From a boson to the standard model Higgs: a case study in confirmation and model dynamics

Abstract

Our paper studies the anatomy of the discovery of the Higgs boson at the Large Hadron Collider (LHC). We investigate the phases of this discovery, which led to a crucial reconfiguration of the model landscape of elementary particle physics and eventually to a confirmation of the Standard Model (SM). A keyword search of preprints covering the electroweak symmetry breaking (EWSB) sector of particle physics, along with an examination of physicists' own understanding of the discovery as documented in semiannual conferences, has allowed us an empirical investigation of its model dynamics. From our analyses we draw two main philosophical lessons concerning the nature of scientific reasoning in a complex experimental and theoretical environment. For one, from a confirmation standpoint, some SM alternatives could be considered even more confirmed by the Higgs discovery than the SM. Nevertheless, the SM largely remains the commonly accepted account of EWSB. We present criteria for comparing degrees of confirmation and expose some limits of a purely logical approach to understanding the Higgs discovery as a victory for the SM. Second, we understand the persistence of SM alternatives in the face of disfavourable evidence by borrowing the Lakatosian concept of a research programme, where the core idea behind a group of models survives, while other aspects adapt to incoming data. In order to apply this framework to the model landscape of EWSB, we must introduce a new category of research programme, the modelgroup, and we test its viability using the example of composite Higgs models.

Explanations and candidate explanations in physics

“…with the same strength.6 These categories are not exclusive or exhaustive, but capture a wide range of popular models. Similar breakdowns are presented in(Borrelli and Stöltzner, 2013;Chall et al, 2019;Stöltzner, 2017).…”

“…Six years after the 2012 discovery of the Higgs boson, there is still a large number and variety of viable models in particle physics that offer potential explanations of particle masses via electroweak symmetry breaking. All of these models are, to some degree, still active research avenues in particle physics, as evidenced in (Chall et al, 2019). The Standard Model features the simplest implementation of the Higgs mechanism, which is a single doublet with one fundamental scalar particle.…”

Model-groups as scientific research programmes

“…Using recent work examining the landscape of models in the EWSB sector during the Higgs boson discovery (see, e.g., Borrelli and Stöltzner, 2013;Stöltzner, 2014;Chall et al, 2019), we can distinguish the primary model-groups within the EWSB sector: supersymmetry, non-SUSY Extended Higgs models, composite Higgs models, and Extra-Dimensional models. 10 These four model-groups do not exhaust the BSM EWSB alternatives, but they comprise the bulk of current SM alternatives.…”

“…Any new models attempting to solve this problem must either provide an explanation for why new particles haven't been discovered by existing experiments, or raise expected energy range for the predicted appearance of the new strong sector beyond the reach of the LHC. In either case, the CH model-group, already winning only modest attention as a SM alternative, has yet to put forth a solution that has convinced many physicists, leaving its problem-solving status fairly stagnant (see Chall et al, 2019).…”

“…3 These worries over the perceived faults of the SM account have driven BSM model-building. Even as the new particle's properties were better determined and a consensus reached that it is indeed a Higgs boson (with a shrinking parameter space for anything besides the SM account), alternative understandings of EWSB are still common, with work from several varieties of BSM models still regularly appearing in publication and the online preprint archive, arXiv.org (see Chall et al, 2019). Though many EWSB models haven't received direct empirical support from data collected at the LHC, they haven't been entirely excluded either.…”