Dilepton Production from Moaton Quasiparticles

The phase diagram of QCD probably exhibits a moat regime over a large region of temperature <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>T</a:mi></a:mrow></a:math> and chemical potential <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi>μ</c:mi><c:mo>≠</c:mo><c:mn>0</c:mn></c:mrow></c:math>. A moat regime is characterized by quasiparticle (pions) whose energy is minimal at nonzero spatial momentum. At <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>μ</e:mi><e:mo>≠</e:mo><e:mn>0</e:mn></e:math>, higher mass dimension operators play a critical role in a moat regime. At dimension six, there are nine possible gauge-invariant couplings between scalars and photons. For back-to-back dilepton production, only one operator contributes, which significantly enhances production near a moat threshold. This enhancement is an experimental signature of moatons.