Search for neutral long-lived particles that decay into displaced jets in the ATLAS calorimeter in association with leptons or jets using $pp$ collisions at $\sqrt{s}=13$ TeV

The ATLAS collaboration
CERN-EP-2024-181, 2024.

Abstract (data abstract)
A search for neutral long-lived particles (LLPs) decaying in the ATLAS hadronic calorimeter using 140~fb$^{-1}$ of proton--proton collisions at $\sqrt{s}=13$ TeV delivered by the LHC is presented. The analysis is composed of three channels. The first targets pair-produced LLPs, where at least one LLP is produced with sufficiently low boost that its decay products can be resolved as separate jets. The second and third channels target LLPs respectively produced in association with a $W$ or $Z$ boson that decays leptonically. In each channel, different search regions target different kinematic regimes, to cover a broad range of LLP mass hypotheses and models. No excesses of events relative to the background predictions are observed. Higgs boson branching fractions to pairs of hadronically decaying neutral LLPs larger than 1% are excluded at 95% confidence level for proper decay lengths in the range of 30~cm to 4.5~m depending on the LLP mass, a factor of three improvement on previous searches in the hadronic calorimeter. The production of long-lived dark photons in association with a $Z$ boson with cross-sections above 0.1~pb is excluded for dark photon mean proper decay lengths in the range of 20~cm to 50~m, improving previous ATLAS results by an order of magnitude. Finally, long-lived photo-phobic axion-like particle models are probed for the first time by ATLAS, with production cross-sections above 0.1~pb excluded in the 0.1~mm to 10~m range.

  • Figure 8a

    Data from Figure 8a

    10.17182/hepdata.153520.v1/t1

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 8b

    Data from Figure 8b

    10.17182/hepdata.153520.v1/t2

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 8c

    Data from Figure 8c

    10.17182/hepdata.153520.v1/t3

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 9a

    Data from Figure 9a

    10.17182/hepdata.153520.v1/t4

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 9b

    Data from Figure 9b

    10.17182/hepdata.153520.v1/t5

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 10a

    Data from Figure 10a

    10.17182/hepdata.153520.v1/t6

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 10b

    Data from Figure 10b

    10.17182/hepdata.153520.v1/t7

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 10c

    Data from Figure 10c

    10.17182/hepdata.153520.v1/t8

    Observed (solid line) and expected (dashed line) upper limits at the 95% CL on the cross-section times branching fraction as...

  • Figure 11a

    Data from Figure 11a

    10.17182/hepdata.153520.v1/t9

    Summary of the observed (solid line) and expected (dashed line) upper limits at the 95% CL on CG as a...

  • Figure 11b

    Data from Figure 11b

    10.17182/hepdata.153520.v1/t10

    Summary of the observed (solid line) and expected (dashed line) upper limits at the 95% CL on CG as a...

  • Figure 12a

    Data from Figure 12a

    10.17182/hepdata.153520.v1/t11

    Regions in the ALP mass versus its coupling to gluons scaled by the ALP energy scale gagg=4CG/fa excluded at 95%...

  • Figure 12b

    Data from Figure 12b

    10.17182/hepdata.153520.v1/t12

    Regions in the ALP mass versus its coupling to gluons scaled by the ALP energy scale gagg=4CG/fa excluded at 95%...

  • Figure 8a of Auxiliary Material

    Data from Figure 8a of Auxiliary Material

    10.17182/hepdata.153520.v1/t13

    Signal efficiencies as a function of cτ for HS signals in the CalR+2J channel for samples with mediator masses (a)...

  • Figure 8b of Auxiliary Material

    Data from Figure 8b of Auxiliary Material

    10.17182/hepdata.153520.v1/t14

    Signal efficiencies as a function of cτ for HS signals in the CalR+2J channel for samples with mediator masses (a)...

  • Figure 9a of Auxiliary Material

    Data from Figure 9a of Auxiliary Material

    10.17182/hepdata.153520.v1/t15

    Signal efficiencies as a function of cτ for WALP and WHS signals in the CalR+W channel for (a) the WALP...

  • Figure 9b of Auxiliary Material

    Data from Figure 9b of Auxiliary Material

    10.17182/hepdata.153520.v1/t16

    Signal efficiencies as a function of cτ for WALP and WHS signals in the CalR+W channel for (a) the WALP...

  • Figure 9c of Auxiliary Material

    Data from Figure 9c of Auxiliary Material

    10.17182/hepdata.153520.v1/t17

    Signal efficiencies as a function of cτ for WALP and WHS signals in the CalR+W channel for (a) the WALP...

  • Figure 10a of Auxiliary Material

    Data from Figure 10a of Auxiliary Material

    10.17182/hepdata.153520.v1/t18

    Signal efficiencies as a function of cτ for ZALP, HZZd and ZHS signals in the CalR+Z channel for (a, b)...

  • Figure 10b of Auxiliary Material

    Data from Figure 10b of Auxiliary Material

    10.17182/hepdata.153520.v1/t19

    Signal efficiencies as a function of cτ for ZALP, HZZd and ZHS signals in the CalR+Z channel for (a, b)...

