Gluino reach and mass extraction at the LHC in radiatively-driven natural SUSY

Abstract

Radiatively-driven natural SUSY (RNS) models enjoy electroweak naturalness at the $10\%$ level while respecting LHC sparticle and Higgs mass constraints. Gluino and top squark masses can range up to several TeV (with other squarks even heavier) but a set of light Higgsinos are required with mass not too far above $m_h\sim 125$ GeV. Within the RNS framework, gluinos dominantly decay via $\tilde{g}\to t{\tilde{t}}_1^{\ast },\bar{t}{\tilde{t}}_1\to t\bar{t}{\tilde{Z}}_{1,2}$ or $t\bar{b}{\tilde{W}}_1^{-}+c.c.$, where the decay products of the higgsino-like ${\tilde{W}}_1$ and ${\tilde{Z}}_2$ are very soft. Gluino pair production is, therefore, signalled by events with up to four hard $b$-jets and large $/E_T$. We devise a set of cuts to isolate a relatively pure gluino sample at the (high luminosity) LHC and show that in the RNS model with very heavy squarks, the gluino signal will be accessible for $m_{\tilde{g}}<2400(2800)$ GeV for an integrated luminosity of 300 (3000) fb${}^{-1}$. We also show that the measurement of the rate of gluino events in the clean sample mentioned above allows for a determination of $m_{\tilde{g}}$ with a statistical precision of $2.5-5\%$ (depending on the integrated luminosity and the gluino mass) over the range of gluino masses where a $5\sigma$ discovery is possible at the LHC.

Comments: 25 pages + frontpage. 13 figures consisting of 20 image files