Excess of charged over neutral $K$ meson production in high-energy collisions of atomic nuclei

Author:

SHINE Collaboration, H. Adhikary, P. Adrich, K. K. Allison, N. Amin, E. V. Andronov, I. C. Arsene

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex), High Energy Physics - Experiment (hep-ex)

journal:

CERN-EP-2023-283

date:

2023-12-11 00:00:00

Abstract

Collisions of atomic nuclei at relativistic velocities produce new particles, predominantly mesons containing one valence quark and one valence anti-quark. These particles are produced in strong interactions, which preserve an approximate symmetry between up ($u$) and down ($d$) quarks. In the case of $K$ meson production, if this symmetry were exact, it would result in equal numbers of charged ($K^+$ and $K^-$) and neutral ($K^0$ and $\overline{K}$$^0$) mesons in the final state. In this Letter, we report a measurement of the relative abundance of charged over neutral $K$ meson production in collisions of argon and scandium nuclei at a center-of-mass energy of 11.9~GeV per nucleon pair. We find that production of $K^+$ and $K^-$ mesons at mid-rapidity displays a significant excess of $(23.3\pm 5.7)\%$ relative to that of the neutral $K$ mesons. The origin of this unexpected excess remains to be elucidated.

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