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Register a new userStrong and electromagnetic amplitudes of the $J/psi$ decays into baryons and their relative phase
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The Feynman amplitude for the decay of the $J/psi$ meson into baryon-antibaryon can be written as a sum of three sub-amplitudes: a purely strong, a purely electromagnetic and a mixed strong-electromagnetic. Assuming that the strong and mixed strong-electromagnetic sub-amplitudes have the same phase, the branching ratio of the decay contains an interference term that depends on the relative phase $varphi$ between strong and electromagnetic sub-amplitudes. In this work we calculate this phase, by using an effective strong Lagrangian density and considering, as final states, pairs of baryons, $mathcal{B}overline{mathcal{B}}$, belonging to the spin-1/2 SU(3) octet. Moreover, we obtain the purely strong, purely electromagnetic and mixed strong-electromagnetic contributions to the total branching ratio and hence the moduli of the corresponding sub-amplitudes, for each pair of baryons. Of particular interest is the mixed strong-electromagnetic contribution that, not only is determined for the first time, but it is proven to be crucial, in the framework of our model, for the correct description of the decay mechanism. Finally we use the purely electromagnetic branching ratio to calculate the Born non-resonant cross section of the annihilation processes $e^+ e^- to mathcal{B}overline{mathcal{B}}$ at the $J/psi$ mass. By taking advantage from all available data, we obtain the relative phase between strong and electromagnetic sub-amplitudes: $varphi = (73pm 8)^circ$.
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The strong, electromagnetic and mixed strong-electromagnetic amplitudes of the $psi(2S)$ decays into baryon-anti-baryon pairs have been obtained by exploiting all available data sets in the framework of an effective Lagrangian model. We observed that at the $psi(2S)$ mass the QCD regime is not completely perturbative, as can be inferred by the relative strength of the strong and the mixed strong-electromagnetic amplitudes. Recently a similar conclusion has been reached also for the $J/psi$ decays. The relative phase between the strong and the electromagnetic amplitudes is $varphi = (58pm 8)^circ$, to be compared with $varphi = (73pm 8)^circ$ obtained for the $J/psi$. On the other hand, in the case of the $psi(2S)$ meson, different values of the ratio between strong and mixed strong-electromagnetic amplitudes are phenomenologically required, while for the $J/psi$ meson only one ratio was enough to describe the data. Finally, we also observed a peculiar behavior of the mixed strong-electromagnetic amplitudes of the decays $psi(2S)toSigma^+ overline Sigma{}^-$ and $psi(2S)toSigma^- overline Sigma{}^+$.
Using 16 energy points of $e^{+}e^{-}$ annihilation data collected in the vicinity of the $J/psi$ resonance with the BESIII detector and with a total integrated luminosity of around 100 pb$^{-1}$, we study the relative phase between the strong and electromagnetic amplitudes of $J/psi$ decays. The relative phase between $Jpsi$ electromagnetic decay and the continuum process ($e^{+}e^{-}$ annihilation without the $J/psi$ resonance) is confirmed to be zero by studying the cross section lineshape of $mu^{+}mu^{-}$ production. The relative phase between $J/psi$ strong and electromagnetic decays is then measured to be $(84.9pm3.6)^circ$ or $(-84.7pm3.1)^circ$ for the $2(pi^{+}pi^{-})pi^{0}$ final state by investigating the interference pattern between the $J/psi$ decay and the continuum process. This is the first measurement of the relative phase between $J/psi$ strong and electromagnetic decays into a multihadron final state using the lineshape of the production cross section. We also study the production lineshape of the multihadron final state $etapi^{+}pi^{-}$ with $etatopi^{+}pi^{-}pi^{0}$, which provides additional information about the phase between the $J/psi$ electromagnetic decay amplitude and the continuum process. Additionally, the branching fraction of $J/psito 2(pi^{+}pi^{-})pi^{0}$ is measured to be $(4.73pm0.44)%$ or $(4.85pm0.45)%$, and the branching fraction of $J/psitoetapi^{+}pi^{-}$ is measured to be $(3.78pm0.68)times10^{-4}$. Both of them are consistent with the world average values. The quoted uncertainties include both statistical and systematic uncertainties, which are mainly caused by the low statistics.
There has been important experimental progress in the sector of heavy baryons in the past several years. We study the strong decays of the S-wave, P-wave, D-wave and radially excited charmed baryons using the $^3P_0$ model. After comparing the calcul
ated decay pattern and total width with the available data, we discuss the possible internal structure and quantum numbers of those charmed baryons observed recently.
An analysis of the decay B0 -> J/psi K*(892)0 is presented using data, corresponding to an integrated luminosity of 1.0fb^-1, collected in pp collisions at a centre-of-mass energy of 7TeV with the LHCb detector. The polarisation amplitudes and the corresponding phases are measured to be |A_{parallel}|^2 = 0.227 +- 0.004 (stat.) +- 0.011 (syst.), |A_{perp}|^2 = 0.201 +- 0.004 (stat.) +- 0.008 (syst.), delta_{parallel} [rad] = -2.94 +- 0.02 (stat.) +- 0.03 (syst.), delta_{perp} [rad] = 2.94 +- 0.02 (stat.) +- 0.02 (syst.). Comparing B0 -> J/psi K*(892)0 and bar{B}0 -> J/psi bar{K}*(892)0 decays, no evidence for direct CP violation is found.
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