Amplitude analysis of Ds+→π+π−π+D_s^{+} \rightarrow \pi^{+} \pi^{-} \pi^{+}

Utilizing the data set corresponding to an integrated luminosity of $3.19$ fb$^{-1}$ collected by the BESIII detector at a center-of-mass energy of 4.178 GeV, we perform an amplitude analysis of the $D_s^+\to\pi^+\pi^-\pi^+$ decay. The sample contains 13,797 candidates with a signal purity of $\sim$80%. The amplitude and phase of the contributing $\pi\pi$ ${\cal S}$ wave are measured based on a quasi-model-independent approach, along with the amplitudes and phases of the ${\cal P}$ and ${\cal D}$ waves parametrized by Breit-Wigner models. The fit fractions of different intermediate decay channels are also reported.Comment: 14 pages, 6 figure

Observation of e+e−→pppˉnˉπ−+c.c.e^+e^- \to p p \bar{p} \bar{n} \pi^{-} + c.c.

Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESIII detector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 $\rm fb^{-1}$, the process $e^+e^- \to p p \bar{p} \bar{n} \pi^{-} + c.c.$ is observed for the first time with a statistical significance of $11.5\sigma$. The average Born cross sections in the energy ranges of (4.160, 4.380) GeV, (4.400, 4.600) GeV and (4.610, 4.700) GeV are measured to be $(21.5\pm5.7\pm1.2)$ fb, $(46.3\pm10.6\pm2.5)$ fb and $(59.0\pm9.4\pm3.2)$ fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the $\bar{p}\bar{n}$ and $pp\pi^-$ invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.Comment: 10 pages, 4 figures. Submitted to Chinese Physics

Search for the charged lepton flavor violating decay J /ψ →eτ

A search for the charged lepton flavor violating decay J/ψ→e±τ with τ →π π0ντ is performed with about 10×109 J/ψ events collected with the BESIII detector at the BEPCII. No significant signal is observed, and an upper limit is set on the branching fraction B(J/ψ→e±τ)<7.5×10-8 at the 90% confidence level. This improves the previously published limit by two orders of magnitude

Study of the process e+e- →φη at center-of-mass energies between 2.00 and 3.08 GeV

The process e+e-→φη is studied at 22 center-of-mass energy points (s) between 2.00 and 3.08 GeV using 715 pb-1 of data collected with the BESIII detector. The measured Born cross section of e+e-→φη is found to be consistent with BABAR measurements, but with improved precision. A resonant structure around 2.175 GeV is observed with a significance of 6.9σ with mass (2163.5±6.2±3.0) MeV/c2 and width (31.1-11.6+21.1±1.1) MeV, where the first uncertainties are statistical and the second are systematic

Measurement of the absolute branching fractions for purely leptonic Ds+ decays

We report new measurements of the branching fraction B(Ds+→ℓ+ν), where is either μ+ or τ+(→π+ν¯τ), based on 6.32 fb-1 of electron-positron annihilation data collected by the BESIII experiment at six center-of-mass energy points between 4.178 and 4.226 GeV. Simultaneously floating the Ds+→μ+νμ and Ds+→τ+ντ components yields B(Ds+→τ+ντ)=(5.21±0.25±0.17)×10-2, B(Ds+→μ+νμ)=(5.35±0.13±0.16)×10-3, and the ratio of decay widths R=Γ(Ds+→τ+ντ)Γ(Ds+→μ+νμ)=9.73-0.58+0.61±0.36, where the first uncertainties are statistical and the second systematic. No evidence of CP asymmetry is observed in the decay rates Ds±→μ±νμ and Ds±→τ±ντ: ACP(μ±ν)=(-1.2±2.5±1.0)% and ACP(τ±ν)=(+2.9±4.8±1.0)%. Constraining our measurement to the Standard Model expectation of lepton universality (R=9.75), we find the more precise results B(Ds+→τ+ντ)=(5.22±0.10±0.14)×10-2 and ACP(τ±ντ)=(-0.1±1.9±1.0)%. Combining our results with inputs external to our analysis, we determine the c→s¯ quark mixing matrix element, Ds+ decay constant, and ratio of the decay constants to be |Vcs|=0.973±0.009±0.014, fDs+=249.9±2.4±3.5 MeV, and fDs+/fD+=1.232±0.035, respectively

Amplitude analysis and branching-fraction measurement of Ds+ → KS0 K-π+π+

Using 6.32 fb-1 of e+e- collision data collected by the BESIII detector at the center-of-mass energies between 4.178 and 4.226 GeV, an amplitude analysis of the Ds+→KS0K-π+π+ decays is performed for the first time to determine the intermediate-resonant contributions. The dominant component is the Ds+→K∗(892)+K̄∗(892)0 decay with a fraction of (40.6±2.9stat±4.9sys)%. Our results of the amplitude analysis are used to obtain a more precise measurement of the branching fraction of the Ds+→KS0K-π+π+ decay, which is determined to be (1.46±0.05stat±0.05sys)%

Study of the Decay D+s → π+π+π−η and Observation of the W-annihilation Decay D+s → a0(980)+ρ0

The decay D+s → π+π+π−η is observed for the first time, using e+e− collision data corresponding to an integrated luminosity of 6.32 fb−1, collected by the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV. The absolute branching fraction for this decay is measured to be B(D+s → π+pi+π−η) = (3.12 ± 0.13stat. ± 0.09syst.)%. The first amplitude analysis of this decay reveals the sub-structures in D+s → π+π+π−η and determines the relative fractions and the phases among these sub-structures. The dominant intermediate process is D+s → a1(1260)+η, a1(1260)+ →ρ(770)0π+ with a branching fraction of (1.73 ± 0.14stat. ± 0.08syst.)%. We also observe the W-annihilation process D+s → a0(980)+ρ(770)0, a0(980)+ → π+η with a branching fraction of (0.21 ±0.08stat. ± 0.05syst.)%, which is larger than the branching fractions of other measured pure Wannihilation decays by one order of magnitude