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Register a new userMeson Emission Model of Psi to N Nbar m Charmonium Strong Decays
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T.Barnes
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In this paper we consider a sequential meson emission mechanism for charmonium decays of the type Psi -> N Nbar m, where Psi is a generic charmonium state, N is a nucleon and m is a light meson. This decay mechanism, which may not be dominant in general, assumes that an NNbar pair is created during charmonium annihilation, and the light meson m is emitted from the outgoing nucleon or antinucleon line. A straightforward generalization of this model can incorporate intermediate N* resonances. We derive Dalitz plot event densities for the cases Psi = eta_c, J/psi, chi_c0, chi_c1} and psi and m = pi0, f0 and omega (and implicitly, any 0^{-+}, 0^{++} or 1^{--} final light meson). It may be possible to separate the contribution of this decay mechanism to the full decay amplitude through characteristic event densities. For the decay subset Psi -> p pbar pi0 the two model parameters are known, so we are able to predict absolute numerical partial widths for Gamma(Psi -> p pbar pi0). In the specific case J/psi -> p pbar pi0 the predicted partial width and M_{p pi0} event distribution are intriguingly close to experiment. We also consider the possibility of scalar meson and glueball searches in Psi -> p pbar f0. If the meson emission contributions to Psi -> N Nbar m decays can be isolated and quantified, they can be used to estimate meson-nucleon strong couplings {g_NNm}, which are typically poorly known, and are a crucial input in meson exchange models of the NN interaction. The determination of g_NNpi from Jpsi -> p pbar pi0 and the (poorly known) g_NNomega and the anomalous strong magnetic coupling kappa_{NNomega} from J/psi -> p pbar omega are considered as examples.
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In this invited talk I discuss two recent applications of charmonium (Psi) decays to N Nbar m final states, where N is a nucleon and m is a light meson. There are several motivations for studying these decays: 1) They are useful for the study of N* spectroscopy; 2) they can be used to estimate cross sections for the associated charmonium production processes p pbar to Psi m, which PANDA plans to exploit in searches for charmonium hybrid exotics; and 3) they may allow the direct experimental measurement of NNm (meson-nucleon) strong couplings, which provide crucial input information for meson exchange models of the NN force. The latter two topics are considered in this talk, which will also compare results from a simple hadron pole model of these decays to recent experimental data.
Although the spectra of heavy quarkonium systems has been successfully explained by certain QCD motivated potential models, their strong decays are difficult to deal with. We perform a microscopic calculation of charmonium strong decays using the same constituent quark model which successfully describes the $cbar{c}$ meson spectrum. We compare the numerical results with the $^{3}P_{0}$ and the experimental data. Comparison with other predictions from similar models are included.
The open-charm strong decays of higher charmonium states up to the mass of the $6P$ multiplet are systematically studied in the $^3P_0$ model. The wave functions of the initial charmonium states are calculated in the linear potential (LP) and screened potential (SP) quark model. The decay widths for most of the well-established charmonium states above the open-charm thresholds can be reasonably described. By comparing our quark model calculations with the experimental observations we also discuss the nature of some of the newly observed charmonium-like states. It is found that (i) the $psi(4415)$ may favor the $psi(4S)$ or $psi_1(3D)$ assignment. There may exist two highly overlapping vector charmonium states around 4.4 GeV; (ii) In the LP model the $J^{PC}=1^{--}$ $Y(4660)$ resonance and the $J^{PC}=0^{++}$ $X(4500)$ resonance may be assigned as the $psi(5S)$ and $chi_{c0}(4P)$, respectively; (iii) The newly observed state $X^*(3860)$ can be assigned as the $chi_{c0}(2P)$ state with a narrow width of about $30$ MeV; (iv) It seems to be difficult to accommodate the $X(4140)$ and $X(4274)$ states in the same potential model as excited $chi_{c1}$ states. (v) The $X(3940)$ resonance can be assigned as the $eta_c(3S)$ state; (vi) The vector charmonium-like states $Y(4230/4260,4360)$ and scalar $X(4700)$ cannot be described by any conventional charmonium states self-consistently in our model.
We study the semileptonic decays of $B_c$ meson to S-wave charmonium states in the framework of relativistic independent quark model based on an average flavor-independent confining potential $U(r)$ in the scalar-vector harmonic form $U(r)=frac{1}{2}(1+gamma^0)(ar^2+V_0)$, where ($a$, $V_0$) are the potential parameters.The form factors for $B_c^+to eta_c /psi e^+ u_e$ transitions are studied in the physical kinematic range. Our predicted branching ratios (BR) for transitions to ground state charmonia are found comparatively large $sim $ $10^{-2}$, compared to those for transitions to radially excited 2S and 3S states. Like all other mpdel predictions, our predicted BR are obtained in the hierarchy: BR($B_c^+to eta_c /psi (3S)$) $<$ BR($B_c^+to eta_c/ psi (2S)$) $<$ BR($B_c^+to eta_c /psi (1S)$). The longitudinal ($Gamma_L$) and transverse polarization ($Gamma_T$) for $B_c to psi(ns)$ decay modes are predicted in the small and large $q^2$ - region as well as in the whole physical region. The ratios for such transitions are obtained $frac {Gamma_L}{Gamma_T} < 1$ throughout the kinematic range which means the $B_c^+$ meson transitions to vector meson charmonium states take place predominantly in transverse polarization mode. The theoretical predictions on these transitions could be tested in the on-going and forthcoming experiments at LHCb.
We use the Paris nucleon-antinucleon optical potential for explanation of experimental data in the process $e^+e^- rightarrow pbar p$ near threshold. It turns out that final-state interaction due to Paris optical potential allows us to reproduce available experimental data. It follows from our consideration that the isoscalar form factor is much larger than the isovector one.
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