Implications of light-quark admixtures on charmonium decays into meson pairs

Feldmann, Thorsten; Kroll, P.

doi:10.1103/physrevd.62.074006

Cited by 51 publications

(43 citation statements)

References 61 publications

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“…Instead of a critical examination of many theoretical arguments (which one can find in the literature [1,[22][23][24]), we will concentrate exclusively on comparing the experimental results, mostly from the BES experiment, to the predictions of these models, in an attempt to differentiate between them.…”

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confidence: 99%

Ratio of hadronic decay rates ofJ/ψandψ(2S)and theρπpuzzle

顾以藩

GGu

2001

Phys. Rev. D

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The so-called ρπ puzzle of J/ψ and ψ(2S) decays is examined using the experimental data available to date. Two different approaches were taken to estimate the ratio of J/ψ and ψ(2S) hadronic decay rates. While one of the estimates could not yield the exact ratio of ψ(2S) to J/ψ inclusive hadronic decay rates, the other, based on a computation of the inclusive ggg decay rate for ψ(2S) (J/ψ) by subtracting other decay rates from the total decay rate, differs by two standard deviations from the naive prediction of perturbative QCD, even though its central value is nearly twice as large as what was naively expected. A comparison between this ratio, upon making corrections for specific exclusive two-body decay modes, and the corresponding experimental data confirms the puzzles in J/ψ and ψ(2S) decays. We find from our analysis that the exclusively reconstructed hadronic decays of the ψ(2S) account for only a small fraction of its total decays, and a ratio exceeding the above estimate should be expected to occur for a considerable number of the remaining decay channels. We also show that the recent new results from the BES experiment provide crucial tests of various theoretical models proposed to explain the puzzle.PACS numbers: 13.25. Gv, 12.38.Qk One of the outstanding problems in heavy quarkonium physics is the strong suppression of the ψ(2S) decays to vector plus pseudoscalar-meson (VP) final states, ρπ and K + K * − + c.c., which is referred to as the ρπ puzzle [1]. Following the first observation of this anomaly [2], meagre experimental progress was made over the years, and theoretical analysis based on limited data often lead to unsatisfactory, sometimes premature, inferences. The situation has been changed dramatically in the last few years. A wealth of interesting new information, which extended the puzzle considerably, has emerged from intense studies of ψ(2S) hadronic decays at the BES experiment, using a large sample of 3.79 million ψ(2S) decays [3]. It is hoped for that new concerted efforts on both the theoretical and experimental side would eventually lead to a solution of this long-standing conundrum.In this paper we seek to examine the ρπ puzzle based purely on existing experimental data. We begin with an analysis for estimating the ratio of hadronic decay rates of J/ψ and ψ(2S), which we shall denote by Q, by using the data compiled by the Particle Data Group [4], in an attempt to avoid as many theoretical ambiguities as possible in the analysis. Two different approaches to this estimate are performed. First we compare the results between themselves, and then the naive prediction of perturbative QCD (PQCD) is used. Subsequently, possible corrections to Q are discussed, as they associate with specific exclusive decay modes, and the corrected values of Q are used as standards to compare with the corresponding experimental data. Comments on the issue of J/ψ and ψ(2S) decays to multi-hadron final states and on the potential similarity of the η c -η c (2S) decays to the ρπ puzzle are profusely added. F...

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confidence: 99%

Ratio of hadronic decay rates ofJ/ψandψ(2S)and theρπpuzzle

顾以藩

GGu

2001

Phys. Rev. D

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“…Experimentally η c → pp is observed to have a branching ratio of order 10 −3 [18]. However, one should be aware that this process also violates the helicity selection rule, and the available pQCD prediction, when taking into account the nonzero light quark mass but still in the collinear quark configuration, is still far smaller than the measured value [53], therefore some nonperturbative mechanism needs to be called for to explain this discrepancy [23]. Because of rather heavy mass of η b , one may hope pQCD framework should provide a reliable prediction for η b → pp.…”

Section: Discussionmentioning

confidence: 99%

“…Among different proposals, a particularly attractive and predictive scheme has been put forward by Feldmann and Kroll (henceforth FK) [23], by generalizing their influential work together with Stech on η − η ′ mixing in quark flavor basis [50], to include η c . FK models the amplitude of η c → V V as the product of a factor governing the small admixture amplitude between η c and η (′) , which presumably can be inferred from QCD U A (1) anomaly, times a soft vertex function parameterizing the amplitude for virtual η, η ′ transiting into V V .…”

Section: Other Decay Channels Of η Bmentioning

confidence: 99%

“…This decay process should be contrasted with the analogous process η c → V V . To account for the unnaturally large measured width of the latter, it is proposed that some nonperturbative mechanisms, e.g., the mixing among pseudo-scalar states η −η ′ −η c , either due to QCD axial anomaly [23], or due to perturbative box diagram [24], together with quark pair creation from vacuum, should play a prominent role. The impact of final state interaction on the doubly-OZI-suppressed process η c → ωφ has also been addressed [35].…”

Section: Color-singlet Model Calculationmentioning

confidence: 99%

“…It is known that perturbative QCD (pQCD) framework has difficulty to account for the large observed widths of the η c → V V decay processes [21,22]. The consensus is that some nonperturbative mechanisms should be invoked to reconcile the discrepancy between the pQCD prediction and the actual measurement [23,24]. On the other hand, due to heavy b and c masses, it is rather reasonable to expect that η b → J/ψJ/ψ can be safely tackled within the pQCD scheme.…”

Section: Introductionmentioning

confidence: 99%

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