Observation of η′ and φ meson production very close to threshold in the reaction

It has been realized for a long time that knowing the η and η ′ wave functions in terms of quark and gluon components probes our understanding of nonperturbative QCD dynamics. Great effort has been given to this challenge, yet no clear picture has emerged even with the most recent KLOE data. We point out which measurements would be most helpful in arriving at a more definite conclusion. A better knowledge of these wave functions will significantly help to disentangle the weight of different decay subprocesses in semileptonic decays of D + , D + s and B + mesons. The resulting insights will be instrumental in treating even nonleptonic B transitions involving η and η ′ and their CP asymmetries; thus they can sharpen the case for or against new physics intervening there.

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“…Direct measurements from 1979 [59] and 1996 [60] on the other hand yield the average Γ η ′ = (0.30 ± 0.09) MeV, which would lead to φ P = (42.7…”

Section: On Improving the Constraints Of The η − η ′ Wave Functionsmentioning

confidence: 99%

η−η′mixing: From electromagnetic transitions to weak decays of charm and beauty hadrons

2012

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“…As a consequence the signal/background ratio is likely to be very unfavourable and a value of ≈ 1/40 was found experimentally at COSY-WASA at Q ≈ 64 MeV [233], and this makes it doubtful as a source of η for decay studies. The preliminary total cross section estimate of ≈ 0.6 nb/sr corresponds to |f (pd → 3 He η )| 2 ≈ 0.2 nb/sr, which is lower than the threshold value of 0.9 ± 0.2 nb/sr [257].…”

Section: Near-threshold Datamentioning

confidence: 59%

“…34, the near-threshold data show no sign of any significant η -proton interaction and any model dependence here is very limited. Furthermore, the production of η in the pd → 3 He η reaction near threshold is about three orders of magnitude weaker than for the η [257]. As a consequence, searches for η -mesic nuclei might be even less fruitful than those for the η.…”

Section: Possible η Nucleimentioning

confidence: 98%

“…In contrast to the extensive data set available for η production, the only published value of the pd → 3 He η cross section was obtained within the context of the threshold study of heavy meson production [257]. It is important to note here the relative weakness of η production, with the ratio of the squares of the threshold amplitudes being a mere |f (pd → 3 He η )| 2 /|f (pd → 3 He η)| 2 ≈ 5 × 10 −4 [257].…”

Section: Near-threshold Datamentioning

confidence: 99%

“…It is important to note here the relative weakness of η production, with the ratio of the squares of the threshold amplitudes being a mere |f (pd → 3 He η )| 2 /|f (pd → 3 He η)| 2 ≈ 5 × 10 −4 [257]. In a two-step model, η production certainly seems to be anomalously weak in this channel compared Figure 40: Angular asymmetry parameter α of the dp → 3 He η reaction defined in Eq.…”

Section: Near-threshold Datamentioning

confidence: 99%

See 2 more Smart Citations

Production of η and η′ mesons on nucleons and nuclei

Krusche¹,

Wilkin²

2015

Progress in Particle and Nuclear Physics

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The production of η and η mesons in photon-and hadron-induced reactions on free and quasifree nucleons and on nuclei is reviewed. The extensive database on γN → ηN , for both proton and neutron targets, is described in detail and its implications for the search for N resonances much heavier than the dominant S 11 (1535) discussed. Though less is currently known about the production of the η or of ηπ pairs, these also offer tantalizing prospects in the search for the missing isobars. The more limited data available on pion-induced production are still necessary ingredients in the partial wave analysis discussed.The production of the η-meson in pp and pn collisions shows once again the strong influence of the S 11 (1535) isobar, which is in contrast to the relatively weak behaviour seen near threshold for η production. This difference is reflected in the important final state interaction effects of the η in nuclei that may even lead to this meson being "bound" in some systems. The evidence for this is reviewed for both γA and pA collisions. The inclusive photoproduction of η, η , and ηπ pairs from nuclei provides further information regarding the production mechanism and the interaction of the η and η with nuclei and the ηπ pairs may even allow access to low mass ηA systems that are forbidden in direct single-meson photoproduction.

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Near threshold production of the pseudoscalar mesons at the COSY-11 facility

et al. 2008

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We summarise measurements of the COSY-11 collaboration concerning the excitation functions of the near threshold pseudoscalar meson production in the proton-proton interaction. The results are discussed in the context of the meson-nucleon and hyperon-nucleon interactions. We conclude that the η-proton interaction is significantly stronger than the η ′ -proton interaction. Similarly, we found that the hyperon Λ interacts with the nucleon considerably stronger than the hyperon Σ, and that the interaction of K − -proton is much stronger than this of the K + -proton.

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Observation of η′ and φ meson production very close to threshold in the reaction

Cited by 23 publications

References 23 publications

η−η′mixing: From electromagnetic transitions to weak decays of charm and beauty hadrons

η−η′mixing: From electromagnetic transitions to weak decays of charm and beauty hadrons

Production of η and η′ mesons on nucleons and nuclei

Near threshold production of the pseudoscalar mesons at the COSY-11 facility

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