  • Figure 10c of Auxiliary Material

    Data from Figure 10c of Auxiliary Material

    10.17182/hepdata.153520.v1/t20

    Signal efficiencies as a function of cτ for ZALP, HZZd and ZHS signals in the CalR+Z channel for (a, b)...

  • Figure 10d of Auxiliary Material

    Data from Figure 10d of Auxiliary Material

    10.17182/hepdata.153520.v1/t21

    Signal efficiencies as a function of cτ for ZALP, HZZd and ZHS signals in the CalR+Z channel for (a, b)...

  • Figure 11a of Auxiliary Material

    Data from Figure 11a of Auxiliary Material

    10.17182/hepdata.153520.v1/t22

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11b of Auxiliary Material

    Data from Figure 11b of Auxiliary Material

    10.17182/hepdata.153520.v1/t23

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11c of Auxiliary Material

    Data from Figure 11c of Auxiliary Material

    10.17182/hepdata.153520.v1/t24

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11d of Auxiliary Material

    Data from Figure 11d of Auxiliary Material

    10.17182/hepdata.153520.v1/t25

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11e of Auxiliary Material

    Data from Figure 11e of Auxiliary Material

    10.17182/hepdata.153520.v1/t26

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11f of Auxiliary Material

    Data from Figure 11f of Auxiliary Material

    10.17182/hepdata.153520.v1/t27

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11g of Auxiliary Material

    Data from Figure 11g of Auxiliary Material

    10.17182/hepdata.153520.v1/t28

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11h of Auxiliary Material

    Data from Figure 11h of Auxiliary Material

    10.17182/hepdata.153520.v1/t29

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 11i of Auxiliary Material

    Data from Figure 11i of Auxiliary Material

    10.17182/hepdata.153520.v1/t30

    95% CL expected (dashed black line) and observed (solid line) upper limits on the cross-section times branching fraction in the...

  • Figure 12a of Auxiliary Material

    Data from Figure 12a of Auxiliary Material

    10.17182/hepdata.153520.v1/t31

    95% CL expected (dashed line) and observed (solid line) upper limits on the cross-section times branching fraction in the WHS...

  • Figure 12b of Auxiliary Material

    Data from Figure 12b of Auxiliary Material

    10.17182/hepdata.153520.v1/t32

    95% CL expected (dashed line) and observed (solid line) upper limits on the cross-section times branching fraction in the WHS...

  • Figure 12c of Auxiliary Material

    Data from Figure 12c of Auxiliary Material

    10.17182/hepdata.153520.v1/t33

    95% CL expected (dashed line) and observed (solid line) upper limits on the cross-section times branching fraction in the WHS...

  • Figure 12d of Auxiliary Material

    Data from Figure 12d of Auxiliary Material

    10.17182/hepdata.153520.v1/t34

    95% CL expected (dashed line) and observed (solid line) upper limits on the cross-section times branching fraction in the WHS...

  • Figure 12e of Auxiliary Material

    Data from Figure 12e of Auxiliary Material

    10.17182/hepdata.153520.v1/t35

    95% CL expected (dashed line) and observed (solid line) upper limits on the cross-section times branching fraction in the WHS...

  • Figure 13a of Auxiliary Material

    Data from Figure 13a of Auxiliary Material

    10.17182/hepdata.153520.v1/t36

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the low-ET WHS selection for...

  • Figure 13b of Auxiliary Material

    Data from Figure 13b of Auxiliary Material

    10.17182/hepdata.153520.v1/t37

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the low-ET WHS selection for...

  • Figure 13c of Auxiliary Material

    Data from Figure 13c of Auxiliary Material

    10.17182/hepdata.153520.v1/t38

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the low-ET WHS selection for...

  • Figure 14a of Auxiliary Material

    Data from Figure 14a of Auxiliary Material

    10.17182/hepdata.153520.v1/t39

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the CalR+Z channel for benchmark...

  • Figure 14b of Auxiliary Material

    Data from Figure 14b of Auxiliary Material

    10.17182/hepdata.153520.v1/t40

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the CalR+Z channel for benchmark...

  • Figure 14c of Auxiliary Material

    Data from Figure 14c of Auxiliary Material

    10.17182/hepdata.153520.v1/t41

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the CalR+Z channel for benchmark...

  • Figure 14d of Auxiliary Material

    Data from Figure 14d of Auxiliary Material

    10.17182/hepdata.153520.v1/t42

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the CalR+Z channel for benchmark...

  • Figure 14e of Auxiliary Material

    Data from Figure 14e of Auxiliary Material

    10.17182/hepdata.153520.v1/t43

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the CalR+Z channel for benchmark...

  • Figure 14f of Auxiliary Material

    Data from Figure 14f of Auxiliary Material

    10.17182/hepdata.153520.v1/t44

    95% CL expected (dashed line) and observed (solid line) limits on the branching fraction in the CalR+Z channel for benchmark...

Loading Data...

Ask a Question


Your question will be emailed to those involved with the submission. Please mention the relevant table.


Please log in to HEPData to send a question.