Physicists discover new particle interaction, confirm fundamental symmetry principle
Researchers at China's BESIII detector observed a rare particle collision for the first time, validating a core principle of physics that underpins our understanding of matter. The finding strengthens confidence in the Standard Model and could refine how scientists predict particle behavior in future experiments.
Originaltitel: Observation of <em>e</em><sup>+</sup><em>e</em><sup><em>−</em></sup> <em>→ π</em><sup>0</sup><em>π</em><sup>0</sup><em>ψ</em><sub>2</sub>(3823)
<p>Using a data sample corresponding to an integrated luminosity of 11.3 fb<sup><em>−</em>1</sup> collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we observe the process <em>e</em><sup>+</sup><em>e</em><sup><em>−</em></sup> <em>→ π</em><sup>0</sup><em>π</em><sup>0</sup><em>ψ</em><sub>2</sub>(3823) for the first time with a statistical significance of 6<em>.</em>0 standard deviations. The ratio of average cross sections for <em>e</em><sup>+</sup><em>e</em><sup><em>−</em></sup> <em>→ π</em><sup>0</sup><em>π</em><sup>0</sup><em>ψ</em><sub>2</sub>(3823) and <em>π</em><sup>+</sup><em>π</em><sup><em>−</em></sup><em>ψ</em><sub>2</sub>(3823) is determined to be R=σ[e+e− → π0π0ψ2(3823)]/σ[e+e− → π+π−ψ2(3823)] = 0.57±0.14±0.05, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the <em>ψ</em><sub>2</sub>(3823) is measured to be <em>M</em>[<em>ψ</em><sub>2</sub>(3823)] = 3824<em>.</em>5 <em>±</em> 2<em>.</em>4 <em>±</em> 1<em>.</em>0 MeV/<em>c</em><sup>2</sup>. Due to the limited data sample, an upper limit of 18.8 MeV at 90% confidence level is set on the intrinsic width of <em>ψ</em><sub>2</sub>(3823).</p>