(AGENPARL) - Roma, 28 Novembre 2023 - (AGENPARL) – mar 28 novembre 2023 MEDIA INFORMATION / INFORMATION PRESSE
ISOLDE.jpg
The ISOLDE set-up used to study the exotic nucleus of aluminium. (Image: CERN)
Exotic atomic nucleus sheds light on the world of quarks
Interestingly, the probability sum involving the up quark is presently in apparent tension with the expected unity, although the strength of the tension depends on the underlying theoretical calculations. This sum includes the respective probabilities of the down quark, the strange quark and the bottom quark transforming into the up quark.
The first of these probabilities manifests itself in the beta decay of an atomic nucleus, in which a neutron (made of one up quark and two down quarks) changes into a proton (composed of two up quarks and one down quark) or vice versa. However, due to the complex structure of the atomic nuclei that undergo beta decays, an exact determination of this probability is generally not feasible. Researchers thus turn to a subset of beta decays that are less sensitive to the effects of nuclear structure to determine the probability. Among the several quantities that are needed to characterise such “superallowed” beta decays is the (charge) radius of the decaying nucleus.
“Charge radii of other nuclei that undergo superallowed beta decays have been measured previously at ISOLDE and other facilities, and efforts are under way to determine the radius of ^54Co at IGISOL,” explains ISOLDE physicist and lead author of the paper, Peter Plattner. “But ^26mAl is a rather unique case as, although it is the most precisely studied of such nuclei, its radius has remained unknown until now, and, as it turns out, it is much larger than assumed in the calculation of the probability of the down quark transforming into the up quark.”
“Searches for new physics beyond the Standard Model, including those based on the probabilities of quarks changing flavour, are often a high-precision game,” says CERN theorist Andreas Juttner. “This result underlines the importance of scrutinising all relevant experimental and theoretical results in every possible way.”
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