Abstract
A study of the lineshape of the χc1(3872) state is made using a data sample corresponding to an integrated luminosity of 3 fb−1 collected in pp collisions at center-of-mass energies of 7 and 8 TeV with the LHCb detector. Candidate χc1(3872) and ψ(2S) mesons from b-hadron decays are selected in the J/ψπ+π− decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting between the χc1(3872) and ψ(2S) states, Δm, and the width of the χc1(3872) state, ΓBW, are determined to be Δm=185.598±0.067±0.068 MeV,ΓBW=1.39±0.24±0.10 MeV, where the first uncertainty is statistical and the second systematic. Using a Flatté-inspired model, the mode and full width at half maximum of the lineshape are determined to be mode=3871.69−0.04−0.13+0.00+0.05 MeV,FWHM=0.22−0.06−0.13+0.07+0.11 MeV. An investigation of the analytic structure of the Flatté amplitude reveals a pole structure, which is compatible with a quasibound D0D¯*0 state but a quasivirtual state is still allowed at the level of 2 standard deviations.4 MoreReceived 29 May 2020Accepted 21 September 2020DOI:https://doi.org/10.1103/PhysRevD.102.092005Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2020 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasHadron-hadron interactionsHadronic decaysPropertiesMassTechniquesHadron collidersPrecision measurementsParticles & Fields
Highlights
The last two decades have seen a resurgence of interest in the spectroscopy of nonconventional charmonium states [1] starting with the observation of the charmoniumlike χc1ð3872Þ state by the Belle Collaboration [2]
Though the existence of the χc1ð3872Þ particle has been confirmed by many experiments [3,4,5,6,7] with quantum numbers measured to be 1þþ [8,9], its nature is still uncertain
Assuming a Breit-Wigner lineshape, this implies that δE ≡ mD0 þ mDÃ0 − mχc1ð3872Þ > 0
Summary
The last two decades have seen a resurgence of interest in the spectroscopy of nonconventional (exotic) charmonium states [1] starting with the observation of the charmoniumlike χc1ð3872Þ state by the Belle Collaboration [2]. Several exotic interpretations have been suggested: e.g., a tetraquark [10], a loosely bound deuteronlike D0D Ã0 molecule [11] or a charmonium-molecule mixture [12]. The nature of the χc1ð3872Þ state can be elucidated by studies of its lineshape This has been analyzed by several experiments assuming a Breit-Wigner function [3,5,14]. The current upper limit on the natural width, ΓBW, is 1.2 MeV at 90% confidence level [15]. In this analysis a sample of χc1ð3872Þ → J=ψπþπ− candidates produced in inclusive b-hadron decays is used to measure precisely the mass and to determine the lineshape of the χc1ð3872Þ meson. The analysis uses a data sample corresponding to an integrated luminosity of 3 fb−1 of data collected in pp collisions at center-of-mass energies of 7 and 8 TeV during 2011 and 2012 using the LHCb detector
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