Model choice and crucial tests. On the empirical epistemology of the Higgs discovery

Abstract

Our paper discusses the epistemic attitudes of particle physicists on the discovery of the Higgs boson at the Large Hadron Collider (LHC). It is based on questionnaires and interviews made shortly before and shortly after the discovery in 2012. We show, to begin with, that the discovery of a Standard Model (SM) Higgs boson was less expected than is sometimes assumed. Once the new particle was shown to have properties consistent with SM expectationsalbeit with significant experimental uncertainties -, there was a broad agreement that 'a' Higgs boson had been found. Physicists adopted a twopronged strategy. On the one hand, they treated the particle as a SM Higgs boson and tried to establish its properties with higher precision; on the other hand, they searched for any hints of physics beyond the SM. This motivates our first philosophical thesis: the Higgs discovery, being of fundamental importance and establishing a new kind of particle, represented a crucial experiment if one interprets this notion in an appropriate sense. By embedding the LHC into the tradition of previous precision experiments and the experimental strategies thus established, Duhemian underdetermination is kept at bay. Second, our case study suggests that criteria of theory (or model) preference should be understood as epistemic and pragmatic values that have to be weighed in factual research practice. The Higgs discovery led to a shift from pragmatic to epistemic values as regards the mechanisms of electroweak symmetry breaking. Complex criteria, such as naturalness, combine epistemic and pragmatic values, but are coherently applied by the community.

What is a Beautiful Experiment?

“…If we take, for instance, one of the most recent discoveries in particle physics, the discovery of the Higgs boson, we can appreciate that there was hardly anything immediate about the discovery. There was a timespan of deliberations before the community decided a new particle had been detected, as Mättig and Stöltzner (2019) have nicely documented, with the community carefully announcing that 'a Higgs-like particle' had been detected. All this is to say that many experiments will not exhibit such clear, immediate results as in the case of the Meselson-Stahl experiments, and there will be lengthy deliberations to establish the significance of the results.…”

Authentication, scale-relativity, and relational kindhood

“…To be precise, the historical details show that the July 2012 discovery was a discovery of a "Higgs-like particle" and neither the CMS nor the ATLAS discovery papers claimed to have definitely discovered the Higgs Boson, but only to have discovered a new boson (see Franklin 2017). 15 In an analysis of the discovery, Dawid (2015) pointed out the ongoing authentication of the Higgs Boson 16 and recently Mättig and Stöltzner (2019) showed that "[w]ith the growing evidence that the newly discovered particle has properties consistent with the SM expectations, most physicists accepted it to be a Higgs, and at least tentatively, a SM Higgs" (p. 93). Besides its relatively complex authentication, what the case of the Higgs Boson illustrates is that discovery does not equal authentication.…”

“…It is not the case that the precise properties of the SM Higgs Boson were known before its authentication or the perspectival development stage. Rather, as Mättig and Stöltzner (2019) point out, in 2011, "physicists were rather undecided whether the SM Higgs Boson would eventually be found" (p. 74) and expected that "finding a particle consistent with the SM Higgs would only be the first step in further investigating the properties of the new particle" (p. 80). Even after the discovery of a 'Higgs-like' particle was announced in 2012, physicists would not even claim that it was definitely the SM Higgs Boson, much less that they knew the nature of the discovered particle.…”

“…Various alternative perspectives to the SM Higgs Boson were still advocated for as late as 2012. For example, perspectives in which the Higgs was seen as a composite particle were still supported by a remarkable number of theorists even post discovery (see Mättig and Stöltzner 2019). What can be suggested is that the discovery precipitated increasing perspectival development on the nature of the discovered Higgs-like particle which led to "growing evidence that the newly discovered particle has properties consistent with the SM expectations" (Mättig and Stöltzner 2019, p. 93) which convinced physicists that it can be accepted "at least tentatively, [as] a SM Higgs boson" (id.).…”

The aesthetics of scientific experiments

“…Many discoveries span over a few years before the community reaches a consensus to consider the experiment ended. Looking at the discovery of the Higgs boson, Mättig and Stöltzner (2019) also emphasise the laborious process and timespan of deliberations when deciding 6 of 9 -IVANOVA whether the data collection at the LHC indicated an event, and whether the event constituted a discovery. Peter Galison's illuminating work on the discovery of positrons, for instance, further illustrates that not only settling the date of the discovery is not straightforward, the discovery can be credited to a number of experimental groups.…”