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Search for pair-produced third-generation squarks decaying via charm quarks or in compressed supersymmetric scenarios in $pp$ collisions at $\sqrt{s}=8~$TeV with the ATLAS detector

The ATLAS collaboration
Phys.Rev. D90 (2014) 052008, 2014

Abstract (data abstract)
CERN-LHC. Results of a search for supersymmetry via direct production of third-generation squarks are reported, using $20.3$ fb$^{-1}$ of proton-proton collision data at $\sqrt{s} = 8$ TeV recorded by the ATLAS experiment at the LHC in 2012. Two different analysis strategies based on monojet-like and $c$-tagged event selections are carried out to optimize the sensitivity for direct top squark pair production in the decay channel to a charm quark and the lightest neutralino ($\tilde{t}_1 \to c + \tilde{\chi}_{1}^{0}$) across the top squark--neutralino mass parameter space. No excess above the Standard Model background expectation is observed. The results are interpreted in the context of direct pair production of top squarks and presented in terms of exclusion limits in the $(m_{\tilde{t}_1}$, $m_{\tilde{\chi}_{1}^{0}})$ parameter space. A top squark of mass up to about 240 GeV is excluded at 95$\%$ confidence level for arbitrary neutralino masses, within the kinematic boundaries. Top squark masses up to 270 GeV are excluded for a neutralino mass of 200 GeV. In a scenario where the top squark and the lightest neutralino are nearly degenerate in mass, top squark masses up to 260 GeV are excluded. The results from the monojet-like analysis are also interpreted in terms of compressed scenarios for top squark pair production in the decay channel $\tilde{t}_1 \to b + ff^{'} + \tilde{\chi}^{0}_{1}$ and sbottom pair production with $\tilde{b}_1 \to b + \tilde{\chi}^{0}_{1}$, leading to a similar exclusion for nearly mass-degenerate third-generation squarks and the lightest neutralino. The results in this paper significantly extend previous results at colliders.

  • Table 1

    Data from Figure 2a

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    Distribution of the discriminator against b-jets, log(Pcharm/Pb), for the first-leading jet. For illustration purposes, the distributions of two different SUSY...

  • Table 2

    Data from Figure 2b

    10.17182/hepdata.65457.v1/t2

    Distribution of the discriminator against b-jets, log(Pcharm/Pu), for the third-leading jet. For illustration purposes, the distributions of two different SUSY...

  • Table 3

    Data from Figure 3a

    10.17182/hepdata.65457.v1/t3

    The measured $E_T^{miss}$ distribution in the $W \rightarrow \mu \nu$ control region, for the M1 selection, compared to the background...

  • Table 4

    Data from Figure 3b

    10.17182/hepdata.65457.v1/t4

    The measured leading jet $p_T$ distribution in the $W \rightarrow \mu \nu$ control region, for the M1 selection, compared to...

  • Table 5

    Data from Figure 3c

    10.17182/hepdata.65457.v1/t5

    The measured $E_T^{miss}$ distribution in the $W \rightarrow e \nu$ control region, for the M1 selection, compared to the background...

  • Table 6

    Data from Figure 3d

    10.17182/hepdata.65457.v1/t6

    The measured leading jet $p_T$ distribution in the $W \rightarrow e \nu$ control region, for the M1 selection, compared to...

  • Table 7

    Data from Figure 3e

    10.17182/hepdata.65457.v1/t7

    The measured $E_T^{miss}$ distribution in the $Z \rightarrow \mu \mu$ control region, for the M1 selection, compared to the background...

  • Table 8

    Data from Figure 3f

    10.17182/hepdata.65457.v1/t8

    The measured leading jet $p_T$ distribution in the $Z \rightarrow \mu \mu$ control region, for the M1 selection, compared to...

  • Table 9

    Data from Figure 4a

    10.17182/hepdata.65457.v1/t9

    The measured $E_T^{miss}$ distribution in the $W\rightarrow \mu \nu$ control region, for the c-tagged selection, compared to the background predictions....

