of both the mass of the excited state and the compositeness scale $\Lambda$, with the strongest mass constraints arising in regions where the mass equals $\Lambda$. In such scenarios, lower mass limits are set at 2.0 TeV for excited electrons and muons, 1.8 TeV for excited taus, and 1.6 TeV for every excited-neutrino flavour. UPDATE (18 MAY 2015): Updated fiducial lepton efficiencies.

  • Table 1

    Data from Table 4

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    Expected and observed event yields for the most inclusive signal regions.

  • Table 2

    Data from Table 5

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    Expected and observed limits on $\sigma_{95}^{\mathrm{vis}}$ for inclusive signal regions, along with confidence intervals of one and two standard deviations...

  • Table 3

    Data from Table 6

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    The fiducial efficiency for electrons, muons, and taus in different $p_{\mathrm{T}}$ ranges ($\epsilon_{\mathrm{fid}}(p_{\mathrm{T}})$). For electrons and muons from tau decays,...

  • Table 4

    Data from Table 7

    10.17182/hepdata.66248.v1/t4

    The fiducial efficiency for electrons and taus in different $\eta$ ranges ($\epsilon_{\mathrm{fid}}(\eta)$). For electrons from tau decays, the $\eta$ is...

  • Table 5

    Data from Table 10

    10.17182/hepdata.66248.v1/t5

    Expected and observed event yields for the $H_{\mathrm{T}}^{\mathrm{leptons}}$ signal regions.

  • Table 6

    Data from Table 11

    10.17182/hepdata.66248.v1/t6

    Expected and observed event yields for the minimum $p_{\mathrm{T}}^{\ell}$ signal regions.

  • Table 7

    Data from Table 12

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    Expected and observed event yields for the $b$-tag signal regions.

  • Table 8

    Data from Table 13

    10.17182/hepdata.66248.v1/t8

    Expected and observed event yields for the inclusive $m_{\mathrm{eff}}$ signal regions.

  • Table 9

    Data from Table 14

    10.17182/hepdata.66248.v1/t9

    Expected and observed event yields for the high-$E_{\mathrm{T}}^{\mathrm{miss}}$, $m_{\mathrm{eff}}$ signal regions.

  • Table 10

    Data from Table 15

    10.17182/hepdata.66248.v1/t10

    Expected and observed event yields for the high-$m_{\mathrm{T}}^{W}$, $m_{\mathrm{eff}}$ signal regions.

  • Table 11

    Data from Table 16

    10.17182/hepdata.66248.v1/t11

    Expected and observed event yields for the high-$H_{\mathrm{T}}^{\mathrm{jets}}$, $E_{\mathrm{T}}^{\mathrm{miss}}$ signal regions.

  • Table 12

    Data from Table 17

    10.17182/hepdata.66248.v1/t12

    Expected and observed event yields for the low-$H_{\mathrm{T}}^{\mathrm{jets}}$, $E_{\mathrm{T}}^{\mathrm{miss}}$ signal regions.

  • Table 13

    Data from Table 18

    10.17182/hepdata.66248.v1/t13

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $H_{\mathrm{T}}^{\mathrm{leptons}}$.

  • Table 14

    Data from Table 19

    10.17182/hepdata.66248.v1/t14

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $p_{\mathrm{T}}^{\ell\mathrm{,min}}$.

  • Table 15

    Data from Table 20

    10.17182/hepdata.66248.v1/t15

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on the...

  • Table 16

    Data from Table 21

    10.17182/hepdata.66248.v1/t16

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $m_{\mathrm{eff}}$.

  • Table 17

    Data from Table 22

    10.17182/hepdata.66248.v1/t17

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $m_{\mathrm{eff}}$...

  • Table 18

    Data from Table 23

    10.17182/hepdata.66248.v1/t18

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $m_{\mathrm{eff}}$...

  • Table 19

    Data from Table 24

    10.17182/hepdata.66248.v1/t19

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $E_{\mathrm{T}}^{\mathrm{miss}}$....

  • Table 20

    Data from Table 25

    10.17182/hepdata.66248.v1/t20

    Expected and observed limits, and corresponding $p$-values and significances (in standard deviations), for signal regions based on cuts on $E_{\mathrm{T}}^{\mathrm{miss}}$....

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