Study of e+e−→ppˉe^+e^- \rightarrow p\bar{p} in the vicinity of ψ(3770)\psi(3770)

Using 2917 $\rm{pb}^{-1}$ of data accumulated at 3.773~$\rm{GeV}$, 44.5~$\rm{pb}^{-1}$ of data accumulated at 3.65~$\rm{GeV}$ and data accumulated during a $\psi(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-\rightarrow p\bar{p}$ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}$, $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p})$, is found to have two solutions, determined to be ($0.059\pm0.032\pm0.012$) pb with the phase angle $\phi = (255.8\pm37.9\pm4.8)^\circ$ ($<$0.11 pb at the 90% confidence level), or $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}) = (2.57\pm0.12\pm0.12$) pb with $\phi = (266.9\pm6.1\pm0.9)^\circ$ both of which agree with a destructive interference. Using the obtained cross section of $\psi(3770)\rightarrow p\bar{p}$, the cross section of $p\bar{p}\rightarrow \psi(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8\pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6\pm42.9)$ nb

Measurement of the Branching Fraction for the Semileptonic Decay D0 (+) →π- (0)μ+νμ and Test of Lepton Flavor Universality

Using a data sample corresponding to an integrated luminosity of 2.93 fb-1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we perform an analysis of the semileptonic decays D0(+)→π-(0)μ+νμ. The branching fractions of D0→π-μ+νμ and D+→π0μ+νμ are measured to be (0.272±0.008stat±0.006syst)% and (0.350±0.011stat±0.010syst)%, respectively, where the former is of much improved precision compared to previous results and the latter is determined for the first time. Using these results along with previous BESIII measurements of D0(+)→π-(0)e+νe, we calculate the branching fraction ratios to be R0≡BD0→π-μ+νμ/BD0→π-e+νe=0.922±0.030stat±0.022syst and R+≡BD+→π0μ+νμ/BD+→π0e+νe=0.964±0.037stat±0.026syst, which are compatible with the theoretical expectation of lepton flavor universality within 1.7σ and 0.5σ, respectively. We also examine the branching fraction ratios in different four-momentum transfer square regions, and find no significant deviations from the standard model predictions

Measurements of absolute branching fractions for D mesons decays into two pseudoscalar mesons

Using a data sample of e(+)e(-) collision data with an integrated luminosity of 2.93 fb(-1) taken at the center-of-mass energy root s = 3.773 GeV with the BESIII detector operating at the BEPCII storage rings, we measure the absolute branching fractions of the two-body hadronic decays D+ -&gt; pi(+)pi(0), K+pi(0), pi(+)eta., K+eta., pi(+)eta', K+eta', K-S(0)pi(+), (KSK+)-K-0, and D-0 -&gt; pi(+)pi(-), K+ K-, K--/+pi(+/-), K-S(0)pi(0), K-S(0)eta, K-S(0)eta' Our results are consistent with previous measurements within uncertainties. Among them, the branching fractions for D+-&gt; pi(+)pi(0), K+pi(0), pi(+)eta, pi(+)eta', (KSK+)-K-0, (KSK+)-K-0 and D-0 -&gt; K-S(0)pi(0), K-S(0)eta, K-S(0)eta' are determined with improved precision compared to the world average values

Observation of a cross-section enhancement near mass threshold in e+e−→ΛΛˉe^{+}e^{-}\rightarrowΛ\barΛ

The process $e^{+}e^{-}\rightarrowΛ\barΛ$ is studied using data samples at $\sqrt{s}$=2.2324, 2.400, 2.800 and 3.080∼GeV collected with the BESIII detector operating at the BEPCII collider. The Born cross section is measured at $\sqrt{s}$=2.2324∼GeV, which is 1.0∼MeV above the $Λ\barΛ$ mass threshold, to be $305\pm45^{+66}_{-36}$~pb, where the first uncertainty is statistical and the second systematic. The substantial cross section near threshold is significantly larger than that expected from theory, which predicts the cross section to vanish at threshold. The Born cross sections at $\sqrt{s}$=2.400, 2.800 and 3.080∼GeV are measured and found to be consistent with previous experimental results, but with improved precision. Finally, the corresponding effective electromagnetic form factors of Lambda are deduced

Observation of D0(+)→KS0π0(+)η′D^{0(+)}\to K^0_S\pi^{0(+)}\eta^\prime and improved measurement of D0→K−π+η′D^0\to K^-\pi^+\eta^\prime

