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Register a new userObservation of $e^+e^- rightarrow D_s^+ overline{D}{}^{(*)0} K^-$ and study of the $P$-wave $D_s$ mesons
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Studies of $e^+e^- to D_s^+ overline{D}{}^{(*)0}K^-$ and the $P$-wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected with the BESIII detector at $sqrt{s}= 4.600$ GeV. The processes of $e^+e^-to D_s^+ overline{D}{*}^{0} K^-$ and $D_s^+ overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$, respectively. The Born cross sections are measured to be $sigma^{B}(e^+e^-to D_s^+ overline{D}{*}^{0} K^-) = (10.1pm2.3pm0.8) pb$ and $sigma^{B}(e^+e^-to D_s^+ overline{D}{}^{0} K^-) = (19.4pm2.3pm1.6) pb$, and the products of Born cross section and the decay branching fraction are measured to be $sigma^{B}(e^+e^-to D_s^+D_{s1}(2536)^- + c.c.)cdotmathcal{B}(D_{s1}(2536)^- to overline{D}{*}^{0} K^-) = (7.5 pm 1.8 pm 0.7) pb$ and $sigma^{B}(e^+e^-to D_s^+ D^*_{s2}(2573)^- + c.c.)cdotmathcal{B}(D^*_{s2}(2573)^- to overline{D}{}^{0} K^-) = (19.7 pm 2.9 pm 2.0) pb$. For the $D_{s1}(2536)^-$ and $D^*_{s2}(2573)^-$ mesons, the masses and widths are measured to be $M(D_{s1}(2536)^-) = (2537.7 pm 0.5 pm 3.1)~MeV/c^2,$ $ Gamma(D_{s1}(2536)^-)) = (1.7pm 1.2 pm 0.6)~rm MeV,$ and $M(D^*_{s2}(2573)^-) = (2570.7pm 2.0 pm 1.7)~MeV/c^2,$ $Gamma(D^*_{s2}(2573)^-) = (17.2 pm 3.6 pm 1.1)~rm MeV.$ The spin-parity of the $D^*_{s2}(2573)^-$ meson is determined to be $J^P=2^{+}$. In addition, the process $e^+e^-to D_s^+ overline{D}{}^{(*)0} K^-$ are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the $90%$ confidence level on the cross sections are determined.
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We report a study of the processes of $e^+e^-to K^+ (D_s^- D^{*0} + D^{*-}_s D^0)$ based on $e^+e^-$ annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7 fb$^{-1}$. An excess over the known contributions of the conventional charmed mesons is observed near the $D_s^- D^{*0}$ and $D^{*-}_s D^0$ mass thresholds in the $K^{+}$ recoil-mass spectrum for events collected at $sqrt{s}=4.681$ GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as $(3982.5^{+1.8}_{-2.6}pm2.1)$ MeV/$c^2$ and $(12.8^{+5.3}_{-4.4}pm3.0)$ MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 $sigma$ over the contributions only from the conventional charmed mesons. This is the first candidate of the charged hidden-charm tetraquark with strangeness, decaying into $D_s^- D^{*0}$ and $D^{*-}_s D^0$. However, the properties of the excess need further exploration with more statistics.
The process $e^+e^-rightarrow poverline{p}pi^0$ has been studied by analyzing data collected at $sqrt{s}=3.773$ GeV, at $sqrt{s}=3.650$ GeV, and during a $psi(3770)$ line shape scan with the BESIII detector at the BEPCII collider. The Born cross section of $p overline{p} pi^0$ in the vicinity of the $psi(3770)$ is measured and the Born cross section of $psi(3770)rightarrow p overline{p} pi^0$ is extracted considering interference between resonant and continuum production amplitudes. Two solutions with the same probability and a significance of 1.5$sigma$ are found, and the Born cross section of $psi(3770)rightarrow p overline{p} pi^0$ is determined to be less than 0.22 pb at 90% confidence level and $33.8pm1.8pm2.1$ pb, respectively. Using the estimated cross section and a constant decay amplitude approximation, the cross section $sigma(poverline{p} rightarrow psi(3770) pi^0)$ is calculated for the kinematic situation of the planned $overline{text{P}}text{ANDA}$ experiment. The maximum cross section corresponding to the two solutions is expected to be less than $0.79$ nb at 90% confidence level and $122pm10$ nb at a center of mass energy of 5.26 GeV.
We have studied Bs0 -> Ds- pi+ and Bs0 -> Ds^(-/+) K^(+/-) decays using 23.6 /fb of data collected at the Upsilon(5S) resonance with the Belle detector at the KEKB e+e- collider. This highly pure Bs0 -> Ds- pi+ sample is used to measure the branching fraction, BR(Bs0 -> Ds- pi+)=[3.67 +0.35,-0.33}(stat.) +0.43,-0.42(syst.) +-0.49(f_s)] x 10^{-3} (f_s=N(Bs(*) Bs(*)bar)/N(bbar b)) and the fractions of Bs0 event types at the Upsilon(5S) energy, {in particular N(Bs* Bs*bar}/N(N(Bs(*) Bs(*)bar)=(90.1 +3.8,-4.0 +-0.2)%. We also determine the masses M(Bs0)=(5364.4 +-1.3 +-0.7) MeV/c^2 and M(Bs*)=(5416.4 +-0.4 +-0.5) MeV/c^2. In addition, we observe Bs0 -> Ds^(-/+) K^(+/-) decays with a significance of 3.5sigma and measure BR(Bs0 -> Ds^(-/+) K^(+/-))=[2.4 +1.2,-1.0(stat.) +-0.3(syst.) +-0.3(f_s)] x 10^{-4}.
A search for the rare radiative leptonic decay $D_s^+togamma e^+ u_e$ is performed for the first time using electron-positron collision data corresponding to an integrated luminosity of 3.19 fb$^{-1}$, collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. No evidence for the $D_s^+togamma e^+ u_e$ decay is seen and an upper limit of $mathcal B(D_s^+togamma e^+ u_e)<1.3times 10^{-4}$ is set on the partial branching fraction at a 90% confidence level for radiative photon energies $E_{gamma}^*>0.01$~GeV.
The first observation of the decay $B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-$ is reported using proton-proton collision data corresponding to an integrated luminosity of 4.7 $mathrm{fb}^{-1}$ collected by the LHCb experiment in 2011, 2012 and 2016. The measurement is performed in the full kinematically allowed range of the decay outside of the $D^{*-}$ region. The ratio of the branching fraction relative to that of the control channel $B^0 rightarrow D^{*-} D^0 K^+$ is measured to be $mathcal{R} = (14.2 pm 1.1 pm 1.0)%$, where the first uncertainty is statistical and the second is systematic. The absolute branching fraction of $B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-$ decays is thus determined to be $mathcal{B}(B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-) = (3.50 pm 0.27 pm 0.26 pm 0.30) times 10^{-4}$, where the third uncertainty is due to the branching fraction of the control channel. This decay mode is expected to provide insights to spectroscopy and the charm-loop contributions in rare semileptonic decays.
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