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Search for metastable heavy charged particles with large ionisation energy loss in pp collisions at $\sqrt{s} = 8$  TeV using the ATLAS experiment

The collaboration
Eur.Phys.J. C75 (2015) 407, 2015

Abstract (data abstract)
Many extensions of the Standard Model predict the existence of charged heavy long-lived particles, such as $R$-hadrons or charginos. These particles, if produced at the Large Hadron Collider, should be moving non-relativistically and are therefore identifiable through the measurement of an anomalously large specific energy loss in the ATLAS pixel detector. Measuring heavy long-lived particles through their track parameters in the vicinity of the interaction vertex provides sensitivity to metastable particles with lifetimes from 0.6 ns to 30 ns. A search for such particles with the ATLAS detector at the Large Hadron Collider is presented, based on a data sample corresponding to an integrated luminosity of 18.4 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 8 TeV. No significant deviation from the Standard Model background expectation is observed, and lifetime-dependent upper limits on $R$-hadrons and chargino production are set. Gluino $R$-hadrons with 10 ns lifetime and masses up to 1185 GeV are excluded at 95$\%$ confidence level, and so are charginos with 15 ns lifetime and masses up to 482 GeV.

• #### Table 1

Data from Figure 1

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Ratio of the reconstructed mass, computed as the most probable value of a fit to a Landau distribution convolved with...

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Data from Figure 2

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Efficiency for the calorimetric MET>80 GeV trigger as a function of the stable R-hadron mass.

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Data from Figure 2

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Efficiency for the calorimetric MET>80 GeV trigger as a function of the metastable R-hadron mass. The R-hadron decays to g/qq...

• #### Table 4

Data from Figure 2

10.17182/hepdata.68640.v1/t4

Efficiency for the calorimetric MET>80 GeV trigger as a function of the metastable R-hadron mass. The R-hadron decays to g/qq...

• #### Table 5

Data from Figure 2

10.17182/hepdata.68640.v1/t5

Efficiency for the calorimetric MET>80 GeV trigger as a function of the metastable R-hadron mass. The R-hadron decays to g/qq...

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Data from Figure 2

10.17182/hepdata.68640.v1/t6

Efficiency for the calorimetric MET>80 GeV trigger as a function of the stable chargino mass.

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Data from Figure 3

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Total selection efficiency as a function of the stable R-hadron mass.

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Data from Figure 3

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Total selection efficiency as a function of the metastable R-hadron mass. The R-hadron decays to g/qq plus neutralino of mass...

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Data from Figure 3

10.17182/hepdata.68640.v1/t9

Total selection efficiency as a function of the metastable R-hadron mass. The R-hadron decays to g/qq plus neutralino of mass...

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Data from Figure 3

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Total selection efficiency as a function of the metastable R-hadron mass. The R-hadron decays to g/qq plus neutralino of mass...

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Data from Figure 3

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Total selection efficiency as a function of the stable chargino mass.

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Data from Figure 4

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Ionisation distribution of all the CR2 tracks, and those not matched to a reconstructed muon. The two distributions are normalised...

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Data from Figure 5a

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Distribution of the mass of selected candidates, derived from the specific ionisation loss, for an example of gluino R-hadron signal,...

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Data from Figure 5a

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Distribution of the mass of selected candidates, derived from the specific ionisation loss, for one example of chargino signal, for...

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Data from Figure 5a

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Distribution of the mass of selected candidates, derived from the specific ionisation loss, for background and data, for searches for...

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Data from Figure 5b

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Distribution of the mass of selected candidates, derived from the specific ionisation loss, for an example of gluino R-hadron signal,...

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Data from Figure 5b

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Distribution of the mass of selected candidates, derived from the specific ionisation loss, for an example of chargino signal, for...

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Data from Figure 5b

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Distribution of the mass of selected candidates, derived from the specific ionisation loss, for background and data. The expected background...

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Data from Figure 6a

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Theoretical values for the cross section of gluino pairs production with their uncertainty.

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Data from Figure 6a

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Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau...

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Data from Figure 6a

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

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Data from Figure 6b

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Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau...

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Data from Figure 6b

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

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Data from Figure 7a

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

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Data from Figure 7a

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

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Data from Figure 7a

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

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Data from Figure 7a

10.17182/hepdata.68640.v1/t27

The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

• #### Table 28

Data from Figure 7a

10.17182/hepdata.68640.v1/t28

The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

• #### Table 29

Data from Figure 7a

10.17182/hepdata.68640.v1/t29

The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

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Data from Figure 7b

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

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Data from Figure 7b

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

• #### Table 32

Data from Figure 7b

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

• #### Table 33

Data from Figure 7b

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

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Data from Figure 7b

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

• #### Table 35

Data from Figure 7b

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into g/qq plus a...

• #### Table 36

Data from Figure 8a

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Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau...

