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Search for direct top squark pair production in events with a Higgs or $Z$ boson, and missing transverse momentum in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector

The ATLAS collaboration
No Journal Information, 2017

Abstract (data abstract)
A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a $Z$ boson or a pair of jets compatible with a Standard Model (SM) Higgs boson ($h$) is presented. Requirements on additional leptons, jets, jets identified as originating from b-quarks, and missing transverse momentum are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at sqrt{s} = 13 TeV collected with the ATLAS detector at the LHC in 2015-2016, corresponding to an integrated luminosity of 36.1 fb$^{−1}$. No excess is observed in the data with respect to the expected SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks ($\tilde{t}_1$) with long decay chains involving $Z$ or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs ($\tilde{t}_2$) decaying via $\tilde{t}_2 \rightarrow Z \tilde{t}_1$ or $\tilde{t}_2 \rightarrow h \tilde{t}_1$. The results exclude at 95% confidence level $\tilde{t}_2$ and $\tilde{t}_1$ masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.

  • Figure 2a

    Tabulated data from the publication's Figure 2a

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    Jet multiplicity distributions in control regions CR$^{3\ell 1b}_{t\bar{t}Z}$, after normalising the $t\bar{t}Z$ and multi-boson background processes via the simultaneous fit...

  • Figure 2b

    Tabulated data from the publication's Figure 2b

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    Jet multiplicity distributions in control region CR$^{3\ell 1b}_{VV}$, after normalising the $t\bar{t}Z$ and multi-boson background processes via the simultaneous fit...

  • Figure 3a

    Tabulated data from the publication's Figure 3a

    10.17182/hepdata.77997.v2/t3

    Jet multiplicity distributions in control regions CR$^{1\ell 4b}_{t\bar{t},A}$, after normalising the $t\bar{t}$ background process via the simultaneous fit described in...

  • Figure 3b

    Tabulated data from the publication's Figure 3b

    10.17182/hepdata.77997.v2/t4

    Jet multiplicity distributions in control regions CR$^{1\ell 4b}_{t\bar{t},B}$, after normalising the $t\bar{t}$ background process via the simultaneous fit described in...

  • Figure 3c

    Tabulated data from the publication's Figure 3c

    10.17182/hepdata.77997.v2/t5

    Jet multiplicity distributions in control regions CR$^{1\ell 4b}_{t\bar{t},C}$, after normalising the $t\bar{t}$ background process via the simultaneous fit described in...

  • Figure 4a

    Tabulated data from the publication's Figure 4a

    10.17182/hepdata.77997.v2/t6

    Distribution of $E^{T}_\text{miss}$ for events passing all the signal candidate selection requirements, except that on $E^{T}_\text{miss}$, for SR$^{3\ell 1b}_A$ after...

  • Figure 4c

    Tabulated data from the publication's Figure 4c

    10.17182/hepdata.77997.v2/t7

    Distribution of $E^{T}_\text{miss}$ for events passing all the signal candidate selection requirements, except that on $E^{T}_\text{miss}$, for SR$^{3\ell 1b}_B$ after...

  • Figure 4e

    Tabulated data from the publication's Figure 4e

    10.17182/hepdata.77997.v2/t8

    Distribution of $E^{T}_\text{miss}$ for events passing all the signal candidate selection requirements, except that on $E^{T}_\text{miss}$, for SR$^{3\ell 1b}_C$ after...

  • Figure 4b

    Tabulated data from the publication's Figure 4b

    10.17182/hepdata.77997.v2/t9

    Distribution of $E^{T}_\text{miss}$ for events passing all the signal candidate selection requirements, except that on $E^{T}_\text{miss}$, for SR$^{1\ell 4b}_A$ after...

  • Figure 4d

    Tabulated data from the publication's Figure 4d

    10.17182/hepdata.77997.v2/t10

    Distribution of $E^{T}_\text{miss}$ for events passing all the signal candidate selection requirements, except that on $E^{T}_\text{miss}$, for SR$^{1\ell 4b}_B$ after...

