What hadron collider is required to discover or falsify natural supersymmetry?

Howard Baer, Vernon Barger, James S. Gainer, Peisi Huang, Michael Savoy, Hasan Serce, Xerxes Tata
Weak scale supersymmetry (SUSY) remains a compelling extension of the Standard Model because it stabilizes the quantum corrections to the Higgs and W, Z boson masses. In natural SUSY models these corrections are, by definition, never much larger than the corresponding masses. Natural SUSY models all have an upper limit on the gluino mass, too high to lead to observable signals even at the high luminosity LHC. However, in models with gaugino mass unification, the wino is sufficiently light that supersymmetry discovery is possible in other channels over the entire natural SUSY parameter space with no worse than 3% fine-tuning. Here, we examine the SUSY reach in more general models with and without gaugino mass unification (specifically, natural generalized mirage mediation), and show that the high energy LHC (HE-LHC), a pp collider with \sqrt{s}=33 TeV, will be able to detect the gluino signal over the entire allowed mass range. Thus, HE-LHC would either discover or conclusively falsify natural SUSY.

Read more at https://arxiv.org/pdf/1702.06588.pdf

Searching for supersymmetry: some frustration but no despair

limitsSupersymmetry is simply beautiful. It is the largest possible space-time symmetry of nature and it relates space and time with a fundamental quantum property of elementary particles, the spin. Supersymmetry predicts a wealth of new particles, superparticles, some of which could constitute the mysterious astrophysical dark matter. There is only one small problem: so far, supersymmetry is not supported by any experimental evidence. This week at a conference in the small Italian ski resort of La Thuile, the experiments at the Large Hadron Collider LHC have reported new results of their quest for supersymmetry.

Unfortunately, no signal has been detected, and only new lower limits on the mass of the superparticles have been presented. These limits are based on many years of theoretical calculations by many theorists, including myself and my colleague and friend Herbi Dreiner, who most likely infected me with the supersymmetry virus. We were hoping that our calculations would help to pin down the exact nature of supersymmetry in the case of discovery, but unfortunately so far they were only useful to derive limits, limits, and more limits. Personally, I am frustrated about the lack of any evidence for supersymmetry, but actually there is no reason for despair. So let’s see why theorists love supersymmetry and why it is still alive…
Read more at: http://www.guardian.co.uk/science/life-and-physics/2013/mar/14/supersymmetry-spell

The Aroma of Stops and Gluinos …

… at the \sqrt{s} = 7 TeV LHC

Tianjun Li, James A. Maxin, Dimitri V. Nanopoulos, Joel W. Walker

In Profumo di SUSY, we presented evidence that CMS&ATLAS may have already registered a handful of deftly camouflaged supersymmetry events at the LHC in the multijet channels. Here, we explore the prospect for corroboration of this suggestion from 5 additional CMS&ATLAS search strategies targeting the production of light stops & gluinos at lower jet counts, which variously depend on heavy flavor tagging and the inclusion or exclusion of associated leptons. The current operating phase of the 7TeV LHC is highly conducive to the production of gluinos & light stops, given the supersymmetric particle mass hierarchy M_t_1<M_g<M_q that naturally evolves from the dynamics of the model named No-Scale FSU5 that we presently study. Moreover, some tension persists against the SM data-driven and MC generated background predictions in certain LHC searches of this variety. We demonstrate that the 1-sigma overlap of the allowed supersymmetric event production for these seven search methodologies roundly envelops the most favorable phenomenological subspace of FSU5, while handily generating a 125GeV Higgs boson mass. In order to test the statistical significance of any correlations across the simulated FSU5 collider response in these seven search strategies, we implement a multi-axis chi^2 fitting procedure, yielding a best overall match in the vicinity of M1/2=610GeV, corresponding to light stop & gluino masses of approximately 665GeV and 830GeV. Consequently, we suggest that FSU5 is a better global fit to the studied LHC data than the SM alone, and moreover that its predictions appear to be meaningfully correlated with observed low-statistics excesses across a wide variety of specialized search strategies. We suspect the already collected 5/fb will be sufficient to either condense or disperse the delicate aroma of stops and gluinos that suffuses the early search…..
Read more:arxiv.org/pdf

Read also: Nanopoulos: Aroma Of Gluinos In LHC Data

The Early History of String Theory and Supersymmetry

Euler beta function

John H. Schwarz
This lecture presents a brief overview of the early history of string theory and supersymmetry.
It describes how the S-matrix theory program for understanding the strong nuclear force evolved into superstring theory, which is a promising framework for constructing a unified quantum theory of all forces including gravity.
The period covered begins with S-matrix theory in the mid 1960s and ends with the widespread acceptance of superstring theory in the mid 1980s.
Further details and additional references can be found in Schwarz (2007)…..
Read more: arxiv.org/pdf

Profumo di SUSY ….

