Observation of the decay η → π0γγ

Binon, Freddy; Bricman, C.; Davydov, Vasily V.A.; Donskov, S.V.; Dufournaud, J.; Duteil, P.; Gouanère, M.; Inyakin, Alexandre A.V.; Kachanov, Vasilij V.A.; Kakauridze, D.B.; Khaustov, G.V.; Kulik, Alexei A.V.; Lagnaux, Jean-Pierre; Lednev, A.A.; Mikhailov, Yu.V.; Peigneux, Jean Pierre; Prokoshkin, Yu Y.D.; Rodnov, Yu Y.V.; Sadovsky, Sergey S.A.; Singovsky, Alexandre A.V.; Starzev, A.V.; Stroot, Jean-Pierre; Sugonyaev, V.P.

doi:10.1007/bf02770988

Cited by 31 publications

(13 citation statements)

References 11 publications

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“…Analysis of scalar/isoscalar states in the mass region below 1900 MeV was performed in the framework of the K-matrix approach in ref. [2] basing on the following data set: GAMS data for π − p → π 0 π 0 n [20], ηηn [21], ηη ′ n [22]; CERN-Münich data for π − p → π + π − n [23]; Crystal Barrel data for pp → π 0 π 0 π 0 , π 0 π 0 η, π 0 ηη [24,25]; BNL data for ππ → KK [26]. The K-matrix elements were used in the form similar to eq.…”

Section: Results Of K-matrix Fit Of 00 ++ Amplitudementioning

confidence: 99%

Scalar Glueball: Analysis of the (IJ PC = 00++)-wave

Anisovich

Sarantsev

1997

Z Phys A - Particles and Fields

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Basing on the previously performed K−matrix analysis of experimental data, we investigate, in the framework of the propagator matrix (D-matrix) technique, the 1100-1900 MeV mass region, where overlapping resonances f 0 (1300), f 0 (1500), f 0 1530 ± 90 250 , and f 0 (1780) are located. Neccessary elements of the D-matrix technique are developed. The D-matrix analysis confirms previous K-matrix results: in the region 900-1900 MeV five scalar/isoscalar states are located. Four of them are members of the two qq-nonets, while one state is an extra for the qq systematics, being a good candidate for the lightest scalar glueball. The D-matrix analysis shows that this extra state, a candidate for the lightest scalar glueball, is dispersed, due to a mixing with qq-states, over three resonances: f 0 (1300), f 0 (1500), and f 0 1530 ± 90 250 . The broad resonance f 0 1530 ± 90 250 is a descendant of the lightest glueball carrying about 50% of the gluonium component, the rest of the gluonium is shared between f 0 (1300) and f 0 (1500).

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Section: Results Of K-matrix Fit Of 00 ++ Amplitudementioning

confidence: 99%

Scalar Glueball: Analysis of the (IJ PC = 00++)-wave

Anisovich

Sarantsev

1997

Z Phys A - Particles and Fields

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“…At the next stage of the 00 ++ wave analysis, the GAMS data on the spectra π 0 π 0 , ηη and ηη ′ have been included; these were obtained in the reactions [24,25,26]:…”

mentioning

confidence: 99%

The lightest scalar glueball

Anisovich¹

1998

Usp. Fiz. Nauk

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Recently performed investigations of meson spectra allow us to determine the resonance structure for the waves IJ P C = 00 ++ , 10 ++ , 02 ++ , 12 ++ = IJ P = 1 2 0 + in the mass region up to 1900 MeV, thus establishing the meson multiplets 1 3 P0qq and 2 3 P0qq. Experimental data demonstrate that there are five scalar/isoscalar states in this mass region. Four of them are qq states, that is, members of the 1 3 P0qq and 2 3 P0qq nonets, while the fifth state is an extra one not accomodated by qq systematics; it has the properties of the lightest scalar glueball. Analysis of the 00 ++ -wave performed within the framework of the dispersion relation technique allows us to reconstruct the mixing of a pure gluonium with neighbouring scalar qq states belonging to 1 3 P0qq and 2 3 P0qq nonets: three scalar mesons share the gluonium state between each other -those are two comparatively narrow resonances f0(1300) and f0(1500) and a broad resonance f0(1530 +90 −250 ). The broad state is a descendant of the gluonium, keeping about 40-50% of its component.1 Introduction: retrospective view and the current state of the problem A great variety of the currently observed mesons and baryons represent systems built of quarks. These are baryons, which are three-quark systems (qqq), and mesons, which are quark-antiquark bound states (qq). More than 20 years ago the problem arose [1] whether additional hadrons exist which are built out of another fundamental QCD particle, the gluon. An intensive search for the glueball -a particle consisting of gluons -was carried out throughout these decades. First evaluation of the glueball masses for different J P C was done in the bag model [2]. According to it, the lightest glueballs are scalars and tensors, 0 ++ and 2 ++ ; then follow pseudoscalar and pseudotensor glueballs, 0 −+ and 2 −+ .Recently considerable progress has been achieved in Lattice QCD calculations. The UKQCD collaboration [3] obtained the following mass values for the lightest gluodynamical glueballs (i.e. the glueball without quark degrees of freedom taken into account):Systematic errors are not included into the values given in Eq. (1.1); they are of the order of 100 MeV.The IBM group obtained a slightly different value for the mass of the lightest scalar glueball [4]:m G (0 ++ ) = 1740 ± 71 MeV , (1.2)The result of Ref.[5] is as follows:m G (0 ++ ) = 1630 ± 60 ± 80 MeV , m G (2 ++ ) = 2400 ± 10 ± 120 MeV .(1.3)

