Using a sample of 448.1×10 6 ψ(3686) events collected with the BESIII detector, a search for the isospin violating decay η c → π⁺π⁻π⁰ via ψ(3686) → γ η c is presented. No signal is observed, and the upper limit on B(ψ(3686) → γ η c ) × B( η c → π⁺π⁻π⁰) is determined to be 1.6 × 10 -6 at the 90% confidence level. In addition, a search for η (1405) → f 0 (980)π 0 in (3686) radiative decays is performed. No signal is observed, and the branching fraction B(ψ(3686) → γη(1405))×B( η (1405) → f 0 (980)π 0 ) × B(f 0 (980) → π⁺π⁻ is calculated to be less than 5.0 × 10 -7 at the 90% confidence level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Branching fraction measurement of J / ψ → K S K L and search for J / ψ → K S K S

Using a sample of 1.31×10 9 J/ψ events collected with the BESIII detector at the BEPCII collider, we study the decays of J/ψ→ K S K L and K S K S . The branching fraction of J/ψ→ K S K L is determined to be B(J/ψ→ K S K L ) = (1:93 0:01 (stat:) 0:05 (syst:))×10 -4 , which signi cantly improves on previous measurements. No clear signal is observed for the J/ψ→ K S K S process, and the upper limit at the 95% con dence level for its branching fraction is determined to be B(J= ! K S K S ) < 1:4×10 -8 , which improves on the previous searches by 2 orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Search for the rare decays J / ψ → D 0 e + e - + c . c . and ψ ( 3686 ) → D 0 e + e - + c . c .

Using the data samples of (1310.6 ± 7.2) × 10 6 J / ψ events and (448.1 ± 2.9) × 106 (3686) events collected with the BESIII detector, we search for the rare decays J / ψ → D 0 e + e - + c.c. and (3686) → D 0 e + e - + c.c.. No significant signals are observed and the corresponding upper limits on the branching fractions at the 90% confidence level are determined to be B( J / ψ → D0e+e- + c.c.) < 8.5 × 10 -8 and B( (3686) → D0e+e- + c.c.) < 1.4 × 10 -7 , respectively. Our limit on B( J / ψ → D 0 e + e - + c.c.) is more stringent by two orders of magnitude than the previous results, and the B( (3686) → D 0 e + e - + c.c.) is measured for the first time.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Observation of the helicity-selection-rule suppressed decay of the χ c 2 charmonium state

The decays of χ c 2 → K + K - π 0 , K S K ± π ∓ , and π + π - π 0 are studied with the ψ ( 3686 ) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χ c 2 → K*$\bar{K}$ , χ c 2 → $a_2^±$(1320)π ∓ /$a_2^0$(1320)π 0 , and χ c 2 → 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). The observations indicate a strong violation of the helicity selection rule in χ c 2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χ c 2 → K*(892)$\bar{K}$ are more than ten times larger than the upper limit of χ c 2 → ρ ( 770 ) ± π ∓ , which is so far the first direct observation of a significant U -spin symmetry breaking effect in charmonium decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Observation of χ c 2 → η ' η ' and χ c 0 , 2 → η η '

Using a sample of 448.1×10 6 ψ(3686) events collected with the BESIII detector in 2009 and 2012, we study the decays χ c 0,2 → η ' η ' and η η ' . The decays χ c 2 → η ' η ' , χ c 0 → η η ' and χ c 2 → η η ' are observed for the first time with statistical significances of 9.6 , 13.4 and 7.5 , respectively. The branching fractions are determined to be B( χ c 0 → η ' η ' ) = (2.19 ± 0.03 ± 0.14) × 10 -3 , B( χ c 2 → η ' η ' ) = (4.76 ± 0.56 ± 0.38) × 10 -5 , B( χ c 0 → η η ' ) = (8.92±0.84±0.65)×10 -5 and B( χ c 2 → η η ' ) = (2.27±0.43±0.25)×10 -5 , where the first uncertainties are statistical and the second are systematic. The precision for the measurement of B( χ c 0 → η ' η ' ) is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for χ c 0 , 2 decays into pseudoscalar meson pairs can be clarified.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2017

Improved measurements of two-photon widths of the χ c J states and helicity analysis for χ c 2 → γ γ

Based on 448.1 x 10 6 ψ(3686) events collected with the BESIII detector, the decays ψ(3686) → γχ cJ ,χ cJ → γγ(J = 0,1,2) are studied in this paper. The decay branching fractions of χ c0,2 → γγ are measured to be β(χ c0 → γγ) = (1.93 ± 0.08 ± 0.05 ± 0.05) x 10 -4 and β(χ c2 → γγ) = (3.10 ± 0.09 ± 0.07 ± 0.11) x 10 -4 , which correspond to two-photon decay widths of Γ γγ (χ c0 ) = 2.03 ± 0.08 ± 0.06 ± 0.13 keV and Γ γγ (χ c2 ) = 0.60 ± 0.02 ± 0.01 ± 0.04 keV with a ratio of R = Γ γγ (χ c2 )/Γ γγ (χ c0 ) = 0.295 ± 0.014 ± 0.007 ± 0.027, where the uncertainties are statistical, systematic and associated with the uncertainties of β(ψ(3686) → γχ c0,2 ) and the total widths Γ(χ c0,2 ), respectively. For the forbidden decay of χ c1 → γγ, no signal is observed, and an upper limit on the two-photon width is obtained to be Γ γγ (χ c1 ) < 5.3 eV at the 90% confidence level. Finally, the ratio of the two-photon widths between helicity-zero and helicity-two components in the decay χ c2 → γγ is also measured to be f 0/2 = Γ λ=0 γγ (χ c2 )/Γ λ=2 γγ (χ c2 ) = (0.0 ± 0.6 ± 1.2) x 10 -2 , where the uncertainties are statistical and systematic, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Search for the rare decay D + → D 0 e + ν e

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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement of cross sections of the interactions e + e − → ϕϕω and e + e − → ϕϕϕ at center-of-mass energies from 4.008 to 4.600 GeV

Not Available

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Dark photon search in the mass range between 1.5 and 3.4 GeV/c2

Not Available

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Measurement of branching fractions for ψ ( 3686 ) → γ η ' , γ η , and γ π 0

In this paper, using a data sample of 448 x 10 6 ψ(3686) events collected with the BESIII detector operating at the BEPCII storage ring, the decays ψ(3686) → γη and ψ(3686) → γπ 0 are observed with a statistical significance of 7.3σ and 6.7σ, respectively. The branching fractions are measured to be β(ψ(3686) → γη) = (0.85 ± 0.18 ± 0.05) x 10 -6 and β(ψ(3686) → γπ 0 ) = (0.95 ± 0.16 ± 0.05) x 10 -6 . Finally, in addition, we measure the branching fraction of ψ(3686) → γη' to be β(ψ(3686) → γη') = (125.1 ± 2.2 ± 6.2) x 10 -6 , which represents an improvement of precision over previous results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Determination of the number of ψ(3686) events at BESIII

The numbers of ψ(3686) events accumulated by the BESIII detector for the data taken during 2009 and 2012 are determined to be $(107.0\pm 0.8)\times {10}^{6}$ and $(341.1\pm 2.1)\times {10}^{6}$, respectively, by counting inclusive hadronic events, where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is $(448.1\pm 2.9)\times {10}^{6}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Observation of the decay Λ c + → Σ − π + π + π 0

Not Available

43 PARTICLE ACCELERATORS↗