Collider signatures of a light NMSSM pseudoscalar in neutralino decays in the light of LHC results

Journal of High Energy Physics 2014.2 (2014): 048 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and determine their observability at the LHC. We concentrate on scenarios which feature two light scalar Higgs bosons (one of them is SM-like with a mass of 125 GeV and a singlet-like lighter one) with a very light (singlet-like) pseudoscalar Higgs in the mass range 2mτ < ma10 < 2mb . We consider neutralino-chargino pair production and the subsequent decay χ̃o 2,3 → χ̃o 1a0 1, which leads to topologies involving multi-leptons and missing transverse energy. We determine a set of selection cuts that can effectively isolate the signal from backgrounds of the Standard Model or the Minimal Supersymmetric Standard Model. We also exemplify the procedure with a set of benchmark points, for which we compute the expected number of events and signal strength for LHC with 8 TeV center of mass energy. We show that this signal can already be probed for some points in the NMSSM parameter spaceDGC is supported by the Ramón y Cajal program of the Spanish MICINN. CBP is supported by the CERN-Korea fellowship through the National Research Foundation of Korea. MP is supported by a MultiDark Scholarship. DGC, PG and MP thank the support of the Consolider-Ingenio 2010 programme under grant MULTIDARK CSD2009-00064, the Spanish MICINN under Grants No. FPA2009-08958 and FPA2012-34694, the Spanish MINECO “Centro de excelencia Severo Ochoa Program” under grant No. SEV-2012-0249, the Community of Madrid under Grant No. HEPHACOS S2009/ESP-1473, and the European Union under the Marie Curie-ITN Program No. PITN-GA-2009-23792