Evidence of a J/ψK_{S}^{0} Structure in B^{0}→J/ψϕK_{S}^{0} Decays

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• The B^{0}→J/ψϕK_{S}^{0} decay is a complex process involving multiple resonances.
• Previous observations of exotic states in related B-meson decays suggest the existence of new hadronic structures.

Purpose of the Study:

• To perform an amplitude analysis of B^{0}→J/ψϕK_{S}^{0} decays to search for new resonant structures.
• To characterize the properties (mass and width) of any observed structures.
• To investigate the relationship between neutral and charged exotic states in B-meson systems.

Main Methods:

• Analysis of a large dataset of proton-proton collisions (9 fb^{-1}) collected by the LHCb detector at 7, 8, and 13 TeV.
• Amplitude analysis of the B^{0}→J/ψϕK_{S}^{0} decay to identify resonant contributions.
• Statistical significance calculation to confirm the presence of new structures.

Main Results:

• Evidence for a new structure, named T_{ψs1}^{θ}(4000)^{0}, in the J/ψK_{S}^{0} system with a significance of 4.0 standard deviations.
• Measured mass and width of the T_{ψs1}^{θ}(4000)^{0} are 3991_{-10}^{+12} MeV/c^{2} and 105_{-25}^{+29} MeV, respectively.
• Assuming isospin symmetry, the combined significance for the neutral and charged T_{ψs1}^{θ}(4000) states increases to 5.4 standard deviations.

Conclusions:

• The observation of the T_{ψs1}^{θ}(4000)^{0} provides strong evidence for a new exotic hadronic state.
• The T_{ψs1}^{θ}(4000)^{0} is likely the isospin partner of the previously observed T_{ψs1}^{θ}(4000)^{+} state.
• This discovery contributes to the understanding of the complex spectroscopy of exotic hadrons within the Standard Model.