  • Figure 4f

    Tabulated data from the publication's Figure 4f

    10.17182/hepdata.77997.v2/t11

    Distribution of $E^{T}_\text{miss}$ for events passing all the signal candidate selection requirements, except that on $E^{T}_\text{miss}$, for SR$^{1\ell 4b}_C$ after...

  • Figure 5 Expected

    Tabulated data from the publication's Figure 5 expected limits

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    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • Figure 5 Observed

    Tabulated data from the publication's Figure 5 observed limits

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    Observed exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • Figure 6a Observed

    Tabulated data from the publication's Figure 6a observed limits

    10.17182/hepdata.77997.v2/t14

    Observed exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • Figure 6a Expected

    Tabulated data from the publication's Figure 6a expected limits

    10.17182/hepdata.77997.v2/t15

    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • Figure 6b Observed

    Tabulated data from the publication's Figure 6b observed limits

    10.17182/hepdata.77997.v2/t16

    Observed exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • Figure 6b Expected

    Tabulated data from the publication's Figure 6b expected limits

    10.17182/hepdata.77997.v2/t17

    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 3l1b Obs limit MSTOP2 = 600 GeV MN01 = 250 GeV

    Tabulated data from the publication's Figure 7 left observed limits

    10.17182/hepdata.77997.v2/t18

    Observed exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 3l1b Exp limit MSTOP2 = 600 GeV MN01 = 250 GeV

    Tabulated data from the publication's Figure 7 left expected limits

    10.17182/hepdata.77997.v2/t19

    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 1l4b Exp limit MSTOP2 = 600 GeV MN01 = 250 GeV

    Tabulated data from the publication's Figure 7 left expected limits

    10.17182/hepdata.77997.v2/t20

    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 3l1b Obs limit MSTOP2 = 650 GeV MN01 = 200 GeV

    Tabulated data from the publication's Figure 7 right observed limits

    10.17182/hepdata.77997.v2/t21

    Observed exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 3l1b Exp limit MSTOP2 = 650 GeV MN01 = 200 GeV

    Tabulated data from the publication's Figure 7 right expected limits

    10.17182/hepdata.77997.v2/t22

    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 1l4b Obs limit MSTOP2 = 650 GeV MN01 = 200 GeV

    Tabulated data from the publication's Figure 7 right observed limits

    10.17182/hepdata.77997.v2/t23

    Observed exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • 1l4b Exp limit MSTOP2 = 650 GeV MN01 = 200 GeV

    Tabulated data from the publication's Figure 7 right expected limits

    10.17182/hepdata.77997.v2/t24

    Expected exclusion limits at 95% CL from the analysis of $36.1 \; \text{fb}^{-1}$ of 13 TeV $pp$ collision data as...

  • Table 7

    Tabulated data from the publication's Table 7

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    Background fit results for the control and validation regions in the 1$\ell$4$b$ selection. The nominal predictions from MC simulation are...

  • Table 8

    Tabulated data from the publication's Table 8

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    Summary of the main systematic uncertainties and their impact (in %) on the total SM background prediction in each of...

  • Table 9 Up

    Tabulated data from the publication's Table 9 Up

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    Observed and expected numbers of events the three 3$\ell$1$b$ Signal regions. The nominal predictions from MC simulation are given for...

  • Table 9 Down

    Tabulated data from the publication's Table 9 Down

    10.17182/hepdata.77997.v2/t28

    Observed and expected numbers of events in the three 1$\ell$4$b$ signal regions. The nominal predictions from MC simulation are given...

  • Aux : Figure 1a

    Tabulated data from the publication's auxiliary material Figure 1a

    10.17182/hepdata.77997.v2/t29

    Illustration of the best expected signal region per signal grid point for the $\tilde{t}_2 \rightarrow h\tilde{t}_1$ models with $\tilde{t}_1\to t\tilde{\chi}^0_1$....

