Abstract
A light stop with mass almost degenerate with the lightest neutralino has important connections with both naturalness and dark matter relic abundance. This region is also very hard to probe at colliders. In this paper, we demonstrate the potential of searching for such stop particles at the LHC from sbottom decays, focusing on two channels with final states mathbf{2}mathbf{ell }+{boldsymbol{mathsf{E}}}_{mathbf{mathsf{T}}}^{mathbf{mathsf{miss}}} and mathbf{1}boldsymbol{mathsf{b}}mathbf{mathsf{1}}mathbf{ell}+{boldsymbol{E}}_{mathbf{T}}^{mathbf{miss}} . We found that, if the lightest sbottom has mass around or below 1 TeV and has a significant branching ratio to decay to stop and Wleft(tilde{b}to tilde{t}Wright) , a stop almost degenerate with neutralino can be excluded up to about 500-600 GeV at the 13 TeV LHC with 300 fb−1 data. The searches we propose are complementary to other SUSY searches at the LHC and could have the best sensitivity to the stop-bino coannihilation region. Since they involve final states which have already been used in LHC searches, a reinterpretation of the search results already has sensitivity. Further optimization could deliver the full potential of these channels.
Highlights
JHEP04(2017)084 discussed in this paper are slightly better if the mass gap is smaller
We demonstrate the potential of searching for such stop particles at the LHC from sbottom decays, focusing on two channels with final states 2 + ETmiss and 1b1 + ETmiss
If the lightest sbottom has mass around or below 1 TeV and has a significant branching ratio to decay to stop and W ( ̃b → tW ), a stop almost degenerate with neutralino can be excluded up to about 500–600 GeV at the 13 TeV LHC with 300 fb−1 data
Summary
With two decay channelsb → tW andb → b χ, a pair of sbottoms produced at the LHC has three ways to decay, as shown in figure 2. The 2 + ETmiss channel is designed to pick up the the symmetric decay chain in figure 2a with both W s decaying leptonically, and should be the optimal search channel if the decayb → tW dominates This channel has been searched at the LHC for the searches of sleptons and electroweakinos [68, 69], for which the main background is top quark pair production (tt) and diboson (W W/W Z/ZZ). One could search in the channel with final states of one lepton, ETmiss and one or two hard jets with no b-jets (1 + jets + Em T iss), which could come from either figure 2a with one W decaying hadronically or figure 2b if the b-jet is not tagged While this channel could contain significant amount of signal events, the backgrounds are large and more complicated. We focus on the simpler leptonic channels as an initial assessment of the potential of these new decay channels
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