The little-hierarchy problem is a little problem: understanding the difference between the big- and little-hierarchy problems with Bayesian probability

Abstract

Experiments are once again under way at the LHC. This time around, however, the mood in the high-energy physics community is pessimistic. There is a growing suspicion that naturalness arguments that predict new physics near the weak scale are faulty and that prospects for a new discovery are limited. We argue that such doubts originate from a misunderstanding of the foundations of naturalness arguments. In spite of the first run at the LHC, which aggravated the little-hierarchy problem, there is no cause for doubting naturalness or natural theories. Naturalness is grounded in Bayesian probability logic - it is not a scientific theory and it makes no sense to claim that it could be falsified or that it is under pressure from experimental data. We should remain optimistic about discovery prospects; natural theories, such as supersymmetry, generally predict new physics close to the weak scale. Furthermore, from a Bayesian perspective, we briefly discuss 't Hooft's technical naturalness and a contentious claim that the little-hierarchy problem hints that the Standard Model is a fundamental theory.