Search for long-lived particles at LHC

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1 EPJ Web of Conferences 96, 5 ( 5) DOI:.5/ epjconf/ C Owne by the authors, publishe by EDP Sciences, 5 Search for long-live particles at LHC Stefano Giagu,a Sapienza Università i Roma an INFN Roma, Roma, IT Abstract. Several scenarios beyon the Stanar Moel preict long-live particles resulting in a wie variety of etector signatures epening on the nature of the particles an the ecay lengths. Signals from long-live particles are investigate by the ATLAS an experiments exploiting ifferent signatures, ranging from abnormal energy losses, to appearing or isappearing tracks, isplace vertices, lepton-jet signatures, long time-of-flight or late calorimetric energy eposits. This contribution summarizes the most recent results of the searches performe at the Large Haron Collier (LHC) with the ATLAS an etectors uring the Run ata taking campaign. No evience of any new physics is observe so far in any analysis, an the results are use to set stringent constraint on supersymmetric or hien sector moels. Introuction A variety of propose theories beyon the Stanar Moel (BSM), such as supersymmetry (SUSY), theories with extra imensions, scenarios with a hien valley, an various others, can lea to the prouction of unusual signatures in etectors at the Large Haron Collier (LHC). These may inclue: long-live particles (LLP), meta-stable particles an collimate jets of isplace leptons or harons. Exploring these signatures is being of great interest toay since they coul give a possibility to evae the current constraints of SM extensions, tightene by the experimental evience of the absence of any signal beyon Stanar Moel in the generic searches performe at LHC. The ATLAS [] an [] collaborations explore ifferent experimental signatures an theoretical moels using ata collecte from proton-proton collisions at LHC. This contribution gives an overview of some of the results of the searches performe on the whole LHC ata taken at s = 7 an 8 TeV. The following results are iscusse here: gluinos being stable an ecaying late in out of bunch crossings in ATLAS [3], heavy stable charge particles in ATLAS an [4, 5], charginos with a significant lifetime giving rise to isappearing tracks in ATLAS [6], searches for long-live neutral particles with a lifetime such that they ecay within the ATLAS an etector, but at a significant isplacement from the primary event vertex (isplace supersymmetry) [4, 7 ], ark an hien sectors inspire long-live particles searches in ATLAS [, ], an [8, 9]. a stefano.giagu@roma.infn.it Supersymmetry inspire long-live particles searches. Stable gluinos an stoppe R-harons The Higgs boson measure at 5 GeV [3, 4] motivates heavy scalar scenarios where the squarks an sleptons are renere heavy while gauginos may still be light (at the TeV scale or below) enough to be prouce at the LHC energies. Split SUSY [5, 6] is a possibility that compromises with the current constraints. In such a scenario, gluinos ecay via internal heavy squark lines, leaing to their significantly long lifetimes an haronic boun states (so-calle R-harons). Massive R-harons coul be etecte as low-β particles leaving activities ue to large energy loss. Especially when they are prouce nearly at the prouction threshol in pp collisions at the LHC energies, they coul come to rest insie the calorimeter an ecay after a significant time, which leas to a unique signature of energetic jets elaye with respect to the collision timing. The ATLAS Stoppe R-Harons analysis search for R-harons by looking for jets in "empty" bunch crossings, BCIDs with no protons in either beam. The search for such a signature is performe by using the full 7 an 8 TeV pp collision ata, an aopting a eicate trigger that selects events containing energetic jets in empty bunch crossings of the LHC. Backgroun events mimicking the signal signature preominantly originate from cosmic rays an upstream beam-halo interactions. Backgroun from cosmic rays is effectively suppresse by vetoing events with reconstructe muon segments. Excluing events with spike-like signals in the calorimeter rejects backgroun from ranom electronic noise an also reuces the contamination from cosmic rays an beam halo. Given the leaing jet energy istribution for the caniate events, no excess above the backgroun expectation is foun an upper limit on the cross section of the pair-gluino prouc- This is an Open Access article istribute uner the terms of the Creative Commons Attribution License 4., which permits unrestricte use, istribution, an reprouction in any meium, provie the original work is properly cite. Article available at or

