Improved measurements of two-photon widths of the ${\chi }_{cJ}$ states and helicity analysis for ${\chi }_{c2}\to \gamma \gamma$

Abstract

Based on $448.1\times 10^6$ $\psi (3686)$ events collected with the BESIII detector, the decays $\psi (3686)\to \gamma {\chi }_{cJ},{\chi }_{cJ}\to \gamma \gamma (J=0,1,2)$ are studied. The decay branching fractions of ${\chi }_{c0,c2}\to \gamma \gamma$ are measured to be $\mathcal{B}({\chi }_{c0}\to \gamma \gamma )=(1.93\pm 0.08\pm 0.05\pm 0.05)\times 10^{-4}$ and $\mathcal{B}({\chi }_{c2}\to \gamma \gamma )=(3.10\pm 0.09\pm 0.07\pm 0.11)\times 10^{-4}$, which correspond to two-photon decay widths of ${\Gamma }_{\gamma \gamma }({\chi }_{c0})=2.03\pm 0.08\pm 0.06\pm 0.13\mathrm{keV}$ and ${\Gamma }_{\gamma \gamma }({\chi }_{c2})=0.60\pm 0.02\pm 0.01\pm 0.04\mathrm{keV}$ with a ratio of $\mathcal{R}={\Gamma }_{\gamma \gamma }({\chi }_{c2})/{\Gamma }_{\gamma \gamma }({\chi }_{c0})=0.295\pm 0.014\pm 0.007\pm 0.027$, where the uncertainties are statistical, systematic and associated with the uncertainties of $\mathcal{B}(\psi (3686)\to \gamma {\chi }_{c0,c2})$ and the total widths $\Gamma ({\chi }_{c0,c2})$, respectively. For the forbidden decay of ${\chi }_{c1}\to \gamma \gamma$, no signal is observed, and an upper limit on the two-photon width is obtained to be ${\Gamma }_{\gamma \gamma }({\chi }_{c1})<5.3\mathrm{eV}$ at the 90\% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay ${\chi }_{c2}\to \gamma \gamma$ is also measured to be $f_{0/2}={\Gamma }_{\gamma \gamma }^{\lambda =0}({\chi }_{c2})/{\Gamma }_{\gamma \gamma }^{\lambda =2}({\chi }_{c2})=(0.0\pm 0.6\pm 1.2)\times 10^{-2}$, where the uncertainties are statistical and systematic, respectively.

arXiv comment11 pages, 4 figures, 4 tables

References in corpus (25)

• Design and Construction of the BESIII Detector
• The Precision Monte Carlo Event Generator KK For Two-Fermion Final States In e+e- Collisions
• Coherent Exclusive Exponentiation For Precision Monte Carlo Calculations
• Properties of heavy quarkonia and B_c mesons in the relativistic quark model
• Charmonium
• Quarkonia and their transitions
• Measurement of the ${\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\pi }^{+}{\pi }^{-}$ Cross Section between 600 and 900 MeV Using Initial State Radiation
• Study of ${\chi }_{cJ}$ radiative decays into a vector meson
• Meson--photon transition form factors and resonance cross-sections in e^+ e^- collisions
• Measurement of the proton form factor by studying $e^{+}{e}^{-}\to p\bar{p}$
• Two-photon decay rates of heavy quarkonia in the relativistic quark model
• Two Photon Decays of Charmonia from Lattice QCD
• Relativistic two-photon and two-gluon decay rates of heavy quarkonia
• Evidence for psi' decays into gamma pi^0 and gamma eta
• Trigger efficiencies at BES III
• Two-photon and two-gluon decays of p-wave heavy quarkonium using a covariant light-front approach
• Effective Lagrangian for Two-photon and Two-gluon Decays of $P$-wave Heavy Quarkonium ${\chi }_{c0,2}$ and ${\chi }_{b0,2}$ states
• Electromagnetic Annihilation Rates of ${\chi }_{c0}$ and ${\chi }_{c2}$ with Both Relativistic and QCD Radiative Corrections
• Two-Photon Widths of the chi_cJ States of Charmonium
• Next-to-next-to-leading-order QCD corrections to ${\chi }_{c0,2}\to \gamma \gamma$
• Two-photon widths of the ${\chi }_{c0,2}$ states and helicity analysis for $χ_{c2}\arγγ$}
• Higher-order multipole amplitude measurement in $\psi (2S)\to \gamma {\chi }_{c2}$
• Measurement of the chi_{c2} Polarization in psi(2S) to gamma chi_{c2}
• Measurement of the branching fraction for $\psi (3770)\to \gamma {\chi }_{c0}$
• Measurement of $\mathcal{B}(\psi (3770)\to \gamma {\chi }_{c1})$ and search for $\psi (3770)\to \gamma {\chi }_{c2}$

Cited by in corpus (6)

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• Study of the reactions $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0{\pi }^0\gamma$ and ${\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0\eta \gamma$ at center-of-mass energies from threshold to 4.35 GeV using initial-state radiation
• Observation of the decay ${\chi }_{cJ}\to {\Omega }^{-}{\bar{\Omega }}^{+}$
• Electroweak production of ${\chi }_{Q1}$ states in $e^{+}{e}^{-}$ collisions: A brief review
• Study of the reactions $e^{+}{e}^{-}\to 2({\pi }^{+}{\pi }^{-}){\pi }^0{\pi }^0{\pi }^0$ and $e^{+}{e}^{-}\to 2({\pi }^{+}{\pi }^{-}){\pi }^0{\pi }^0\eta$ at center-of-mass energies from threshold to 4.5 GeV using initial-state radiation
• Observation of the decays ${\chi }_{cJ}\to \varphi \varphi \eta$