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Regular version of the site

Article

Study of the lineshape of the χc1(3872) state

Borisyak M., Derkach D., Belavin V., Arzymatov K., Guschin M., Ratnikov F., Kazeev N., Курбатов Е. О., Ustyuzhanin A., Boldyrev A., Ryzhikov A., Maevskiy A., LHCb c., Попов С. А.

A study of the lineshape of theχc1ð3872Þstate is made using a data sample corresponding to anintegrated luminosity of3fb−1collected inppcollisions at center-of-mass energies of 7 and 8 TeV withthe LHCb detector. Candidateχc1ð3872Þandψð2SÞmesons fromb-hadron decays are selected in theJ=ψπþπ−decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting betweentheχc1ð3872Þandψð2SÞstates,Δm, and the width of theχc1ð3872Þstate,ΓBW, are determined to beΔm¼185.5980.0670.068MeV;ΓBW¼1.390.240.10MeV;where the first uncertainty is statistical and the second systematic. Using a Flatt ́e-inspired model, the mode and full width at half maximum of the lineshape are determined to bemode¼3871.69þ0.00þ0.05−0.04−0.13MeV;FWHM¼0.22þ0.07þ0.11−0.06−0.13MeV:An investigation of the analytic structure of the Flatt ́e amplitude reveals a polestructure, which is compatible with a quasiboundD0 ̄D0state but a quasivirtual state is still allowed at thelevel of 2 standard deviations.