O(1) GeV dark matter in SUSY and a very light pseudoscalar at the LHC

Abstract: We analyze the prospects of the detection of an O(1) $$ GeV neutralino dark matter, (Formula Presented.), in the Next-to-Minimal Supersymmetric Standard Model at the 14 TeV LHC. We perform dedicated scans of the relevant parameter space of the model and find a large number of points where the thermal relic abundance due to such a dark matter is consistent with the PLANCK measurement. We note that this dark matter is highly singlino-dominated and is always accompanied by a pseudoscalar, A₁, with a mass around twice its own, which is responsible for its resonant annihilation. For two benchmark points from our scan, we then carry out a detector-level signal-to-background analysis of the pair production of a heavier higgsino neutralino and a chargino. The higgsino thus produced decays into the dark matter and either the Z boson or the A₁. For the Z-associated production of (Formula Presented.), we investigate the scope of the trilepton search channel. For the A₁-associated production mode, in order to identify the two collimated muons coming from the decay of the A₁, we employ an unconventional method, of clustering them together into one jet-like object. Using this method, for certain parameter space configurations, a much larger sensitivity can be obtained at the 14 TeV LHC for the (Formula Presented.) channel compared to the Z(Formula Presented.) channel, with an integrated luminosity of 300 fb⁻¹.