Supersymmetry: aspirations and prospects

Abstract

The realization in the early 1980s that weak scale supersymmetry stabilizes the Higgs sector of the spectacularly successful Standard Model led several authors to explore whether low energy supersymmetry could play a role in particle physics. Among these were Richard Arnowitt, Ali Chamseddine and Pran Nath who constructed a viable locally supersymmetric Grand Unified Theory (GUT), laying down the foundation for supergravity GUT models of particle physics. Supergravity models continue to be explored as one of the most promising extensions of the Standard Model. After a quick overview of some of the issues and aspirations of early researchers working to bring supersymmetry into the mainstream of particle physics, we re-examine early arguments that seemed to imply that superpartners would be revealed in experiments at LEP2 or at the Tevatron. Our purpose is to assess whether the absence of any superpartners in searches at LHC8 presents a crisis for supersymmetry. Toward this end, we re-evaluate fine-tuning arguments that lead to upper bounds on (some) superpartner masses. We conclude that phenomenologically viable superpartner spectra that could arise within a high scale model tuned no worse than a few percent are perfectly possible. While no viable underlying model of particle physics that leads to such spectra has yet emerged, we show that the (supergravity-based) Radiatively-driven Natural Supersymmetry (RNS) framework serves as a surrogate for a phenomenological analysis of an underlying theory with modest fine-tuning. We outline the phenomenological implications of this framework, with emphasis on those LHC and electron-positron collider signatures that might point to the underlying natural origin of gauge and Higgs boson masses. We conclude that the supergravity GUT paradigm laid down in 1982 by Arnowitt, Chamseddine and Nath, and others, remains a vibrant possibility. *

The muong− 2 and degenerate supersymmetry

“…In conclusion, the low energy SUSY with wide mass spectrum is seemingly pushed to a corner by the LHC and, according to some authors, losing its appeal as a solution to the hierarchy problem: see however Ref. [6][7][8], and references therein.…”

Multichannel assault on natural supersymmetry at the high luminosity LHC

“…The simplest and most elegant protection, known as supersymmetry (SUSY) [3], relates fermions to bosons in exactly the right way to cancel these dangerous corrections. Indirect evidence for softly broken SUSY with weak scale superpartners exists in that 1. the coupling strengths of the strong and electroweak forces, as measured to high precision at the CERN LEP e + e − collider at energy scale √ s = m Z , enjoy an impressive unification at Q 2 × 10 16 GeV when extrapolated to high energies [4]. 2. the top mass, measured to be m t 173.2 GeV, lies in the range required to trigger a radiatively-induced breakdown of electroweak symmetry [5].…”

“…An alternative response was to scrutinize the validity of the earlier naturalness calculations [13][14][15][16]. The simplest, most conservative naturalness measure ∆ EW , proposed in Refs.…”

Supersymmetry and unification: a status update

“…Along with the discussions on constraints from muon g − 2 and dark matter, discovery prospects at high luminosity (HL)-LHC and High Energy (HE)-LHC are also presented. A status review of Natural SUSY models is given in reference [2]. Here the author emphasized the importance of electroweak fine-tuning quantified by a measure ∆ EW to explore the prospect of SUSY discovery.…”

“…The author outlined strategies for searching at the LHC along with its luminosity and energy upgrades, as well as at future electron-positron colliders with √ s > ∼ 600 GeV. Naturalness was further explored in reference [3], but in contrast to reference [2] the authors explored "stringy naturalness". The article involves general considerations from the string theory landscape that favor large values of soft terms, subject to the vacuum selection criteria that electroweak symmetry is properly broken (no charge and/or color breaking (CCB) minima) and the resulting magnitude of the weak scale is not too far from our measured value.…”