2 EPJ Web of Conferences tion is set as a function of the gluino mass for a given range of lifetime values, as shown in Fig.. Depening on moel parameters, limits excluing m g < GeVan m q < GeVcan be set. (a) The reconstructe mass istribution Figure. Limits on gluino mass versus its lifetime with R- haron lifetimes in the plateau acceptance region between 5 an 3 secons.. Heavy stable charge particles Heavy stable charge particles, traversing the ATLAS an etectors, are ientifie by their velocities significantly lower than the spee of light an resulting large ionization losses. The ATLAS search utilizes the β measurements base on the time-of-flight measure in the muon spectrometer an calorimeters. Resolution on β is optimize using large calibration ata sample of muons from Z ecays. The reconstructe mass is finally obtaine by averaging the two β measurements in ifferent etector elements. Backgroun tracks ominantly originate from muons with mismeasure β; the mass spectrum of these tracks are estimate using a convolution of momentum an β istributions of the signal search sample, relying on the fact that these two kinematic variables are fully uncorrelate for the backgroun tracks. The observe mass spectrum from ATLAS is shown in Figure (a) in which the caniate events are require to have two tracks with p T > 5 GeV an. <β<.95; no significant excess above the backgroun expectation is foun. In the same figure also the expecte istribution from signals from staus preicte in gauge-meiate SUSY breaking (GMSB) moels is also shown. Assuming that the stau is stable upper limits on the cross section of fb at 95% CL in the stau mass range from 5 to 5 GeV are obtaine. These results can be interprete in the context of gauge-meiate SUSY breaking [7] scenarios where a slepton is the next-to-lightest superpartner with a significantly long lifetime, as shown in Fig. (b). The experiment analysis is performe in five separate channels, to account for the wie variety of types of HSCP: (b) Limits on the prouction cross section in GMSB scenarios Figure. The reconstructe mass istribution(a) an limits on the prouction cross section as a function of stau mass in GMSB scenarios(b). the tracker+tof analysis searches for singly-charge HSCPs requiring both a track in the inner tracker an in the muon system. the tracker-only analysis searches for singly-charge HSCPs requiring only a track in the inner tracker, to account for the possibility of material interactions causing the HSCPs to become neutral in their passage through the etector. the muon-only analysis searches for singly-charge HSCPs requiring only a track in the muon system. the fractionally-charge analysis searches for HSCPs with Q < e, requiring a track in the inner tracker with ae/x smaller than that for a SM particle. the multiply-charge analysis searches for HSCPs with Q > e, requiring tracks in the inner tracker an muon system with a much higher E/x than for the singly-charge analysis. 5-p.

3 ± Dark Matter, Haron Physics an Fusion Physics In all cases, the observations agree with the expecte backgroun, so limits are set for ifferent signal moels, as shown in Figure 3. 95% CL limit on σ (pb) 95% CL limit on σ (pb) Tracker + TOF Theoretical Preiction gluino (NLO+NLL) stop (NLO+NLL) stau, ir. pro. (NLO) stau (NLO) Q = e/3 (LO) Q = e (LO) Q <e s = 8 TeV, L = 8.8 fb gluino; 5% gg gluino; % gg stop stau; ir. pro. stau Q = e/3 Q = e 5 5 Mass (GeV/c ) Theoretical Preiction Q = e/3 (LO) Q = e/3 (LO) s = 8 TeV, L = 8.8 fb Q = e/3 Q = e/3 4 6 Mass (GeV/c ) 95% CL limit on σ (pb) 95% CL limit on σ (pb) Muon - Only Theoretical Preiction gluino (NLO+NLL) stop (NLO+NLL) Q >e s = 8 TeV, L = 8.8 fb gluino; % gg gluino; 5% gg gluino; % gg stop 5 5 Mass (GeV/c ) s = 8 TeV, L = 8.8 fb Theoretical Preiction Q = e (LO) Q = e (LO) Q = 3e (LO) Q = 4e (LO) Q = 5e (LO) Q = 6e (LO) Q = 7e (LO) Q = 8e (LO) Q = e Q = e Q = 3e Q = 4e Q = 5e Q = 6e Q = 7e Q = 8e Mass (GeV/c ) Figure 3. Limits for four of the HSCP analysis channels. Top from left to right: tracker+tof, muon-only. Bottom from left to right: fractionally-charge, an multiply-charge. The ifferent lines correspon to the ifferent signal moels for which the limits are set. The obtaine result can be reinterprete in the context of ifferent signal moels [8], by constructing efficiency maps for reconstructing the long-live particles as a function of β an η in bins of p T. Figure 4 shows an example of the application of this technique use to show points in the parameter space of the phenomenological minimal supersymmetric moel (pmssm) that can be exclue by this analysis..3 Disappearing tracks The ATLAS Disappearing Tracks