Reviews of topical problems

Strong isospin symmetry breaking in light scalar meson production

S.L. Sobolev Institute for Mathematics, Siberian Branch of the Russian Academy of Sciences, prosp. akad. Koptyuga 4, Novosibirsk, 630090, Russian Federation

Isospin symmetry breaking is discussed as a tool for studying the nature and production mechanisms of light scalar mesons. We are concerned with isospin breaking effects with amplitude $\sim\sqrt{m_{\rm d}-m_{\rm u}}$ (instead of the usual $\sim (m_{\rm d}-m_{\rm u})$), where $m_{\rm u}$ and $m{\rm _d}$ are the u and d quark masses, respectively, whose magnitude and phase vary with energy in a resonance-like way characteristic of the ${\rm K}\bar {\rm K}$ threshold region. The review considers a variety of reactions that can reveal (or have revealed) experimentally the mixing of ${\rm a}^0_0(980)$- and ${\rm f}_0(980)$ resonances that breaks the isotopic invariance due to the mass difference of the ${\rm K}^+$ and ${\rm K}^0$ mesons. The experimental results on the search for the ${\rm a}^0_0(980)-{\rm f}_0(980)$ mixing in the ${\rm f}_1(1285)\to {\rm f}_0(980)\pi^0\to\pi^+\pi^-\pi^0$ и $\eta(1405)\to {\rm f}_0(980)\pi^0\to\pi^+\pi^-\pi^0$ decays have suggested a broader perspective on the isotopic symmetry breaking effects due to the ${\rm K}^+{\rm K}^0$ mass difference. It has become clear that not only the ${\rm }a^0_0(980)-{\rm f}_0(980)$ mixing but also any mechanism producing ${\rm K}\bar {\rm K}$ pairs with a definite isospin in the 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 violation in the $\eta(1405) \to {\rm f}_0(980)\pi^0 \to \pi^+\pi^-\pi^0$ decay due to the occurrence of anomalous Landau thresholds (logarithmic triangle singularities), i.e., due to the $\eta(1405)\to({\rm K}^*\bar {\rm K}+\bar {\rm K}^*{\rm K})\to({\rm K}^+{\rm K}^-+{\rm K}^0\bar {\rm K}^0)\pi^0\to {\rm f}_0(980)\pi^0\to\pi^+\pi^-\pi^0$ transition (where the ${\rm K}^*$ meson should be crucially considered to be of finite width).

Fulltext is available at IOP
Keywords: physics of light scalar mesons, isospin symmetry breaking, resonance mixing, reaction mechanisms, experimental investigations
PACS: 11.30.Ly, 12.38.Qk, 13.30.Eg, 13.75.Lb (all)
DOI: 10.3367/UFNe.2018.01.038281
Citation: Achasov N N, Shestakov G N "Strong isospin symmetry breaking in light scalar meson production" Phys. Usp. 62 3–31 (2019)
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Received: 11th, December 2017, revised: 1st, January 2018, 16th, January 2018

Оригинал: Ачасов Н Н, Шестаков Г Н «Сильное нарушение изотопической симметрии при рождении лёгких скалярных мезонов» УФН 189 3–32 (2019); DOI: 10.3367/UFNr.2018.01.038281

References (197) Cited by (11) Similar articles (20) ↓

  1. N.N. Achasov, G.N. Shestakov “Light scalar mesons in photon—photon collisions54 799–828 (2011)
  2. N.N. Achasov, S.A. Devyanin, G.N. Shestakov “The problem of scalar mesons27 161–180 (1984)
  3. Yu.S. Kalashnikova, A.V. Nefediev “X(3872) in the molecular model62 568–595 (2019)
  4. G.V. Pakhlova, P.N. Pakhlov, S.I. Eidel’man “Exotic charmonium53 219–241 (2010)
  5. A.I. Vainshtein, V.I. Zakharov “Partial conservation of axial current in processes involving ’soft’ mesons13 73–100 (1970)
  6. V.V. Anisovich “Systematics of quark-antiquark states and scalar exotic mesons47 45–67 (2004)
  7. N.N. Achasov, G.N. Shestakov “Summary of the search for four-quark states in γγ collisions34 (6) 471–496 (1991)
  8. Ch. Grojean “New approaches to electroweak symmetry breaking50 1–35 (2007)
  9. I.V. Andreev “Chromodynamics as a theory of the strong interaction29 971–979 (1986)
  10. M.I. Vysotskii “Supersymmetric models of elementary particles—the physics for new-generation accelerators?28 667–693 (1985)
  11. E.O. Okonov “Decay properties of heavy mesons and hyperons2 119–149 (1959)
  12. Ya.A. Smorodinskii “The unitary symmetry of elementary particles7 637–655 (1965)
  13. M.K. Volkov, A.B. Arbuzov “Meson production processes in electron—positron collisions and tau lepton decays within the extended Nambu—Jona-Lasinio model60 643–666 (2017)
  14. A.D. Dolgov “Massive and supermassive black holes in the contemporary and early Universe and problems in cosmology and astrophysics61 115–132 (2018)
  15. V.A. Matveev, V.A. Rubakov et alNonconservation of baryon number under extremal conditions31 916–939 (1988)
  16. A.Yu. Morozov “Anomalies in gauge theories29 993–1039 (1986)
  17. A.G. Polnarev, M.Yu. Khlopov “Cosmology, primordial black holes, and supermassive particles28 213–232 (1985)
  18. Yu.M. Makeenko “The Monte Carlo method in lattice gauge theories27 401–430 (1984)
  19. K.N. Mukhin, O.O. Patarakin “The pion-pion interaction (review of experimental data)24 161–186 (1981)
  20. S.G. Matinyan “Toward the unification of weak, electromagnetic, and strong interactions: SU(5)23 1–20 (1980)

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