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arXiv · 1809.00160

Search for muoproduction of the X(3872) at COMPASS

Alexey Guskov
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Abstract

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 $J/ψπ^+π^-$ with the statistical significance of 4.1 $σ$ was observed in the reaction $μ^+~N \rightarrow μ^+(J/ψπ^+π^- )π^{\pm} N'$. Its mass and width are consistent with those of the $X(3872)$. The shape of the $π^+π^-$ mass distribution from the observed decay into $J/ψπ^+π^-$ 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.

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Alexey Guskov. 2018-09-01. Search for muoproduction of the X(3872) at COMPASS. https://doi.org/10.1088/1742-6596%2F1137%2F1%2F012019

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