Abstract: Isospin symmetry breaking is discussed as a tool for studying the nature and production mech- anisms of light scalar mesons. We are concerned with isospin breaking effects with an amplitude ∼ √md − mu (instead of the usual ∼ md − mu), where mu and md are the u and d quark masses, whose magnitude and phase vary with energy in a resonance-like way characteristic of the K ̄K threshold region. We consider a variety of reactions that can experimentally reveal (or have revealed) the mixing of a0 0(980) and f0(980) resonances that breaks the isotopic invariance due to the mass difference between K+ and K0 mesons. Experimental results on the search for a0 0(980) − f0(980) mixing in f1(1285) → f0(980)π0 → π+π−π0 and η(1405) → f0(980)π0 → π+π−π0 decays suggest a broader perspective on the isotopic symmetry breaking effects due to the K+ and K0 mass difference. It has become clear that not only the a0 0(980) − f0(980) mixing but also any mechanism producing K ̄K pairs with a definite isospin in an S wave gives rise to such effects, thus suggesting a new tool for studying the nature and production mechanisms of light scalars. Of particular interest is the case of a large isotopic symmetry breaking in the η(1405) → f0(980)π0 → π+π−π0 decay due to the occurrence of anomalous Landau thresholds (logarithmic triangle singularities), i.e., due to the η(1405) → (K∗ ̄K + ̄K∗K) → (K+K− + K0 ̄K0)π0 → f0(980)π0 → π+π−π0 transition (where it is of fundamental importance that the K∗ meson has a finite width).

Cite: Achasov N.N. , Shestakov G.N.
Strong isospin symmetry breaking in light scalar meson production
Physics-Uspekhi. 2019. V.62. N1. P.3-31. DOI: 10.3367/ufne.2018.01.038281 WOS Scopus OpenAlex

Identifiers:

Web of science:	WOS:000462478600001
Scopus:	2-s2.0-85065492647
OpenAlex:	W2943933404

Citing:

DB	Citing
Scopus	12
OpenAlex	8
Web of science	13

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