Physicists Spot Rare Particle Decay, Filling Gap in Standard Model
Researchers using China's BESIII detector have observed a previously undetected decay pattern in exotic particles, confirming theoretical predictions about how matter behaves at extreme energies. The finding helps validate the Standard Model of particle physics and could inform future research into fundamental forces underlying all matter.
Originaltitel: Observation of η<em><sub>c</sub></em> (2<em>S</em>) â <em>K</em><sup>+</sup><em>K</em><sup>-</sup> η
<p>By analyzing (27.12 +/- 0.14) x 10(8) psi(3686) events accumulated with the BESIII detector, the decay eta(c)(2S) -> K+K-eta is observed for the first time with a significance of 6.2 sigma after considering systematic uncertainties. The product of the branching fractions of psi(3686) -> gamma eta(c)(2S) and eta(c)(2S) -> K+K-eta is measured to be B(psi(3686) -> gamma eta(c)(2S)) x B(eta(c)(2S) -> K+K-eta) = (2.39 +/- 0.32 +/- 0.34) x 10(-6), where the first uncertainty is statistical, and the second one is systematic. The branching fraction of eta(c)(2S) -> K+K-eta is determined to be B(eta(c)(2S) -> K+K-eta) = (3.42 +/- 0.46 +/- 0.48 +/- 2.44) x 10(-3), where the third uncertainty is due to the branching fraction of psi(3686) -> gamma eta(c)(2S). Using a recent BESIII measurement of B(eta(c)(2S) -> K+K-pi(0)+, we also determine the ratio between the branching fractions of eta(c)(2S) -> K+K-eta and eta(c)(2S) -> K+K- pi(0)to be 1.49 +/- 0.22 +/- 0.25, which is consistent with the previous result of BABAR at a comparable precision level.</p>