  • Table 10

    Data from Figure 4b

    10.17182/hepdata.65457.v1/t10

    The measured leading jet $p_T$ distribution in the $W\rightarrow \mu \nu$ control region, for the c-tagged selection, compared to the...

  • Table 11

    Data from Figure 4c

    10.17182/hepdata.65457.v1/t11

    The measured $E_T^{miss}$ distribution in the $W\rightarrow e \nu$ control region, for the c-tagged selection, compared to the background predictions....

  • Table 12

    Data from Figure 4d

    10.17182/hepdata.65457.v1/t12

    The measured leading jet $p_T$ distribution in the $W\rightarrow e \nu$ control region, for the c-tagged selection, compared to the...

  • Table 13

    Data from Figure 4e

    10.17182/hepdata.65457.v1/t13

    The measured $E_T^{miss}$ distribution in the $Z\rightarrow ll$ control region, for the c-tagged selection, compared to the background predictions. The...

  • Table 14

    Data from Figure 4f

    10.17182/hepdata.65457.v1/t14

    The measured leading jet $p_T$ distribution in the $Z\rightarrow ll$ control region, for the c-tagged selection, compared to the background...

  • Table 15

    Data from Figure 5a

    10.17182/hepdata.65457.v1/t15

    The measured $E_T^{miss}$ distribution in the t-(anti)-t control region, for the c-tagged selection, compared to the background predictions. The latter...

  • Table 16

    Data from Figure 5b

    10.17182/hepdata.65457.v1/t16

    The measured leading jet $p_T$ distribution in the t-(anti)-t control region, for the c-tagged selection, compared to the background predictions....

  • Table 17

    Data from Figure 6a

    10.17182/hepdata.65457.v1/t17

    Measured leading jet $p_T$ distribution for the V3 selections compared to the SM predictions.

  • Table 18

    Data from Figure 6b

    10.17182/hepdata.65457.v1/t18

    Measured $E_T^{miss}$ distribution for the V4 selections compared to the SM predictions.

  • Table 19

    Data from Figure 6c

    10.17182/hepdata.65457.v1/t19

    Measured leading jet $p_T$ distribution for the V5 selections compared to the SM predictions.

  • Table 20

    Data from Figure 6d

    10.17182/hepdata.65457.v1/t20

    Measured $E_T^{miss}$ distribution for the V5 selections compared to the SM predictions.

  • Table 21

    Data from Figure 7a

    10.17182/hepdata.65457.v1/t21

    Measured $E_T^{miss}$ distribution for the M1 selection compared to the SM predictions. For illustration purposes, the distribution of two different...

  • Table 22

    Data from Figure 7b

    10.17182/hepdata.65457.v1/t22

    Measured leading jet $p_T$ distribution for the M1 selection compared to the SM predictions. For illustration purposes, the distribution of...

  • Table 23

    Data from Figure 7c

    10.17182/hepdata.65457.v1/t23

    Measured $E_T^{miss}$ distribution for the M2 selection compared to the SM predictions. For illustration purposes, the distribution of two different...

  • Table 24

    Data from Figure 7d

    10.17182/hepdata.65457.v1/t24

    Measured leading jet $p_T$ distribution for the M2 selection compared to the SM predictions. For illustration purposes, the distribution of...

  • Table 25

    Data from Figure 7e

    10.17182/hepdata.65457.v1/t25

    Measured $E_T^{miss}$ distribution for the M3 selection compared to the SM predictions. For illustration purposes, the distribution of two different...

  • Table 26

    Data from Figure 7f

    10.17182/hepdata.65457.v1/t26

    Measured leading jet $p_T$ distribution for the M3 selection compared to the SM predictions. For illustration purposes, the distribution of...

  • Table 27

    Data from Figure 8a

    10.17182/hepdata.65457.v1/t27

    Measured $E_T^{miss}$ distribution for the C1 selection before the cut in the variable shown is applied. The data are compared...

