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Search for Displaced Leptons in $\sqrt{s} = 13$ TeV $pp$ Collisions with the ATLAS Detector

The collaboration
Phys.Rev.Lett. 127 (2021) 051802, 2021.

Abstract
A search for charged leptons with large impact parameters using 139 fb$^{-1}$ of $\sqrt{s} = 13$ TeV $pp$ collision data from the ATLAS detector at the LHC is presented, addressing a long-standing gap in coverage of possible new physics signatures. Results are consistent with the background prediction. This search provides unique sensitivity to long-lived scalar supersymmetric lepton-partners (sleptons). For lifetimes of 0.1 ns, selectron, smuon and stau masses up to 720 GeV, 680 GeV, and 340 GeV are respectively excluded at 95% confidence level, drastically improving on the previous best limits from LEP.

• #### Cutflow SR-ee

Table aux12

10.17182/hepdata.98796.v2/t1

Cutflow for SR-$ee$ for 5 representative signal points. For the following $\tilde{e}$ mass and lifetime points, the number of Monte...

• #### Cutflow SR-em

Table aux14

10.17182/hepdata.98796.v2/t2

Cutflow for SR-$e\mu$ for 2 representative signal points. For the $\tilde{\tau}$ mass and lifetime points, the number of Monte Carlo...

• #### Cutflow SR-mm

Table aux13

10.17182/hepdata.98796.v2/t3

Cutflow for SR-$\mu\mu$ for 5 representative signal points. For the following $\tilde{\mu}$ mass and lifetime points, the number of Monte...

• #### co-NLSP upper limit on cross section

Figure aux10a

10.17182/hepdata.98796.v2/t4

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, where all slepton flavors are mass degenerate (co-NLSP).

• #### selectron upper limit on cross section

Figure aux10c

10.17182/hepdata.98796.v2/t5

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the selectron signal model. Selectron ($\tilde{e}_{L, R}$) refers to the scalar...

• #### LH selectron upper limit on cross section

Figure aux11a

10.17182/hepdata.98796.v2/t6

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the superpartners of the left-handed electrons, $\tilde{e}_L$.

• #### RH selectron upper limit on cross section

Figure aux11c

10.17182/hepdata.98796.v2/t7

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the superpartners of the right-handed electrons, $\tilde{e}_R$.

• #### smuon upper limit on cross section

Figure aux10d

10.17182/hepdata.98796.v2/t8

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the smuon signal model. Smuon ($\tilde{\mu}_{L, R}$) refers to the scalar...

• #### LH smuon upper limit on cross section

Figure aux11b

10.17182/hepdata.98796.v2/t9

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the superpartners of the left-handed muons, $\tilde{\mu}_L$.

• #### RH smuon upper limit on cross section

Figure aux11d

10.17182/hepdata.98796.v2/t10

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the superpartners of the right-handed muons, $\tilde{\mu}_R$.

• #### stau upper limit on cross section

Figure aux10b

10.17182/hepdata.98796.v2/t11

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for the stau signal model. Staus, $\tilde{\tau}_{1,2}$ are the mixed states of...

• #### LH stau upper limit on cross section

Figure aux12

10.17182/hepdata.98796.v2/t12

Upper limits on observed signal cross section, $\sigma_\text{obs}^\text{95}$, for $\tilde{\tau}_L$ production, where $\tilde{\tau}_L$ is pure-state superpartner of the left-handed $\tau$.

• #### yields

Table 1

10.17182/hepdata.98796.v2/t13

The expected and observed yields in the signal regions. Combined statistical and systematic uncertainties are presented. Estimates are truncated at...

• #### pt-d0 electron efficiency

Figure aux19a

10.17182/hepdata.98796.v2/t14

Reconstruction efficiency as a function of $|d_{0}|$ and $p_\text{T}$ for signal electrons. Monte Carlo samples with $\tilde{e}$ or $\tilde{\mu}$ with...

• #### pt-d0 muon efficiency

Figure aux19a

10.17182/hepdata.98796.v2/t15

Reconstruction efficiency as a function of $|d_{0}|$ and $p_\text{T}$ for signal muons. Monte Carlo samples with $\tilde{e}$ or $\tilde{\mu}$ with...

• #### Selectron acceptance

Figure aux13a

10.17182/hepdata.98796.v2/t16

Acceptance for $\tilde{e}$ of various masses and lifetimes in SR-$ee$. Acceptance is defined as the number of accepted events at...

• #### Smuon acceptance

Figure aux14a

10.17182/hepdata.98796.v2/t17

Acceptance for $\tilde{\mu}$ of various masses and lifetimes in SR-$\mu\mu$. Acceptance is defined as the number of accepted events at...

• #### Selectron efficiency

Figure aux13b

10.17182/hepdata.98796.v2/t18

Efficiency for $\tilde{e}$ of various masses and lifetimes in SR-$ee$. Efficiency is defined as the number of selected reconstruced events...

• #### Smuon efficiency

Figure aux14b

10.17182/hepdata.98796.v2/t19

Efficiency for $\tilde{\mu}$ of various masses and lifetimes in SR-$\mu\mu$. Efficiency is defined as the number of selected reconstruced events...

