ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider

Abstract

This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton–proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 of collisions at a centre-of-mass energy of TeV, although in some case an additional of collision data at TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models.

Impact of jet veto resummation on slepton searches

“…This amounts to placing a veto on additional jets above a certain transverse momentum p cut T arising from QCD initial-state or final-state radiation. Typical examples are supersymmetry (SUSY) searches for third generation squarks requiring two signal jets and vetoing a third jet [1][2][3], or electroweakino/slepton searches usually requiring 0 signal jets [4][5][6][7][8]. Jet vetoes are also applied in other BSM searches, including anomalous triple-gauge couplings [9], unparticles [10], large extra dimensions and dark matter candidates in mono-photon, mono-Z and mono-jet events [11][12][13].…”

Proposing a new LHC search for light compressed stop squarks

“…The very nature of the selection criteria is such that the search is most sensitive near the ∆m = m b region where the stop decay products are soft. On the contrary, the searches [3,9] are sensitive for larger values of ∆m. This is so because these searches require the presence of one or two leptons, respectively, in the final state that need to be sufficiently hard to be reconstructed.…”

“…has been targeted by the ATLAS searches [3,7,9], in which 100% BR is assumed. However, under these assumptions, there is still a small unconstrained region at stop masses around 100 GeV.…”

“…The searches [3,7,9], introduced in the above discussion, cover complementary kinematical regions. The search [7] is basically a monojet search in which at least one hard jet is required in order to have a sufficient recoil that gives rise to a large amount of E / T .…”

“…Figure 1 (left) summarizes the status of searches for light stops in the squeezed region with the assumption of a 100% BR into a four-body final state. There is an unconstrained region for 80 GeV mt 1 110 GeV GeV, bounded by the exclusion curves from the ATLAS one and two lepton searches [3,9], the ATLAS monojet search [7] and LEP [10].…”