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

Abstract

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...

Di-electron and two-photon widths in charmonium

“…For η c (1S), χ c0 , χ c2 the larger effective coupling, α s = 0.195, is needed to fit experimental numbers for two-photon widths. Also close value of α s = 0.187 provides good description of the annihilation widths for the J/ψ → ggg and J/ψ → γgg processes, so that B(J/ψ → light hadrons) = 70% is obtained (its value in experiment is (69 ± 3)% [16], [17]). …”

“…However, to describe experimental branching fraction, B(ψ ′ → light hadrons) = 16.7 ± 3.0% [16], [17], larger α s = 0.238 is needed, for which we obtain Γ(ψ ′ → ggg) = 52.7 keV and Γ(ψ ′ → γgg) = 3.5 keV, so that their sum is equal Γ(ψ ′ → light hadrons) = 56.2 keV, which corresponds to experimental branching fraction. Then the ratio of the branching fractions:…”

“…Even larger α s = 0.25(2) provides correct number for the ψ ′ width Γ(ψ ′ → 3g). Thus our analysis shows that low-lying charmonium states have no an universal scale for different annihilation decays and therefore any ratio of their widths cannot be used to extract characteristic strong coupling (for the discussion see [16], [17]); in particular, they are different for the J/ψ and ψ ′ three-gluon annihilation rates.…”

Study ofψdecays to theΞ−Ξ¯+andAblikim1, Ачасов2, Ai3 et al. 2016Phys. Rev. D422200View full textAdd to dashboardCite

“…This rule was first observed to be violated in the process ψ → ρπ, which is known as the "ρπ puzzle", and was subsequently further tested in a wide variety of experimental measurements [3]. Recently, a review of the theoretical and experimental results [4] concluded that the current theoretical explanations are unsatisfactory, especially for the baryon pair decays of ψ mesons. Therefore, more experimental measurements on baryon-antibaryon (BB) pair final states, e.g.…”

Study ofψ(3686)→ωKK¯πdecays

“…The ψ(3686), which was the second charmonium state discovered [1], has been extensively studied both experimentally [2][3][4][5][6] and theoretically [7][8][9][10]. Perturbative QCD [11,12] predicts that the partial widths for J/ψ and ψ(3686) decays into an exclusive hadronic state h are proportional to the squares of the cc wave-function overlap at zero quark separation, which are well determined from the leptonic widths.…”