Determination of Spin-Parity Quantum Numbers for the Narrow Structure near the p¯Λ Threshold in e+e−→pK−¯Λ+c.c.

• A narrow structure in the p¯Λ system near the mass threshold, named as X(2085), is observed in the process e+e−→pK−¯Λ with a statistical significance greater than 20σ. Its spin and parity are determined for the first time to be JP=1+ in an amplitude analysis, with a statistical significance greater than 5σ over other quantum numbers (0−,1− and 2+). The pole positions of X(2085) are measured to be Mpole=(2084+4−2±9)  MeV and Γpole=(58+4−3±25)  MeV, where the first uncertainties are statistical and the second ones are systematic. The analysis is based on the study of the process e+e−→pK−¯Λ and uses the data samples collected with the BESIII detector at the center-of-mass energies √s=4.008, 4.178, 4.226, 4.258, 4.416, and 4.682 GeV with a total integrated luminosity of 8.35  fb−1.

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

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

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