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Register a new userTriangle Singularity in the Production of $X(3872)$ and a Photon in $e^+e^-$ Annihilation
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If the $X(3872)$ is a weakly bound charm-meson molecule, it can be produced in $e^+ e^-$ annihilation by the creation of $D^{*0} bar D^{*0}$ from a virtual photon followed by the rescattering of the charm-meson pair into $X$ and a photon. A triangle singularity produces a narrow peak in the cross section for $e^+ e^- to X gamma$ about 2.2 MeV above the $D^{*0} bar{D}^{*0}$ threshold. We predict the normalized cross section in the region near the peak. The peak from the triangle singularity may be observable by the BESIII detector.
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If the $X(3872)$ is a weakly bound charm-meson molecule, it can be produced in $e^+ e^-$ annihilation by the creation of $D^{*0} bar D^{*0}$ from a virtual photon followed by the rescattering of the P-wave charm-meson pair into the $X$ and a photon. A triangle singularity produces a narrow peak in the cross section for $e^+ e^- to X gamma$ 2.2 MeV above the $D^{*0} bar{D}^{*0}$ threshold. We predict the normalized cross section in the region of the peak. We show that the absorptive contribution to the cross section for $e^+ e^- to D^{*0} bar D^{*0} to X gamma$, which was calculated previously by Dubynskiy and Voloshin, does not give a good approximation to the peak from the triangle singularity.
We study, at leading order in the large number of colours expansion and within the Resonance Chiral Theory framework, the odd-intrinsic-parity $e^+ e^- rightarrow pi^+ pi^- (pi^0, eta)$ cross-sections in the energy regime populated by hadron resonances, namely $3 , m_{pi} lsim E lsim 2 , mbox{GeV}$. In addition we implement our results in the Monte Carlo generator PHOKHARA 7.0 and we simulate hadron production through the radiative return method.
A vector-dominance two-photon exchange model is proposed to explain the recently observed production of $rho^0rho^0$ and $rho^0phi$ pairs in $e^+e^-$ annihilation at 10.58 GeV with the BaBar detector. All the observed features of the data --angular and decay distributions, rates-- are in agreement with the model. Predictions are made for yet-unobserved final states.
The production cross sections of $J/psi~eta_b$, $Upsilon;eta_c$ pairs in a single boson $e^+e^-$ annihilation have been studied in a wide range of energies, which will be achieved at future $e^+e^-$ colliders. The main color singlet contributions to the production processes are taken into account, including the one loop QCD contribution.
It was recently proposed that the $X(3872)$ binding energy, the difference between the $D^0bar D^{*0}$ threshold and the $X(3872)$ mass, can be precisely determined by measuring the $gamma X(3872)$ line shape from a short-distance $D^{*0}bar D^{*0}$ source produced at high-energy experiments. Here, we investigate the feasibility of such a proposal by estimating the cross sections for the $e^+e^-topi^0gamma X(3872)$ and $pbar ptogamma X(3872)$ processes considering the $D^{*0}bar D^{*0}D^0/bar D^{*0}D^{*0}bar D^0$ triangle loops. These loops can produce a triangle singularity slightly above the $D^{*0}bar D^{*0}$ threshold. It is found that the peak structures originating from the $D^{*0}bar D^{*0}$ threshold cusp and the triangle singularity are not altered much by the energy dependence introduced by the $e^+e^-topi^0D^{*0}bar D^{*0}$ and $pbar ptobar D^{*0}D^{*0}$ production parts or by considering a finite width for the $X(3872)$. We find that $sigma(e^+e^-topi^0gamma X(3872)) times {rm Br}(X(3872)topi^+pi^-J/psi)$ is $mathcal{O}(0.1~{rm fb})$ with the $gamma X(3872)$ invariant mass integrated from 4.01 to 4.02 GeV and the c.m. energy of the $e^+e^-$ pair fixed at 4.23 GeV. The cross section $sigma(pbar ptogamma X(3872))times {rm Br}(X(3872)topi^+pi^-J/psi)$ is estimated to be of $mathcal{O}(10~{rm pb})$. Our results suggest that a precise measurement of the $X(3872)$ binding energy can be done at PANDA.
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