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Register a new userSearch for muoproduction of $X(3872)$ at COMPASS and indication of a new state $widetilde{X}(3872)$
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We have searched for exclusive production of exotic charmonia in the reaction $mu^+~N rightarrow mu^+ (J!/!psipi^+pi^-)pi^{pm}~N$ using COMPASS data collected with incoming muons of 160 GeV/$c$ and 200 GeV/$c$ momentum. In the $J!/!psipi^+pi^-$ mass distribution we observe a signal with a statistical significance of 4.1 $sigma$. Its mass and width are consistent with those of the $X(3872)$. The shape of the $pi^+pi^-$ mass distribution from the observed decay into $J!/!psipi^+pi^-$ shows disagreement with previous observations for $X(3872)$. The observed signal may be interpreted as a possible evidence of a new charmonium state. It could be associated with a neutral partner of $X(3872)$ with $C = -1$ predicted by a tetraquark model. The product of cross section and branching fraction of the decay of the observed state into $J!/!psipi^+pi^-$ is determined to be 71$pm$28(stat)$pm$39(syst) pb.
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Exotic charmonium-like states have been observed by various experiments over the last 15 years, but their nature is still under discussion. Photo-(muo)production is a new promising instrument to study them. COMPASS, a fixed target experiment at CERN, analyzed the full set of the data collected with a muon beam between 2002 and 2011, covering the range from 7 GeV to 19 GeV in the centre-of-mass energy of the virtual photon-nucleon system. A signal in the mass spectrum of $J/psipi^+pi^-$ with the statistical significance of 4.1 $sigma$ was observed in the reaction $mu^+~N rightarrow mu^+(J/psipi^+pi^- )pi^{pm} N$. Its mass and width are consistent with those of the $X(3872)$. The shape of the $pi^+pi^-$ mass distribution from the observed decay into $J/psipi^+pi^-$ is different from previous observations for $X(3872)$. The observed signal may be interpreted as possible evidence of a new charmonium state $widetilde{X}(3872)$. It could be associated with a neutral partner of $X(3872)$ with $C = -1$ predicted by a tetraquark model.
We report a study of $Bto (J/psi gamma) K$ and $Bto (psi gamma)K$ decay modes using $772times 10^{6}$ $Bbar{B}$ events collected at the Upsilon(4S)$ resonance with the Belle detector at the KEKB energy-asymmetric $e^+ e^-$ collider. We observe $X(3872) to J/psi gamma$ and report the first evidence for $chi_{c2} to J/psi gamma$ in $Bto (X_{cbar{c}}gamma) K$ decays, while in a search for $X(3872) to psi gamma$ no significant signal is found. We measure the branching fractions, $mathcal{B}(B^{pm} to X(3872) K^{pm}) mathcal{B}(X(3872) to J/psigamma)$ $=$ $(1.78^{+0.48}_{-0.44}pm 0.12)times 10^{-6}$, $mathcal{B} (B^{pm} tochi_{c2} K^{pm})$$=$ $(1.11^{+0.36}_{-0.34} pm 0.09) times 10^{-5}$, $mathcal{B}(B^{pm} to X(3872) K^{pm}) mathcal{B}(X(3872) to psigamma)$ $<$ $3.45times 10^{-6}$ (upper limit at 90% C.L.) and also provide upper limits for other searches.
We report the first observation of $B^0 to X(3872) (K^{+}pi^{-})$ and evidence for $B^+ to X(3872) (K^{0}pi^{+})$. We measure the product of branching fractions for the former to be ${cal B}(B^0 to X(3872) (K^+ pi^-)) times {cal B}(X(3872) to J/psi pi^+ pi^-) = (7.9 pm 1.3(mbox{stat.})pm 0.4(mbox{syst.})) times 10^{-6}$ and find that $B^{0}to X(3872) K^{*}(892)^{0}$ does not dominate the $B^{0}to X(3872)K^{+}pi^{-}$ decay mode. We also measure ${cal B}(B^+ to X(3872) (K^0 pi^+)) times {cal B}(X(3872) to J/psi pi^+ pi^-) = (10.6 pm 3.0(mbox{stat.}) pm 0.9(mbox{syst.})) times 10^{-6}$. This study is based on the full data sample of 711~fb$^{-1}$ ($772times 10^6 Bbar B$ pairs) collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB collider.
We report the results of a search for the decay $B^0 to X(3872)(to J/psi pi^+ pi^-) gamma$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711,{rm fb}^{-1}$ and containing $772 times 10^6 Bbar{B}$ pairs, collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider running at the $Upsilon(4S)$ resonance energy. We find no evidence for a signal and place an upper limit of $mathcal{B}(B^0 to X(3872)gamma)times mathcal{B}(X(3872) to J/psi pi^+ pi^-) < 5.1 times 10^{-7}$ at 90% confidence level.
Monte-Carlo simulations for a resonance scan of the charmonium-like state X(3872) at Panda are performed. Final state radiation hadronic background reactions are taken into account. The signal reconstruction uses a realistic pattern recognition (track finder and track fitter) and electron/pion discrimination.
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