analysis consiers Anomaly Meiate SUSY Breaking (AMSB) [9, ] moels with almost a mass egenerate lightest chargino an neutralino. This can occur in scenarios where they are ominantly wino or higgsino, that are of interest as these retain a goo caniate for ark matter, an coul in principle accommoate the measure Higgs mass. One interesting feature of these scenarios is that the chargino has a consierable lifetime an preominantly ecays into a neutralino plus a low-momentum charge pion. The lowmomentum charge pion track is rarely reconstructe ue to its large isplacement an a small number of interactions in the tracking system, therefore, a ecaying chargino is typically recognize as a isappearing track that has few associate hits in the outer tracking volume. These signatures are ientifie in the ATLAS inner etector by searching for isolate, high p T tracks that have well measure hits in the inner silicon trackers, but have a low number of hits in the outer straw tracker. Backgroun in the signal region mostly comprises lower p T tracks that have been mis-measure, with non-ientifie muons also contributing. The results of the ATLAS search for events with isappearing-track signature is shown in Figure 5, where the p T spectrum of caniates tracks is compare to the expectation for the backgroun an for signals corresponing to various choices of the chargino mass an lifetime. In the absence of a signal, constraints are set on the parameter space of the minimal AMSB moel. In the context of the ecouple AMSB a lower limit on the lightest chargino mass of m χ ± > 7 GeV at 95% CL is set, that irectly constrains the wino ark matter mass. cτ (m) ] log [ χ 5 Preliminary - Exclue by EXO3-6 s = 8 TeV - L = 8.8 fb ± χ Mass (GeV/c ) Figure 4. Parameter points in the pmssm that can be exclue by reinterpretation of the HSCP search as escribe in the text. Figure 5. The p T spectrum of isappearing-track caniates in the isappearing-track signature analysis performe by the AT- LAS experiment. 5-p.3

4 EPJ Web of Conferences.4 Search for isplace Supersymmetry A specific search technique is use by the experiment to explore a region of parameter space not covere by previous searches. In this tecnique a SUSY moel where long-live stop quarks are pair-prouce an then unergo an R-parity violating ecay to a b quark an a lepton ( t bl) is consiere. The analysis then searches for events in which one of the leptons is an electron an the other a muon, thus substantially reucing the backgroun from SM processes. The leptons are require to be isplace, but they are not require to form a vertex, allowing the search to remain sensitive to a variety of new physics scenarios. Signal caniate events are ientifie by looking for an event with a muon an an electron of opposite charge, both of which are require to be isolate an have p T > 5 GeV. The leptons are require to have a transverse impact parameter less than cm, so that the tracking efficiency for the leptons remains high. Backgroun from QCD HF events in the signal region is obtaine using ata riven methos, while backgroun from other sources is estimate from simulation. In all search regions stuie by, the observations agree with the expecte backgroun, so limits are set on the stop quark mass as a function of lifetime as shown in Figure 6. its result is interprete in the context of a R-parity violating scenario in which non-zero value of λ ij allows the lightest neutralino to ecay into a muon an jets. Caniate events are selecte with the requirements of a high-p T muon an a isplace vertex. In orer to suppress backgroun events containing isplace vertices originating from seconary interactions, only vertices locate outsie the material of the inner etector are consiere. The vertex is finally require to have a mass (m DV ) above GeV an a charge multiplicity (N trk ) larger than 4. No event is foun in the signal region while the expecte number of backgroun events (preominantly originating from ranom combinations of tracks an haron interactions with air molecules) is. ±.. This translate in an upper limit of.4 fb is set on the visible cross section at 95% CL. The corresponing 95% CL upper limits on the prouction cross section is also set for some squark an neutralino masses as a function of the neutralino lifetime, as shown in Fig. 7. Stop cτ [cm] ± σ expecte ± σ expecte Expecte limit Observe limit 9.7 fb (8 TeV) Exclue region M [GeV] t Figure 7. Upper limit on the squark-pair prouction cross section as a function of the neutralino lifetime for ifferent combinations of squark an neutralino masses. The labels in the plot inicate the squark neutralino masses in GeV: (MH), 7 8 (ML), an 8 (HL). The branching