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Register a new userEvidence for $X(3872)rightarrow J/psi pi^+pi^-$ produced in single-tag two-photon interactions
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We report the first evidence for $X(3872)$ production in two-photon interactions by tagging either the electron or the position in the final state, exploring the highly virtual photon region. The search is performed in $e^+e^- rightarrow e^+e^-J/psipi^+pi^-$, using 825 fb$^{-1}$ of data collected by the Belle detector operated at the KEKB $e^+e^-$ collider. We observe three $X(3872)$ candidates with an expected background of $0.11pm 0.10$ events, with a significance of 3.2$sigma$. We obtain an estimated value for $tilde{Gamma}_{gammagamma}{cal B}(X(3872)rightarrow J/psipi^+pi^-$) assuming the $Q^2$ dependence predicted by a $cbar{c}$ meson model, where $-Q^2$ is the invariant mass-squared of the virtual photon. No $X(3915)rightarrow J/psipi^+pi^-$ candidates are found.
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We present measurements of the decays B+ -> X(3872) K+ and B0 -> X(3872) K0 with X(3872) -> Jpsi pi+ pi-. The data sample used, collected with the BABAR detector at the PEP-II e+e- asymmetric-energy storage ring, corresponds to 455 x 10^6 BBbar pairs. Branching fraction measurements of BF(B+ -> X(3872) K+) x BF(X(3872) -> Jpsi pi+ pi-) = (8.4 +/- 1.5 +/- 0.7) x 10^{-6} and BF(B0 -> X(3872) K0) x BF(X(3872) -> Jpsi pi+ pi- = (3.5 +/- 1.9 +/- 0.4) x 10^{-6} are obtained. We set an upper limit on the natural width of the X(3872) of Gamma < 3.3 MeV/c^2 at the 90% confidence level.
Using a data sample of $448.1times10^6$ $psi(3686)$ events collected with the BESIII detector operating at the BEPCII, we perform search for the hadronic transition $h_crightarrowpi^+pi^-J/psi$ via $psi(3686)rightarrowpi^0h_c$. No signals of the transition are observed, and the upper limit on the product branching fraction $mathcal{B}(psi(3686)rightarrowpi^0h_c)mathcal{B}(h_crightarrowpi^+pi^-J/psi)$ at the 90% confidence level is determined to be $2.0times10^{-6}$. This is the most stringent upper limit to date.
New spectroscopy from the B factories, the advent of CLEO-c and the BES upgrade renewed the interest in charmonia. Among the new measurements, the state X(3872) has received special attention due to its unexpected properties. Its structure has been studied with different theoretical approaches, most of them being able to reproduce the measured mass. A further test for the theoretical descriptions of the X(3872) is to explain its narrow decay width. In this work we address the decays $Xto J/psi pi^+pi^-pi^0$ and $Xto J/psi pi^+ pi^-$, using QCD sum rules with the hypothesis that $X$ is a four quark state.
The decays $B^+rightarrow J/psi 3pi^+ 2pi^-$ and $B^+rightarrow psi(2S) pi^+pi^+pi^-$ are observed for the first time using a data sample corresponding to an integrated luminosity of $3.0fb^{-1}$, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV. The branching fractions relative to that of $B^+ rightarrow psi(2S)K^+$ are measured to be begin{eqnarray*} frac {mathcal{B}left(B^+rightarrow J/psi 3pi^+ 2pi^- right)} {mathcal{B}left(B^+ rightarrow psi(2S)K^+ right)} & = & left(1.88pm0.17pm0.09right)times10^{-2}, frac {mathcal{B}left(B^+rightarrow psi(2S) pi^+pi^+pi^- right)} {mathcal{B}left(B^+ rightarrow psi(2S)K^+ right)} & = & left(3.04pm0.50pm0.26right)times10^{-2}, end{eqnarray*} where the first uncertainties are statistical and the second are systematic.
We report a measurement of the differential cross section of $pi^0$ pair production in single-tag two-photon collisions, $gamma^* gamma to pi^0 pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to 30 GeV$^2$, where $Q^2$ is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and $|cos theta^*|$ < 1.0 for the total energy and pion scattering angle, respectively, in the $gamma^* gamma$ center-of-mass system. The results are based on a data sample of 759 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The transition form factor of the $f_0(980)$ and that of the $f_2(1270)$ with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.
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