A model-independent partial-wave analysis of the π+π− system produced at low four-momentum transfer in the reaction π−p ↑ → π+π−n at 17.2 GeV/c

Becker, H.; Blanar, G.; Blum, W.; Cerrada, M.; Dietl, H.; Gallivan, J.; Gottschalk, B.; Grayer, G.; Hentschel, G.; Lorenz, E.; Lütjens, G.; Lütz, G.; Männer, W.; Notz, D.; Richter, R.; Stierlin, U.; Stringfellow, B.; Chabaud, V.; Hyams, B.; Papadopoulou, Th. D.; Groot, Joanna de; Görlich, L.; Niczyporuk, B. B.; Rybicki, K.; Zalewska, A.

doi:10.1016/0550-3213(79)90426-7

“…Furthermore, it is observed that the two poles contribute a mild total phase shift of about 180 • . Their contributions to the smooth rise of the phase shift is consistent with the one measured in the π p experiments [5][6][7].…”

Section: Introductionsupporting

confidence: 86%

“…The lowest scalar meson predicted in the potential models is located at above 1.0 GeV [2]. However, the I = 0 ππ scattering phase shift rises smoothly and passes 90 • at a e-mail: zhouzhy@seu.edu.cn b e-mail: xiaozg@ustc.edu.cn (corresponding author) about 850 MeV [5][6][7], so it was believed that there exists a broad structure contributing to the phase shift in the energy region from the ππ threshold to above 1.0 GeV [8]. Many phenomenological studies have been devoted to proving the existence of this structure which is dubbed f 0 (500) now in the particle data group (PDG) table [9], and its pole position, is confirmed and determined by model-independent methods such as in Refs.…”

Section: Introductionmentioning

confidence: 99%

Relativistic Friedrichs–Lee model and quark-pair creation model

Zhou

¹

,

Xiao

²

2020

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In this paper, we present how the Friedrichs–Lee model could be extended to the relativistic scenario and be combined with the relativistic quark pair creation model in a consistent way. This scheme could be applied to study the “unquenched” effect of the meson spectra. As an example, if the lowest $$J^{PC}=0^{++}$$ J PC = 0 + + $$(u\bar{u}+d\bar{d})/\sqrt{2}$$ ( u u ¯ + d d ¯ ) / 2 bound state in the potential model is coupled to the $$\pi \pi $$ π π continuum, two resonance poles could be found from the scattering amplitude for the continuum states. One of them could correspond to the $$f_0(500)/\sigma $$ f 0 ( 500 ) / σ and the other probably $$f_0(1370)$$ f 0 ( 1370 ) . This scheme might shed more light on why extra states could appear in the hadron spectrum other than the prediction of the quark potential model.

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“…The results of the CERN-Munich collaboration are published in [208][209][210][211][212][213][214][215]. For later data, a polarised target was used (CERN-Munich-Krakow collaboration) [216,217].…”

Section: The Cern-munich Experimentsmentioning

confidence: 99%

“…More generally speaking, it was assumed that the phase does not depend on the projection of the orbital angular momentum onto the flight direction with which it is produced (phase coherence) and that the ratio of flip and non-flip amplitudes is universal ('spin coherence'). Later, the experiment (performed by a CERN-Krakow-Munich collaboration) included a polarised target [216], and the assumptions on spin and phase coherence were verified to a good approximation in a model-independent analysis. For large t, neither phase nor spin coherence is granted, and feedthrough of higher partial waves into the scalar wave cannot be excluded without exploiting a polarised target.…”

