Revisiting fine-tuning in the MSSM

Abstract

Abstract:We evaluate the amount of fine-tuning in constrained versions of the minimal supersymmetric standard model (MSSM), with different boundary conditions at the GUT scale. Specifically we study the fully constrained version as well as the cases of non-universal Higgs and gaugino masses. We allow for the presence of additional nonholomorphic soft-terms which we show further relax the fine-tuning. Of particular importance is the possibility of a Higgsino mass term and we discuss possible origins for such a term in UV complete models. We point out that loop corrections typically lead to a reduction in the fine-tuning by a factor of about two compared to the estimate at treelevel, which has been overlooked in many recent works. Taking these loop corrections into account, we discuss the impact of current limits from SUSY searches and dark matter on the fine-tuning. Contrary to common lore, we find that the MSSM fine-tuning can be as small as 10 while remaining consistent with all experimental constraints. If, in addition, the dark matter abundance is fully explained by the neutralino LSP, the fine-tuning can still be as low as ∼ 20 in the presence of additional non-holomorphic soft-terms. We also discuss future prospects of these models and find that the MSSM will remain natural even in the case of a non-discovery in the foreseeable future.

Digging deeper for new physics in the LHC data

“…On the other hand, the resonant φ model seems to fit well. 11 11 As the number of jets and their pT distributions are among the primary features characterizing this excess, it is important to be confident in their modeling. In particular, a more correct procedure would be to generate the hard events in MadGraph5 and Pythia8 matched to extra jets using the MLM scheme [29].…”

Impact of an extra gauge interaction on naturalness of supersymmetry

“…[39][40][41][42][43][44][45][46][47][48][49]. In the present paper we remain agnostic about any such correlations and take purely phenomenological point of view and calculate the fine-tuning measure as a function of physical masses of sparticles.…”

Exploring non-holomorphic soft terms in the framework of gauge mediated supersymmetry breaking

“…Staying within an MSSM setup terms like φ 2 φ * or a higgsino mass term like ψψ can be soft SUSY breaking in nature if there is no presence of a gauge singlet field [71]. There have been several works over the past two decades [69][70][71][72][73][74][75][76][77][78][79][80][81][82] that analyzed the effects of introducing NH soft terms. 2 There are three distinct signatures i) the trilinear NH terms may enhance L-R mixing thus influencing various phenomenologies, ii) higgsinos get an additional soft-term source, iii) the Higgs potential remains unaffected at the tree level thus electroweak fine-tuning may hardly change.…”