ratio of the ecay chain from squark to neutralino to muon-plus-jets is set to %. Figure 6. Expecte an observe 95% CL cross section exclusion contours for top squark pair prouction in the plane of top squark lifetime (cτ) an top squark mass. These limits assume a branching fraction of % through the RPV vertex t bl, where the branching fraction to any lepton flavor is equal to /3. As inicate in the plot, the region to the left of the contours is exclue by this search. The ATLAS experiment search for signals from R- parity violating isplace supersymmetry by exploiting an enhance track reconstruction to efficiently ientify isplace vertices originating from heavy ecaying particles with the lifetime range from O( )too( 9 ) secons. The present search is performe using events with a multitrack isplace vertex that contains a high-p T muon, an 3 Dark an Hien sectors inspire Long-Live Particles searches Several possible extensions of the Stanar Moel preict the existence of a hien sector that is weakly couple to the visible one (e.g. refs. [ 6]). Depening on the structure of the hien sector an its coupling to the SM, some unstable hien states may be prouce at colliers an ecay back to SM particles with sizeable branching fractions. For example, in supersymmetric theories, the lightest visible super-partner may ecay into hien particles, some of which can ecay back to the visible sector (see e.g. refs. [, 6, 7]). Several other istinct, nonsupersymmetric, examples exist (see e.g. refs. [, 3 5]). If the lightest unstable hien states have masses 5-p.4

5 Dark Matter, Haron Physics an Fusion Physics in the MeV to GeV range, they woul ecay mainly to leptons an possibly light mesons. A particle from the hien sector can be prouce in certain weak interaction ecays, such as that of the Higgs boson, with the behavior of the prouce particle etermining the signature. If the particle itself couples weakly to the SM then it may travel some istance before ecaying into SM particles. This makes the particle a neutral long-live particle an can give rise to isplace vertex signatures in the etector. The particle may also prouce a shower in the hien sector. If ark photons are prouce in these showers an couple to the SM, they may ecay into highly collimate pairs of light SM particles, specifically electrons, muons or harons. Multiple ark photons may be raiate by the same hien sector particle, with the resulting overlapping ones leaing to jets with multiple pairs of particles. Decays of ark photons to heavier particle pairs, such as protons, are kinematically forbien. Highly collimate jets of leptons o not occur in the SM, an are the subject of BSM searches. The ark photon may be long-live, which can result in jets of lepton pairs originating from isplace vertices. 3. Hien Valley isplace ecays The experiment performe a search for isplace lepton sensitive to a wie class of moels that contain long-live particles ecaying to leptons. For illustration purposes a specific signal moel is escribe here: a non- Stanar Moel (SM) Higgs ecays to a long-live spinless boson X (H XX), which then ecays into a pair of leptons (either X ee or X μμ). Although in this moel the long-live particles are pair-prouce an so we woul expect to observe up to two isplace vertices per event, for maximum generality this search only requires one isplace vertex to be foun. The ata is collecte using a pair of triggers, one for each channel, requiring either two high-energy eposits in the electromagnetic calorimeter or two high-momentum tracks in the muon etector. In both cases, the tracker information is not use in the trigger, as the track reconstruction at the high-level trigger (HLT) is not necessarily efficient for isplace tracks. In the muon case, the muons are reconstructe without any primary vertex constraint, an muons from cosmic rays are vetoe by requiring that the three-imensional angle between the two muons be less than.5 raians. Long-live particle caniates are ientifie by looking for two isolate, energetic electrons (with E T > 4 GeV) or muons (with p T > 6 GeV) that form a goo vertex, an are require to be significantly isplace from the primary vertex (the significance of the transverse impact parameter /σ > ). The backgroun is estimate using a ata-riven metho, exploiting the fact that the angle Δφ between the flight irection to the seconary vertex an the ilepton momentum shoul be close to for a true long-live particle event, but ranomly istribute for backgroun. The estimate backgroun is zero events, an zero events are observe, so limits are set. Figure 8 shows some sample limits obtaine in the H XX moel for a variety of ifferent m X values an