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Search for direct top squark pair production in events with a Z boson, b-jets and missing transverse momentum in sqrt(s)=8 TeV pp collisions with the ATLAS detector

The ATLAS collaboration
Eur.Phys.J. C74 (2014) 2883, 2014

Abstract (data abstract)
CERN-LHC. A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the Z boson mass, jets tagged as originating from b-quarks and missing transverse momentum. The analysis is performed with proton-proton collision data at sqrt(s) = 8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb^-1. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top squark state (t2) followed by the decay to the lighter top squark state (t1) via t2 --> Z t1, and for t1 pair production in natural gauge-mediated supersymmetry breaking scenarios where the neutralino (chi1^0) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino (G) via the chi1^0 --> Z G process.

  • Table 1

    Data from Figure 1A

    10.17182/hepdata.63210.v1/t1

    PT(ll) distribution in SR2A for stop GMSB model (data+/-stat, bkg+/-(stat+syst), signal+/-stat), m(stop1)=500 GeV, m(neutralino1)=400 GeV.

  • Table 2

    Data from Figure 1B

    10.17182/hepdata.63210.v1/t2

    njet_3l (data+/-stat, bkg+/-(stat+syst), signal+/-stat).

  • Table 3

    Data from Figure 2A

    10.17182/hepdata.63210.v1/t3

    Missing ET distribution in SR2A for stop GMSB model (data+/-stat, bkg+/-(stat+syst), signal+/-stat), m(stop1)=500 GeV, m(neutralino1)=400 GeV.

  • Table 4

    Data from Figure 2B

    10.17182/hepdata.63210.v1/t4

    Missing ET distribution in SR2B for stop GMSB model (data+/-stat, bkg+/-(stat+syst), signal+/-stat), m(stop1)=500 GeV, m(neutralino1)=400 GeV.

  • Table 5

    Data from Figure 2C

    10.17182/hepdata.63210.v1/t5

    Missing ET distribution in SR2C for stop GMSB model (data+/-stat, bkg+/-(stat+syst), signal+/-stat), m(stop1)=500 GeV, m(neutralino1)=400 GeV.

  • Table 6

    Data from Figure 3A

    10.17182/hepdata.63210.v1/t6

    met_sr3a (data+/-stat, bkg+/-(stat+syst), signal+/-stat).

  • Table 7

    Data from Figure 3B

    10.17182/hepdata.63210.v1/t7

    met_sr3b (data+/-stat, bkg+/-(stat+syst), signal+/-stat).

  • Table 8

    Data from Figure 4

    10.17182/hepdata.63210.v1/t8

    Expected exclusion limits at 95% CL for stop2 grid.

  • Table 9

    Data from Figure 4

    10.17182/hepdata.63210.v1/t9

    Expected exclusion limits +1sigma at 95% CL for stop2 grid.

  • Table 10

    Data from Figure 4

    10.17182/hepdata.63210.v1/t10

    Expected exclusion limits -1sigma at 95% CL for stop2 grid.

  • Table 11

    Data from Figure 4

    10.17182/hepdata.63210.v1/t11

    Observed exclusion limits at 95% CL for stop2 grid.

  • Table 12

    Data from Figure 4

    10.17182/hepdata.63210.v1/t12

    Observed exclusion limits +1sigma SUSY cross section uncertainty at 95% CL for stop2 grid.

  • Table 13

    Data from Figure 4

    10.17182/hepdata.63210.v1/t13

    Observed exclusion limits -1sigma SUSY cross section uncertainty at 95% CL for stop2 grid.

  • Table 14

    Data from Figure 5

    10.17182/hepdata.63210.v1/t14

    t2_350_n1_20_Observed.

  • Table 15

    Data from Figure 5

    10.17182/hepdata.63210.v1/t15

    t2_350_n1_20_Expected.

  • Table 16

    Data from Figure 5

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    t2_500_n1_20_Observed.