  • Aux : Figure 1b

    Tabulated data from the publication's auxiliary material Figure 1b

    10.17182/hepdata.77997.v2/t30

    Illustration of the best expected signal region per signal grid point for the $\tilde{t}_2 \rightarrow Z\tilde{t}_1$ models with $\tilde{t}_1\to t\tilde{\chi}^0_1$....

  • Aux : Figure 2a

    Tabulated data from the publication's auxiliary material Figure 2a

    10.17182/hepdata.77997.v2/t31

    Jet multiplicity distributions in VR$^{1\ell 4b}_C$ for an integrated luminosity of 36.1 fb$^{-1}$. The contributions from all SM backgrounds are...

  • Aux : Figure 2b

    Tabulated data from the publication's auxiliary material Figure 2b

    10.17182/hepdata.77997.v2/t32

    Jet multiplicity distributions in VR$^{1\ell 4b}_B$ for an integrated luminosity of 36.1 fb$^{-1}$. The contributions from all SM backgrounds are...

  • Aux : Figure 2c

    Tabulated data from the publication's auxiliary material Figure 2c

    10.17182/hepdata.77997.v2/t33

    Jet multiplicity distributions in VR$^{1\ell 4b}_A$ for an integrated luminosity of 36.1 fb$^{-1}$. The contributions from all SM backgrounds are...

  • Aux : Figure 3a

    Tabulated data from the publication's auxiliary material Figure 3a

    10.17182/hepdata.77997.v2/t34

    E$^{T}_\text{miss}$ distributions in VR$^{1\ell 4b}_C$ for an integrated luminosity of 36.1 fb$^{-1}$. The contributions from all SM backgrounds are shown...

  • Aux : Figure 3b

    Tabulated data from the publication's auxiliary material Figure 3b

    10.17182/hepdata.77997.v2/t35

    E$^{T}_\text{miss}$ distributions in VR$^{1\ell 4b}_B$ for an integrated luminosity of 36.1 fb$^{-1}$. The contributions from all SM backgrounds are shown...

  • Aux : Figure 3c

    Tabulated data from the publication's auxiliary material Figure 3c

    10.17182/hepdata.77997.v2/t36

    $E^{T}_\text{miss}$ distributions in VR$^{1\ell 4b}_A$ for an integrated luminosity of 36.1 fb$^{-1}$. The contributions from all SM backgrounds are shown...

  • Aux : Figure 4a

    Tabulated data from the publication's auxiliary material Figure 4a

    10.17182/hepdata.77997.v2/t37

    Jet multiplicity for events with at least 3 jets, one $b$-tagged jets for an integrated luminosity of 36.1 fb$^{-1}$. The...

  • Aux : Figure 4b

    Tabulated data from the publication's auxiliary material Figure 4b

    10.17182/hepdata.77997.v2/t38

    $E^{T}_\text{miss}$ for events with at least 3 jets, one $b$-tagged jets for an integrated luminosity of 36.1 fb$^{-1}$. The contributions...

  • Aux : Figure 4c

    Tabulated data from the publication's auxiliary material Figure 4c

    10.17182/hepdata.77997.v2/t39

    $p_{\rm T}^{\ell\ell}$ for events with at least 3 jets, one $b$-tagged jets for an integrated luminosity of 36.1 fb$^{-1}$. The...

  • Aux : Figure 5

    Tabulated data from the publication's auxiliary material Figure 5

    10.17182/hepdata.77997.v2/t40

    Distribution of $m_{bb}$ for events passing all the signal selection requirements, except that on $m_{bb}$, for SR$^{1\ell 4b}_A$ after the...

  • Aux : Figure 6a

    Tabulated data from the publication's auxiliary material Figure 6

    10.17182/hepdata.77997.v2/t41

    Upper limits on cross-sections (in fb) at 95% CL for $\tilde{t}_1$ pair production with $\tilde{t}_1 \to t \tilde{\chi}^0_2$ and $\tilde{\chi}^0_2...

