(Never say never again ...) Tomorrow never dies*

... but no sparticle now (and for a while?)
In this paper we revisit prospects for discovery of natural SUSY in the Run 2 of the LHC as well as after the future high luminosity (HL) upgrade...

One of the main motivations of the current study is the question of what is the potential future discovery reach with increased centre-of-mass energy and integrated luminosity assuming that no signal would be observed this year after collecting 20–30 fb−1 of data. This is a relevant issue since 95% confidence level (C.L.) exclusion limits advance much faster than the discovery reach that conservatively requires 5-σ significance for serious consideration. Therefore, if null results are obtained this year, the question is can we still hope to make a discovery at the LHC? We find that the answer has a significant dependence on how well systematic uncertainties can be reduced in the future and we therefore consider different scenarios for their future evolution...

Our most important results, however, are regarding the expected discovery reach of the LHC at high-luminosity (3000 fb−1 at 14 TeV). We come to the rather sobering conclusion that assuming the systematic errors remain constant, there are relatively few parameter points that can be discovered that are not already excluded with 20 fb−1 at 13 TeV. Essentially, if natural SUSY is to be discovered at the LHC, the first hints probably need to start appearing this summer. The situation changes slightly if the systematic errors can be reduced as more data is collected at the LHC. If we again take the scenario that the systematic uncertainty scales as 1/√ L, the prospects of a natural SUSY discovery at the high luminosity become more optimistic. For gluinos we find a mass band 1800 TeV<mg<2400TeV where spectra that are not excluded with 20 fb−1 at 13 TeV can still eventually be discovered. A similar mass band 900TeV < mt <1400TeV exists for stops and this shows the importance of reducing the systematic uncertainties to fully exploit the discovery potential of the high luminosity LHC.
(Submitted on 21 Jun 2016)

//update 8 August 2016



ATLAS data (black points) are compared to the contribution expected from known particles (the filled histograms) in a number of control selections where no signal is expected (left of the dashed line) as well as in a number of selections where a supersymmetric signal, if it exists, would be enhanced (right of the dashed line). The statistical compatibility is reported on the lower panel, where a value above 5 in the signal selections would indicate a discovery. (Image: ATLAS Experiment/CERN).


By ATLAS Collaboration, 4th August 2016



Mass reach of ATLAS searches for Supersymmetry. Only a representative selection of the available results is shown. 

Status of figure: August 2016


//last edit 9 August 2016
* Retrospectively this post appears to be the first of an August holiday series whose common thread is the inspiration for the title... Now it happens that Never say never again is not an official James Bond film thus I have decided to change this post title for a better one that belongs to the list ;-)

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