  • Table 17

    Data from Figure 5

    10.17182/hepdata.63210.v1/t17

    t2_500_n1_20_Expected.

  • Table 18

    Data from Figure 5

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    t2_500_n1_120_Observed.

  • Table 19

    Data from Figure 5

    10.17182/hepdata.63210.v1/t19

    t2_500_n1_120_Expected.

  • Table 20

    Data from Figure 6

    10.17182/hepdata.63210.v1/t20

    Expected exclusion limits at 95% CL for stop GMSB model.

  • Table 21

    Data from Figure 6

    10.17182/hepdata.63210.v1/t21

    Expected exclusion limits +1sigma at 95% CL for stop GMSB model.

  • Table 22

    Data from Figure 6

    10.17182/hepdata.63210.v1/t22

    Expected exclusion limits -1sigma at 95% CL for stop GMSB model.

  • Table 23

    Data from Figure 6

    10.17182/hepdata.63210.v1/t23

    Observed exclusion limits at 95% CL for stop GMSB model.

  • Table 24

    Data from Figure 6

    10.17182/hepdata.63210.v1/t24

    Observed exclusion limits +1sigma SUSY cross section uncertainty at 95% CL for stop GMSB model.

  • Table 25

    Data from Figure 6

    10.17182/hepdata.63210.v1/t25

    Observed exclusion limits -1sigma SUSY cross section uncertainty at 95% CL for stop GMSB model.

  • Table 26

    Data from Auxiliary Figure 1A

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    met_3l2j (data+/-stat, bkg+/-(stat+syst), signal+/-stat).

  • Table 27

    Data from Auxiliary Figure 1B

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    met_3l3j (data+/-stat, bkg+/-(stat+syst), signal+/-stat).

  • Table 28

    Data from Auxiliary Figure 3

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    The best expected signal region for stop2 model, where 1 and 2 mean SR3A and SR3B.

  • Table 29

    Data from Auxiliary Figure 4

    10.17182/hepdata.63210.v1/t29

    The best expected signal region for stop GMSB model, where 1 and 2 mean SR2A and SR2B.

  • Table 30

    Data from Auxiliary Figure 5A

    10.17182/hepdata.63210.v1/t30

    The best expected signal region for stop2 mass 350 GeV and neutralino1 mass 20 GeV, where 1 and 2 mean...

  • Table 31

    Data from Auxiliary Figure 5B

    10.17182/hepdata.63210.v1/t31

    The best expected signal region for stop2 mass 500 GeV and neutralino1 mass 20 GeV, where 1 and 2 mean...

  • Table 32

    Data from Auxiliary Figure 5C

    10.17182/hepdata.63210.v1/t32

    The best expected signal region for stop2 mass 500 GeV and neutralino1 mass 120 GeV, where 1 and 2 mean...

  • Table 33

    Data from Auxiliary Figure 6

    10.17182/hepdata.63210.v1/t33

    Observed upper limit on the signal cross section for stop2 grid.

  • Table 34

    Data from Auxiliary Figure 9B

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    Number of generated MC events for stop Natural GMSB model.

  • Table 35

    Data from Auxiliary Figure 9A

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    Cross section for stop Natural GMSB model.

  • Table 36

    Data from Auxiliary Figure 10A

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    xsec_stop2.

  • Table 37

    Data from Auxiliary Figure 10B

    10.17182/hepdata.63210.v1/t37

    Ntot_stop2.

  • Table 38

    Data from Auxiliary Figure 11C

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    Acceptance of stop GMSB model for SR2A.

  • Table 39

    Data from Auxiliary Figure 11D

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    Efficiency of stop GMSB model for SR2A.

  • Table 40

    Data from Auxiliary Figure 11A

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    Number of expected signal events of stop GMSB model for SR2A.

  • Table 41

    Data from Auxiliary Figure 11B

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    Total systematic uncertainty of stop GMSB model for SR2A.

