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Register a new userNear-threshold $Dbar{D}$ spectroscopy and observation of a new charmonium state
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Using proton-proton collision data, corresponding to an integrated luminosity of 9$fb^{-1}$, collected with the~LHCb detector between 2011 and 2018, a new narrow charmonium state, the $X(3842)$ resonance, is observed in the decay modes $X(3842)rightarrow D^0bar{D}^0$ and $X(3842)rightarrow D^+D^-$. The mass and the natural width of this state are measured to be begin{eqnarray*} m_{X(3842)} & = & 3842.71 pm 0.16 pm 0.12 MeV/c^2,, Gamma_{X(3842)} & = & 2.79 pm 0.51 pm 0.35 MeV,, end{eqnarray*} where the first uncertainty is statistical and the~second is systematic. The observed mass and narrow natural width suggest the~interpretation of the new state as the~unobserved spin obreakdash-3 $psi_3mathrm{left(1^3D_3right)}$ charmonium state. In addition, prompt hadroproduction of the $psi(3770)$~and $chi_{c2}(3930)$ states is observed for the first time, and the parameters of these~states are measured to be begin{eqnarray*} m_{psi(3770)} & = & 3778.1 pm 0.7 pm 0.6 MeV/c^2,, m_{chi_{c2}(3930)} & = & 3921.9 pm 0.6 pm 0.2 MeV/c^2,, Gamma_{chi_{c2}(3930)} & = &36.6 pm 1.9 pm 0.9 MeV,, end{eqnarray*} where the first uncertainty is statistical and the~second is systematic.
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A neutral structure in the $Dbar{D}^{*}$ system around the $Dbar{D}^{*}$ mass threshold is observed with a statistical significance greater than 10$sigma$ in the processes $e^{+}e^{-}rightarrow D^{+}D^{*-}pi^{0}+c.c.$ and $e^{+}e^{-}rightarrow D^{0}bar{D}^{*0}pi^{0}+c.c.$ at $sqrt{s}$ = 4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as $Z_{c}(3885)^{0}$. Assuming the presence of a resonance, its pole mass and width are determined to be ($3885.7^{+4.3}_{-5.7}$(stat)$pm 8.4$(syst)) MeV/$c^{2}$ and ($35^{+11}_{-12}$(stat)$ pm 15$(syst)) MeV, respectively. The Born cross sections are measured to be $sigma(e^{+}e^{-}to Z_{c}(3885)^{0}pi^{0}, Z_{c}(3885)^{0} to Dbar{D}^{*})=(77 pm 13$(stat)$pm 17$(syst)) pb at 4.226 GeV and ($47 pm 9$(stat)$ pm 10$(syst)) pb at 4.257 GeV. The ratio of decay rates $frac{mathcal{B}({Z_{c}(3885)^{0} to D^{+}D^{*-}+c.c.})}{mathcal{B}({Z_{c}(3885)^{0} to D^{0}bar{D}^{*0}+c.c.})}$ is determined to be $0.96 pm 0.18$(stat)$pm 0.12$(syst), consistent with no isospin violation in the process $Z_{c}(3885)^{0}to Dbar{D}^*$.
We report the first observation of the charge symmetry breaking d + d -> 4He + pi0 reaction near threshold at the Indiana University Cyclotron Facility. Kinematic reconstruction permitted the separation of 4He + pi0 events from double radiative capture 4He + gamma + gamma events. We measured total cross sections for neutron pion production of 12.7 +- 2.2 pb at 228.5 MeV and 15.1 +- 3.1 pb at 231.8 MeV. The uncertainty is dominated by statistical errors.
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.
Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5 fb$^{-1}$, the observation of a new excited $Xi_b^0$ resonance decaying to the $Xi_b^-pi^+$ final state is presented. The state, referred to as $Xi_b(6227)^0$, has a measured mass and natural width of $m(Xi_b(6227)^0) = 6227.1^{,+1.4}_{,-1.5}pm0.5$ MeV, $Gamma(Xi_b(6227)^0) = 18.6^{,+5.0}_{,-4.1}pm1.4$ MeV, where the uncertainties are statistical and systematic. The production rate of the $Xi_b(6227)^0$ state relative to that of the $Xi_b^-$ baryon in the kinematic region $2<eta<5$ and $p_{rm T}<30$ GeV is measured to be $frac{f_{Xi_b(6227)^0}}{f_{Xi_b^-}}{mathcal{B}}(Xi_b(6227)^0toXi_b^-pi^+) = 0.045pm0.008pm0.004$, where ${mathcal{B}}(Xi_b(6227)^0toXi_b^-pi^+)$ is the branching fraction of the decay, and $f_{Xi_b(6227)^0}$ and $f_{Xi_b^-}$ represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed $Xi_b(6227)^-$ state, along with the mass of the $Xi_b^-$ baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.
Very recently it was predicted the existence of a charged state near the $D_sbar{D}^*/D^*_sbar{D}$ threshold. This state, that we call $Z_{cs}^+$, would be the strange partner of the recently observed $Z_c^pm(3900)$. Using standard techniques of QCD sum rules, we evaluate the three-point function for the vertices $Z_{cs}^+ , J/psi , K^+$, $Z_{cs}^+ , eta_c , K^{*+}$ and $Z_{cs}^+ , D_s^+bar{D}^{*0}$ and we make predictions for the corresponding decay widths in these channels.
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