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“…To resolve these alternatives, the spectra in KK, ηη and ηη ′ channels need to be investigated in the region 1550-1900 MeV: the existence of a strange component in these mesons favours a search for the ss-rich states. The ηη and ηη ′ spectra obtained by the GAMS collaboration [2,3] give a good opportunity for this study. The aim here is to extend the analysis of the 00 ++ -wave to a mass of 1900 MeV, including the ηη and ηη ′ GAMS spectra into the simultaneous fitting procedure.…”

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confidence: 99%

Nonet classification of scalar/isoscalar resonances below 1900 MeV: the existence of an extra scalar state in the region 1200–1600 MeV

1996

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A classification of the IJ P C = 00 ++ mesons is performed on the basis of the Kmatrix analysis of meson spectra in the reactions: (i) GAMS data on πp → π 0 π 0 n, ηηn, ηη ′ n [1, 2, 3]; (ii) Crystal Barrel data on pp (at rest) → π 0 π 0 π 0 , π 0 π 0 η, π 0 ηη [4,5]; (iii) CERN-Münich data on πp → π + π − n [6]; (iiii) BNL data on πN → KKN [7]. The analysis points to the existence of four comparatively narrow scalar resonances which correspond to the following poles of the scattering amplitude (in MeV): (1015 ± 15) − i(43 ± 8), (1300 ± 20) − i(120 ± 20), (1499 ± 8) − i(65 ± 10) and (1780±30)−i(125±70). The scattering amplitude also has a fifth pole f 0 (1530 +90 −250 ) at the complex mass (1530 +90 −250 ) − i(560 ± 140). The masses of the K-matrix poles (bare states) are at 720 ± 100 MeV, 1230 ± 50 MeV, 1260 ± 30 MeV, 1600 ± 50 MeV and 1810 ± 30 MeV. The quark content of the bare states is analyzed using the values of their couplings to the ππ, KK, ηη and ηη ′ . It is shown that one of the bare states in the mass region 1200-1600 MeV is superfluous for the qq classification and should be considered as the lightest glueball. The search for and classification of scalar/isoscalar IJ P C = 00 ++ states is the direct and possibly the only way for identification of the lightest scalar glueball. In refs. [8,9] the K-matrix analysis of the 00 ++ -wave was performed in the mass region up to 1550 MeV, where four scalar resonances (the T-matrix poles at the complex masses: (1008 ± 10) −i(43 ±5), (1290 ±25) −i(120 ±15), (1497 ±6) −i(61 ±5), (1430 ±150) −i(600 ±100), in MeV) were found. Correspondingly, four bare states were determined: the lightest bare state with mass 750 ± 100 MeV is dominantly ss, while three other states, with masses 1240 ± 30 MeV, 1280 ± 30 MeV and 1615 ± 50 MeV, do not contain a large ss component. One of these states, either the state with mass 1240 MeV or the state with mass 1280 MeV, is a natural qq-partner of the lightest bare state. For the other two states two scenarios arose in ref.[9]:(a) both these states are qq mesons; then, in the region 1550-1900 MeV, two ss-rich states exist as the nonet partners of the low-lying 00 ++ -mesons;(b) in the region 1550-1900 MeV there is only one ss-rich 00 ++ state; then one of the low-lying states is exotic, probably the lightest glueball.To resolve these alternatives, the spectra in KK, ηη and ηη ′ channels need to be investigated in the region 1550-1900 MeV: the existence of a strange component in these mesons favours a search for the ss-rich states. The ηη and ηη ′ spectra obtained by the GAMS collaboration [2,3] give a good opportunity for this study. The aim here is to extend the analysis of the 00 ++ -wave to a mass of 1900 MeV, including the ηη and ηη ′ GAMS spectra into the simultaneous fitting procedure. The main purpose is to identify the ss-rich states: the analysis of the π 0 π 0 and π + π − spectra from refs. [9,10] definitely indicates that in the region 1550-1900 MeV there are no 00 ++ resonances with a significant ππ branching ratio...

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Observation of the decay η → π0γγ

Cited by 31 publications

References 11 publications

Scalar Glueball: Analysis of the (IJ PC = 00++)-wave

Scalar Glueball: Analysis of the (IJ PC = 00++)-wave

The lightest scalar glueball

Nonet classification of scalar/isoscalar resonances below 1900 MeV: the existence of an extra scalar state in the region 1200–1600 MeV

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