Abstract
Using data samples collected with the BESIII detector at center-of-mass energies s=4.23, 4.26, 4.36, and 4.42 GeV, we measure the branching fractions of ηc→K+K−π0, KS0K±π∓, 2(π+π−π0), and pp¯, via the process e+e−→π+π−hc, hc→γηc. The corresponding results are (1.15±0.12±0.10)%, (2.60±0.21±0.20)%, (15.2±1.8±1.7)%, and (0.120±0.026±0.015)%, respectively. Here the first uncertainties are statistical, and the second ones systematic. Additionally, the charged track multiplicity of ηc decays is measured for the first time.Received 13 March 2019DOI:https://doi.org/10.1103/PhysRevD.100.012003Published 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.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionHadronic decaysParticles & Fields
Highlights
Many new charmonium or charmoniumlike states have been discovered recently [1], which broaden our horizon on understanding the charmonium family
The cylindrical core of the BESIII detector consists of a helium-based multilayer drift chamber (MDC), a plastic scintillator time-of-flight system (TOF), and a CsI(Tl) electromagnetic calorimeter (EMC), which are all enclosed in a superconducting solenoidal magnet providing a 1.0 T magnetic field
The inclusive Monte Carlo (MC) samples have the equivalent luminosities the same as the data samples. They consist of the production of open charm processes, the initial state radiation (ISR) production of vector charmonium(like) states, and the continuum processes incorporated in KKMC [14]
Summary
Many new charmonium or charmoniumlike states have been discovered recently [1], which broaden our horizon on understanding the charmonium family. The reason is that most of the measurements involving ηc were performed using the magnetic dipole (M1) transitions from J=ψ or hindered M1 transitions from ψð3686Þ In these decays, the interference between ηc and non-ηc amplitudes affects the ηc line shape [2]. The hc production proceeds via ψð3686Þ → π0hc, where the interference effect between ηc and non-ηc is much less than that in J=ψ; ψð3686Þ radiative transition. The total number of hc events in all these data samples combined is comparable to that from ψð3686Þ → π0hc decays in BESIII data, according to the measured cross section and the corresponding integrated luminosity at each energy point. We report a measurement of the BFs of four ηc exclusive decays via the process eþe− → πþπ−hc, hc → γηc. Apart from the BF measurement mentioned above, we measure the charged tracks multiplicities in inclusive ηc decays by using an unfolding method [10]
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