• #### Table 37

Data from Figure 8a

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

• #### Table 38

Data from Figure 8b

10.17182/hepdata.68640.v1/t38

Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau...

• #### Table 39

Data from Figure 8b

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

• #### Table 40

Data from Figure 9a

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 41

Data from Figure 9a

10.17182/hepdata.68640.v1/t41

The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 42

Data from Figure 9a

10.17182/hepdata.68640.v1/t42

The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 43

Data from Figure 9a

10.17182/hepdata.68640.v1/t43

The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 44

Data from Figure 9a

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 45

Data from Figure 9a

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 46

Data from Figure 9b

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

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Data from Figure 9b

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

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Data from Figure 9b

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The expected excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 49

Data from Figure 9b

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 50

Data from Figure 9b

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 51

Data from Figure 9b

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The observed excluded range of lifetimes as a function of gluino mass for gluino R-hadrons decaying into tt plus a...

• #### Table 52

Data from Figure 10

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Theoretical values for the production cross section of charginos or chargino/neutralino pairs, with their uncertainty.

• #### Table 53

Data from Figure 10

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Expected upper limits on the production cross section as a function of mass for metastable charginos, with lifetime tau =1.0...

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Data from Figure 10

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable charginos, with lifetime...

• #### Table 55

Data from Figure 11

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The expected excluded range of lifetimes as a function of chargino mass for charginos decaying into neutralino plus pion, with...

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Data from Figure 11

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The expected excluded range of lifetimes as a function of chargino mass for charginos decaying into neutralino plus pion, with...

• #### Table 57

Data from Figure 11

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The expected excluded range of lifetimes as a function of chargino mass for charginos decaying into neutralino plus pion, with...

• #### Table 58

Data from Figure 11

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The observed excluded range of lifetimes as a function of chargino mass for charginos decaying into neutralino plus pion, with...

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Data from Figure 11

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The observed excluded range of lifetimes as a function of chargino mass for charginos decaying into neutralino plus pion, with...

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Data from Figure 11

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The observed excluded range of lifetimes as a function of gluino mass for chargino mass for charginos decaying into neutralino...

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Data from Auxiliary Figure 12

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dEdx ionization for data, 1 TeV gluino R-hadrons stable and decaying in 100 GeV neutralinos with a 10 ns lifetime...

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Data from Auxiliary Figure 13

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Expected upper limits on the production cross section as a function of mass for stable gluino R-hadrons, in case of...

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Data from Auxiliary Figure 13

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Observed 95 PCT upper limits on the production cross section as a function of mass for stable gluino R-hadrons.

• #### Table 64

Data from Auxiliary Figure 14

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Theoretical values for the cross section of squark pairs production with their uncertainty.

• #### Table 65

Data from Auxiliary Figure 14

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Expected upper limits on the production cross section as a function of mass for stable sbottom R-hadrons, in case of...

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Data from Auxiliary Figure 14

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Observed 95 PCT upper limits on the production cross section as a function of mass for stable sbottom $R$-hadrons. Cross...

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Data from Auxiliary Figure 15

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Expected upper limits on the production cross section as a function of mass for stop R-hadrons, in case of background...

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Data from Auxiliary Figure 15

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Observed 95 PCT upper limits on the production cross section as a function of mass for stop R-hadrons.

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Data from Auxiliary Figure 16

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Expected upper limits on the production cross section as a function of mass for stable charginos, in case of background...

• #### Table 70

Data from Auxiliary Figure 16

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Observed 95 PCT upper limits on the production cross section as a function of mass for stable charginos.

• #### Table 71

Data from Auxiliary Figure 17a

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Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau=1.0...

• #### Table 72

Data from Auxiliary Figure 17a

10.17182/hepdata.68640.v1/t72

Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

• #### Table 73

Data from Auxiliary Figure 17b

10.17182/hepdata.68640.v1/t73

Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau=1.0...

• #### Table 74

Data from Auxiliary Figure 17b

10.17182/hepdata.68640.v1/t74

Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

• #### Table 75

Data from Auxiliary Figure 18a

10.17182/hepdata.68640.v1/t75

Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau=1.0...

• #### Table 76

Data from Auxiliary Figure 18a

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

• #### Table 77

Data from Auxiliary Figure 18b

10.17182/hepdata.68640.v1/t77

Expected upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with lifetime tau=1.0...

• #### Table 78

Data from Auxiliary Figure 18b

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Observed 95 PCT upper limits on the production cross section as a function of mass for metastable gluino R-hadrons, with...

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Data from Auxiliary Figure 19

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Expected upper limits on the production cross section as a function of mass for metastable charginos, with lifetime tau =15...

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Data from Auxiliary Figure 19

10.17182/hepdata.68640.v1/t80

Observed 95 PCT upper limits on the production cross section as a function of mass for metastable charginos, with lifetime...