A study of the inclusive reaction , the ABC effect, and I = 0 meson resonances

Banaigs, J.; Berger, J.‐P.; Goldzahl, L.; Hai, Liu; Cottereau, M.; Brun, C. Le; Fabbri, F. L.; Picozza, P.

doi:10.1016/0550-3213(76)90060-2

Cited by 61 publications

(60 citation statements)

References 22 publications

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“…3 exhibits a threepeak structure, similar to those reported in ref. [25]. This is a reflection of the well-known ABC effect [26], which leads to kinematic enhancements of the two-pion mass spectrum at both small masses (the outer peaks) and at maximum mass (the central peak) [27].…”

Section: Methodsmentioning

confidence: 99%

Near-threshold η-meson production in the dd↦He η reaction

et al. 2005

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Abstract. The dd → 4 He η reaction has been investigated near threshold using the ANKE facility at COSY-Jülich. Both total and differential cross sections have been measured at two excess energies, Q = 2.6 MeV and 7.7 MeV, with a subthreshold measurement being undertaken at Q = −2.6 MeV to study the physical background. While consistent with isotropy at the lower energy, the angular distribution reveals a pronounced anisotropy at the higher one, indicating the presence of higher partial waves. Options for the decomposition into partial amplitudes and their consequences for determination of the s-wave η-α scattering length are discussed.PACS. 13.60.Le meson production -25.10.+s nuclear reaction involving few-nucleons systems -25.45.-z 2 H induced reactions -11.80.Et partial-wave analysis

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Section: Methodsmentioning

confidence: 99%

Near-threshold η-meson production in the dd↦He η reaction

et al. 2005

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“…Subsequent measurements showed that this enhancement also persists in the fusion reactions to d and 4 He [18][19][20][21][22][23][24][25][26][27][28], if the produced pion pair is of isoscalar nature. Since there was no plausible explanation for this effect, it got named after the initials of the authors of the first publication on that issue.…”

Section: Abc Effectmentioning

confidence: 99%

Examination of the nature of the ABC effect

2017

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Recently it has been shown by exclusive and kinematically complete experiments that the appearance of a narrow resonance structure in double-pionic fusion reactions is strictly correlated with the appearance of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the ππ-invariant mass spectrum. Whereas the resonance structure got its explanation by the d * (2380) dibaryonic resonance, a satisfactory explanation for the ABC effect is still pending. In this paper we discuss possible explanations of the ABC effect and their consequences for the internal structure of the d * dibaryon. To this end we examine and review a variety of proposed explanations for the ABC effect, add a new hypothesis and confront all of them with the experimental results for the np → dπ 0 π 0 and np → npπ 0 π 0 reactions, which are the most challenging ones for this topic.

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“…However, the large conventional cross sections in these channels make it very difficult to search for the resonance there. [29] (square) as well as inclusive measurements at CELSIUS [42] (star), Birmingham [43] (inverted triangle) and Saclay [7] (triangle). The dotted line shows the energy dependence of the conventional t-channel ∆∆ process, arbitrarily scaled in height.…”

Section: Discussionmentioning

confidence: 99%

“…Subsequent bubble-chamber [2,3] and single-arm magnetic spectrometer measurements [4][5][6][7][8][9][10][11] suggested this enhancement to be correlated with the production of an isoscalar pion pair in fusion reactions to light nuclei. Its explanation has been a puzzle since more than 50 years.…”

Section: Introductionmentioning

confidence: 99%

ABC Effect in Double-Pionic Fusion – a New Resonance?

Pricking

Bashkanov

Clement

et al. 2012

EPJ Web of Conferences

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Abstract. The ABC effect, an intriguing low-mass enhancement in the ππ invariant mass spectrum -known since more than 50 years from inclusive measurements of double-pionic fusion reactions -is reexamined. To this end exclusive and kinematically complete high-statistics experiments of the fusion reactions to d, 3 He and 4 He have been carried out with WASA at COSY. These measurements cover the full energy region, where the ABC effect has been observed previously. They also complement the systematic measurements of nucleon-nucleon induced two-pion production. An isospin decomposition of all three basic double-pionic fusion reactions leading to the deuteron uniquely shows that solely the isoscalar reaction part exhibits the ABC effect tightly correlated with a narrow resonance structure in the total cross section. The peak energy of the resonance structure is about 90 MeV below the nominal ∆∆ threshold of 2 m ∆ and its width of only 70 MeV is much less than the 2 Γ ∆ expected from the conventional t-channel ∆∆ process. Based on angular distributions the quantum numbers I(J P ) = 0(3 + ) have been assigned. In the double-pionic fusion reaction dd → 4 Heπ 0 π 0 again the ABC effect is observed to be correlated with the appearance of a resonance-like structure in the total cross section at the same excess energy. From this we conclude that this resonance structure obviously is strong enough to survive even in nuclei.

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A study of the inclusive reaction , the ABC effect, and I = 0 meson resonances

Cited by 61 publications

References 22 publications

Near-threshold η-meson production in the dd↦He η reaction

Near-threshold η-meson production in the dd↦He η reaction

Examination of the nature of the ABC effect

ABC Effect in Double-Pionic Fusion – a New Resonance?

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