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arXiv · 2604.23473

Possible Evidence for Neutral Color-Singlet $q\bar q$ Quark Matter from High-Energy Pb-Emulsion Collisions

Cheuk-Yin Wong
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Abstract

The invariant mass spectrum of $e^+e^-$ pairs produced in high-energy Pb-emulsion collisions at 160 A GeV at CERN SPS exhibits a highly complex structure of a broad enhancement at 11$\pm$1 MeV with a full width of about 10 MeV, and additional many narrow resonances within the experimental bin width of 2 MeV, including a prominent narrow resonance at 19 $\pm$1 MeV that provides an independent support for the hypothetical X17 particle. We show that the highly complex spectrum may be coherently described as the signatures for the neutral color-singlet $q\bar q$ quark matter in both its deconfined phase as well as its confined phase. That is, the broad enhancement at 11$\pm$1 MeV may arise from thermal annihilation of QED(U(1))-deconfined quarks and antiquarks into $e^+e^-$ pairs at the phase transition temperature $T_c$(QED), which can be theoretically estimated to be 4.75 $\pm$ 1.04 MeV from the transitional equilibrium condition. The observed narrow resonances at 3$\pm$1 and 7$\pm$1 MeV may correspond to the QED(U(1))-deconfined $u\bar u$ and $d\bar d$ Coulomb bound states near their quark rest masses, respectively, whereas the observed narrow resonance at 19 $\pm$ 1 MeV may correspond to the QED(U(1))-confined isoscalar QED meson. The approximate agreement between the theoretical and the experimental spectrum suggests tentatively that both QED(U(1))-confined and QED(U(1))-deconfined neutral color-singlet $q\bar q$ quark matter may have been produced in these high-energy Pb-emulsion collision, pending confirmation of the Pb-emulsion collision data. We propose future experiments to confirm or refute these findings.

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Cheuk-Yin Wong. 2026-04-25. Possible Evidence for Neutral Color-Singlet $q\bar q$ Quark Matter from High-Energy Pb-Emulsion Collisions. https://arxiv.org/abs/2604.23473

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