Abstract
The decays χ_{c1}→J/ψμ^{+}μ^{-} and χ_{c2}→J/ψμ^{+}μ^{-} are observed and used to study the resonance parameters of the χ_{c1} and χ_{c2} mesons. The masses of these states are measured to be m(χ_{c1})=3510.71±0.04(stat)±0.09(syst) MeV and m(χ_{c2})=3556.10±0.06(stat)±0.11(syst) MeV, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(χ_{c2})-m(χ_{c1})=45.39±0.07(stat)±0.03(syst) MeV. The natural width of the χ_{c2} meson is measured to be Γ(χ_{c2})=2.10±0.20(stat)±0.02(syst) MeV. These results are in good agreement with and have comparable precision to the current world averages.
Highlights
Studies of the properties and production of quarkonia at hadron colliders provide an important testing ground for quantum chromodynamics [1]
The BESIII Collaboration [9] reported the first observation of the electromagnetic Dalitz decays [10] of χc0, χc1 and χc2 mesons into the J=ψeþe− final state
The event topology with four muons in the final state provides a clean signature that is ideal for studies in hadron collisions
Summary
Studies of the properties and production of quarkonia at hadron colliders provide an important testing ground for quantum chromodynamics [1]. These decays are used to measure the χc1 and χc2 masses together with the χc2 natural width. The χc1 and χc2 signals are modeled by relativistic Breit-Wigner functions with Blatt-Weisskopf form factors [33] with a meson radius parameter of 3 GeV−1. The parameters of the resolution model are determined by a simultaneous fit to the χc1 and χc2 simulated samples.
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