Cornering natural SUSY at LHC Run II and beyond

Abstract

Abstract:We derive the latest constraints on various simplified models of natural SUSY with light higgsinos, stops and gluinos, using a detailed and comprehensive reinterpretation of the most recent 13 TeV ATLAS and CMS searches with ∼ 15 fb −1 of data. We discuss the implications of these constraints for fine-tuning of the electroweak scale. While the most "vanilla" version of SUSY (the MSSM with R-parity and flavor-degenerate sfermions) with 10% fine-tuning is ruled out by the current constraints, models with decoupled valence squarks or reduced missing energy can still be fully natural. However, in all of these models, the mediation scale must be extremely low (< 100 TeV). We conclude by considering the prospects for the high-luminosity LHC era, where we expect the current limits on particle masses to improve by up to ∼ 1 TeV, and discuss further model-building directions for natural SUSY that are motivated by this work.

Low fine-tuning in Yukawa-deflected gauge mediation

“…This case is in principle testable at the LHC (relying on stop/gluino production) through searches for events with b-jets and missing energy aiming at standard 'natural SUSY' scenarios. According to the recent study [63], a spectrum like that of model A2 already lies at the edge of the exclusion provided by the early 13 TeV LHC data, which approximately corresponds to m t 1 1 TeV for m g = 2 TeV. Therefore, we expect that the present LHC run will start testing at least the bottom-left corner of the left plot in Fig.…”

“…Gluinos and RH squarks lie above 2 TeV, while LH squarks and sleptons are multi-TeV again because of the large Wino mass. Therefore, this class of models is a remarkable example of SUSY scenarios with low fine tuning but spectra that can be easily evade current LHC searches, 5 in contrast to the classical 'natural SUSY' framework whose status has been recently studied in [63]. This feature is shared by other SUSY setups, for instance in the context of gravity mediation by 'radiatively natural' models (for recent discussions see [79,80]).…”

Impact of an extra gauge interaction on naturalness of supersymmetry

“…For the 10 TeV squarks the physical stop masses may be about 20% larger than their tree-level value, as was recently emphasized in ref. [23]. After taking this into account, the range of stop masses with the tuning better than 1% is essentially unaffected by heavy 1st/2nd generation of sfermions.…”

“…The most notable examples of such models are Next-To-Minimal Supersymmetric Standard Model (NMSSM) [6][7][8][9][10][11][12][13][14] and models with non-decoupling D-terms of some new gauge interactions under which the Higgs is charged [15][16][17][18][19][20][21][22]. However, even if the observed Higgs mass is obtained with light stops the fine-tuning is still present due to constraints on supersymmetric particles, especially on stops and gluino, from direct LHC searches [23,24].…”

Minimal non-abelian supersymmetric Twin Higgs

“…Fine-tuning of the EW scale in minimal SUSY models implied by the LHC searches was recently quantified in refs. [5,6], which demonstrated that the current limits on stop and gluino masses exclude regions with fine-tuning better than 10%, even if a very low mediation scale of the SUSY breaking of 100 TeV is assumed. 1 The fine-tuning quickly gets worse for larger mediation scales due to longer RG running of the soft Higgs mass.…”