lifetimes. ) [pb] - σ(h XX)B(X μ + μ - - Observe limits m X = 5 GeV/c m X = GeV/c Expecte limits (±σ) = 5 GeV/c m H.5 fb (8 TeV) cτ [cm] Figure 8. The 95% CL upper limits on σ(h XX)B(X μμ) for Higgs boson masses of 5 GeVas a function of the X lifetime. Results are shown for several ifferent X boson masses. Shae bans show the ±σ range of variation of the expecte 95% CL limits. searche also for isplace jets preicte in a similar way as one for the isplace leptons analysis, to cover the case where the long-live neutral particle ecays haronically. In this case for the H XX moel, the X bosons has been chosen to ecay via X qq. Caniate events are selecte by searching for two isplace jets with momentum > 6 GeV. In aition, requirements are place on the number of prompt tracks an fraction of energy carrie by prompt tracks, where a prompt track here is efine as a track with a transverse impact parameter less than 5 μm. The jets are then require to form a goo-quality vertex. Finally, the tracks in the jet are hierarchically clustere an a likelihoo iscriminant is built for the jets base on the seconary vertex track multiplicity, the cluster root-mean-square (RMS), an the fraction of the seconary vertex tracks having a positive value of the impact parameter. The selection criteria are optimize separately for moels with lower ecay lengths (L xy < cm) an higher (> cm). In the final results, two events are observe passing the low L xy selection an one passing the high L xy selection, both consistent with the expecte backgroun. Limits are thus set on the signal moels; Figure 9 shows a sample of the limits for one of the stuie cases. The ATLAS experiment uses a specialist trigger to search for long-live neutral particles preicte by Hien Valley moels ecaying in jets insie the ATLAS haron calorimeter. The results are interprete in the context of an HV moel with a π v long-live particle [, 5]. The specialist trigger calle "CalRatio trigger" is tune for narrow jets with anomalous energy eposition in the haronic calorimeter (E H ) compare with the eposit in the elec- 5-p.5

6 EPJ Web of Conferences qq) [pb] (X ) B X X σ(h -, 95% CL limits: m X =5 GeV m X =35 GeV s = 8 TeV, L t = 8.5 fb Exp. limits (± σ) m H = GeV X cτ [cm] Figure 9. The 95% CL upper limits on σ(h XX)B (X qq) for Higgs boson masses of GeVas a function of the X lifetime. Results are shown for two ifferent X boson masses. Shae bans show the ±σ range of variation of the expecte 95% CL limits. tromagnetic calorimeter (E EM ), an no associate tracks in the inner tracking etector. The analysis itself then reenforces these trigger conitions by requiring two jets with log (E H /E EM ) >. an no goo associate charge tracks with p T > GeV. Figure shows the jet energy istribution ratio between the haronic calorimeter an the electromagnetic calorimeter for SM jets in ata an MC signal samples an for a possible Hien Valley signal. Using the full statistic collecte at s = 8 TeV, ATLAS exclues at 95% CL ecay lengths.37 m < cτ πv < 5. m for m πv = 5 GeV an m h = 6 GeV []. Fraction of Jets ATLAS Preliminary Multijets: Full Data Signal: ecay in HCal Signal: ecay in ID s = 8 TeV log (E /E EM ) H Figure. Jet energy istribution ratio between the haronic calorimeter an the electromagnetic calorimeter for SM jets in ata an MC signal samples an for a possible Hien Valley signal. 3. Search for isplace Dark photons ecays An extensively stuie case is one in which the SM an the hien sectors couple via the vector portal, in which a light hien photon (ark photon, γ ) mixes kinetically with the SM photon. If the hien photon is the lightest state in the hien sector, it ecays back to SM particles with branching fractions that epen on its mass [6, 8, 9]. For the case in which the γ kinetically mixes with hypercharge, one fins that ɛ, the kinetic mixing parameter, controls both the γ ecay branching fractions an lifetime. More generally, however, the branching fractions an lifetime are moel-epenent an may epen on aitional parameters. Due to their small mass, these particles are typically prouce with a large boost an, ue to their weak interactions, can have non-negligible lifetime. As a result one may expect, from ark photon ecays, collimate jetlike structures containing pairs of electrons an/or muons an/or charge pions ( lepton jets, LJs) that can be prouce far from the primary interaction vertex of the event (isplace LJs). Neutral particles which ecay far from the interaction point into collimate final states represent a challenge both for the trigger an for the reconstruction capabilities of the LHC etectors. Collimate charge particles in the final state can be ifficult to isentangle