Two Shades of Quark Color: Parallel Canons across the Cold War Divide

TL;DR

This paper explores two distinct conceptualizations of quark color during the Cold War, contrasting the gauge charge perspective with the structural label approach, and examines how historical narratives favored the former.

Contribution

It uncovers the parallel development of color as a gauge charge and as a structural label, highlighting epistemic and political influences on their historical prominence.

Findings

The Dubna approach emphasized observable amplitudes and global constraints.

The QCD approach focused on micro-dynamics and gauge theory.

Historical dominance of QCD marginalized alternative color concepts.

Abstract

The introduction of the color quantum number is conventionally narrated as a linear progression from the quark-model statistics paradox to quantum chromodynamics (QCD). This paper challenges that teleology by arguing that "color" emerged as two conceptually distinct constructs during the Cold War. The first, originating with Han and Nambu and culminating in QCD, conceived of color as a local gauge charge, the source of a fundamental force mediated by gluons. The second, developed at the Joint Institute for Nuclear Research (JINR) in Dubna, treated color as a hidden, three-valued label--a statistical and structural property within a composite, S-matrix-inflected hadron model. We trace these parallel narratives, linking the Dubna approach to a holist epistemology that prioritizes observable amplitudes and global constraints, and the QCD approach to a reductionist program grounded in micro-dynamics. A case study of Fermilab's E-36 experimental chain (1970--78) shows how an observables-first design-tuned to S-matrix and Regge constraints on forward elastic scattering--performed robustly within its natural domain but was ultimately discontinued amid declining theoretical interest and involvement. The subsequent hegemony of QCD retroactively projected its gauge-theoretic conception of color onto history, erasing this epistemic diversity. We conclude that the marginalization of Dubna's structural color was not merely a political outcome of the Cold War but a result of deep ontological and philosophical divergences, advocating for a domain-sensitive pluralism in the historiography of particle physics.