Abstract
Searches for heavy long-lived charged particles are performed using a data sample of 19.8 fb$^{-1}$ from proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. No excess is observed above the estimated background and limits are placed on the mass of long-lived particles in various supersymmetric models. Long-lived tau sleptons in models with gauge-mediated symmetry breaking are excluded up to masses between 440 and 385 GeV for $\tan\beta$ between 10 and 50, with a 290 GeV limit in the case where only direct tau slepton production is considered. In the context of simplified LeptoSUSY models, where sleptons are stable and have a mass of 300 GeV, squark and gluino masses are excluded up to a mass of 1500 and 1360 GeV, respectively. Directly produced charginos, in simplified models where they are nearly degenerate to the lightest neutralino, are excluded up to a mass of 620 GeV. $R$-hadrons, composites containing a gluino, bottom squark or top squark, are excluded up to a mass of 1270, 845 and 900 GeV, respectively, using the full detector; and up to a mass of 1260, 835 and 870 GeV using an approach disregarding information from the muon spectrometer.
Highlights
Heavy long-lived particles (LLP) are predicted in a range of extensions of the Standard Model (SM) [1]
The calorimeters, Resistive plate chambers (RPC) and monitored drift tube (MDT) have sufficiently accurate timing to distinguish between highly relativistic SM particles and slower LLPs of interest to the searches described in this article
The mass distributions observed in data together with the background estimate, its systematic uncertainty and examples of expected signal are shown in figures 2–4 for the slepton, chargino and R-hadron searches, respectively
Summary
Heavy long-lived particles (LLP) are predicted in a range of extensions of the Standard Model (SM) [1]. R-parity-conserving supersymmetry (SUSY) [2,3,4,5,6,7,8,9,10,11,12,13,14,15] models, such as split SUSY [16, 17], gauge-mediated SUSY breaking (GMSB) [18,19,20,21,22,23,24,25] and LeptoSUSY [26, 27], as well as other scenarios such as universal extra dimensions [28] and leptoquark extensions [29], allow for a variety of LLP states stable enough to be directly identified by the ATLAS detector These states include long-lived super-partners of the leptons, quarks and gluons; sleptons ( ̃), squarks (q) and gluinos (g), respectively; as well as charginos (χ±1,2), which together with neutralinos (χ01−4) are a mixture of super-partners of the Higgs and W /Z bosons, known as Higgsinos, winos and binos. Previous collider searches for charged LLPs have been performed at LEP [36,37,38,39], HERA [40], the Tevatron [41,42,43], and the LHC [35, 44, 45]
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