By analyzing 2.93 fb$^{−1}$ of data taken at a center-of-mass energy of 3.773~GeV with the BESIII detector, we measure the branching fractions of the Cabibbo-favored hadronic decays $D^0\to K^-\pi^+\eta^\prime$, $D^0\to K^0_S\pi^0\eta^\prime$ and $D^+\to K^0_S\pi^+\eta^\prime$, which are determined to be $(6.43 \pm 0.15_{\rm stat.} \pm 0.31_{\rm syst.})\times 10^{-3}$, $(2.52 \pm 0.22_{\rm stat.} \pm 0.15_{\rm syst.})\times 10^{-3}$ and $(1.90 \pm 0.17_{\rm stat.} \pm 0.13_{\rm syst.})\times 10^{-3}$, respectively. The precision of the branching fraction of $D^0\to K^-\pi^+\eta^\prime$ is significantly improved, and the processes $D^0\to K^0_S\pi^0\eta^\prime$ and $D^+\to K^0_S\pi^+\eta^\prime$ are observed for the first time

Study of η(1475)η(1475) and X(1835)X(1835) in radiative J/ψJ/ψ decays to γϕγϕ

The decay $J/\psi \rightarrow \gamma \gamma \phi$ is studied using a sample of 1.31×109 J/ψ events collected with the BESIII detector. Two structures around 1475 MeV/c$^2$ and 1835 MeV/c$^2$ are observed in the $γϕ$ invariant mass spectrum for the first time. With a fit on the $γϕ$ invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/c$^2$ is found to favor an assignment as the $η(1475)$ and the mass and width for the structure around 1835 MeV/c$^2$ are consistent with the $X(1835)$. The statistical significances of the two structures are 13.5σ and 6.3σ, respectively. The results indicate that both $η(1475)$ and $X(1835)$ contain a sizeable $s\bar{s}$ component

Search for h(c) -&gt; pi(+)pi(-) J/psi via psi(3686) -&gt; pi(0)pi(+)pi(-) J/psi

Using a data sample of 448.1 x 10(6) psi(3686) events collected with the BESIII detector operating at the BEPCII, we perform search for the hadronic transition h(c)-&gt; pi(+)pi(-) J/psi via psi (3686) -&gt; pi(0)hc. No signals of the transition are observed, and the upper limit on the product branching fraction B(sigma(3686) -&gt; pi(0)h(c))B(h(c) -&gt; pi(+)pi(-) J/psi) at the 90% confidence level (C. L.) is determined to be 2.0 x 10(-6). This is the most stringent upper limit to date

Precision Study of η′→γπ+π−\eta^\prime\rightarrow\gamma\pi^+\pi^- Decay Dynamics

Using a low background data sample of $9.7×10^5$ $J\psi\rightarrow\gamma\eta^\prime$, $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ are studied with both model-dependent and model-independent approaches. The contributions of ω and the ρ(770)−ω interference are observed for the first time in the decays $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ in both approaches. Additionally, a contribution from the box anomaly or the ρ(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach

Measurement of singly Cabibbo-suppressed decays D-0 → π0π0π0, π0π0η, π0ηη and ηηη

Using a data sample of e(+)e(-) collision data corresponding to an integrated luminosity of 2.93 fb(-1) collected with the BESIII detector at a center-of-mass energy of root s = 3.773 GeV, we search for the singly Cabibbo-suppressed decays D-0 -&gt; pi(0)pi(0)pi(0), pi(0)pi(0)eta, pi(0)eta eta and eta eta eta using the double tag method. The absolute branching fractions are measured to be B(D-0 -&gt; pi(0)pi(0)pi(0)) = (2.0 +/- 0.4 +/- 0.3) x 10(-4), B(D-0 -&gt; pi(0)pi(0)eta) = (3.8 +/- 1.1 +/- 0.7) x 10(-4) and B(D-0 -&gt; pi(0)eta eta) = (7.3 +/- 1.6 +/- 1.5) x 10(-4) with the statistical significances of 4.8 sigma, 3.8 sigma and 5.5 sigma, respectively, where the first uncertainties are statistical and the second ones systematic. No significant signal of D-0 -&gt; eta eta eta is found, and the upper limit on its decay branching fraction is set to be B(D-0 -&gt; eta eta eta) &lt; 1.3 x 10(-4) at the 90% confidence level

Observation of ψ (3686) →n n ̄ and improved measurement of ψ (3686) →p p ̄

We observe the decay ψ(3686)→nn̄ for the first time and measure ψ(3686)→pp̄ with improved accuracy by using 1.07×108 ψ(3686) events collected with the BESIII detector. The measured branching fractions are B(ψ(3686)→nn̄)=(3.06±0.06±0.14)×10-4 and B(ψ(3686)→pp̄)=(3.05±0.02±0.12)×10-4. Here, the first uncertainties are statistical, and the second ones are systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey 1+αcos2θ, we determine the α parameters to be αnn̄=0.68±0.12±0.11 and αpp̄=1.03±0.06±0.03 for ψ(3686)→nn̄ and ψ(3686)→pp̄, respectively