Searches for heavy long-lived charged particles with the ATLAS detector in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV

Abstract

Searches for heavy long-lived charged particles are performed using a data sample of 19.1 fb −1 from proton-proton collisions at a centre-of-mass energy of √ 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 β 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.

Heavy fermion bound states for diphoton excess at 750 GeV — collider and cosmological constraints

“…It is also preferable to explain its small decay width to enhance the diphoton signal strength. Note that an extremely small width predicts a long-lived colored particle and again strongly constrained by R-hadron searches [33,34]. In this paper, we consider a scenario with a multiplicatively conserved Z 2 symmetry, and assume that a new colored SU(2) L singlet and Z 2 odd fermion X with hypercharge Y X decays into a stable and neutral Z 2 odd particle χ through higher dimensional operators.…”

“…The mass of X is denoted by m X . The fermion X have sufficiently short lifetime so that one can avoid stringent constraints from long-lived colored particle searches at the LHC [33,34] and to be consistent with cosmology. The above Lagrangian should thus involve some interactions inducing such a decay, and will be discussed in the next section, because those are not relevant to the discussion here.…”

Long-lived colored scalars at the LHC

“…The ATLAS and CMS collaborations have carried out an extensive list of analysis targeting different topologies for the decay products of long-lived particles within the inner detector as well as particles with large enough lifetimes to escape the detector. In particular, both collaborations have carried out an analysis sensitive to very long-lived charged particles using time-of-flight (TOF) and energy loss, dE/dx information [1,2]. This class of searches is highly model independent since a main requirement for a e-mail: apuente@physics.carleton.ca b e-mail: szynkman@fisica.unlp.edu.ar an event to pass the experimental cuts is the appearance of a muon-like object in the muon spectrometer matched to a track in the inner detector.…”

Probing light stops with stoponium

“…Since the decay of the stop is through a 2-body process, the RPV coupling must be somewhat suppressed in order for the condition (2.3) to apply. In fact, this may be [75,81,82]. Stops with prompt RPV decays in the red-shaded region are also constrained from RPV searches [76].…”

“…Note also that if the RPV coupling is extremely small, λ O(10 −7 ) then the stop will have a macroscopic lifetime. In this case, there are additional strong constraints from searches for displaced dijets [75,80] or long-lived colored/charged particles [75,81,82]. In figure 10 we display the RPV stop LSP phase diagram.…”