Six flavor quark matter

• Published in: The journal of high energy physics 2018-06, Vol.2018 (6), p.1-33, Article 72
• Main Authors: Bai, Yang, Long, Andrew J.
• Format: Article
• Language: English
• Subjects: Classical and Quantum Gravitation; Computer simulation; Confinement; Cosmology of Theories beyond the SM; Dark matter; Elementary Particles; Flavor (particle physics); Flux density; Gravitational lenses; Gravitational waves; Higgs Physics; High energy physics; Phase Diagram of QCD; Phase transitions; Photon emission; Physics; Physics and Astronomy; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Quantum chromodynamics; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quarks; Regular Article - Theoretical Physics; Relativity Theory; Standard model (particle physics); String Theory; Universe
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP06(2018)072

A bstract Macroscopic nuggets of quark matter were proposed several decades ago as a candidate for dark matter. The formation of these objects in the early universe requires the QCD phase transition to be first order — a requirement that is not satisfied in the Standard Model where lattice simulations reveal a continuous crossover instead. In this article we point out that new physics may supercool the electroweak phase transition to below the QCD scale, and the QCD phase transition with six massless quarks becomes first-order. As a result, the quark nuggets composed of six-flavor quark matter (6FQM) may survive as a viable dark matter candidate. The size of a 6FQM nugget is estimated to be around 10 10 grams in mass and 10 −2 cm in radius. The calculated relic abundance of 6FQM nuggets is comparable to the observed dark matter energy density; therefore, this scenario provides a compelling explanation for the coincident energy densities of dark and baryonic matter. We have explored various potential signatures — including a gravitational wave background, gravitational lensing, and transient photon emission from collisions with compact stars and other nuggets — and demonstrated that the favored region of parameter space is still allowed by current constraints while discovery of 6FQM nugget dark matter may require new experimental probes.