  • Table 28

    Data from Figure 8b

    10.17182/hepdata.65457.v1/t28

    Measured leading jet $p_T$ distribution for the C1 selection before the cut in the variable shown is applied. The data...

  • Table 29

    Data from Figure 8c

    10.17182/hepdata.65457.v1/t29

    Measured leading jet $p_T$ for the C2 selection. The data are compared to the SM predictions. For illustration purposes, the...

  • Table 30

    Data from Figure 8d

    10.17182/hepdata.65457.v1/t30

    Measured jet multiplicity for the C2 selection. The data are compared to the SM predictions. For illustration purposes, the distribution...

  • Table 31

    Data from Auxiliary Figure 2

    10.17182/hepdata.65457.v1/t31

    The measured $W$ transverse mass distribution in the $W \rightarrow \mu \nu$ control region for the M1 monojet-like selection, compared...

  • Table 32

    Data from Auxiliary Figure 3

    10.17182/hepdata.65457.v1/t32

    The measured $W$ transverse mass distribution in the $W \rightarrow e \nu$ control region for the M1 monojet-like selection, compared...

  • Table 33

    Data from Auxiliary Figure 4

    10.17182/hepdata.65457.v1/t33

    The measured dimuon invariant mass distribution in the $Z \rightarrow \mu \mu$ control region for the M1 monojet-like selection, compared...

  • Table 34

    Data from Auxiliary Figure 5

    10.17182/hepdata.65457.v1/t34

    The measured $E_T^{miss}$ distribution in a multijet control sample for the monojet-like analysis. This region is defined with similar $E_T^{miss}$...

  • Table 35

    Data from Auxiliary Figure 6a

    10.17182/hepdata.65457.v1/t35

    Measured jet multiplicity in the $W \rightarrow e \nu$ control region for the c-tagged analysis, compared to background predictions. The...

  • Table 36

    Data from Auxiliary Figure 6b

    10.17182/hepdata.65457.v1/t36

    Measured jet multiplicity in the $W \rightarrow \mu \nu$ control region for the c-tagged analysis, compared to background predictions. The...

  • Table 37

    Data from Auxiliary Figure 6c

    10.17182/hepdata.65457.v1/t37

    Measured jet multiplicity in the $Z \rightarrow ll$ control region for the c-tagged analysis, compared to background predictions. The latter...

  • Table 38

    Data from Auxiliary Figure 6d

    10.17182/hepdata.65457.v1/t38

    Measured jet multiplicity in the t-(anti)-t control region for the c-tagged analysis, compared to background predictions. The latter include the...

  • Table 39

    Data from Auxiliary Figure 7

    10.17182/hepdata.65457.v1/t39

    Measured dilepton invariant mass in the $Z \rightarrow ll$ control region for the c-tagged analysis. The predictions include the global...

  • Table 40

    Data from Auxiliary Figure 8a

    10.17182/hepdata.65457.v1/t40

    Measured jet multiplicity distribution for the M1 selection compared to the SM predictions. For illustration purposes, the impact of two...

  • Table 41

    Data from Auxiliary Figure 8b

    10.17182/hepdata.65457.v1/t41

    Measured leading jet $\eta$ distribution for the M1 selection compared to the SM predictions. For illustration purposes, the impact of...

  • Table 42

    Data from Auxiliary Figure 8c

    10.17182/hepdata.65457.v1/t42

    Measured $\Delta \phi (jet, p_T^{miss})$ distribution for the M1 selection compared to the SM predictions. For illustration purposes, the impact...

  • Table 43

    Data from Auxiliary Figure 9

    10.17182/hepdata.65457.v1/t43

    Measured $E_T^{miss}$ distribution after preselection cuts compared to background predictions.

  • Table 44

    Data from Auxiliary Figure 10a

    10.17182/hepdata.65457.v1/t44

    Measured jet multiplicity distribution in the C1 c-tagged selection compared to background predictions.

  • Table 45

    Data from Auxiliary Figure 10b

    10.17182/hepdata.65457.v1/t45

    Multiplicity of jets with loose heavy-flavor tags in the C1 selection.

