Observation of a Resonant Structure near the D+sD−s Threshold in the B+ → D+sD−sK+ Decay

• An amplitude analysis of the B+→D+sD−sK+ decay is carried out to study for the first time its intermediate resonant contributions, using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. A near-threshold peaking structure, referred to as X(3960), is observed in the D+sD−s invariant-mass spectrum with significance greater than 12 standard deviations. The mass, width, and the quantum numbers of the structure are measured to be 3956±5±10  MeV, 43±13±8  MeV, and JPC=0++, respectively, where the first uncertainties are statistical and the second systematic. The properties of the new structure are consistent with recent theoretical predictions for a state composed of c¯cs¯s quarks. Evidence for an additional structure is found around 4140 MeV in the D+sD−s invariant mass, which might be caused either by a new resonance with the 0++ assignment or by a J/ψϕ↔D+sD−s coupled-channel effect.

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NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

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