138 Search Results

The decays of ${\chi }_{c2}$ → K⁺K^-π⁰, K_SK^±π^∓, and π⁺π^-π⁰ are studied with the ψ ( 3686 ) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of ${\chi }_{c2}$ → K*$$\bar{K}$$ , ${\chi }_{c2}$ → $$a_2^±$$(1320)π^∓/$$a_2^0$$(1320)π⁰, and ${\chi }_{c2}$ → ρ( 770 )^±π^∓ are measured. Here, K*$$\bar{K}$$ denotes both K*^±K^∓ and its isospin-conjugated process K*⁰$$\bar{K}$$⁰+c.c., and K* denotes the resonances K*(892), $$K_2^*$$(1430), and $$K_3^*$$(1780). Themore » 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 ${\chi }_{c2}$ → K*(892)$$\bar{K}$$ are more than ten times larger than the upper limit of ${\chi }_{c2}$ → ρ ( 770 )^±π^∓, which is so far the first direct observation of a significant U -spin symmetry breaking effect in charmonium decays.« less

Using a data set with an integrated luminosity of $$2.93\text{ }\text{ }{\mathrm{fb}}^{{-}1}$$ collected at $$\sqrt{s}=3.773\text{ }\mathrm{GeV}$$ with the BESIII detector operating at the BEPCII storage rings, we search for the rare decay $${D}^{+}{\rightarrow}{D}^{0}{e}^{+}{{\nu}}_{e}$$. No signal events are observed. We set the upper limit on the branching fraction for $${D}^{+}{\rightarrow}{D}^{0}{e}^{+}{{\nu}}_{e}$$ to be $$1.0\times{}1{0}^{{-}4}$$ at the 90% confidence level.