Exploring the nearly degenerate stop region with sbottom decays

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 2 + E miss T and 1b1 + E miss T . 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 W (b →t W ), 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.

Enhancing the discovery prospects for SUSY-like decays with a forgotten kinematic variable

“…8 The spirit of these curves is similar to a receiving operator characteristic (ROC) curve, even though they are not technically ROC curves. 9 We verify that the procedure outlined here is not sensitive to the choice of binning. We point out that the performance curves of any two variables may be meaningfully compared independently of the overall signal and background normalizations, since any change in the signal and background normalizations will multiply the performance curve of all variables by the same common factor.…”

“…This attitude is supported by the flurry of theoretical activity in recent years in designing models which "hide" the new physics from the LHC. One of the standard methods for doing so is to arrange for a "compressed" mass spectrum with a mass degeneracy of the relevant particles, such as supersymmetric (SUSY) partners, so that the resulting decay products are too soft to be triggered upon and tagged in the experimental analysis [4][5][6][7][8][9][10][11][12][13], or a "stealth" mass spectrum, where the new physics signature becomes identical to the SM background, since the additional particles are too soft to make any appreciable difference [14][15][16][17][18][19][20]. Our aim will be to highlight a kinematic variable that, either by itself or in conjunction with more conventional variables, can more effectively select signal over background when the signal spectrum is compressed and when signal events contain multi-stage cascade decays.…”

Stop co-annihilation in the minimal supersymmetric standard model revisited

“…If the splitting is less than M W , (b → bχ) robustly excludes mb < 625 GeV [48]. A phenomenological projection [49] suggests that a combined search for all the different decay modes of the sbottom could ultimately probe mb 900 GeV with 300 fb −1 of data.…”

Uncover compressed supersymmetry via boosted bosons from the heavier stop/sbottom

“…This motivates the searches for the signal oft 2 pair production witht 2 →t 1 h/Z decay at the LHC run-I [40,41]. Moreover, through searching for the final state of multi-leptons and/or multi-b-jets [42], the heavier stop/sbottom with masses below ∼ 1 TeV decaying intot 1 and heavy bosons are found to be detectable at the 13/14 TeV LHC with an integrated luminosity of O(100) fb −1 [43][44][45][46].…”