• #### pt-pt selectron acceptance

Figure aux18a

10.17182/hepdata.98796.v2/t20

Acceptance as a function of the generator-level $p_\text{T}$ of the leading and subleading lepton in SR-$ee$ from $\tilde{e}$ decays. The...

• #### pt-pt smuon acceptance

Figure aux18b

10.17182/hepdata.98796.v2/t21

Acceptance as a function of the generator-level $p_\text{T}$ of the leading and subleading lepton in SR-$\mu\mu$ from $\tilde{\mu}$ decays. The...

• #### Stau SRee acceptance

Figure aux16a

10.17182/hepdata.98796.v2/t22

Acceptance for $\tilde{\tau}$ of various masses and lifetimes in SR-$ee$. Acceptance is defined as the number of accepted events at...

• #### Stau SRem acceptance

Figure aux17a

10.17182/hepdata.98796.v2/t23

Acceptance for $\tilde{\tau}$ of various masses and lifetimes in SR-$e\mu$. Acceptance is defined as the number of accepted events at...

• #### Stau SRmm acceptance

Figure aux15a

10.17182/hepdata.98796.v2/t24

Acceptance for $\tilde{\tau}$ of various masses and lifetimes in SR-$\mu\mu$. Acceptance is defined as the number of accepted events at...

• #### Stau SRee efficiency

Figure aux16b

10.17182/hepdata.98796.v2/t25

Efficiency for $\tilde{\tau}$ of various masses and lifetimes in SR-$ee$. Efficiency is defined as the number of selected reconstruced events...

• #### Stau SRem efficiency

Figure aux17b

10.17182/hepdata.98796.v2/t26

Efficiency for $\tilde{\tau}$ of various masses and lifetimes in SR-$e\mu$. Efficiency is defined as the number of selected reconstruced events...

• #### Stau SRmm efficiency

Figure aux15b

10.17182/hepdata.98796.v2/t27

Efficiency for $\tilde{\tau}$ of various masses and lifetimes in SR-$\mu\mu$. Efficiency is defined as the number of selected reconstruced events...

• #### pt-pt stau acceptance

Figure aux18c

10.17182/hepdata.98796.v2/t28

Acceptance as a function of the generator-level $p_\text{T}$ of the leading and subleading lepton in SR-$e\mu$ from $\tilde{\tau}$ decays. The...

• #### Observed co-NSLP limits

Figure aux6

10.17182/hepdata.98796.v2/t29

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane where all slepton flavors and...

• #### Expected co-NSLP limits

Figure aux6

10.17182/hepdata.98796.v2/t30

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane where all slepton flavors and...

• #### Observed selectron limits

Figure aux4a

10.17182/hepdata.98796.v2/t31

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$ee$ targeting selectron production....

• #### Expected selectron limits

Figure aux4a

10.17182/hepdata.98796.v2/t32

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$ee$ targeting selectron production....

• #### Observed LH selectron limits

Figure aux8a

10.17182/hepdata.98796.v2/t33

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$ee$ targeting selectron production....

• #### Expected LH selectron limits

Figure aux8a

10.17182/hepdata.98796.v2/t34

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$ee$ targeting selectron production....

• #### Observed RH selectron limits

Figure aux7a

10.17182/hepdata.98796.v2/t35

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$ee$ targeting selectron production....

• #### Expected RH selectron limits

Figure aux7a

10.17182/hepdata.98796.v2/t36

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$ee$ targeting selectron production....

• #### Observed smuon limits

Figure aux4b

10.17182/hepdata.98796.v2/t37

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$\mu\mu$ targeting smuon production....

• #### Expected smuon limits

Figure aux4b

10.17182/hepdata.98796.v2/t38

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$\mu\mu$ targeting smuon production....

• #### Observed LH smuon limits

Figure aux8b

10.17182/hepdata.98796.v2/t39

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$\mu\mu$ targeting smuon production....

• #### Expected LH smuon limits

Figure aux8b

10.17182/hepdata.98796.v2/t40

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$\mu\mu$ targeting smuon production....

• #### Observed RH smuon limits

Figure aux7b

10.17182/hepdata.98796.v2/t41

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$\mu\mu$ targeting smuon production....

• #### Expected RH smuon limits

Figure aux7b

10.17182/hepdata.98796.v2/t42

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\ell})$ plane in SR-$\mu\mu$ targeting smuon production....

• #### Observed stau limits

Figure aux5

10.17182/hepdata.98796.v2/t43

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\tau})$ plane. Staus, $\tilde{\tau}_{1,2}$ are the mixed...

• #### Expected stau limits

Figure aux5

10.17182/hepdata.98796.v2/t44

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\tau})$ plane. Staus, $\tilde{\tau}_{1,2}$ are the mixed...

• #### Observed LH stau limits

Figure aux9

10.17182/hepdata.98796.v2/t45

Observed 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\tau}_L)$ plane, where $\tilde{\tau}_L$ is the pure-state...

• #### Expected LH stau limits

Figure aux9

10.17182/hepdata.98796.v2/t46

Expected 95% CL exclusion sensitivity. The limit is displayed in the lifetime vs. $m(\tilde{\tau}_L)$ plane, where $\tilde{\tau}_L$ is the pure-state...

Version 2 modifications: Updating Fake + Heavy-Flavor estimate in SR-mm, Table 1