…. Suggestive Correlations in the ATLAS and CMS High Jet Multiplicity Data
Tianjun Li, James A. Maxin, Dimitri V. Nanopoulos, Joel W. Walker
We present persistently amassing evidence that the CMS and ATLAS Collaborations may indeed be already registering supersymmetry events at the Large Hadron Collider (LHC).
Our analysis is performed in the context of a highly phenomenologically favorable model named No-Scale F-SU(5), which represents the unification of the F-lipped SU(5) Grand Unified Theory (GUT), two pairs of hypothetical TeV-scale vector-like supersymmetric multiplets derived out of F-Theory, and the dynamically established boundary conditions of No-Scale supergravity.
We document highly suggestive correlations between the first inverse femtobarn of observations by CMS and ATLAS, where seductive excesses in multijet events, particularly those with nine or more jets, are unambiguously accounted for by a precision Monte-Carlo simulation of the F-SU(5) model space.
This intimate correspondence is optimized by a unified gaugino mass in the neighborhood of M_{1/2}=518 GeV. We supplement this analysis by extrapolating for the expected data profile to be realized with five inverse femtobarns of integrated luminosity, as expected to be observed at the LHC by the conclusion of 2011. Significantly, we find that this luminosity may be sufficient to constitute a SUSY discovery for the favored benchmark spectrum. Indeed, the winds wafting our way from Geneva may already be heavy with the delicate perfume of Supersymmetry…..

Read more: http://arxiv.org/pdf

LHC results put supersymmetry theory ‘on the spot’

By Pallab Ghosh
Results from the Large Hadron Collider (LHC) have all but killed the simplest version of an enticing theory of sub-atomic physics.

Supersymmetry predicts the existence of mysterious super particles.

Researchers failed to find evidence of so-called “supersymmetric” particles, which many physicists had hoped would plug holes in the current theory.
Theorists working in the field have told BBC News that they may have to come up with a completely new idea.
Data were presented at the Lepton Photon science meeting in Mumbai.
They come from the LHC Beauty (LHCb) experiment, one of the four main detectors situated around the collider ring at the European Organisation for Nuclear Research (Cern) on the Swiss-French border.
According to Dr Tara Shears of Liverpool University, a spokesman for the LHCb experiment: “It does rather put supersymmetry on the spot”.

The experiment looked at the decay of particles called “B-mesons” in hitherto unprecedented detail.

If supersymmetric particles exist, B-mesons ought to decay far more often than if they do not exist.
There also ought to be a greater difference in the way matter and antimatter versions of these particles decay.
The results had been eagerly awaited following hints from earlier results, most notably from the Tevatron particle accelerator in the US, that the decay of B-mesons was influenced by supersymmetric particles.
LHCb’s more detailed analysis however has failed to find this effect.
Bitten the dust
This failure to find indirect evidence of supersymmetry, coupled with the fact that two of the collider’s other main experiments have not yet detected supersymmetic particles, means that the simplest version of the theory has in effect bitten the dust.

Collisions inside the LHC should have found some evidence of Supersymmetry by now

The theory of supersymmetry in its simplest form is that as well as the subatomic particles we know about, there are “super-particles” that are similar, but have slightly different characteristics.
The theory, which was developed 20 years ago, can help to explain why there is more material in the Universe than we can detect – so-called “dark matter”.
According to Professor Jordan Nash of Imperial College London, who is working on one of the LHC’s experiments, researchers could have seen some evidence of supersymmetry by now.
“The fact that we haven’t seen any evidence of it tells us that either our understanding of it is incomplete, or it’s a little different to what we thought – or maybe it doesn’t exist at all,” he said…. Continue reading LHC results put supersymmetry theory ‘on the spot’