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Register a new userOn leptonic width of $X(4260)$
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New measurements on cross sections in $e^+e^-to J/psipi^+pi^-$, $h_cpi^+pi^-$, $D^0D^{*-}pi^++c.c.$, $psi(2S)pi^+pi^-$, $omegachi_{c0}$ and $J/psieta$ channels have been carried out by BESIII, Belle and BABAR collaborations, and also in the $D_s^*bar D_s^*$ channel. We perform extensive numerical analyses by combining all these data available, together with those in $Dbar D^*$ and $D^*bar D^*$ channels. Though the latter show no evident peak around $sqrt{s}=4.230$ GeV, the missing $X(4260)$ is explained as that it is concealed by the interference effects of the well established charmonia $psi(4040)$, $psi(4160)$ and $psi(4415)$. Our analyses reveal that the leptonic decay width of $X(4260)$ ranges from $O(10^2)$ eV to $O(1)$ keV, and hence may be explained in the conventional quark model picture. That is, the $X(4260)$ may well be interpreted as a mixture of $4^3S_1$ and $3^3D_1$ states.
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The observed Y(4260)to gamma + X(3872) decay is a natural consequence of the diquark-antidiquark description of Y and X resonances. In this note we attempt an estimate of the transition rate, Gamma_{rm rad}, by a non-relativistic calculation of the electric dipole term of a diquarkonium bound state. We compute Gamma_{rm rad} for generic composition values of the isospin of X and Y. Specializing to I=0 for X(3872), we find Gamma_{rm rad}= 496~keV for Y(4260) with I=0 and Gamma_{rm rad}= 179~keV for I=1. Combining with BESIII data, we derive upper bounds to B(Yto J/Psi+pi+pi) and to Gamma(Yto mu^+ mu^-). We expect to confront these results with forthcoming data from electron-positron and hadron colliders.
We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M $e^{+}e^{-}$ collider. The measured values of the J/psi parameters are: Gamma_{ee}timesGamma_{ee}/Gamma = 0.3323 pm 0.0064 (stat.) pm 0.0048 (syst.) keV Gamma_{ee}timesGamma_{mumu}/Gamma=0.3318 pm 0.0052 (stat.) pm 0.0063 (syst.) keV. Assuming $emu$ universality and using the table value of the branching ratios the leptonic Gamma_{ll}= 5.59 pm 0.12 keV width and the total Gamma=94.1 pm 2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow resonance.
Using a data set of 2.93 fb$^{-1}$ taken at a center-of-mass energy of $sqrt{s}$ = 3.773 GeV with the BESIII detector at the BEPCII collider, we measure the process $e^+e^-rightarrow J/psigammarightarrow mu^+mu^-gamma$ and determine the product of the branching fraction and the electronic width $mathcal B_{mumu}cdot Gamma_{ee} = (333.4 pm 2.5_{rm stat} pm 4.4_{rm sys})$~eV. Using the earlier-published BESIII result for $mathcal B_{mumu}$ = (5.973 $pm$ 0.007$_{rm stat}$ $pm$ 0.037$_{rm sys}$)%, we derive the $J/psi$ electronic width $Gamma_{ee}$~= (5.58 $pm$ 0.05$_{rm stat}$ $pm$ 0.08$_{rm sys}$) keV.
The $Y(4260)$ has been one of the most puzzling pieces among the so-called $XYZ$ states. In this paper, we try to gain insights into the structure of the $Y(4260)$ from the light-quark perspective. We study the dipion invariant mass spectrum of the $e^+ e^- to Y(4260) to J/psi pi^+pi^-$ process and the ratio of the cross sections ${sigma(e^+e^- to J/psi K^+ K^-)}/{sigma(e^+e^- to J/psi pi^+pi^-)}$. In particular, we consider the effects of different light-quark SU(3) eigenstates inside the $Y(4260)$. The strong pion-pion final-state interactions as well as the $Kbar{K}$ coupled channel in the $S$-wave are taken into account in a model-independent way using dispersion theory. We find that the SU(3) octet state plays a significant role in these transitions, implying that the $Y(4260)$ contains a large light-quark component. Our findings suggest that the $Y(4260)$ is neither a hybrid nor a conventional charmonium state, and they are consistent with the $Y(4260)$ having a sizeable $bar D D_1$ component which, however, is not completely dominant.
We present a comprehensive update of the bounds on R-Parity violating supersymmetric couplings from lepton-flavour- and lepton-number-violating decay processes. We consider tau and mu decays as well as leptonic and semi-leptonic decays of mesons. We present several new bounds resulting from tau, eta and Kaon decays and correct some results in the literature concerning B-meson decays.
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