First Observation of the Rare Purely Baryonic Decay B^{0}→pp[over ¯]

Area of Science:

• Particle Physics
• High-Energy Physics
• Hadron Spectroscopy

Background:

• B mesons are fundamental particles in particle physics.
• Understanding B meson decays provides insights into the Standard Model.
• Baryonic decays are rare and challenging to observe.

Purpose of the Study:

• To report the first observation of the B^{0} meson decaying into a proton-antiproton final state (B^{0}→pp[over ¯]).
• To measure the branching fraction of this rare decay.
• To investigate the B_{s}^{0}→pp[over ¯] decay and set an upper limit.

Main Methods:

• Analysis of proton-proton collision data collected by the LHCb experiment at 7 and 8 TeV.
• Utilizing an integrated luminosity of 3.0 fb^{-1}.
• Statistical and systematic uncertainty analysis for branching fraction determination.

Main Results:

• The first observation of the B^{0}→pp[over ¯] decay with a branching fraction of (1.25±0.27±0.18)×10^{-8}.
• This decay is the rarest B^{0} meson decay observed to date.
• No significant signal for B_{s}^{0}→pp[over ¯] was observed, with an upper limit set at <1.5×10^{-8} (90% CL).

Conclusions:

• The observation of B^{0}→pp[over ¯] enriches the understanding of B meson decay modes.
• The rarity of this decay provides a stringent test for theoretical models.
• The null result for B_{s}^{0}→pp[over ¯] further constrains its potential branching fraction.