  • Table 42

    Data from Auxiliary Figure 11E

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    Observed CL_s of stop GMSB model for SR2A.

  • Table 43

    Data from Auxiliary Figure 11F

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    Expected CL_s of stop GMSB model for SR2A.

  • Table 44

    Data from Auxiliary Figure 12C

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    Acceptance of stop GMSB model for SR2B.

  • Table 45

    Data from Auxiliary Figure 12D

    10.17182/hepdata.63210.v1/t45

    Efficiency of stop GMSB model for SR2B.

  • Table 46

    Data from Auxiliary Figure 12A

    10.17182/hepdata.63210.v1/t46

    Number of expected signal events of stop GMSB model for SR2B.

  • Table 47

    Data from Auxiliary Figure 12B

    10.17182/hepdata.63210.v1/t47

    Total systematic uncertainty of stop GMSB model for SR2B.

  • Table 48

    Data from Auxiliary Figure 12E

    10.17182/hepdata.63210.v1/t48

    Observed CL_s of stop GMSB model for SR2B.

  • Table 49

    Data from Auxiliary Figure 12F

    10.17182/hepdata.63210.v1/t49

    Expected CL_s of stop GMSB model for SR2B.

  • Table 50

    Data from Auxiliary Figure 13C

    10.17182/hepdata.63210.v1/t50

    Acceptance of stop GMSB model for SR2C.

  • Table 51

    Data from Auxiliary Figure 13D

    10.17182/hepdata.63210.v1/t51

    Efficiency of stop GMSB model for SR2C.

  • Table 52

    Data from Auxiliary Figure 13A

    10.17182/hepdata.63210.v1/t52

    Number of expected signal events of stop GMSB model for SR2C.

  • Table 53

    Data from Auxiliary Figure 13B

    10.17182/hepdata.63210.v1/t53

    Total systematic uncertainty of stop GMSB model for SR2C.

  • Table 54

    Data from Auxiliary Figure 13E

    10.17182/hepdata.63210.v1/t54

    Observed CL_s of stop GMSB model for SR2C.

  • Table 55

    Data from Auxiliary Figure 13F

    10.17182/hepdata.63210.v1/t55

    Expected CL_s of stop GMSB model for SR2C.

  • Table 56

    Data from Auxiliary Figure 14A

    10.17182/hepdata.63210.v1/t56

    Nexp_SR3A.

  • Table 57

    Data from Auxiliary Figure 14B

    10.17182/hepdata.63210.v1/t57

    RelUnc_SR3A.

  • Table 58

    Data from Auxiliary Figure 14C

    10.17182/hepdata.63210.v1/t58

    Acc_SR3A.

  • Table 59

    Data from Auxiliary Figure 14D

    10.17182/hepdata.63210.v1/t59

    Eff_SR3A.

  • Table 60

    Data from Auxiliary Figure 14F

    10.17182/hepdata.63210.v1/t60

    CLsExp_SR3A.

  • Table 61

    Data from Auxiliary Figure 14E

    10.17182/hepdata.63210.v1/t61

    CLs_SR3A.

  • Table 62

    Data from Auxiliary Figure 15A

    10.17182/hepdata.63210.v1/t62

    Nexp_SR3B.

  • Table 63

    Data from Auxiliary Figure 15B

    10.17182/hepdata.63210.v1/t63

    RelUnc_SR3B.

  • Table 64

    Data from Auxiliary Figure 15C

    10.17182/hepdata.63210.v1/t64

    Acc_SR3B.

  • Table 65

    Data from Auxiliary Figure 15D

    10.17182/hepdata.63210.v1/t65

    Eff_SR3B.

  • Table 66

    Data from Auxiliary Figure 15F

    10.17182/hepdata.63210.v1/t66

    CLsExp_SR3B.

  • Table 67

    Data from Auxiliary Figure 15E

    10.17182/hepdata.63210.v1/t67

    CLs_SR3B.

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