Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at sqrt(s) = 8 TeV

CMS Collaboration [--] Khachatryan, Vardan [Yerevan Phys. Inst.] Basegmez, Suzan [UCL] Beluffi, Camille [UCL] Bruno, Giacomo [UCL] Castello, Roberto [UCL] Caudron, Adrien [UCL] Ceard, Ludivine [UCL] Da Silveira, Gustavo Gil [UCL] Delaere, Christophe [UCL] Du Pree, Tristan [UCL] Favart, Denis [UCL] Forthomme, Laurent [UCL] Giammanco, Andrea [UCL] Hollar, Jonathan [UCL] Jez, Pavel [UCL] Komm, Matthias [UCL] Lemaitre, Vincent [UCL] Liao, Junhui [UCL] Nuttens, Claude [UCL] Pagano, Davide [UCL] Perrini, Lucia [UCL] Pin, Arnaud [UCL] Piotrzkowski, Krzysztof [UCL] Popov, Andrey [UCL] Quertenmont, Loic [UCL] Selvaggi, Michele [UCL] Vidal Maroño, Miguel [UCL] Vizan Garcia, Jesús Manuel [UCL] et al.

A search for supersymmetry through the direct pair production of top squarks, with Higgs (H) or Z bosons in the decay chain, is performed using a data sample of proton–proton collisions at View the MathML sources=8 TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5 fb−1. The search is performed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background prediction is observed. The results are interpreted in the context of simplified supersymmetric models with pair production of a heavier top-squark mass eigenstate View the MathML sourcet˜2 decaying to a lighter top-squark mass eigenstate View the MathML sourcet˜1 via either View the MathML sourcet˜2→Ht˜1 or View the MathML sourcet˜2→Zt˜1, followed in both cases by View the MathML sourcet˜1→tχ˜10, where View the MathML sourceχ˜10 is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the View the MathML sourcet˜1 and View the MathML sourceχ˜10 states is approximately equal to the top-quark mass (View the MathML sourcemt˜1−mχ˜10≃mt), which is not probed by searches for direct View the MathML sourcet˜1 squark pair production. The analysis excludes top squarks with masses View the MathML sourcemt˜2<575 GeV and View the MathML sourcemt˜1<400 GeV at a 95% confidence level.