  • Table 46

    Data from Auxiliary Figure 10c

    10.17182/hepdata.65457.v1/t46

    Multiplicity of jets with medium heavy-flavor tags in the C1 selection.

  • Table 47

    Data from Auxiliary Figure 18, 19a, 19b, 19c, 19d, 22a, 23a, 24a

    10.17182/hepdata.65457.v1/t47

    Expected and observed CLs, number of events, acceptance and efficiency for M1 SR for $\tilde{t}_1 \rightarrow c + \tilde{\chi}^0_1$. The...

  • Table 48

    Data from Auxiliary Figure 18, 20a, 20b, 20c, 20d, 22b, 23b, 24b

    10.17182/hepdata.65457.v1/t48

    Expected and observed CLs, number of events, acceptance and efficiency for M2 SR for $\tilde{t}_1 \rightarrow c + \tilde{\chi}^0_1$. The...

  • Table 49

    Data from Auxiliary Figure 18, 21a, 21b, 21c, 21d, 22c, 23c, 24c

    10.17182/hepdata.65457.v1/t49

    Expected and observed CLs, number of events, acceptance and efficiency for M3 SR for $\tilde{t}_1 \rightarrow c + \tilde{\chi}^0_1$. The...

  • Table 50

    Data from Auxiliary Figure 18, 25a, 25b, 25c, 25d, 27a, 28a, 29a

    10.17182/hepdata.65457.v1/t50

    Expected and observed CLs, number of events, acceptance and efficiency for C1 SR for $\tilde{t}_1 \rightarrow c + \tilde{\chi}^0_1$. The...

  • Table 51

    Data from Auxiliary Figure 18, 26a, 26b, 26c, 26d, 27b, 28b, 29b

    10.17182/hepdata.65457.v1/t51

    Expected and observed CLs, number of events, acceptance and efficiency for C2 SR for $\tilde{t}_1 \rightarrow c + \tilde{\chi}^0_1$. The...

  • Table 52

    Data from Auxiliary Figure 30, 32a, 32b, 32c, 32d, 35a, 36a, 37a

    10.17182/hepdata.65457.v1/t52

    Expected and observed CLs, number of events, acceptance and efficiency for M1 SR for $\tilde{b}_1 \rightarrow b + \tilde{\chi}^0_1$. The...

  • Table 53

    Data from Auxiliary Figure 30, 33a, 33b, 33c, 33d, 35b, 36b, 37b

    10.17182/hepdata.65457.v1/t53

    Expected and observed CLs, number of events, acceptance and efficiency for M2 SR for $\tilde{b}_1 \rightarrow b + \tilde{\chi}^0_1$. The...

  • Table 54

    Data from Auxiliary Figure 30, 34a, 34b, 34c, 34d, 35c, 35c, 37c

    10.17182/hepdata.65457.v1/t54

    Expected and observed CLs, number of events, acceptance and efficiency for M3 SR for $\tilde{b}_1 \rightarrow b + \tilde{\chi}^0_1$. The...

  • Table 55

    Data from Auxiliary Figure 38, 40a, 40b, 40c, 40d, 43a, 44a, 45a

    10.17182/hepdata.65457.v1/t55

    Expected and observed CLs, number of events, acceptance and efficiency for M1 SR for $\tilde{t}_1 \rightarrow b + ff' +...

  • Table 56

    Data from Auxiliary Figure 38, 41a, 41b, 41c, 41d, 43b, 44b, 45b

    10.17182/hepdata.65457.v1/t56

    Expected and observed CLs, number of events, acceptance and efficiency for M2 SR for $\tilde{t}_1 \rightarrow b + ff' +...

  • Table 57

    Data from Auxiliary Figure 38, 42a, 42b, 42c, 42d, 43c, 44c, 45c

    10.17182/hepdata.65457.v1/t57

    Expected and observed CLs, number of events, acceptance and efficiency for M3 SR for $\tilde{t}_1 \rightarrow b + ff' +...

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