Observation of the helicity-selection-rule suppressed decay of the ${\chi }_{c2}$ charmonium state

Abstract

The decays of ${\chi }_{c2}\to K^{+}{K}^{-}{\pi }^0$, $K_S{K}^{\pm }{\pi }^{\mp }$ and ${\pi }^{+}{\pi }^{-}{\pi }^0$ are studied with the $\psi (3686)$ data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of ${\chi }_{c2}\to K^{\ast }\overline{K}$, ${\chi }_{c2}\to a_2^{\pm }(1320){\pi }^{\mp }/a_2^0(1320){\pi }^0$ and ${\chi }_{c2}\to \rho (770{)}^{\pm }{\pi }^{\mp }$ are measured. Here $K^{\ast }\overline{K}$ denotes both $K^{\ast \pm }{K}^{\mp }$ and $K^{\ast 0}\overline{K}{}^0+c.c.$, and $K^{\ast }$ denotes the resonances $K^{\ast }(892)$, $K_2^{\ast }(1430)$ and $K_3^{\ast }(1780)$. The observations indicate a strong violation of the helicity selection rule in ${\chi }_{c2}$ decays into vector and pseudoscalar meson pairs. The measured branching fractions of ${\chi }_{c2}\to K^{\ast }(892)\overline{K}$ are more than 10 times larger than the upper limit of ${\chi }_{c2}\to \rho (770{)}^{\pm }{\pi }^{\mp }$, which is so far the first direct observation of a significant $U$-spin symmetry breaking effect in charmonium decays.

arXiv comment7 pages, 3 figures

References in corpus (11)

• Design and Construction of the BESIII Detector
• Charmonium
• Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics
• Gauge Invariant Lagrangians for Free and Interacting Higher Spin Fields. A Review of the BRST formulation
• Search for hadronic transition ${\chi }_{cJ}\to {\eta }_c{\pi }^{+}{\pi }^{-}$ and observation of ${\chi }_{cJ}\to K\bar{K}\pi \pi \pi$
• Study of ${\chi }_{cJ}$ radiative decays into a vector meson
• The evasion of helicity selection rule in ${\chi }_{c1}\to VV$ and ${\chi }_{c2}\to VP$ via intermediate charmed meson loops
• Determination of the number of ${\psi }^{\prime }$ event at BESIII
• Observation of ${\chi }_{c1}$ decays into vector meson pairs $\varphi \varphi$, $\omega \omega$, and $\omega \varphi$
• Higher-order multipole amplitude measurement in $\psi (2S)\to \gamma {\chi }_{c2}$
• Experimental study of psi' decays to K+K- pi^0 and K+K- eta

Cited by in corpus (4)

• Partial wave analysis of $\psi (3686)\to K^{+}{K}^{-}\eta$
• Detecting the polarization in ${\chi }_{cJ}\to \varphi \varphi$ decays to probe hadronic loop effect
• Exclusive decays ${\chi }_{cJ}\to K^{\ast }(892)K$ within the effective field theory framework
• Search for the decays $X(3872)\to K_S^0{K}^{\pm }{\pi }^{\mp }$ and $K^{\ast }(892)\bar{K}$ at BESIII