Physicists Close the Door on Hidden Particles in Exotic Matter Decay
Researchers using China's BESIII detector searched for previously undetected particles in the decay of rare exotic matter but found none. The null result refines the limits on where to look for new physics and validates existing theoretical models—findings that help focus billion-dollar particle physics investments worldwide.
Originaltitel: Measurement of Born cross sections of e<sup>+</sup>e<sup>−</sup> → Ξ<sup>0</sup> ¯ Ξ<sup>0</sup> and search for charmonium(-like) states at √s = 3.51–4.95 GeV
<p>Using <em>e</em><sup>+</sup><em>e</em><sup><em>−</em></sup> collision data collected by the BESIII detector at BEPCII corresponding to an integrated luminosity of 30 fb<sup><em>−</em>1</sup>, we measure Born cross sections and effective form factors for the process e<sup>+</sup>e<sup>−</sup> → Ξ<sup>0</sup> ¯ Ξ<sup>0</sup> at forty-five center-of-mass energies between 3.51 and 4.95 GeV. The dressed cross section is fitted, assuming a power-law function plus a charmonium(-like) state, i.e., <em>ψ</em>(3770), <em>ψ</em>(4040), <em>ψ</em>(4160), <em>ψ</em>(4230), <em>ψ</em>(4360), <em>ψ</em>(4415) or <em>ψ</em>(4660). No significant charmonium(-like) state decaying into Ξ<sup>0</sup> ¯ Ξ<sup>0</sup> is observed. Upper limits at the 90% confidence level on the product of the branching fraction and the electronic partial width are provided for each decay. In addition, ratios of the Born cross sections and the effective form factors for e<sup>+</sup>e<sup>−</sup> → Ξ<sup>0</sup> ¯ Ξ<sup>0</sup> and e<sup>+</sup>e<sup>−</sup> → Ξ ¯ Ξ<sup>−+</sup> are also presented to test isospin symmetry and the vector meson dominance model.</p>