Are you one of the authors of this paper? Email us from your institutional or work email address mentioning this article's arXiv ID and we'll verify you and give you edit access to this page.
Are you an author who sees something we missed or got wrong? Write to us — the subject line already carries the paper id. We read every note and correct the write-up.
At a Chinese collider, scientists have for the first time observed a short-lived particle transforming into a pair of xi hyperons.
📄 Showing the "Simple" version — "Advanced" is not ready yet. Add it to favorites to help prioritize it.
In the BEPCII accelerator, electrons and positrons collide, producing billions of particles. Among them is the J/ψ meson, which lives for less than a billionth of a second. Its decay sometimes yields an eta meson (ηc), an even shorter-lived clump of quarks. For the first time, researchers have observed this eta meson transforming into a pair of xi hyperons — particles that contain a strange quark.
Xi hyperons are like rare butterflies in the particle world: they live billions of times longer than typical resonances, yet still vanish within billionths of a second.
Measuring the probability of such a decay is delicate work. One must separate the desired signal from background and account for interference (wave superposition) from direct xi hyperon production. Two values were obtained depending on the type of interference: 0.133% and 0.163%. This helps refine how strongly quarks interact inside hadrons.
The eta meson consists of a charmed quark and its antiquark, like a pair of twins swirling in a dance that lasts only an instant.
The BESIII detector has accumulated 10 billion J/ψ events. This is like sifting through sand on a beach to find a few golden grains — rare decays.
Using $$(10087\pm 44)\times 10^6$$ $$J/\psi$$ events collected with the BESIII detector at the BEPCII collider, we report the first observation of the decay $$\eta_{c} \to \Xi^{0} \bar{\Xi}^{0}$$. The interference between $$J/\psi\to\gamma\eta_c\to\gamma\Xi^0\bar{\Xi}^0$$ and $$J/\psi\to\gamma\Xi^0\bar{\Xi}^0|_{\rm non-resonance}$$ is considered in the $$\Xi^0 \bar{\Xi}^0$$ mass spectrum fits. The branching fractions are measured to be $$B(\eta_c \to \Xi^0 \bar{\Xi}^0)=(1.33 \pm 0.03 \pm 0.18) \times 10^{-3}$$ for the constructive interference and $$B(\eta_c \to \Xi^0 \bar{\Xi}^0)=(1.63 \pm 0.04 \pm 0.21) \times 10^{-3}$$ for the destructive interference, where the first uncertainties are statistical and the second are systematic.
Xi hyperons contain a strange quark, which is lighter than the charmed quark but heavier than the up and down quarks. It is this 'strangeness' that makes their behavior unusual and valuable for study.
In Liu Cixin's novel 'The Three-Body Problem,' experiments at particle accelerators are mentioned where physicists search for new particles — similar research is conducted at BESIII.