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تسجيل مستخدم جديدProspects for X(3872) Detection at Panda
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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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The recently discovered $X$(3872) has many possible interpretations. We study the production of $X$(3872) with PANDA at GSI for the antiproton-proton collision with two possible interpretations of X(3872). One is as a loosely-bound molecule of $D$-me
sons, while another is a 2P charmonium state $chi_{c1}$ (2P). Using effective couplings we are able to give numerical predictions for the production near the threshold and the production associated with $pi^0$. The produced $X$(3872) can be identified with its decay $J/psi pi^+pi^-$. We also study the possible background near the threshold production for $X(3872) to J/psi pi^+pi^-$. With the designed luminosity $1.5{rm fb}^{-1}$ per year of PANDA we find that the event number of $pbar p to J/psi pi^+pi^-$ near the threshold is at the order of $10^6 sim 10^8$, where the large uncertainty comes from the total decay width of X(3872). Our study shows that at the threshold more than about 60% events come from the decay of X(3872) and two interpretations are distinguishable from the line-shape of the production. With our results we except that the PANDA experiments will shed light on the property of X(3872).
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.
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 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 ${cal B}(B^0 to X(3872) (K^+ pi^-)) times {cal B}(X(3872) to J/psi p
i^+ pi^-) = (7.9 pm 1.3(mbox{stat.})pm 0.4(mbox{syst.})) times 10^{-6}$ 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.
The X(3872) and Z(4430) are candidates of tetraquark state with a ccbar pair. We present results from Belle recently updated for the mass, branching fractions etc. in different production/decay processes of the X(3872). Results from a Dalitz analysis
for B --> Z(4430) K --> psi pi^+- K are also presented.
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