ue to the limite granularity of the etector. Moreover, in the absence of information from the inner tracking system, it is necessary to use the muon spectrometer (MS) for the reconstruction of tracks which originate from a seconary ecay far from the primary interaction vertex (IP). The high-resolution, high-granularity measurement capability of the ATLAS air-core MS is ieal for this type of search. In aition, the ATLAS inner tracking system can be use to efine isolation criteria to significantly reuce, for ecay vertices far from the interaction point, the otherwise overwhelming SM backgroun from proton proton collisions. The results of the ATLAS search [] performe on the complete ataset collecte uring the run at 8 TeV, for LJ prouction are use to set upper limits on the Higgs boson ecay branching fraction to LJs as a function of the γ mean lifetime, accoring to the FRVZ moels. The resulting exclusion limits on the σ BR, assuming the Higgs boson SM gluon fusion prouction cross section σ SM = 9. pb, are shown in figure as a function of the γ mean lifetime (expresse as cτ) for two benchmark moels in which the SM Higgs ecay in two an four ark photons. These results are also interprete in the context of the Vector portal moel as exclusion contours in the kinetic mixing parameter ɛ vs γ mass plane [3, 3] as shown in figure. Assuming Higgs ecay branching fractions into γ of 5///4% an the NNLO gluon fusion Higgs prouction cross section, the lifetime limits can be converte into kinetic mixing parameter ɛ limits. While the other limits are moel-inepenent because they prouce the hien photon through the vector portal coupling, this limit oes epen on the aitional 5-p.6

7 Dark Matter, Haron Physics an Fusion Physics +X ) [pb] 95% CL Limit on σ BR(H γ BR(H γ +X ) = % FRVZ γ moel = 4 MeV m γ expecte ± σ expecte ± σ ATLAS.3 fb s = 8 TeV BR(H γ +X ) = % Dark photon cτ [mm] observe limit expecte limit 3 Kinetic mixing parameter a e a μ,5σ a μ,±σ favoure E774 - HADES E4 m γ Orsay KLOE BaBar A APEX U7 ATLAS.3 fb [GeV] SN 9% CL BR 4% BR % BR % BR 5% CHARM E37 LSND ATLAS s = 8 TeV +X ) [pb] 95% CL Limit on σ BR(H 4γ BR(H 4γ +X ) = % FRVZ 4γ moel m γ = 4 MeV expecte ± σ expecte ± σ ATLAS.3 fb s = 8 TeV BR(H 4γ +X ) = % Dark photon cτ [mm] observe limit expecte limit Figure. he 95% upper limits on the σ BR for the processes H γ + X (left) an H 4γ + X (right), as a function of the γ lifetime (cτ) for the FRVZ benchmark samples. The expecte limit is shown as the ashe curve an the almost ientical soli curve shows the observe limit. The horizontal lines correspon to σ BR for two values of the BR of the Higgs boson ecay to ark photons. assumption on the Higgs branching fraction to the hien sector. The resulting 9% CL exclusion regions for H γ + X are shown in figure ; the γ mass interval (.5.5) GeVcorrespons to the values in which the γ ecay branching fractions an the etection efficiencies are comparable with those for the.4 GeVγ mass. The systematic uncertainties ue to the etection efficiency an ecay branching fraction variations as a function of the γ mass were estimate an inclue in the 9% CL exclusion region evaluations. 4 Conclusions Long-live particle an leptonic jet signatures, if observe, woul be a clear inication of new physics beyon the 3 Figure. Parameter space exclusion plot for ark photons as a function of the γ mass an of the kinetic mixing parameter ɛ. The 9% CL exclusion limits from the ATLAS search, assuming the FRVZ moel H γ + X with ecay branching fraction to γ of 5///4% an the NNLO gluon fusion Higgs prouction cross section, are shown. Stanar Moel. The ATLAS an experiments have performe a systematic program of searches for these signatures using the whole LHC Run ata, without fining any hint of signals from new physics to ate. The next start of the Run- of LHC represents new potential for iscovery ue to the increase energy an luminosity, that in conjunction with novel sophisticate analysis techniques an etector an reconstruction improvements uner evelopment in both ATLAS an may open avenues to search for signatures of new physics ue to long-live particles. References [] ATLAS Collaboration, JINST 3 (8) S83. [] Collaboration, JINST 3 (8) S84. [3] ATLAS Collaboration, Phys. Rev. D 88, no., 3 (3) [arxiv: [hep-ex]]. [4] ATLAS collaboration, ATLAS-CONF-3-58, [5] Collaboration, JHEP 37 (3), [arxiv:35.49 [hep-ex]]. [6] ATLAS Collaboration, Phys. Rev. D 88, no., 6 (3) [arxiv: [hep-ex]]. [7] ATLAS collaboration, ATLAS-CONF-3-9, [8] Collaboration, -PAS-EXO-37, [9] Collaboration, -PAS-EXO-38, [] Collaboration, Submitte to PRL, [arxiv: [hep-ex]]. 5-p.7

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