Section: Scatteringmentioning

confidence: 99%

Glueballs, hybrids, multiquarks

Klempt

¹

,

Zaǐtsev

²

2007

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Glueballs, hybrids and multiquark states are predicted as bound states in models guided by quantum chromo dynamics (QCD), by QCD sum rules or QCD on a lattice. Estimates for the (scalar) glueball ground state are in the mass range from 1000 to 1800 MeV, followed by a tensor and a pseudoscalar glueball at higher mass. Experiments have reported evidence for an abundance of meson resonances with 0 −+ , 0 ++ and 2 ++ quantum numbers. In particular, the sector of scalar mesons is full of surprises starting from the elusive and mesons. The a 0 (980) and f 0 (980), discussed extensively in the literature, are reviewed with emphasis on their Janus-like appearance as KK molecules, tetraquark states or qq mesons. Most exciting is the possibility that the three mesons f 0 (1370), f 0 (1500), and f 0 (1710) might reflect the appearance of a scalar glueball in the world of quarkonia. However, the existence of f 0 (1370) is not beyond doubt and there is evidence that both f 0 (1500) and f 0 (1710) are flavour octet states, possibly in a tetraquark composition. We suggest a scheme in which the scalar glueball is dissolved into the wide background into which all scalar flavour-singlet mesons collapse.There is an abundance of meson resonances with the quantum numbers of the . Three states are reported below 1.5 GeV/c 2 whereas quark models expect only one, perhaps two. One of these states, (1440), was the prime glueball candidate for a long time. We show that (1440) is the first radial excitation of the meson.Hybrids may have exotic quantum numbers which are not accessible by qq mesons. There are several claims for J P C = 1 −+ exotics, some of them with properties as predicted from the flux tube model interpreting the quark-antiquark binding by a gluon string. The evidence for these states depends partly on the assumption that meson-meson interactions are dominated by s-channel resonances. Hybrids with non-exotic quantum numbers should appear as additional states. Light-quark mesons exhibit a spectrum of (squared) masses which are proportional to the sum of orbital angular momentum and radial quantum numbers. Two states do not fall under this classification. They are discussed as hybrid candidates.The concept of multiquark states has received revived interest due to new resonances in the spectrum of states with open and hidden charm. The new states are surprisingly narrow and their masses and their decay modes often do not agree with simple quark-model expectations.Lattice gauge theories have made strong claims that glueballs and hybrids should appear in the meson spectrum. However, the existence of a scalar glueball, at least with a reasonable width, is highly questionable. It is possible that hybrids will turn up in complex multibody final states even though so far, no convincing case has been made for them by experimental data. Lattice gauge theories fail to identify the nonet of scalar mesons. Thus, at the present status of approximations, lattice gauge theories seem not to provide a trustworthy guide into unknown territory ...

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“…For s and p waves, ðL ab ; I ab Þ ¼ ð0; 0Þ; ð1; 1Þ, the high-quality fits are obtained only when two bare R states are included. It is noted that a partial-wave analysis using more recent data [56] has found a unique solution for W $ 1000-1800 MeV. Although our present model is reasonable enough to address the question on the importance of the Z graphs, those data should be considered for a more quantitative application of our model.…”

Section: A Determinations Of Model Parameters 1 Fits To Amplitudesmentioning

confidence: 78%

Unitary coupled-channels model for three-mesons decays of heavy mesons

Kamano

¹

,

Nakamura

²

,

Lee

³

et al. 2011

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A unitary coupled-channels model is presented for investigating the decays of heavy mesons and excited meson states into three light pseudoscalar mesons. The model accounts for the three-mesons final state interactions in the decay processes, as required by both the three-body and two-body unitarity conditions. In the absence of the Z-diagram mechanisms that are necessary consequences of the three-body unitarity, our decay amplitudes are reduced to a form similar to those used in the so-called isobar-model analysis. We apply our coupled-channels model to the three-pions decays of a1(1260), pi2(1670), pi2(2100), and D0 mesons, and show that the Z-diagram mechanisms can contribute to the calculated Dalitz plot distributions by as much as 30% in magnitudes in the regions where f0(600), rho(770), and f2(1270) dominate the distributions. Also, by fitting to the same Dalitz plot distributions, we demonstrate that the decay amplitudes obtained with the unitary model and the isobar model can be rather different, particularly in the phase that plays a crucial role in extracting the CKM CP-violating phase from the data of B meson decays. Our results indicate that the commonly used isobar model analysis must be extended to account for the final state interactions required by the three-body unitarity to reanalyze the three-mesons decays of heavy mesons, thereby exploring hybrid or exotic mesons, and signatures of physics beyond the standard model.Comment: 32 pages, 10 figures. Version to appear in PR

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A model-independent partial-wave analysis of the π+π− system produced at low four-momentum transfer in the reaction π−p ↑ → π+π−n at 17.2 GeV/c

Cited by 98 publications

References 14 publications

Relativistic Friedrichs–Lee model and quark-pair creation model

Relativistic Friedrichs–Lee model and quark-pair creation model

Glueballs, hybrids, multiquarks

Unitary coupled-channels model for three-mesons decays of heavy mesons

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