  • Aux : Figure 6b

    Tabulated data from the publication's auxiliary material Figure 6b

    10.17182/hepdata.77997.v2/t42

    Upper limits on cross-sections (in fb) at 95% CL for $\tilde{t}_2$ pair production with $\tilde{t}_2 \to \tilde{t}_1 h$ with $\tilde{t}_1...

  • Aux : Figure 6c

    Tabulated data from the publication's auxiliary material Figure 6c

    10.17182/hepdata.77997.v2/t43

    Upper limits on cross-sections (in fb) at 95% CL for $\tilde{t}_2$ pair production with $\tilde{t}_2 \to \tilde{t}_1 Z$ with $\tilde{t}_1...

  • Aux : Figure 7a

    Tabulated data from the publication's auxiliary material Figure 7a

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    SR$^{3\ell 1b}_A$ acceptance for each signal model.

  • Aux : Figure 7b

    Tabulated data from the publication's auxiliary material Figure 7b

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    SR$^{3\ell 1b}_B$ acceptance for each signal model.

  • Aux : Figure 7c

    Tabulated data from the publication's auxiliary material Figure 7c

    10.17182/hepdata.77997.v2/t46

    SR$^{3\ell 1b}_C$ acceptance for each signal model.

  • Aux : Figure 8a

    Tabulated data from the publication's auxiliary material Figure 8a

    10.17182/hepdata.77997.v2/t47

    SR$^{1\ell 4b}_A$ acceptance for each signal model

  • Aux : Figure 8b

    Tabulated data from the publication's auxiliary material Figure 8b

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    SR$^{1\ell 4b}_B$ acceptance for each signal model

  • Aux : Figure 8c

    Tabulated data from the publication's auxiliary material Figure 8c

    10.17182/hepdata.77997.v2/t49

    SR$^{1\ell 4b}_C$ acceptance for each signal model

  • Aux : Figure 9a

    Tabulated data from the publication's auxiliary material Figure 9a

    10.17182/hepdata.77997.v2/t50

    SR$^{3\ell 1b}_A$ efficiency for each signal model

  • Aux : Figure 9b

    Tabulated data from the publication's auxiliary material Figure 9b

    10.17182/hepdata.77997.v2/t51

    SR$^{3\ell 1b}_B$ efficiency for each signal model

  • Aux : Figure 9c

    Tabulated data from the publication's auxiliary material Figure 9c

    10.17182/hepdata.77997.v2/t52

    SR$^{3\ell 1b}_C$ efficiency for each signal model

  • Aux : Figure 10a

    Tabulated data from the publication's auxiliary material Figure 10a

    10.17182/hepdata.77997.v2/t53

    SR$^{1\ell 4b}_A$ efficiency for each signal model

  • Aux : Figure 10b

    Tabulated data from the publication's auxiliary material Figure 10b

    10.17182/hepdata.77997.v2/t54

    SR$^{1\ell 4b}_B$ efficiency for each signal model

  • Aux : Figure 10c

    Tabulated data from the publication's auxiliary material Figure 10c

    10.17182/hepdata.77997.v2/t55

    SR$^{1\ell 4b}_C$ efficiency for each signal model

  • Aux : Table 1

    Tabulated data from the publication's auxiliary material Table 1

    10.17182/hepdata.77997.v2/t56

    Number of signal events selected at different stages for some scenarios in the $\tilde{t}_2 \rightarrow h\tilde{t}_1$ with $\tilde{t}_1\to t\tilde{\chi}^0_1$ model.

  • Aux : Table 2

    Tabulated data from the publication's auxiliary material Table 2

    10.17182/hepdata.77997.v2/t57

    Number of signal events selected at different stages for some scenarios in the $\tilde{t}_2 \rightarrow Z\tilde{t}_1$ with $\tilde{t}_1\to t\tilde{\chi}^0_1$ model.

Version 2 modifications: Images for figures 3a and 3c had been swapped in the initial revision, this is now corrected.

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