Sneha Malde

Abstract:

The radiative decays χc1(3872) → ψ(2S) γ and χc1(3872) → J/ψγ are used to probe the nature of the χc1(3872) state using proton-proton collision data collected with the LHCb detector, corresponding to an integrated luminosity of 9 fb−1. Using the B+ → χc1(3872)K+ decay, the χc1(3872) → ψ(2S) γ process is observed for the first time and the ratio of its partial width to that of the χc1(3872) → J/ψγ decay is measured to beΓχc13872→ψ2SγΓχc13872→J/ψγ=1.67±0.21±0.12±0.04, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainties on the branching fractions of the ψ(2S) and J/ψ mesons. The measured ratio makes the interpretation of the χc1(3872) state as a pure D0D¯∗0 + D¯0 D*0 molecule questionable and strongly indicates a sizeable compact charmonium or tetraquark component within the χc1(3872) state.

Abstract:

Using 7.33 fb−1 of e+e− collision data samples collected with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, we search for the radiative decay Ds+→γρ770+ for the first time. A hint of Ds+→γρ770+ is observed with a statistical significance of 2.5σ. The branching fraction of Ds+→γρ770+ is measured to be (2.2 ± 0.9stat. ± 0.2syst.) × 10−4, corresponding to an upper limit of 6.1 × 10−4 at the 90% confidence level.

Abstract:

Using e+e− collision data collected by the BESIII detector at BEPCII corresponding to an integrated luminosity of 30 fb−1, we measure Born cross sections and effective form factors for the process e+e−→Ξ0Ξ¯0 at forty-five center-of-mass energies between 3.51 and 4.95 GeV. The dressed cross section is fitted, assuming a power-law function plus a charmonium(-like) state, i.e., ψ(3770), ψ(4040), ψ(4160), ψ(4230), ψ(4360), ψ(4415) or ψ(4660). No significant charmonium(-like) state decaying into Ξ0Ξ¯0 is observed. Upper limits at the 90% confidence level on the product of the branching fraction and the electronic partial width are provided for each decay. In addition, ratios of the Born cross sections and the effective form factors for e+e−→Ξ0Ξ¯0 and e+e−→Ξ−Ξ¯+ are also presented to test isospin symmetry and the vector meson dominance model.